evaluate_path_expressions.gni

# Copyright 2022 The Pigweed Authors
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may not
# use this file except in compliance with the License. You may obtain a copy of
# the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations under
# the License.

import("python_action.gni")

# Scans files for special GN target expressions and evaluates them, modifying
# the files in-place.
#
# The supported expressions are the same as within the arguments list of a
# pw_python_action target, namely:
#
#   <TARGET_FILE(//some/label:here)> - expands to the
#       output file (such as a .a or .elf) from a GN target
#   <TARGET_FILE_IF_EXISTS(//some/label:here)> - expands to
#       the output file if the target exists, or nothing
#   <TARGET_OBJECTS(//some/label:here)> - expands to the
#       object files produced by the provided GN target
#
# This template may be useful, for example, to generate an artifact file
# containing a list of binary objects produced by targets within a build.
# Typically, this is used as a subtarget of a larger template, rather than a
# standalone target.
#
# Args:
#   files: List of scopes containing `source` and `dest` files. `source` is
#          scanned for expressions, and the result is written to `dest`.
#
# Example:
#
#   template("executable_with_artifacts") {
#     executable("${target_name}.exe") {
#       sources = invoker.sources
#     }
#
#     _artifacts_input = "$target_gen_dir/${target_name}_artifacts.json.in"
#     _artifacts_output = "$target_gen_dir/${target_name}_artifacts.json"
#     _artifacts = {
#       binary = "<TARGET_FILE(:${target_name}.exe)>"
#       objects = "<TARGET_OBJECTS(:${target_name}.exe)>"
#     }
#     write_file(_artifacts_input, _artifacts, "json")
#
#     pw_evaluate_path_expressions("${target_name}.evaluate") {
#       files = [
#         {
#           source = _artifacts_input
#           dest = _artifacts_output
#         },
#       ]
#     }
#
#     group(target_name) {
#       deps = [
#         ":${target_name}.exe",
#         ":${target_name}.evaluate",
#       ]
#     }
#   }
#
template("pw_evaluate_path_expressions") {
  assert(defined(invoker.files),
         "pw_evaluate_path_expressions requires input files to scan")

  _script_args = [
    "--gn-root",
    rebase_path("//", root_build_dir),
    "--current-path",
    rebase_path(".", root_build_dir),
    "--default-toolchain",
    default_toolchain,
    "--current-toolchain",
    current_toolchain,
  ]

  _inputs = []
  _outputs = []

  foreach(_file, invoker.files) {
    _inputs += [ _file.source ]
    _outputs += [ _file.dest ]
    _arg = rebase_path(_file.source) + ":" + rebase_path(_file.dest)
    _script_args += [ _arg ]
  }

  pw_python_action(target_name) {
    script = "$dir_pw_build/py/pw_build/gn_resolver.py"
    inputs = _inputs
    outputs = _outputs
    args = _script_args
  }
}