diff --git a/syntax/testdata/scan.star b/syntax/testdata/scan.star
index 3b87c63b..4f62ba94 100644
--- a/syntax/testdata/scan.star
+++ b/syntax/testdata/scan.star
@@ -72,502 +72,532 @@ cgo_filetype = FileType([
 ################
 
 def go_environment_vars(ctx):
-  """Return a map of environment variables for use with actions, based on
-  the arguments. Uses the ctx.fragments.cpp.cpu attribute, if present,
-  and picks a default of target_os="linux" and target_arch="amd64"
-  otherwise.
-
-  Args:
-    The starlark Context.
-
-  Returns:
-    A dict of environment variables for running Go tool commands that build for
-    the target OS and architecture.
-  """
-  default_toolchain = {"GOOS": "linux", "GOARCH": "amd64"}
-  bazel_to_go_toolchain = {
-    "k8": {"GOOS": "linux", "GOARCH": "amd64"},
-    "piii": {"GOOS": "linux", "GOARCH": "386"},
-    "darwin": {"GOOS": "darwin", "GOARCH": "amd64"},
-    "darwin_x86_64": {"GOOS": "darwin", "GOARCH": "amd64"},
-    "freebsd": {"GOOS": "freebsd", "GOARCH": "amd64"},
-    "armeabi-v7a": {"GOOS": "linux", "GOARCH": "arm"},
-    "arm": {"GOOS": "linux", "GOARCH": "arm"}
-  }
-  env = {}
-  if hasattr(ctx.file, "go_tool"):
-    env["GOROOT"] = ctx.file.go_tool.dirname + "/.."
-  env.update(bazel_to_go_toolchain.get(ctx.fragments.cpp.cpu, default_toolchain))
-  return env
+    """Return a map of environment variables for use with actions, based on
+    the arguments. Uses the ctx.fragments.cpp.cpu attribute, if present,
+    and picks a default of target_os="linux" and target_arch="amd64"
+    otherwise.
+
+    Args:
+      The starlark Context.
+
+    Returns:
+      A dict of environment variables for running Go tool commands that build for
+      the target OS and architecture.
+    """
+    default_toolchain = {"GOOS": "linux", "GOARCH": "amd64"}
+    bazel_to_go_toolchain = {
+        "k8": {"GOOS": "linux", "GOARCH": "amd64"},
+        "piii": {"GOOS": "linux", "GOARCH": "386"},
+        "darwin": {"GOOS": "darwin", "GOARCH": "amd64"},
+        "darwin_x86_64": {"GOOS": "darwin", "GOARCH": "amd64"},
+        "freebsd": {"GOOS": "freebsd", "GOARCH": "amd64"},
+        "armeabi-v7a": {"GOOS": "linux", "GOARCH": "arm"},
+        "arm": {"GOOS": "linux", "GOARCH": "arm"},
+    }
+    env = {}
+    if hasattr(ctx.file, "go_tool"):
+        env["GOROOT"] = ctx.file.go_tool.dirname + "/.."
+    env.update(bazel_to_go_toolchain.get(ctx.fragments.cpp.cpu, default_toolchain))
+    return env
 
 def _is_darwin_cpu(ctx):
-  cpu = ctx.fragments.cpp.cpu
-  return cpu == "darwin" or cpu == "darwin_x86_64"
+    cpu = ctx.fragments.cpp.cpu
+    return cpu == "darwin" or cpu == "darwin_x86_64"
 
 def _emit_generate_params_action(cmds, ctx, fn):
-  cmds_all = [
-      # Use bash explicitly. /bin/sh is default, and it may be linked to a
-      # different shell, e.g., /bin/dash on Ubuntu.
-      "#!/bin/bash",
-      "set -e",
-  ]
-  cmds_all += cmds
-  cmds_all_str = "\n".join(cmds_all) + "\n"
-  f = ctx.new_file(ctx.configuration.bin_dir, fn)
-  ctx.file_action(
-      output = f,
-      content = cmds_all_str,
-      executable = True)
-  return f
+    cmds_all = [
+        # Use bash explicitly. /bin/sh is default, and it may be linked to a
+        # different shell, e.g., /bin/dash on Ubuntu.
+        "#!/bin/bash",
+        "set -e",
+    ]
+    cmds_all += cmds
+    cmds_all_str = "\n".join(cmds_all) + "\n"
+    f = ctx.new_file(ctx.configuration.bin_dir, fn)
+    ctx.file_action(
+        output = f,
+        content = cmds_all_str,
+        executable = True,
+    )
+    return f
 
 def _emit_go_asm_action(ctx, source, hdrs, out_obj):
-  """Construct the command line for compiling Go Assembly code.
-  Constructs a symlink tree to accomodate for workspace name.
-  Args:
-    ctx: The starlark Context.
-    source: a source code artifact
-    hdrs: list of .h files that may be included
-    out_obj: the artifact (configured target?) that should be produced
-  """
-  params = {
-      "go_tool": ctx.file.go_tool.path,
-      "includes": [f.dirname for f in hdrs] + [ctx.file.go_include.path],
-      "source": source.path,
-      "out": out_obj.path,
-  }
-
-  inputs = hdrs + ctx.files.toolchain + [source]
-  ctx.action(
-      inputs = inputs,
-      outputs = [out_obj],
-      mnemonic = "GoAsmCompile",
-      executable = ctx.executable._asm,
-      arguments = [json_marshal(params)],
-  )
+    """Construct the command line for compiling Go Assembly code.
+    Constructs a symlink tree to accomodate for workspace name.
+    Args:
+      ctx: The starlark Context.
+      source: a source code artifact
+      hdrs: list of .h files that may be included
+      out_obj: the artifact (configured target?) that should be produced
+    """
+    params = {
+        "go_tool": ctx.file.go_tool.path,
+        "includes": [f.dirname for f in hdrs] + [ctx.file.go_include.path],
+        "source": source.path,
+        "out": out_obj.path,
+    }
+
+    inputs = hdrs + ctx.files.toolchain + [source]
+    ctx.action(
+        inputs = inputs,
+        outputs = [out_obj],
+        mnemonic = "GoAsmCompile",
+        executable = ctx.executable._asm,
+        arguments = [json_marshal(params)],
+    )
 
 def _go_importpath(ctx):
-  """Returns the expected importpath of the go_library being built.
-
-  Args:
-    ctx: The starlark Context
-
-  Returns:
-    Go importpath of the library
-  """
-  path = ctx.attr.importpath
-  if path != "":
+    """Returns the expected importpath of the go_library being built.
+
+    Args:
+      ctx: The starlark Context
+
+    Returns:
+      Go importpath of the library
+    """
+    path = ctx.attr.importpath
+    if path != "":
+        return path
+    path = ctx.attr.go_prefix.go_prefix
+    if path.endswith("/"):
+        path = path[:-1]
+    if ctx.label.package:
+        path += "/" + ctx.label.package
+    if ctx.label.name != _DEFAULT_LIB:
+        path += "/" + ctx.label.name
+    if path.rfind(_VENDOR_PREFIX) != -1:
+        path = path[len(_VENDOR_PREFIX) + path.rfind(_VENDOR_PREFIX):]
+    if path[0] == "/":
+        path = path[1:]
     return path
-  path = ctx.attr.go_prefix.go_prefix
-  if path.endswith("/"):
-    path = path[:-1]
-  if ctx.label.package:
-    path += "/" + ctx.label.package
-  if ctx.label.name != _DEFAULT_LIB:
-    path += "/" + ctx.label.name
-  if path.rfind(_VENDOR_PREFIX) != -1:
-    path = path[len(_VENDOR_PREFIX) + path.rfind(_VENDOR_PREFIX):]
-  if path[0] == "/":
-    path = path[1:]
-  return path
 
 def _emit_go_compile_action(ctx, sources, deps, libpaths, out_object, gc_goopts):
-  """Construct the command line for compiling Go code.
-
-  Args:
-    ctx: The starlark Context.
-    sources: an iterable of source code artifacts (or CTs? or labels?)
-    deps: an iterable of dependencies. Each dependency d should have an
-      artifact in d.transitive_go_libraries representing all imported libraries.
-    libpaths: the set of paths to search for imported libraries.
-    out_object: the object file that should be produced
-    gc_goopts: additional flags to pass to the compiler.
-  """
-  if ctx.coverage_instrumented():
-    sources = _emit_go_cover_action(ctx, sources)
-
-  # Compile filtered files.
-  args = [
-      "-cgo",
-      ctx.file.go_tool.path,
-      "tool", "compile",
-      "-o", out_object.path,
-      "-trimpath", "-abs-.",
-      "-I", "-abs-.",
-  ]
-  inputs = depset(sources + ctx.files.toolchain)
-  for dep in deps:
-    inputs += dep.transitive_go_libraries
-  for path in libpaths:
-    args += ["-I", path]
-  args += gc_goopts + [("" if i.basename.startswith("_cgo") else "-filter-") + i.path for i in sources]
-  ctx.action(
-      inputs = list(inputs),
-      outputs = [out_object],
-      mnemonic = "GoCompile",
-      executable = ctx.executable._filter_exec,
-      arguments = args,
-      env = go_environment_vars(ctx),
-  )
-
-  return sources
+    """Construct the command line for compiling Go code.
+
+    Args:
+      ctx: The starlark Context.
+      sources: an iterable of source code artifacts (or CTs? or labels?)
+      deps: an iterable of dependencies. Each dependency d should have an
+        artifact in d.transitive_go_libraries representing all imported libraries.
+      libpaths: the set of paths to search for imported libraries.
+      out_object: the object file that should be produced
+      gc_goopts: additional flags to pass to the compiler.
+    """
+    if ctx.coverage_instrumented():
+        sources = _emit_go_cover_action(ctx, sources)
+
+    # Compile filtered files.
+    args = [
+        "-cgo",
+        ctx.file.go_tool.path,
+        "tool",
+        "compile",
+        "-o",
+        out_object.path,
+        "-trimpath",
+        "-abs-.",
+        "-I",
+        "-abs-.",
+    ]
+    inputs = depset(sources + ctx.files.toolchain)
+    for dep in deps:
+        inputs += dep.transitive_go_libraries
+    for path in libpaths:
+        args += ["-I", path]
+    args += gc_goopts + [("" if i.basename.startswith("_cgo") else "-filter-") + i.path for i in sources]
+    ctx.action(
+        inputs = list(inputs),
+        outputs = [out_object],
+        mnemonic = "GoCompile",
+        executable = ctx.executable._filter_exec,
+        arguments = args,
+        env = go_environment_vars(ctx),
+    )
+
+    return sources
 
