Support experiments in the build script (#3467)

Fixes #3466

Author: jakemac53

.github/workflows/dart.yml

@@ -63,7 +63,9 @@ void main() {
       ]);
 
       expect(result.exitCode, isNot(0));
-      expect(result.stdout, contains('Unknown experiment: fake-experiment'));
+      expect(result.stdout, contains('Failed to precompile build script'));
+      expect(result.stdout, contains('Unknown experiment: fake-experiment'),
+          skip: 'https://github.com/dart-lang/webdev/issues/2003');
     });
   });
 

_test/test/build_integration_test.dart

@@ -2,6 +2,7 @@
 
 - Mention --build-filter option in the README.
 - Update to build_daemon 4.0.
+- Support enabling experiments in build scripts.
 
 ## 2.4.0
 

build_runner/CHANGELOG.md

@@ -95,7 +95,9 @@ Future<void> main(List<String> args) async {
   if (localCommandNames.contains(commandName)) {
     exitCode = await commandRunner.runCommand(parsedArgs) ?? 1;
   } else {
-    while ((exitCode = await generateAndRun(args)) == ExitCode.tempFail.code) {}
+    var experiments = parsedArgs.command!['enable-experiment'] as List<String>?;
+    while ((exitCode = await generateAndRun(args, experiments: experiments)) ==
+        ExitCode.tempFail.code) {}
   }
   await logListener.cancel();
 }

build_runner/bin/build_runner.dart

@@ -1,3 +1,10 @@
+presets:
+  experiments:
+    include_tags: experiments
+
 tags:
   integration:
     timeout: 16x
+  experiments:
+    skip: 'Only ran if `-P experiments` is passed'
+    presets: {experiments: {skip: false}}

build_runner/dart_test.yaml

@@ -28,11 +28,13 @@ final _logger = Logger('Bootstrap');
 /// If an exit code of 75 is returned, this function should be re-ran.
 Future<int> generateAndRun(
   List<String> args, {
+  List<String>? experiments,
   Logger? logger,
   Future<String> Function() generateBuildScript = generateBuildScript,
   void Function(Object error, StackTrace stackTrace) handleUncaughtError =
       _defaultHandleUncaughtError,
 }) async {
+  experiments ??= [];
   logger ??= _logger;
   ReceivePort? exitPort;
   ReceivePort? errorPort;
@@ -66,7 +68,7 @@ Future<int> generateAndRun(
       return ExitCode.config.code;
     }
 
-    scriptExitCode = await _createKernelIfNeeded(logger);
+    scriptExitCode = await _createKernelIfNeeded(logger, experiments);
     if (scriptExitCode != 0) return scriptExitCode!;
 
     exitPort = ReceivePort();
@@ -133,7 +135,8 @@ Future<int> generateAndRun(
 ///
 /// Returns zero for success or a number for failure which should be set to the
 /// exit code.
-Future<int> _createKernelIfNeeded(Logger logger) async {
+Future<int> _createKernelIfNeeded(
+    Logger logger, List<String> experiments) async {
   var assetGraphFile = File(assetGraphPathFor(scriptKernelLocation));
   var kernelFile = File(scriptKernelLocation);
   var kernelCacheFile = File(scriptKernelCachedLocation);
@@ -145,7 +148,7 @@ Future<int> _createKernelIfNeeded(Logger logger) async {
       await kernelFile.rename(scriptKernelCachedLocation);
       logger.warning(
           'Invalidated precompiled build script due to missing asset graph.');
-    } else if (!await _checkImportantPackageDeps()) {
+    } else if (!await _checkImportantPackageDepsAndExperiments(experiments)) {
       await kernelFile.rename(scriptKernelCachedLocation);
       logger.warning(
           'Invalidated precompiled build script due to core package update');
@@ -157,6 +160,7 @@ Future<int> _createKernelIfNeeded(Logger logger) async {
       scriptLocation,
       scriptKernelCachedLocation,
       'lib/_internal/vm_platform_strong.dill',
+      enabledExperiments: experiments,
       printIncrementalDependencies: false,
     );
 
@@ -209,7 +213,7 @@ This is likely caused by a misconfigured builder definition.
       return ExitCode.config.code;
     }
     // Create _previousLocationsFile.
-    await _checkImportantPackageDeps();
+    await _checkImportantPackageDepsAndExperiments(experiments);
   }
   return 0;
 }
@@ -222,28 +226,30 @@ final _previousLocationsFile =
     File(p.url.join(p.url.dirname(scriptKernelLocation), '.packageLocations'));
 
