chore: remove comments on BUILD licenses() (#4112)

Google internally now recommends avoiding comments on the
`licenses()` rule, arguing that they cause confusion and easily
become out of sync with the source-of-truth LICENSE file.

This adds a CI check in the GitHub Actions workflow to check
for license comments.

Tested that the CI action works in the test PR:
#4113
https://github.com/tensorflow/tensorboard/pull/4113/checks?check_run_id=1053651164

See also
https://opensource.google/docs/thirdparty/linter/#build-licenses-comment%20.no-toc
Googlers: cl/326102766

.github/workflows/ci.yml

@@ -20,8 +20,9 @@ on:
   pull_request: {}
 
 env:
-  BUILDIFIER: '3.0.0'
+  BUILDTOOLS_VERSION: '3.0.0'
   BUILDIFIER_SHA256SUM: 'e92a6793c7134c5431c58fbc34700664f101e5c9b1c1fcd93b97978e8b7f88db'
+  BUILDOZER_SHA256SUM: '3d58a0b6972e4535718cdd6c12778170ea7382de7c75bc3728f5719437ffb84d'
 
 jobs:
   lint-python-flake8:
@@ -113,8 +114,12 @@ jobs:
       - uses: actions/checkout@v1
       - name: 'Set up Buildifier'
         run: |
-          ci/download_buildifier.sh "${BUILDIFIER}" "${BUILDIFIER_SHA256SUM}" ~/buildifier
+          ci/download_buildifier.sh "${BUILDTOOLS_VERSION}" "${BUILDIFIER_SHA256SUM}" ~/buildifier
           sudo mv ~/buildifier /usr/local/bin/buildifier
+      - name: 'Set up Buildozer'
+        run: |
+          ci/download_buildozer.sh "${BUILDTOOLS_VERSION}" "${BUILDOZER_SHA256SUM}" ~/buildozer
+          sudo mv ~/buildozer /usr/local/bin/buildozer
       - name: 'Lint BUILD files'
         # TODO(tensorboard-team): address all lint warnings and remove the exemption.
         run:
@@ -125,6 +130,11 @@ jobs:
         # Use | to start a literal so YAML doesn't complain about the '!' character.
         run: |
           ! git grep 'python_version = "PY2"' '*BUILD'
+      - name: 'No comments on licenses rule'
+        # Assert buildozer error code for 'success, when no changes were made'.
+        # https://github.com/bazelbuild/buildtools/blob/master/buildozer/README.md#error-code
+        run: |
+          buildozer '//tensorboard/...:%licenses' remove_comment && false || test $? = 3
 
   lint-proto:
     runs-on: ubuntu-16.04

BUILD

@@ -1,6 +1,6 @@
 load("@npm_bazel_typescript//:index.bzl", "ts_config")
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 exports_files(["tsconfig.json"])
 

ci/download_buildifier.sh

@@ -24,7 +24,7 @@ die() {
 }
 
 if [ "$#" -ne 3 ]; then
-  die "Usage: $0 <version> <sha256sum> <destination-file>"
+  die "Usage: $0 <buildtools-version> <sha256sum> <destination-file>"
 fi
 
 version="$1"

ci/download_buildozer.sh

@@ -0,0 +1,38 @@
+#!/bin/sh
+# Copyright 2020 The TensorFlow Authors. All Rights Reserved.
+#
+# 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
+#
+#     http://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.
+# ==============================================================================
+
+# Script to download Buildozer binary directly onto a build machine.
+
+set -e
+
+die() {
+  printf >&2 "%s\n" "$1"
+  exit 1
+}
+
+if [ "$#" -ne 3 ]; then
+  die "Usage: $0 <buildtools-version> <sha256sum> <destination-file>"
+fi
+
+version="$1"
+checksum="$2"
+dest="$3"
+
+mirror_url="http://mirror.tensorflow.org/github.com/bazelbuild/buildtools/releases/download/${version}/buildozer"
+github_url="https://github.com/bazelbuild/buildtools/releases/download/${version}/buildozer"
+
+exec "$(dirname "$0")/download_executable.sh" "${checksum}" "${dest}" \
+    "${mirror_url}" "${github_url}"

tensorboard/tools/mirror_urls_test.sh

@@ -41,11 +41,13 @@ check_urls_resolve() {
     url_pcre='(?<=")https?://mirror\.tensorflow\.org/[^"]*'
     exclude_bazel=':!ci/download_bazel.sh'  # uses a '${version}' format string
     exclude_buildifier=':!ci/download_buildifier.sh'  # likewise
+    exclude_buildozer=':!ci/download_buildozer.sh'  # likewise
     # We use `git-grep` to efficiently get an initial result set, then
     # filter it down with GNU `grep` separately, because `git-grep` only
     # learned `-o` in Git v2.19; Travis uses v2.15.1.
     unresolved_urls_file="${tmpdir}/unresolved_urls"
     git grep -Ph "${url_pcre}" "${exclude_bazel}" "${exclude_buildifier}" \
+        "${exclude_buildozer}" \
         | grep -o 'https\?://mirror\.tensorflow\.org/[^"]*' \
         | sort -u \
         >"${unresolved_urls_file}"

tensorboard/webapp/plugins/npmi/views/annotations_list/BUILD

@@ -3,7 +3,7 @@ load("//tensorboard/defs:defs.bzl", "tf_sass_binary", "tf_ts_library")
 
 package(default_visibility = ["//tensorboard:internal"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 tf_sass_binary(
     name = "annotations_list_component_styles",

tensorboard/webapp/plugins/npmi/views/annotations_list/annotations_list_toolbar/BUILD

@@ -3,7 +3,7 @@ load("//tensorboard/defs:defs.bzl", "tf_sass_binary", "tf_ts_library")
 
 package(default_visibility = ["//tensorboard:internal"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 tf_sass_binary(
     name = "annotations_list_toolbar_component_styles",

tensorboard/webapp/plugins/npmi/views/annotations_list/annotations_list_toolbar/annotations_search/BUILD

@@ -3,7 +3,7 @@ load("//tensorboard/defs:defs.bzl", "tf_sass_binary", "tf_ts_library")
 
 package(default_visibility = ["//tensorboard:internal"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 tf_sass_binary(
     name = "annotations_search_component_styles",

third_party/bleach.BUILD

@@ -1,8 +1,10 @@
 # Description:
 #   Build file for Bleach.
+# License:
+#   Apache 2.0
 package(default_visibility = ["//visibility:public"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 exports_files(["LICENSE"])