 def _emit_go_pack_action(ctx, out_lib, objects):
-  """Construct the command line for packing objects together.
-
-  Args:
-    ctx: The starlark Context.
-    out_lib: the archive that should be produced
-    objects: an iterable of object files to be added to the output archive file.
-  """
-  ctx.action(
-      inputs = objects + ctx.files.toolchain,
-      outputs = [out_lib],
-      mnemonic = "GoPack",
-      executable = ctx.file.go_tool,
-      arguments = ["tool", "pack", "c", out_lib.path] + [a.path for a in objects],
-      env = go_environment_vars(ctx),
-  )
+    """Construct the command line for packing objects together.
 
-def _emit_go_cover_action(ctx, sources):
-  """Construct the command line for test coverage instrument.
-
-  Args:
-    ctx: The starlark Context.
-    sources: an iterable of Go source files.
-
-  Returns:
-    A list of Go source code files which might be coverage instrumented.
-  """
-  outputs = []
-  # TODO(linuxerwang): make the mode configurable.
-  count = 0
-
-  for src in sources:
-    if not src.path.endswith(".go") or src.path.endswith("_test.go"):
-      outputs += [src]
-      continue
-
-    cover_var = "GoCover_%d" % count
-    out = ctx.new_file(src, src.basename[:-3] + '_' + cover_var + '.cover.go')
-    outputs += [out]
+    Args:
+      ctx: The starlark Context.
+      out_lib: the archive that should be produced
+      objects: an iterable of object files to be added to the output archive file.
+    """
     ctx.action(
-        inputs = [src] + ctx.files.toolchain,
-        outputs = [out],
-        mnemonic = "GoCover",
+        inputs = objects + ctx.files.toolchain,
+        outputs = [out_lib],
+        mnemonic = "GoPack",
         executable = ctx.file.go_tool,
-        arguments = ["tool", "cover", "--mode=set", "-var=%s" % cover_var, "-o", out.path, src.path],
+        arguments = ["tool", "pack", "c", out_lib.path] + [a.path for a in objects],
         env = go_environment_vars(ctx),
     )
-    count += 1
 
-  return outputs
+def _emit_go_cover_action(ctx, sources):
+    """Construct the command line for test coverage instrument.
+
+    Args:
+      ctx: The starlark Context.
+      sources: an iterable of Go source files.
+
+    Returns:
+      A list of Go source code files which might be coverage instrumented.
+    """
+    outputs = []
+
+    # TODO(linuxerwang): make the mode configurable.
+    count = 0
+
+    for src in sources:
+        if not src.path.endswith(".go") or src.path.endswith("_test.go"):
+            outputs += [src]
+            continue
+
+        cover_var = "GoCover_%d" % count
+        out = ctx.new_file(src, src.basename[:-3] + "_" + cover_var + ".cover.go")
+        outputs += [out]
+        ctx.action(
+            inputs = [src] + ctx.files.toolchain,
+            outputs = [out],
+            mnemonic = "GoCover",
+            executable = ctx.file.go_tool,
+            arguments = ["tool", "cover", "--mode=set", "-var=%s" % cover_var, "-o", out.path, src.path],
+            env = go_environment_vars(ctx),
+        )
+        count += 1
+
+    return outputs
 
 def go_library_impl(ctx):
-  """Implements the go_library() rule."""
-
-  sources = depset(ctx.files.srcs)
-  go_srcs = depset([s for s in sources if s.basename.endswith('.go')])
-  asm_srcs = [s for s in sources if s.basename.endswith('.s') or s.basename.endswith('.S')]
-  asm_hdrs = [s for s in sources if s.basename.endswith('.h')]
-  deps = ctx.attr.deps
-  dep_runfiles = [d.data_runfiles for d in deps]
-
-  cgo_object = None
-  if hasattr(ctx.attr, "cgo_object"):
-    cgo_object = ctx.attr.cgo_object
-
-  if ctx.attr.library:
-    go_srcs += ctx.attr.library.go_sources
-    asm_srcs += ctx.attr.library.asm_sources
-    asm_hdrs += ctx.attr.library.asm_headers
-    deps += ctx.attr.library.direct_deps
-    dep_runfiles += [ctx.attr.library.data_runfiles]
-    if ctx.attr.library.cgo_object:
-      if cgo_object:
-        fail("go_library %s cannot have cgo_object because the package " +
-             "already has cgo_object in %s" % (ctx.label.name,
-                                               ctx.attr.library.name))
-      cgo_object = ctx.attr.library.cgo_object
-  if not go_srcs:
-    fail("may not be empty", "srcs")
-
-  transitive_cgo_deps = depset([], order="topological")
-  if cgo_object:
-    dep_runfiles += [cgo_object.data_runfiles]
-    transitive_cgo_deps += cgo_object.cgo_deps
-
-  extra_objects = [cgo_object.cgo_obj] if cgo_object else []
-  for src in asm_srcs:
-    obj = ctx.new_file(src, "%s.dir/%s.o" % (ctx.label.name, src.basename[:-2]))
-    _emit_go_asm_action(ctx, src, asm_hdrs, obj)
-    extra_objects += [obj]
-
-  lib_name = _go_importpath(ctx) + ".a"
-  out_lib = ctx.new_file(lib_name)
-  out_object = ctx.new_file(ctx.label.name + ".o")
-  search_path = out_lib.path[:-len(lib_name)]
-  gc_goopts = _gc_goopts(ctx)
-  transitive_go_libraries = depset([out_lib])
-  transitive_go_library_paths = depset([search_path])
-  for dep in deps:
-    transitive_go_libraries += dep.transitive_go_libraries
-    transitive_cgo_deps += dep.transitive_cgo_deps
-    transitive_go_library_paths += dep.transitive_go_library_paths
-
-  go_srcs = _emit_go_compile_action(ctx,
-      sources = go_srcs,
-      deps = deps,
-      libpaths = transitive_go_library_paths,
-      out_object = out_object,
-      gc_goopts = gc_goopts,
-  )
-  _emit_go_pack_action(ctx, out_lib, [out_object] + extra_objects)
-
-  dylibs = []
-  if cgo_object:
-    dylibs += [d for d in cgo_object.cgo_deps if d.path.endswith(".so")]
-
-  runfiles = ctx.runfiles(files = dylibs, collect_data = True)
-  for d in dep_runfiles:
-    runfiles = runfiles.merge(d)
-
-  return struct(
-    label = ctx.label,
-    files = depset([out_lib]),
-    runfiles = runfiles,
-    go_sources = go_srcs,
-    asm_sources = asm_srcs,
-    asm_headers = asm_hdrs,
-    cgo_object = cgo_object,
-    direct_deps = ctx.attr.deps,
-    transitive_cgo_deps = transitive_cgo_deps,
-    transitive_go_libraries = transitive_go_libraries,
-    transitive_go_library_paths = transitive_go_library_paths,
-    gc_goopts = gc_goopts,
-  )
-
-def _c_linker_options(ctx, blacklist=[]):
-  """Extracts flags to pass to $(CC) on link from the current context
-
-  Args:
-    ctx: the current context
-    blacklist: Any flags starts with any of these prefixes are filtered out from
-      the return value.
-
-  Returns:
-    A list of command line flags
-  """
-  cpp = ctx.fragments.cpp
-  features = ctx.features
-  options = cpp.compiler_options(features)
-  options += cpp.unfiltered_compiler_options(features)
-  options += cpp.link_options
-  options += cpp.mostly_static_link_options(ctx.features, False)
-  filtered = []
-  for opt in options:
-    if any([opt.startswith(prefix) for prefix in blacklist]):
-      continue
-    filtered.append(opt)
-  return filtered
+    """Implements the go_library() rule."""
+
+    sources = depset(ctx.files.srcs)
+    go_srcs = depset([s for s in sources if s.basename.endswith(".go")])
+    asm_srcs = [s for s in sources if s.basename.endswith(".s") or s.basename.endswith(".S")]
+    asm_hdrs = [s for s in sources if s.basename.endswith(".h")]
+    deps = ctx.attr.deps
+    dep_runfiles = [d.data_runfiles for d in deps]
+
+    cgo_object = None
+    if hasattr(ctx.attr, "cgo_object"):
+        cgo_object = ctx.attr.cgo_object
+
+    if ctx.attr.library:
+        go_srcs += ctx.attr.library.go_sources
+        asm_srcs += ctx.attr.library.asm_sources
+        asm_hdrs += ctx.attr.library.asm_headers
+        deps += ctx.attr.library.direct_deps
+        dep_runfiles += [ctx.attr.library.data_runfiles]
+        if ctx.attr.library.cgo_object:
+            if cgo_object:
+                fail("go_library %s cannot have cgo_object because the package " +
+                     "already has cgo_object in %s" % (
+                         ctx.label.name,
+                         ctx.attr.library.name,
+                     ))
+            cgo_object = ctx.attr.library.cgo_object
+    if not go_srcs:
+        fail("may not be empty", "srcs")
+
+    transitive_cgo_deps = depset([], order = "topological")
+    if cgo_object:
+        dep_runfiles += [cgo_object.data_runfiles]
+        transitive_cgo_deps += cgo_object.cgo_deps
+
+    extra_objects = [cgo_object.cgo_obj] if cgo_object else []
+    for src in asm_srcs:
+        obj = ctx.new_file(src, "%s.dir/%s.o" % (ctx.label.name, src.basename[:-2]))
+        _emit_go_asm_action(ctx, src, asm_hdrs, obj)
+        extra_objects += [obj]
+
+    lib_name = _go_importpath(ctx) + ".a"
+    out_lib = ctx.new_file(lib_name)
+    out_object = ctx.new_file(ctx.label.name + ".o")
+    search_path = out_lib.path[:-len(lib_name)]
+    gc_goopts = _gc_goopts(ctx)
+    transitive_go_libraries = depset([out_lib])
+    transitive_go_library_paths = depset([search_path])
+    for dep in deps:
+        transitive_go_libraries += dep.transitive_go_libraries
+        transitive_cgo_deps += dep.transitive_cgo_deps
+        transitive_go_library_paths += dep.transitive_go_library_paths
+
+    go_srcs = _emit_go_compile_action(
+        ctx,
+        sources = go_srcs,
+        deps = deps,
+        libpaths = transitive_go_library_paths,
+        out_object = out_object,
+        gc_goopts = gc_goopts,
+    )
+    _emit_go_pack_action(ctx, out_lib, [out_object] + extra_objects)
+
+    dylibs = []
+    if cgo_object:
+        dylibs += [d for d in cgo_object.cgo_deps if d.path.endswith(".so")]
+
+    runfiles = ctx.runfiles(files = dylibs, collect_data = True)
+    for d in dep_runfiles:
+        runfiles = runfiles.merge(d)
+
+    return struct(
+        label = ctx.label,
+        files = depset([out_lib]),
+        runfiles = runfiles,
+        go_sources = go_srcs,
+        asm_sources = asm_srcs,
+        asm_headers = asm_hdrs,
+        cgo_object = cgo_object,
+        direct_deps = ctx.attr.deps,
+        transitive_cgo_deps = transitive_cgo_deps,
+        transitive_go_libraries = transitive_go_libraries,
+        transitive_go_library_paths = transitive_go_library_paths,
+        gc_goopts = gc_goopts,
+    )
+
+def _c_linker_options(ctx, blocklist = []):
+    """Extracts flags to pass to $(CC) on link from the current context
+
+    Args:
+      ctx: the current context
+      blocklist: Any flags starts with any of these prefixes are filtered out from
+        the return value.
+
+    Returns:
+      A list of command line flags
+    """
+    cpp = ctx.fragments.cpp
+    features = ctx.features
+    options = cpp.compiler_options(features)
+    options += cpp.unfiltered_compiler_options(features)
+    options += cpp.link_options
+    options += cpp.mostly_static_link_options(ctx.features, False)
+    filtered = []
+    for opt in options:
+        if any([opt.startswith(prefix) for prefix in blocklist]):
+            continue
+        filtered.append(opt)
+    return filtered
 
