Adds a Dart library for loading and parsing build configs

ci/builders/linux_unopt.json

@@ -69,6 +69,10 @@
                     "language": "dart",
                     "name": "test: Lint android host",
                     "script": "flutter/tools/android_lint/bin/main.dart"
+                },
+                {
+                    "name": "Check build configs",
+                    "script": "flutter/ci/check_build_configs.sh"
                 }
             ]
         },

ci/builders/mac_android_aot_engine.json

@@ -239,6 +239,6 @@
             }
         }
     ],
-    "generators": [],
+    "generators": {},
     "archives": []
 }

ci/check_build_configs.sh

@@ -0,0 +1,41 @@
+#!/bin/bash
+#
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+set -e
+
+# Needed because if it is set, cd may print the path it changed to.
+unset CDPATH
+
+# On Mac OS, readlink -f doesn't work, so follow_links traverses the path one
+# link at a time, and then cds into the link destination and find out where it
+# ends up.
+#
+# The function is enclosed in a subshell to avoid changing the working directory
+# of the caller.
+function follow_links() (
+  cd -P "$(dirname -- "$1")"
+  file="$PWD/$(basename -- "$1")"
+  while [[ -h "$file" ]]; do
+    cd -P "$(dirname -- "$file")"
+    file="$(readlink -- "$file")"
+    cd -P "$(dirname -- "$file")"
+    file="$PWD/$(basename -- "$file")"
+  done
+  echo "$file"
+)
+
+SCRIPT_DIR=$(follow_links "$(dirname -- "${BASH_SOURCE[0]}")")
+SRC_DIR="$(cd "$SCRIPT_DIR/../.."; pwd -P)"
+FLUTTER_DIR="$(cd "$SCRIPT_DIR/.."; pwd -P)"
+DART_BIN="${SRC_DIR}/third_party/dart/tools/sdks/dart-sdk/bin"
+DART="${DART_BIN}/dart"
+
+cd "$SCRIPT_DIR"
+"$DART" \
+  --disable-dart-dev \
+  "$SRC_DIR/flutter/tools/pkg/engine_build_configs/bin/check.dart" \
+  "$SRC_DIR"
+

testing/run_tests.py

@@ -972,6 +972,25 @@ def gather_build_bucket_golden_scraper_tests(build_dir):
     )
 
 
+def gather_engine_build_configs_tests(build_dir):
+  test_dir = os.path.join(
+      BUILDROOT_DIR, 'flutter', 'tools', 'pkg', 'engine_build_configs'
+  )
+  dart_tests = glob.glob('%s/*_test.dart' % test_dir)
+  for dart_test_file in dart_tests:
+    opts = [
+        '--disable-dart-dev',
+        dart_test_file,
+    ]
+    yield EngineExecutableTask(
+        build_dir,
+        os.path.join('dart-sdk', 'bin', 'dart'),
+        None,
+        flags=opts,
+        cwd=test_dir
+    )
+
+
 def gather_engine_repo_tools_tests(build_dir):
   test_dir = os.path.join(
       BUILDROOT_DIR, 'flutter', 'tools', 'pkg', 'engine_repo_tools'
@@ -1269,6 +1288,7 @@ def main():
     tasks += list(gather_githooks_tests(build_dir))
     tasks += list(gather_clang_tidy_tests(build_dir))
     tasks += list(gather_build_bucket_golden_scraper_tests(build_dir))
+    tasks += list(gather_engine_build_configs_tests(build_dir))
     tasks += list(gather_engine_repo_tools_tests(build_dir))
     tasks += list(gather_api_consistency_tests(build_dir))
     tasks += list(gather_path_ops_tests(build_dir))

tools/pkg/engine_build_configs/analysis_options.yaml

@@ -0,0 +1,5 @@
+include: ../../../analysis_options.yaml
+
+linter:
+  rules:
+    public_member_api_docs: false

tools/pkg/engine_build_configs/bin/check.dart

@@ -0,0 +1,67 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io' as io;
+
+import 'package:engine_build_configs/engine_build_configs.dart';
+import 'package:engine_repo_tools/engine_repo_tools.dart';
+import 'package:path/path.dart' as p;
+
+// Usage:
+// $ dart bin/check.dart [/path/to/engine/src]
+
+void main(List<String> args) {
+  final String? engineSrcPath;
+  if (args.isNotEmpty) {
+    engineSrcPath = args[0];
+  } else {
+    engineSrcPath = null;
+  }
+
+  // Find the engine repo.
+  final Engine engine;
+  try {
+    engine = Engine.findWithin(engineSrcPath);
+  } catch (e) {
+    io.stderr.writeln(e);
+    io.exitCode = 1;
+    return;
+  }
+
+  // Find and parse the engine build configs.
+  final io.Directory buildConfigsDir = io.Directory(p.join(
+    engine.flutterDir.path, 'ci', 'builders',
+  ));
+  final BuildConfigLoader loader = BuildConfigLoader(
+    buildConfigsDir: buildConfigsDir,
+  );
+
+  // Treat it as an error if no build configs were found. The caller likely
+  // expected to find some.
+  final Map<String, BuildConfig> configs = loader.configs;
+  if (configs.isEmpty) {
+    io.stderr.writeln(
+      'Error: No build configs found under ${buildConfigsDir.path}',
+    );
+    io.exitCode = 1;
+    return;
+  }
+  if (loader.errors.isNotEmpty) {
+    loader.errors.forEach(io.stderr.writeln);
+    io.exitCode = 1;
+  }
+
+  // Check the parsed build configs for validity.
+  for (final String name in configs.keys) {
+    final BuildConfig buildConfig = configs[name]!;
+    final List<String> buildConfigErrors = buildConfig.check(name);
+    if (buildConfigErrors.isNotEmpty) {
+      io.stderr.writeln('Errors in ${buildConfig.path}:');
+      io.exitCode = 1;
+    }
+    for (final String error in buildConfigErrors) {
+      io.stderr.writeln('    $error');
+    }
+  }
+}

tools/pkg/engine_build_configs/lib/engine_build_configs.dart

@@ -0,0 +1,24 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/// This is a library for parsing the Engine CI configurations that live under
+/// flutter/ci/builders. They describe how CI builds, tests, archives, and
+/// uploads the engine to cloud storage. The documentation and spec for the
+/// format is at:
+///
+///    https://github.com/flutter/engine/blob/main/ci/builders/README.md
+///
+/// The code in this library is *not* used by CI to run these configurations.
+/// Rather, that code executes these configs on CI is part of the "engine_v2"
+/// recipes at:
+///
+///   https://cs.opensource.google/flutter/recipes/+/main:recipes/engine_v2
+///
+/// This library exposes two main classes, [BuildConfigLoader], which reads and
+/// loads all build configurations under a directory, and [BuildConfig], which
+/// is the Dart representation of a single build configuration.
+library;
+
+export 'src/build_config.dart';
+export 'src/build_config_loader.dart';