Add source links to dartdoc output.

Dartdoc > 0.18.1 allows generation of source code links
to documented objects.  Enable this for the Dart SDK build.

Change-Id: Ib385d3e51f6f5852f37e591d7a60ba7b4e7f93c1
Reviewed-on: https://dart-review.googlesource.com/c/92303
Reviewed-by: Alexander Thomas <athom@google.com>
Commit-Queue: Janice Collins <jcollins@google.com>

dartdoc_options.yaml

@@ -1,2 +0,0 @@
-dartdoc:
-  categoryOrder: ["Core", VM", "Web"]

sdk/BUILD.gn

@@ -856,14 +856,20 @@ copy("copy_license") {
   ]
 }
 
-# This rule copies the dartdoc_options.yaml file.
-copy("copy_dartdoc_options") {
+# This rule generates a custom dartdoc_options.yaml file.
+action("write_dartdoc_options") {
   visibility = [ ":create_common_sdk" ]
-  sources = [
-    "../dartdoc_options.yaml",
+  inputs = [
+    "../.git/logs/HEAD",
   ]
+  output = "$root_out_dir/dart-sdk/dartdoc_options.yaml"
   outputs = [
-    "$root_out_dir/dart-sdk/dartdoc_options.yaml",
+    output,
+  ]
+  script = "../tools/write_dartdoc_options_file.py"
+  args = [
+    "--output",
+    rebase_path(output),
   ]
 }
 
@@ -886,13 +892,13 @@ group("create_common_sdk") {
     ":copy_api_readme",
     ":copy_dart",
     ":copy_dartdoc_files",
-    ":copy_dartdoc_options",
     ":copy_headers",
     ":copy_libraries_dart",
     ":copy_license",
     ":copy_libraries_specification",
     ":copy_readme",
     ":copy_vm_dill_files",
+    ":write_dartdoc_options",
     ":write_revision_file",
     ":write_version_file",
   ]

tools/write_dartdoc_options_file.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python
+# Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
+# for details. All rights reserved. Use of this source code is governed by a
+# BSD-style license that can be found in the LICENSE file.
+
+import argparse
+import sys
+import utils
+
+def ParseArgs(args):
+  args = args[1:]
+  parser = argparse.ArgumentParser(
+      description='A script to write a custom dartdoc_options.yaml to a file')
+
+  parser.add_argument('--output', '-o',
+      type=str,
+      required=True,
+      help='File to write')
+
+  return parser.parse_args(args)
+
+
+def Main(argv):
+  args = ParseArgs(argv)
+  # TODO(jcollins-g): switch to version numbers when github has its tags synced
+  revision = utils.GetGitRevision()
+  if revision is None:
+    revision = 'master'
+  output = '''dartdoc:
+  categoryOrder: ["Core", "VM", "Web"]
+  linkToSource:
+    root: '.'
+    uriTemplate: 'https://github.com/dart-lang/sdk/blob/%s/sdk/%%f%%#L%%l%%'
+''' % revision
+  with open(args.output, 'w') as f:
+    f.write(output)
+  return 0
+
+if __name__ == '__main__':
+  sys.exit(Main(sys.argv))