 def _gc_goopts(ctx):
-  gc_goopts = [ctx.expand_make_variables("gc_goopts", f, {})
-               for f in ctx.attr.gc_goopts]
-  if ctx.attr.library:
-    gc_goopts += ctx.attr.library.gc_goopts
-  return gc_goopts
+    gc_goopts = [
+        ctx.expand_make_variables("gc_goopts", f, {})
+        for f in ctx.attr.gc_goopts
+    ]
+    if ctx.attr.library:
+        gc_goopts += ctx.attr.library.gc_goopts
+    return gc_goopts
 
 def _gc_linkopts(ctx):
-  gc_linkopts = [ctx.expand_make_variables("gc_linkopts", f, {})
-                 for f in ctx.attr.gc_linkopts]
-  for k, v in ctx.attr.x_defs.items():
-    gc_linkopts += ["-X", "%s='%s'" % (k, v)]
-  return gc_linkopts
+    gc_linkopts = [
+        ctx.expand_make_variables("gc_linkopts", f, {})
+        for f in ctx.attr.gc_linkopts
+    ]
+    for k, v in ctx.attr.x_defs.items():
+        gc_linkopts += ["-X", "%s='%s'" % (k, v)]
+    return gc_linkopts
 
 def _extract_extldflags(gc_linkopts, extldflags):
-  """Extracts -extldflags from gc_linkopts and combines them into a single list.
-
-  Args:
-    gc_linkopts: a list of flags passed in through the gc_linkopts attributes.
-      ctx.expand_make_variables should have already been applied.
-    extldflags: a list of flags to be passed to the external linker.
-
-  Return:
-    A tuple containing the filtered gc_linkopts with external flags removed,
-    and a combined list of external flags.
-  """
-  filtered_gc_linkopts = []
-  is_extldflags = False
-  for opt in gc_linkopts:
-    if is_extldflags:
-      is_extldflags = False
-      extldflags += [opt]
-    elif opt == "-extldflags":
-      is_extldflags = True
-    else:
-      filtered_gc_linkopts += [opt]
-  return filtered_gc_linkopts, extldflags
-
-def _emit_go_link_action(ctx, transitive_go_library_paths, transitive_go_libraries, cgo_deps, libs,
-                         executable, gc_linkopts):
-  """Sets up a symlink tree to libraries to link together."""
-  config_strip = len(ctx.configuration.bin_dir.path) + 1
-  pkg_depth = executable.dirname[config_strip:].count('/') + 1
-
-  ld = "%s" % ctx.fragments.cpp.compiler_executable
-  extldflags = _c_linker_options(ctx) + [
-      "-Wl,-rpath,$ORIGIN/" + ("../" * pkg_depth),
-  ]
-  for d in cgo_deps:
-    if d.basename.endswith('.so'):
-      short_dir = d.dirname[len(d.root.path):]
-      extldflags += ["-Wl,-rpath,$ORIGIN/" + ("../" * pkg_depth) + short_dir]
-  gc_linkopts, extldflags = _extract_extldflags(gc_linkopts, extldflags)
-
-  link_cmd = [
-      ctx.file.go_tool.path,
-      "tool", "link",
-      "-L", "."
-  ]
-  for path in transitive_go_library_paths:
-    link_cmd += ["-L", path]
-  link_cmd += [
-      "-o", executable.path,
-  ] + gc_linkopts + ['"${STAMP_XDEFS[@]}"']
-
-  # workaround for a bug in ld(1) on Mac OS X.
-  # http://lists.apple.com/archives/Darwin-dev/2006/Sep/msg00084.html
-  # TODO(yugui) Remove this workaround once rules_go stops supporting XCode 7.2
-  # or earlier.
-  if not _is_darwin_cpu(ctx):
-    link_cmd += ["-s"]
-
-  link_cmd += [
-      "-extld", ld,
-      "-extldflags", "'%s'" % " ".join(extldflags),
-  ] + [lib.path for lib in libs]
-
-  # Avoided -s on OSX but but it requires dsymutil to be on $PATH.
-  # TODO(yugui) Remove this workaround once rules_go stops supporting XCode 7.2
-  # or earlier.
-  cmds = ["export PATH=$PATH:/usr/bin"]
-
-  cmds += [
-      "STAMP_XDEFS=()",
-  ]
-
-  stamp_inputs = []
-  if ctx.attr.linkstamp:
-    # read workspace status files, converting "KEY value" lines
-    # to "-X $linkstamp.KEY=value" arguments to the go linker.
-    stamp_inputs = [ctx.info_file, ctx.version_file]
-    for f in stamp_inputs:
-      cmds += [
-          "while read -r key value || [[ -n $key ]]; do",
-          "  STAMP_XDEFS+=(-X \"%s.$key=$value\")" % ctx.attr.linkstamp,
-          "done < " + f.path,
-      ]
-
-  cmds += [' '.join(link_cmd)]
-
-  f = _emit_generate_params_action(cmds, ctx, lib.basename + ".GoLinkFile.params")
-
-  ctx.action(
-      inputs = [f] + (list(transitive_go_libraries) + [lib] + list(cgo_deps) +
-                ctx.files.toolchain + ctx.files._crosstool) + stamp_inputs,
-      outputs = [executable],
-      command = f.path,
-      mnemonic = "GoLink",
-      env = go_environment_vars(ctx),
-  )
+    """Extracts -extldflags from gc_linkopts and combines them into a single list.
+
+    Args:
+      gc_linkopts: a list of flags passed in through the gc_linkopts attributes.
+        ctx.expand_make_variables should have already been applied.
+      extldflags: a list of flags to be passed to the external linker.
+
+    Return:
+      A tuple containing the filtered gc_linkopts with external flags removed,
+      and a combined list of external flags.
+    """
+    filtered_gc_linkopts = []
+    is_extldflags = False
+    for opt in gc_linkopts:
+        if is_extldflags:
+            is_extldflags = False
+            extldflags += [opt]
+        elif opt == "-extldflags":
+            is_extldflags = True
+        else:
+            filtered_gc_linkopts += [opt]
+    return filtered_gc_linkopts, extldflags
+
+def _emit_go_link_action(
+        ctx,
+        transitive_go_library_paths,
+        transitive_go_libraries,
+        cgo_deps,
+        libs,
+        executable,
+        gc_linkopts):
+    """Sets up a symlink tree to libraries to link together."""
+    config_strip = len(ctx.configuration.bin_dir.path) + 1
+    pkg_depth = executable.dirname[config_strip:].count("/") + 1
+
+    ld = "%s" % ctx.fragments.cpp.compiler_executable
+    extldflags = _c_linker_options(ctx) + [
+        "-Wl,-rpath,$ORIGIN/" + ("../" * pkg_depth),
+    ]
+    for d in cgo_deps:
+        if d.basename.endswith(".so"):
+            short_dir = d.dirname[len(d.root.path):]
+            extldflags += ["-Wl,-rpath,$ORIGIN/" + ("../" * pkg_depth) + short_dir]
+    gc_linkopts, extldflags = _extract_extldflags(gc_linkopts, extldflags)
+
+    link_cmd = [
+        ctx.file.go_tool.path,
+        "tool",
+        "link",
+        "-L",
+        ".",
+    ]
+    for path in transitive_go_library_paths:
+        link_cmd += ["-L", path]
+    link_cmd += [
+        "-o",
+        executable.path,
+    ] + gc_linkopts + ['"${STAMP_XDEFS[@]}"']
+
+    # workaround for a bug in ld(1) on Mac OS X.
+    # http://lists.apple.com/archives/Darwin-dev/2006/Sep/msg00084.html
+    # TODO(yugui) Remove this workaround once rules_go stops supporting XCode 7.2
+    # or earlier.
+    if not _is_darwin_cpu(ctx):
+        link_cmd += ["-s"]
+
+    link_cmd += [
+        "-extld",
+        ld,
+        "-extldflags",
+        "'%s'" % " ".join(extldflags),
+    ] + [lib.path for lib in libs]
+
+    # Avoided -s on OSX but but it requires dsymutil to be on $PATH.
+    # TODO(yugui) Remove this workaround once rules_go stops supporting XCode 7.2
+    # or earlier.
+    cmds = ["export PATH=$PATH:/usr/bin"]
+
+    cmds += [
+        "STAMP_XDEFS=()",
+    ]
+
+    stamp_inputs = []
+    if ctx.attr.linkstamp:
+        # read workspace status files, converting "KEY value" lines
+        # to "-X $linkstamp.KEY=value" arguments to the go linker.
+        stamp_inputs = [ctx.info_file, ctx.version_file]
+        for f in stamp_inputs:
+            cmds += [
+                "while read -r key value || [[ -n $key ]]; do",
+                "  STAMP_XDEFS+=(-X \"%s.$key=$value\")" % ctx.attr.linkstamp,
+                "done < " + f.path,
+            ]
+
+    cmds += [" ".join(link_cmd)]
+
+    f = _emit_generate_params_action(cmds, ctx, lib.basename + ".GoLinkFile.params")
+
+    ctx.action(
+        inputs = [f] + (list(transitive_go_libraries) + [lib] + list(cgo_deps) +
+                        ctx.files.toolchain + ctx.files._crosstool) + stamp_inputs,
+        outputs = [executable],
+        command = f.path,
+        mnemonic = "GoLink",
+        env = go_environment_vars(ctx),
+    )
 
 def go_binary_impl(ctx):
-  """go_binary_impl emits actions for compiling and linking a go executable."""
-  lib_result = go_library_impl(ctx)
-  _emit_go_link_action(
-    ctx,
-    transitive_go_libraries=lib_result.transitive_go_libraries,
-    transitive_go_library_paths=lib_result.transitive_go_library_paths,
-    cgo_deps=lib_result.transitive_cgo_deps,
-    libs=lib_result.files,
-    executable=ctx.outputs.executable,
-    gc_linkopts=_gc_linkopts(ctx))
-
-  return struct(
-      files = depset([ctx.outputs.executable]),
-      runfiles = lib_result.runfiles,
-      cgo_object = lib_result.cgo_object,
-  )
+    """go_binary_impl emits actions for compiling and linking a go executable."""
+    lib_result = go_library_impl(ctx)
+    _emit_go_link_action(
+        ctx,
+        transitive_go_libraries = lib_result.transitive_go_libraries,
+        transitive_go_library_paths = lib_result.transitive_go_library_paths,
+        cgo_deps = lib_result.transitive_cgo_deps,
+        libs = lib_result.files,
+        executable = ctx.outputs.executable,
+        gc_linkopts = _gc_linkopts(ctx),
+    )
+
+    return struct(
+        files = depset([ctx.outputs.executable]),
+        runfiles = lib_result.runfiles,
+        cgo_object = lib_result.cgo_object,
+    )
 
 def go_test_impl(ctx):
-  """go_test_impl implements go testing.
-
-  It emits an action to run the test generator, and then compiles the
-  test into a binary."""
-
-  lib_result = go_library_impl(ctx)
-  main_go = ctx.new_file(ctx.label.name + "_main_test.go")
-  main_object = ctx.new_file(ctx.label.name + "_main_test.o")
-  main_lib = ctx.new_file(ctx.label.name + "_main_test.a")
-  go_import = _go_importpath(ctx)
-
-  cmds = [
-      'UNFILTERED_TEST_FILES=(%s)' %
-          ' '.join(["'%s'" % f.path for f in lib_result.go_sources]),
-      'FILTERED_TEST_FILES=()',
-      'while read -r line; do',
-      '  if [ -n "$line" ]; then',
-      '    FILTERED_TEST_FILES+=("$line")',
-      '  fi',
-      'done < <(\'%s\' -cgo "${UNFILTERED_TEST_FILES[@]}")' %
-          ctx.executable._filter_tags.path,
-      ' '.join([
-          "'%s'" % ctx.executable.test_generator.path,
-          '--package',
-          go_import,
-          '--output',
-          "'%s'" % main_go.path,
-          '"${FILTERED_TEST_FILES[@]}"',
-      ]),
-  ]
-  f = _emit_generate_params_action(
-      cmds, ctx, ctx.label.name + ".GoTestGenTest.params")
-  inputs = (list(lib_result.go_sources) + list(ctx.files.toolchain) +
-            [f, ctx.executable._filter_tags, ctx.executable.test_generator])
-  ctx.action(
-      inputs = inputs,
-      outputs = [main_go],
-      command = f.path,
-      mnemonic = "GoTestGenTest",
-      env = dict(go_environment_vars(ctx), RUNDIR=ctx.label.package))
-
-  _emit_go_compile_action(
-    ctx,
-    sources=depset([main_go]),
-    deps=ctx.attr.deps + [lib_result],
-    libpaths=lib_result.transitive_go_library_paths,
-    out_object=main_object,
-    gc_goopts=_gc_goopts(ctx),
-  )
-  _emit_go_pack_action(ctx, main_lib, [main_object])
-  _emit_go_link_action(
-    ctx,
-    transitive_go_library_paths=lib_result.transitive_go_library_paths,
-    transitive_go_libraries=lib_result.transitive_go_libraries,
-    cgo_deps=lib_result.transitive_cgo_deps,
-    libs=[main_lib],
-    executable=ctx.outputs.executable,
-    gc_linkopts=_gc_linkopts(ctx))
-
-  # TODO(bazel-team): the Go tests should do a chdir to the directory
-  # holding the data files, so open-source go tests continue to work
-  # without code changes.
-  runfiles = ctx.runfiles(files = [ctx.outputs.executable])
-  runfiles = runfiles.merge(lib_result.runfiles)
-  return struct(
-      files = depset([ctx.outputs.executable]),
-      runfiles = runfiles,
-  )
+    """go_test_impl implements go testing.
+
+    It emits an action to run the test generator, and then compiles the
+    test into a binary."""
+
+    lib_result = go_library_impl(ctx)
+    main_go = ctx.new_file(ctx.label.name + "_main_test.go")
+    main_object = ctx.new_file(ctx.label.name + "_main_test.o")
+    main_lib = ctx.new_file(ctx.label.name + "_main_test.a")
+    go_import = _go_importpath(ctx)
+
+    cmds = [
+        "UNFILTERED_TEST_FILES=(%s)" %
+        " ".join(["'%s'" % f.path for f in lib_result.go_sources]),
+        "FILTERED_TEST_FILES=()",
+        "while read -r line; do",
+        '  if [ -n "$line" ]; then',
+        '    FILTERED_TEST_FILES+=("$line")',
+        "  fi",
+        'done < <(\'%s\' -cgo "${UNFILTERED_TEST_FILES[@]}")' %
+        ctx.executable._filter_tags.path,
+        " ".join([
+            "'%s'" % ctx.executable.test_generator.path,
+            "--package",
+            go_import,
+            "--output",
+            "'%s'" % main_go.path,
+            '"${FILTERED_TEST_FILES[@]}"',
+        ]),
+    ]
+    f = _emit_generate_params_action(
+        cmds,
+        ctx,
+        ctx.label.name + ".GoTestGenTest.params",
+    )
+    inputs = (list(lib_result.go_sources) + list(ctx.files.toolchain) +
+              [f, ctx.executable._filter_tags, ctx.executable.test_generator])
+    ctx.action(
+        inputs = inputs,
+        outputs = [main_go],
+        command = f.path,
+        mnemonic = "GoTestGenTest",
+        env = dict(go_environment_vars(ctx), RUNDIR = ctx.label.package),
+    )
+
+    _emit_go_compile_action(
+        ctx,
+        sources = depset([main_go]),
+        deps = ctx.attr.deps + [lib_result],
+        libpaths = lib_result.transitive_go_library_paths,
+        out_object = main_object,
+        gc_goopts = _gc_goopts(ctx),
+    )
+    _emit_go_pack_action(ctx, main_lib, [main_object])
+    _emit_go_link_action(
+        ctx,
+        transitive_go_library_paths = lib_result.transitive_go_library_paths,
+        transitive_go_libraries = lib_result.transitive_go_libraries,
+        cgo_deps = lib_result.transitive_cgo_deps,
+        libs = [main_lib],
+        executable = ctx.outputs.executable,
+        gc_linkopts = _gc_linkopts(ctx),
+    )
+
+    # TODO(bazel-team): the Go tests should do a chdir to the directory
+    # holding the data files, so open-source go tests continue to work
+    # without code changes.
+    runfiles = ctx.runfiles(files = [ctx.outputs.executable])
+    runfiles = runfiles.merge(lib_result.runfiles)
+    return struct(
+        files = depset([ctx.outputs.executable]),
+        runfiles = runfiles,
+    )
 
 go_env_attrs = {
     "toolchain": attr.label(
@@ -704,51 +734,51 @@ go_test = rule(
 )
 
 def _pkg_dir(workspace_root, package_name):
-  if workspace_root and package_name:
-    return workspace_root + "/" + package_name
-  if workspace_root:
-    return workspace_root
-  if package_name:
-    return package_name
-  return "."
+    if workspace_root and package_name:
+        return workspace_root + "/" + package_name
+    if workspace_root:
+        return workspace_root
+    if package_name:
+        return package_name
+    return "."
 
 def _exec_path(path):
-  if path.startswith('/'):
-    return path
-  return '${execroot}/' + path
+    if path.startswith("/"):
+        return path
+    return "${execroot}/" + path
 
 def _cgo_filter_srcs_impl(ctx):
-  srcs = ctx.files.srcs
-  dsts = []
-  cmds = []
-  for src in srcs:
-    stem, _, ext = src.path.rpartition('.')
-    dst_basename = "%s.filtered.%s" % (stem, ext)
-    dst = ctx.new_file(src, dst_basename)
-    cmds += [
-        "if '%s' -cgo -quiet '%s'; then" %
+    srcs = ctx.files.srcs
+    dsts = []
+    cmds = []
+    for src in srcs:
+        stem, _, ext = src.path.rpartition(".")
+        dst_basename = "%s.filtered.%s" % (stem, ext)
+        dst = ctx.new_file(src, dst_basename)
+        cmds += [
+            "if '%s' -cgo -quiet '%s'; then" %
             (ctx.executable._filter_tags.path, src.path),
-        "  cp '%s' '%s'" % (src.path, dst.path),
-        "else",
-        "  echo -n >'%s'" % dst.path,
-        "fi",
-    ]
-    dsts.append(dst)
-
-  if ctx.label.package == "":
-    script_name = ctx.label.name + ".CGoFilterSrcs.params"
-  else:
-    script_name = ctx.label.package + "/" + ctx.label.name + ".CGoFilterSrcs.params"
-  f = _emit_generate_params_action(cmds, ctx, script_name)
-  ctx.action(
-      inputs = [f, ctx.executable._filter_tags] + srcs,
-      outputs = dsts,
-      command = f.path,
-      mnemonic = "CgoFilterSrcs",
-  )
-  return struct(
-      files = depset(dsts),
-  )
+            "  cp '%s' '%s'" % (src.path, dst.path),
+            "else",
+            "  echo -n >'%s'" % dst.path,
+            "fi",
+        ]
+        dsts.append(dst)
+
+    if ctx.label.package == "":
+        script_name = ctx.label.name + ".CGoFilterSrcs.params"
+    else:
+        script_name = ctx.label.package + "/" + ctx.label.name + ".CGoFilterSrcs.params"
+    f = _emit_generate_params_action(cmds, ctx, script_name)
+    ctx.action(
+        inputs = [f, ctx.executable._filter_tags] + srcs,
+        outputs = dsts,
+        command = f.path,
+        mnemonic = "CgoFilterSrcs",
+    )
+    return struct(
+        files = depset(dsts),
+    )
 
 _cgo_filter_srcs = rule(
     implementation = _cgo_filter_srcs_impl,
@@ -767,90 +797,90 @@ _cgo_filter_srcs = rule(
 )
 
 def _cgo_codegen_impl(ctx):
-  go_srcs = ctx.files.srcs
-  srcs = go_srcs + ctx.files.c_hdrs
-  linkopts = ctx.attr.linkopts
-  copts = ctx.fragments.cpp.c_options + ctx.attr.copts
-  deps = depset([], order="topological")
-  for d in ctx.attr.deps:
-    srcs += list(d.cc.transitive_headers)
-    deps += d.cc.libs
-    copts += ['-D' + define for define in d.cc.defines]
-    for inc in d.cc.include_directories:
-      copts += ['-I', _exec_path(inc)]
-    for hdr in ctx.files.c_hdrs:
-        copts += ['-iquote', hdr.dirname]
-    for inc in d.cc.quote_include_directories:
-      copts += ['-iquote', _exec_path(inc)]
-    for inc in d.cc.system_include_directories:
-      copts += ['-isystem',  _exec_path(inc)]
-    for lib in d.cc.libs:
-      if lib.basename.startswith('lib') and lib.basename.endswith('.so'):
-        linkopts += ['-L', lib.dirname, '-l', lib.basename[3:-3]]
-      else:
-        linkopts += [lib.path]
-    linkopts += d.cc.link_flags
-
-  p = _pkg_dir(ctx.label.workspace_root, ctx.label.package) + "/"
-  if p == "./":
-    p = "" # workaround when cgo_library in repository root
-  out_dir = (ctx.configuration.genfiles_dir.path + '/' +
-             p + ctx.attr.outdir)
-  cc = ctx.fragments.cpp.compiler_executable
-  cmds = [
-      # We cannot use env for CC because $(CC) on OSX is relative
-      # and '../' does not work fine due to symlinks.
-      'export CC=$(cd $(dirname {cc}); pwd)/$(basename {cc})'.format(cc=cc),
-      'export CXX=$CC',
-      'objdir="%s/gen"' % out_dir,
-      'execroot=$(pwd)',
-      'mkdir -p "$objdir"',
-      'unfiltered_go_files=(%s)' % ' '.join(["'%s'" % f.path for f in go_srcs]),
-      'filtered_go_files=()',
-      'for file in "${unfiltered_go_files[@]}"; do',
-      '  stem=$(basename "$file" .go)',
-      '  if %s -cgo -quiet "$file"; then' % ctx.executable._filter_tags.path,
-      '    filtered_go_files+=("$file")',
-      '  else',
-      '    grep --max-count 1 "^package " "$file" >"$objdir/$stem.go"',
-      '    echo -n >"$objdir/$stem.c"',
-      '  fi',
-      'done',
-      'if [ ${#filtered_go_files[@]} -eq 0 ]; then',
-      '  echo no buildable Go source files in %s >&1' % str(ctx.label),
-      '  exit 1',
-      'fi',
-      '"$GOROOT/bin/go" tool cgo -objdir "$objdir" -- %s "${filtered_go_files[@]}"' %
-          ' '.join(['"%s"' % copt for copt in copts]),
-      # Rename the outputs using glob so we don't have to understand cgo's mangling
-      # TODO(#350): might be fixed by this?.
-      'for file in "${filtered_go_files[@]}"; do',
-      '  stem=$(basename "$file" .go)',
-      '  mv "$objdir/"*"$stem.cgo1.go" "$objdir/$stem.go"',
-      '  mv "$objdir/"*"$stem.cgo2.c" "$objdir/$stem.c"',
-      'done',
-      'rm -f $objdir/_cgo_.o $objdir/_cgo_flags',
+    go_srcs = ctx.files.srcs
+    srcs = go_srcs + ctx.files.c_hdrs
+    linkopts = ctx.attr.linkopts
+    copts = ctx.fragments.cpp.c_options + ctx.attr.copts
+    deps = depset([], order = "topological")
+    for d in ctx.attr.deps:
+        srcs += list(d.cc.transitive_headers)
+        deps += d.cc.libs
+        copts += ["-D" + define for define in d.cc.defines]
+        for inc in d.cc.include_directories:
+            copts += ["-I", _exec_path(inc)]
+        for hdr in ctx.files.c_hdrs:
+            copts += ["-iquote", hdr.dirname]
+        for inc in d.cc.quote_include_directories:
+            copts += ["-iquote", _exec_path(inc)]
+        for inc in d.cc.system_include_directories:
+            copts += ["-isystem", _exec_path(inc)]
+        for lib in d.cc.libs:
+            if lib.basename.startswith("lib") and lib.basename.endswith(".so"):
+                linkopts += ["-L", lib.dirname, "-l", lib.basename[3:-3]]
+            else:
+                linkopts += [lib.path]
+        linkopts += d.cc.link_flags
+
+    p = _pkg_dir(ctx.label.workspace_root, ctx.label.package) + "/"
+    if p == "./":
+        p = ""  # workaround when cgo_library in repository root
+    out_dir = (ctx.configuration.genfiles_dir.path + "/" +
+               p + ctx.attr.outdir)
+    cc = ctx.fragments.cpp.compiler_executable
+    cmds = [
+        # We cannot use env for CC because $(CC) on OSX is relative
+        # and '../' does not work fine due to symlinks.
+        "export CC=$(cd $(dirname {cc}); pwd)/$(basename {cc})".format(cc = cc),
+        "export CXX=$CC",
+        'objdir="%s/gen"' % out_dir,
+        "execroot=$(pwd)",
+        'mkdir -p "$objdir"',
+        "unfiltered_go_files=(%s)" % " ".join(["'%s'" % f.path for f in go_srcs]),
+        "filtered_go_files=()",
+        'for file in "${unfiltered_go_files[@]}"; do',
+        '  stem=$(basename "$file" .go)',
+        '  if %s -cgo -quiet "$file"; then' % ctx.executable._filter_tags.path,
+        '    filtered_go_files+=("$file")',
+        "  else",
+        '    grep --max-count 1 "^package " "$file" >"$objdir/$stem.go"',
+        '    echo -n >"$objdir/$stem.c"',
+        "  fi",
+        "done",
+        "if [ ${#filtered_go_files[@]} -eq 0 ]; then",
+        "  echo no buildable Go source files in %s >&1" % str(ctx.label),
+        "  exit 1",
+        "fi",
+        '"$GOROOT/bin/go" tool cgo -objdir "$objdir" -- %s "${filtered_go_files[@]}"' %
+        " ".join(['"%s"' % copt for copt in copts]),
+        # Rename the outputs using glob so we don't have to understand cgo's mangling
+        # TODO(#350): might be fixed by this?.
+        'for file in "${filtered_go_files[@]}"; do',
+        '  stem=$(basename "$file" .go)',
+        '  mv "$objdir/"*"$stem.cgo1.go" "$objdir/$stem.go"',
+        '  mv "$objdir/"*"$stem.cgo2.c" "$objdir/$stem.c"',
+        "done",
+        "rm -f $objdir/_cgo_.o $objdir/_cgo_flags",
     ]
 
-  f = _emit_generate_params_action(cmds, ctx, out_dir + ".CGoCodeGenFile.params")
-
-  inputs = (srcs + ctx.files.toolchain + ctx.files._crosstool +
-            [f, ctx.executable._filter_tags])
-  ctx.action(
-      inputs = inputs,
-      outputs = ctx.outputs.outs,
-      mnemonic = "CGoCodeGen",
-      progress_message = "CGoCodeGen %s" % ctx.label,
-      command = f.path,
-      env = go_environment_vars(ctx) + {
-          "CGO_LDFLAGS": " ".join(linkopts),
-      },
-  )
-  return struct(
-      label = ctx.label,
-      files = depset(ctx.outputs.outs),
-      cgo_deps = deps,
-  )
+    f = _emit_generate_params_action(cmds, ctx, out_dir + ".CGoCodeGenFile.params")
+
+    inputs = (srcs + ctx.files.toolchain + ctx.files._crosstool +
+              [f, ctx.executable._filter_tags])
+    ctx.action(
+        inputs = inputs,
+        outputs = ctx.outputs.outs,
+        mnemonic = "CGoCodeGen",
+        progress_message = "CGoCodeGen %s" % ctx.label,
+        command = f.path,
+        env = go_environment_vars(ctx) + {
+            "CGO_LDFLAGS": " ".join(linkopts),
+        },
+    )
+    return struct(
+        label = ctx.label,
+        files = depset(ctx.outputs.outs),
+        cgo_deps = deps,
+    )
 
 _cgo_codegen_rule = rule(
     _cgo_codegen_impl,
@@ -878,91 +908,102 @@ _cgo_codegen_rule = rule(
     output_to_genfiles = True,
 )
 
-def _cgo_codegen(name, srcs, c_hdrs=[], deps=[], copts=[], linkopts=[],
-                 go_tool=None, toolchain=None):
-  """Generates glue codes for interop between C and Go
-
-  Args:
-    name: A unique name of the rule
-    srcs: list of Go source files.
-      Each of them must contain `import "C"`.
-    c_hdrs: C/C++ header files necessary to determine kinds of
-      C/C++ identifiers in srcs.
-    deps: A list of cc_library rules.
-      The generated codes are expected to be linked with these deps.
-    linkopts: A list of linker options,
-      These flags are passed to the linker when the generated codes
-      are linked into the target binary.
-  """
-  outdir = name + ".dir"
-  outgen = outdir + "/gen"
-
-  go_thunks = []
-  c_thunks = []
-  for s in srcs:
-    if not s.endswith('.go'):
-      fail("not a .go file: %s" % s)
-    basename = s[:-3]
-    if basename.rfind("/") >= 0:
-      basename = basename[basename.rfind("/")+1:]
-    go_thunks.append(outgen + "/" + basename + ".go")
-    c_thunks.append(outgen + "/" + basename + ".c")
-
-  outs = struct(
-      name = name,
-
-      outdir = outgen,
-      go_thunks = go_thunks,
-      c_thunks = c_thunks,
-      c_exports = [
-          outgen + "/_cgo_export.c",
-          outgen + "/_cgo_export.h",
-      ],
-      c_dummy = outgen + "/_cgo_main.c",
-      gotypes = outgen + "/_cgo_gotypes.go",
-  )
-
-  _cgo_codegen_rule(
-      name = name,
-      srcs = srcs,
-      c_hdrs = c_hdrs,
-      deps = deps,
-      copts = copts,
-      linkopts = linkopts,
-
-      go_tool = go_tool,
-      toolchain = toolchain,
-
-      outdir = outdir,
-      outs = outs.go_thunks + outs.c_thunks + outs.c_exports + [
-          outs.c_dummy, outs.gotypes,
-      ],
-
-      visibility = ["//visibility:private"],
-  )
-  return outs
+def _cgo_codegen(
+        name,
+        srcs,
+        c_hdrs = [],
+        deps = [],
+        copts = [],
+        linkopts = [],
+        go_tool = None,
+        toolchain = None):
+    """Generates glue codes for interop between C and Go
+
+    Args:
+      name: A unique name of the rule
+      srcs: list of Go source files.
+        Each of them must contain `import "C"`.
+      c_hdrs: C/C++ header files necessary to determine kinds of
+        C/C++ identifiers in srcs.
+      deps: A list of cc_library rules.
+        The generated codes are expected to be linked with these deps.
+      linkopts: A list of linker options,
+        These flags are passed to the linker when the generated codes
+        are linked into the target binary.
+    """
+    outdir = name + ".dir"
+    outgen = outdir + "/gen"
+
+    go_thunks = []
+    c_thunks = []
+    for s in srcs:
+        if not s.endswith(".go"):
+            fail("not a .go file: %s" % s)
+        basename = s[:-3]
+        if basename.rfind("/") >= 0:
+            basename = basename[basename.rfind("/") + 1:]
+        go_thunks.append(outgen + "/" + basename + ".go")
+        c_thunks.append(outgen + "/" + basename + ".c")
+
+    outs = struct(
+        name = name,
+        outdir = outgen,
+        go_thunks = go_thunks,
+        c_thunks = c_thunks,
+        c_exports = [
+            outgen + "/_cgo_export.c",
+            outgen + "/_cgo_export.h",
+        ],
+        c_dummy = outgen + "/_cgo_main.c",
+        gotypes = outgen + "/_cgo_gotypes.go",
+    )
+
+    _cgo_codegen_rule(
+        name = name,
+        srcs = srcs,
+        c_hdrs = c_hdrs,
+        deps = deps,
+        copts = copts,
+        linkopts = linkopts,
+        go_tool = go_tool,
+        toolchain = toolchain,
+        outdir = outdir,
+        outs = outs.go_thunks + outs.c_thunks + outs.c_exports + [
+            outs.c_dummy,
+            outs.gotypes,
+        ],
+        visibility = ["//visibility:private"],
+    )
+    return outs
 
 def _cgo_import_impl(ctx):
-  cmds = [
-      (ctx.file.go_tool.path + " tool cgo" +
-       " -dynout " + ctx.outputs.out.path +
-       " -dynimport " + ctx.file.cgo_o.path +
-       " -dynpackage $(%s %s)"  % (ctx.executable._extract_package.path,
-                                   ctx.file.sample_go_src.path)),
-  ]
-  f = _emit_generate_params_action(cmds, ctx, ctx.outputs.out.path + ".CGoImportGenFile.params")
-  ctx.action(
-      inputs = (ctx.files.toolchain +
-                [f, ctx.file.go_tool, ctx.executable._extract_package,
-                 ctx.file.cgo_o, ctx.file.sample_go_src]),
-      outputs = [ctx.outputs.out],
-      command = f.path,
-      mnemonic = "CGoImportGen",
-      env = go_environment_vars(ctx),
-  )
-  return struct(
-      files = depset([ctx.outputs.out]),
-  )
+    cmds = [
+        (ctx.file.go_tool.path + " tool cgo" +
+         " -dynout " + ctx.outputs.out.path +
+         " -dynimport " + ctx.file.cgo_o.path +
+         " -dynpackage $(%s %s)" % (
+             ctx.executable._extract_package.path,
+             ctx.file.sample_go_src.path,
+         )),
+    ]
+    f = _emit_generate_params_action(cmds, ctx, ctx.outputs.out.path + ".CGoImportGenFile.params")
+    ctx.action(
+        inputs = (ctx.files.toolchain +
+                  [
+                      f,
+                      ctx.file.go_tool,
+                      ctx.executable._extract_package,
+                      ctx.file.cgo_o,
+                      ctx.file.sample_go_src,
+                  ]),
+        outputs = [ctx.outputs.out],
+        command = f.path,
+        mnemonic = "CGoImportGen",
+        env = go_environment_vars(ctx),
+    )
+    return struct(
+        files = depset([ctx.outputs.out]),
+    )
 
 _cgo_import = rule(
     _cgo_import_impl,
@@ -988,15 +1029,15 @@ _cgo_import = rule(
 )
 
 def _cgo_genrule_impl(ctx):
-  return struct(
-    label = ctx.label,
-    go_sources = ctx.files.srcs,
-    asm_sources = [],
-    asm_headers = [],
-    cgo_object = ctx.attr.cgo_object,
-    direct_deps = ctx.attr.deps,
-    gc_goopts = [],
-  )
+    return struct(
+        label = ctx.label,
+        go_sources = ctx.files.srcs,
+        asm_sources = [],
+        asm_headers = [],
+        cgo_object = ctx.attr.cgo_object,
+        direct_deps = ctx.attr.deps,
+        gc_goopts = [],
+    )
 
 _cgo_genrule = rule(
     _cgo_genrule_impl,
@@ -1030,40 +1071,43 @@ Args:
 """
 
 def _cgo_object_impl(ctx):
-  arguments = _c_linker_options(ctx, blacklist=[
-      # never link any dependency libraries
-      "-l", "-L",
-      # manage flags to ld(1) by ourselves
-      "-Wl,"])
-  arguments += [
-      "-o", ctx.outputs.out.path,
-      "-nostdlib",
-      "-Wl,-r",
-  ]
-  if _is_darwin_cpu(ctx):
-    arguments += ["-shared", "-Wl,-all_load"]
-  else:
-    arguments += ["-Wl,-whole-archive"]
-
-  lo = ctx.files.src[-1]
-  arguments += [lo.path]
-
-  ctx.action(
-      inputs = [lo] + ctx.files._crosstool,
-      outputs = [ctx.outputs.out],
-      mnemonic = "CGoObject",
-      progress_message = "Linking %s" % ctx.outputs.out.short_path,
-      executable = ctx.fragments.cpp.compiler_executable,
-      arguments = arguments,
-  )
-  runfiles = ctx.runfiles(collect_data = True)
-  runfiles = runfiles.merge(ctx.attr.src.data_runfiles)
-  return struct(
-      files = depset([ctx.outputs.out]),
-      cgo_obj = ctx.outputs.out,
-      cgo_deps = ctx.attr.cgogen.cgo_deps,
-      runfiles = runfiles,
-  )
+    arguments = _c_linker_options(ctx, blocklist = [
+        # never link any dependency libraries
+        "-l",
+        "-L",
+        # manage flags to ld(1) by ourselves
+        "-Wl,",
+    ])
+    arguments += [
+        "-o",
+        ctx.outputs.out.path,
+        "-nostdlib",
+        "-Wl,-r",
+    ]
+    if _is_darwin_cpu(ctx):
+        arguments += ["-shared", "-Wl,-all_load"]
+    else:
+        arguments += ["-Wl,-whole-archive"]
+
+    lo = ctx.files.src[-1]
+    arguments += [lo.path]
+
+    ctx.action(
+        inputs = [lo] + ctx.files._crosstool,
+        outputs = [ctx.outputs.out],
+        mnemonic = "CGoObject",
+        progress_message = "Linking %s" % ctx.outputs.out.short_path,
+        executable = ctx.fragments.cpp.compiler_executable,
+        arguments = arguments,
+    )
+    runfiles = ctx.runfiles(collect_data = True)
+    runfiles = runfiles.merge(ctx.attr.src.data_runfiles)
+    return struct(
+        files = depset([ctx.outputs.out]),
+        cgo_obj = ctx.outputs.out,
+        cgo_deps = ctx.attr.cgogen.cgo_deps,
+        runfiles = runfiles,
+    )
 
 _cgo_object = rule(
     _cgo_object_impl,
@@ -1092,182 +1136,189 @@ Args:
 """
 
 def _setup_cgo_library(name, srcs, cdeps, copts, clinkopts, go_tool, toolchain):
-  go_srcs = [s for s in srcs if s.endswith('.go')]
-  c_hdrs = [s for s in srcs if any([s.endswith(ext) for ext in hdr_exts])]
-  c_srcs = [s for s in srcs if not s in (go_srcs + c_hdrs)]
-
-  # Split cgo files into .go parts and .c parts (plus some other files).
-  cgogen = _cgo_codegen(
-      name = name + ".cgo",
-      srcs = go_srcs,
-      c_hdrs = c_hdrs,
-      deps = cdeps,
-      copts = copts,
-      linkopts = clinkopts,
-      go_tool = go_tool,
-      toolchain = toolchain,
-  )
-
-  # Filter c_srcs with build constraints.
-  c_filtered_srcs = []
-  if len(c_srcs) > 0:
-    c_filtered_srcs_name = name + "_filter_cgo_srcs"
-    _cgo_filter_srcs(
-        name = c_filtered_srcs_name,
-        srcs = c_srcs,
+    go_srcs = [s for s in srcs if s.endswith(".go")]
+    c_hdrs = [s for s in srcs if any([s.endswith(ext) for ext in hdr_exts])]
+    c_srcs = [s for s in srcs if not s in (go_srcs + c_hdrs)]
+
+    # Split cgo files into .go parts and .c parts (plus some other files).
+    cgogen = _cgo_codegen(
+        name = name + ".cgo",
+        srcs = go_srcs,
+        c_hdrs = c_hdrs,
+        deps = cdeps,
+        copts = copts,
+        linkopts = clinkopts,
+        go_tool = go_tool,
+        toolchain = toolchain,
+    )
+
+    # Filter c_srcs with build constraints.
+    c_filtered_srcs = []
+    if len(c_srcs) > 0:
+        c_filtered_srcs_name = name + "_filter_cgo_srcs"
+        _cgo_filter_srcs(
+            name = c_filtered_srcs_name,
+            srcs = c_srcs,
+        )
+        c_filtered_srcs.append(":" + c_filtered_srcs_name)
+
+    pkg_dir = _pkg_dir(
+        "external/" + REPOSITORY_NAME[1:] if len(REPOSITORY_NAME) > 1 else "",
+        PACKAGE_NAME,
+    )
+
+    # Platform-specific settings
+    native.config_setting(
+        name = name + "_windows_setting",
+        values = {
+            "cpu": "x64_windows_msvc",
+        },
+    )
+    platform_copts = select({
+        ":" + name + "_windows_setting": ["-mthreads"],
+        "//conditions:default": ["-pthread"],
+    })
+    platform_linkopts = select({
+        ":" + name + "_windows_setting": ["-mthreads"],
+        "//conditions:default": ["-pthread"],
+    })
+
+    # Bundles objects into an archive so that _cgo_.o and _all.o can share them.
+    native.cc_library(
+        name = cgogen.outdir + "/_cgo_lib",
+        srcs = cgogen.c_thunks + cgogen.c_exports + c_filtered_srcs + c_hdrs,
+        deps = cdeps,
+        copts = copts + platform_copts + [
+            "-I",
+            pkg_dir,
+            "-I",
+            "$(GENDIR)/" + pkg_dir + "/" + cgogen.outdir,
+            # The generated thunks often contain unused variables.
+            "-Wno-unused-variable",
+        ],
+        linkopts = clinkopts + platform_linkopts,
+        linkstatic = 1,
+        # _cgo_.o and _all.o keep all objects in this archive.
+        # But it should not be very annoying in the final binary target
+        # because _cgo_object rule does not propagate alwayslink=1
+        alwayslink = 1,
+        visibility = ["//visibility:private"],
+    )
+
+    # Loadable object which cgo reads when it generates _cgo_import.go
+    native.cc_binary(
+        name = cgogen.outdir + "/_cgo_.o",
+        srcs = [cgogen.c_dummy],
+        deps = cdeps + [cgogen.outdir + "/_cgo_lib"],
+        copts = copts,
+        linkopts = clinkopts,
+        visibility = ["//visibility:private"],
     )
-    c_filtered_srcs.append(":" + c_filtered_srcs_name)
-
-  pkg_dir = _pkg_dir(
-      "external/" + REPOSITORY_NAME[1:] if len(REPOSITORY_NAME) > 1 else "",
-      PACKAGE_NAME)
-
-  # Platform-specific settings
-  native.config_setting(
-      name = name + "_windows_setting",
-      values = {
-          "cpu": "x64_windows_msvc",
-      },
-  )
-  platform_copts = select({
-      ":" + name + "_windows_setting": ["-mthreads"],
-      "//conditions:default": ["-pthread"],
-  })
-  platform_linkopts = select({
-      ":" + name + "_windows_setting": ["-mthreads"],
-      "//conditions:default": ["-pthread"],
-  })
-
-  # Bundles objects into an archive so that _cgo_.o and _all.o can share them.
-  native.cc_library(
-      name = cgogen.outdir + "/_cgo_lib",
-      srcs = cgogen.c_thunks + cgogen.c_exports + c_filtered_srcs + c_hdrs,
-      deps = cdeps,
-      copts = copts + platform_copts + [
-          "-I", pkg_dir,
-          "-I", "$(GENDIR)/" + pkg_dir + "/" + cgogen.outdir,
-          # The generated thunks often contain unused variables.
-          "-Wno-unused-variable",
-      ],
-      linkopts = clinkopts + platform_linkopts,
-      linkstatic = 1,
-      # _cgo_.o and _all.o keep all objects in this archive.
-      # But it should not be very annoying in the final binary target
-      # because _cgo_object rule does not propagate alwayslink=1
-      alwayslink = 1,
-      visibility = ["//visibility:private"],
-  )
-
-  # Loadable object which cgo reads when it generates _cgo_import.go
-  native.cc_binary(
-      name = cgogen.outdir + "/_cgo_.o",
-      srcs = [cgogen.c_dummy],
-      deps = cdeps + [cgogen.outdir + "/_cgo_lib"],
-      copts = copts,
-      linkopts = clinkopts,
-      visibility = ["//visibility:private"],
-  )
-  _cgo_import(
-      name = "%s.cgo.importgen" % name,
-      cgo_o = cgogen.outdir + "/_cgo_.o",
-      out = cgogen.outdir + "/_cgo_import.go",
-      sample_go_src = go_srcs[0],
-      go_tool = go_tool,
-      toolchain = toolchain,
-      visibility = ["//visibility:private"],
-  )
-
-  _cgo_object(
-      name = cgogen.outdir + "/_cgo_object",
-      src = cgogen.outdir + "/_cgo_lib",
-      out = cgogen.outdir + "/_all.o",
-      cgogen = cgogen.name,
-      visibility = ["//visibility:private"],
-  )
-  return cgogen
-
-def cgo_genrule(name, srcs,
-                copts=[],
-                clinkopts=[],
-                cdeps=[],
-                **kwargs):
-  cgogen = _setup_cgo_library(
-      name = name,
-      srcs = srcs,
-      cdeps = cdeps,
-      copts = copts,
-      clinkopts = clinkopts,
-      toolchain = None,
-      go_tool = None,
-  )
-  _cgo_genrule(
-      name = name,
-      srcs = cgogen.go_thunks + [
-          cgogen.gotypes,
-          cgogen.outdir + "/_cgo_import.go",
-      ],
-      cgo_object = cgogen.outdir + "/_cgo_object",
-      **kwargs
-  )
-
-def cgo_library(name, srcs,
-                toolchain=None,
-                go_tool=None,
-                copts=[],
-                clinkopts=[],
-                cdeps=[],
-                **kwargs):
-  """Builds a cgo-enabled go library.
-
-  Args:
-    name: A unique name for this rule.
-    srcs: List of Go, C and C++ files that are processed to build a Go library.
-      Those Go files must contain `import "C"`.
-      C and C++ files can be anything allowed in `srcs` attribute of
-      `cc_library`.
-    copts: Add these flags to the C++ compiler.
-    clinkopts: Add these flags to the C++ linker.
-    cdeps: List of C/C++ libraries to be linked into the binary target.
-      They must be `cc_library` rules.
-    deps: List of other libraries to be linked to this library target.
-    data: List of files needed by this rule at runtime.
-
-  NOTE:
-    `srcs` cannot contain pure-Go files, which do not have `import "C"`.
-    So you need to define another `go_library` when you build a go package with
-    both cgo-enabled and pure-Go sources.
-
-    ```
-    cgo_library(
-        name = "cgo_enabled",
-        srcs = ["cgo-enabled.go", "foo.cc", "bar.S", "baz.a"],
+    _cgo_import(
+        name = "%s.cgo.importgen" % name,
+        cgo_o = cgogen.outdir + "/_cgo_.o",
+        out = cgogen.outdir + "/_cgo_import.go",
+        sample_go_src = go_srcs[0],
+        go_tool = go_tool,
+        toolchain = toolchain,
+        visibility = ["//visibility:private"],
+    )
+
+    _cgo_object(
+        name = cgogen.outdir + "/_cgo_object",
+        src = cgogen.outdir + "/_cgo_lib",
+        out = cgogen.outdir + "/_all.o",
+        cgogen = cgogen.name,
+        visibility = ["//visibility:private"],
+    )
+    return cgogen
+
+def cgo_genrule(
+        name,
+        srcs,
+        copts = [],
+        clinkopts = [],
+        cdeps = [],
+        **kwargs):
+    cgogen = _setup_cgo_library(
+        name = name,
+        srcs = srcs,
+        cdeps = cdeps,
+        copts = copts,
+        clinkopts = clinkopts,
+        toolchain = None,
+        go_tool = None,
+    )
+    _cgo_genrule(
+        name = name,
+        srcs = cgogen.go_thunks + [
+            cgogen.gotypes,
+            cgogen.outdir + "/_cgo_import.go",
+        ],
+        cgo_object = cgogen.outdir + "/_cgo_object",
+        **kwargs
+    )
+
+def cgo_library(
+        name,
+        srcs,
+        toolchain = None,
+        go_tool = None,
+        copts = [],
+        clinkopts = [],
+        cdeps = [],
+        **kwargs):
+    """Builds a cgo-enabled go library.
+
+    Args:
+      name: A unique name for this rule.
+      srcs: List of Go, C and C++ files that are processed to build a Go library.
+        Those Go files must contain `import "C"`.
+        C and C++ files can be anything allowed in `srcs` attribute of
+        `cc_library`.
+      copts: Add these flags to the C++ compiler.
+      clinkopts: Add these flags to the C++ linker.
+      cdeps: List of C/C++ libraries to be linked into the binary target.
+        They must be `cc_library` rules.
+      deps: List of other libraries to be linked to this library target.
+      data: List of files needed by this rule at runtime.
+
+    NOTE:
+      `srcs` cannot contain pure-Go files, which do not have `import "C"`.
+      So you need to define another `go_library` when you build a go package with
+      both cgo-enabled and pure-Go sources.
+
+      ```
+      cgo_library(
+          name = "cgo_enabled",
+          srcs = ["cgo-enabled.go", "foo.cc", "bar.S", "baz.a"],
+      )
+
+      go_library(
+          name = "go_default_library",
+          srcs = ["pure-go.go"],
+          library = ":cgo_enabled",
+      )
+      ```
+    """
+    cgogen = _setup_cgo_library(
+        name = name,
+        srcs = srcs,
+        cdeps = cdeps,
+        copts = copts,
+        clinkopts = clinkopts,
+        go_tool = go_tool,
+        toolchain = toolchain,
     )
 
     go_library(
-        name = "go_default_library",
-        srcs = ["pure-go.go"],
-        library = ":cgo_enabled",
+        name = name,
+        srcs = cgogen.go_thunks + [
+            cgogen.gotypes,
+            cgogen.outdir + "/_cgo_import.go",
+        ],
+        cgo_object = cgogen.outdir + "/_cgo_object",
+        go_tool = go_tool,
+        toolchain = toolchain,
+        **kwargs
     )
-    ```
-  """
-  cgogen = _setup_cgo_library(
-      name = name,
-      srcs = srcs,
-      cdeps = cdeps,
-      copts = copts,
-      clinkopts = clinkopts,
-      go_tool = go_tool,
-      toolchain = toolchain,
-  )
-
-  go_library(
-      name = name,
-      srcs = cgogen.go_thunks + [
-          cgogen.gotypes,
-          cgogen.outdir + "/_cgo_import.go",
-      ],
-      cgo_object = cgogen.outdir + "/_cgo_object",
-      go_tool = go_tool,
-      toolchain = toolchain,
-      **kwargs
-  )