 /// Returns whether the [_importantPackages] are all pointing at same locations
-/// from the previous run.
+/// from the previous run, and [experiments] are the same as the last run.
 ///
 /// Also updates the [_previousLocationsFile] with the new locations if not.
 ///
 /// This is used to detect potential changes to the user facing api and
 /// pre-emptively resolve them by precompiling the build script again, see
 /// https://github.com/dart-lang/build/issues/1929.
-Future<bool> _checkImportantPackageDeps() async {
+Future<bool> _checkImportantPackageDepsAndExperiments(
+    List<String> experiments) async {
   var currentLocations = await Future.wait(_importantPackages.map((pkg) =>
       Isolate.resolvePackageUri(
           Uri(scheme: 'package', path: '$pkg/fake.dart'))));
-  var currentLocationsContent = currentLocations.join('\n');
+  var fileContents =
+      currentLocations.map((uri) => '$uri').followedBy(experiments).join('\n');
 
   if (!_previousLocationsFile.existsSync()) {
     _logger.fine('Core package locations file does not exist');
-    _previousLocationsFile.writeAsStringSync(currentLocationsContent);
+    _previousLocationsFile.writeAsStringSync(fileContents);
     return false;
   }
 
-  if (currentLocationsContent != _previousLocationsFile.readAsStringSync()) {
+  if (fileContents != _previousLocationsFile.readAsStringSync()) {
     _logger.fine('Core packages locations have changed');
-    _previousLocationsFile.writeAsStringSync(currentLocationsContent);
+    _previousLocationsFile.writeAsStringSync(fileContents);
     return false;
   }
 

build_runner/lib/src/build_script_generate/bootstrap.dart

@@ -1,4 +1,5 @@
 sdk:
+- dev
 - main
 
 stages:
@@ -8,10 +9,13 @@ stages:
     - analyze: --fatal-infos .
 - unit_test:
   - test: -x integration --test-randomize-ordering-seed=random
+  - test: -P experiments --test-randomize-ordering-seed=random
+    sdk:
+    - 3.0.0-277.0.dev
 - e2e_test:
   # TODO: enable stack trace chaining https://github.com/dart-lang/build/issues/2894
-  - test: -t integration --total-shards 5 --shard-index 0 --test-randomize-ordering-seed=random --no-chain-stack-traces
-  - test: -t integration --total-shards 5 --shard-index 1 --test-randomize-ordering-seed=random --no-chain-stack-traces
-  - test: -t integration --total-shards 5 --shard-index 2 --test-randomize-ordering-seed=random --no-chain-stack-traces
-  - test: -t integration --total-shards 5 --shard-index 3 --test-randomize-ordering-seed=random --no-chain-stack-traces
-  - test: -t integration --total-shards 5 --shard-index 4 --test-randomize-ordering-seed=random --no-chain-stack-traces
+  - test: -t integration --total-shards 5 --shard-index 0 --test-randomize-ordering-seed=random --no-chain-stack-traces -j 1
+  - test: -t integration --total-shards 5 --shard-index 1 --test-randomize-ordering-seed=random --no-chain-stack-traces -j 1
+  - test: -t integration --total-shards 5 --shard-index 2 --test-randomize-ordering-seed=random --no-chain-stack-traces -j 1
+  - test: -t integration --total-shards 5 --shard-index 3 --test-randomize-ordering-seed=random --no-chain-stack-traces -j 1
+  - test: -t integration --total-shards 5 --shard-index 4 --test-randomize-ordering-seed=random --no-chain-stack-traces -j 1

build_runner/mono_pkg.yaml

@@ -0,0 +1,34 @@
+// Copyright (c) 2023, 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.
+
+@Tags(['experiments'])
+@TestOn('vm')
+import 'package:build_runner/build_script_generate.dart';
+import 'package:logging/logging.dart';
+import 'package:test/test.dart';
+
+void main() {
+  test('build scripts can use experiments', () async {
+    final logger = Logger.detached('test')..level = Level.ALL;
+    logger.onRecord.listen((r) => printOnFailure(r.message));
+    final exitCode = await generateAndRun(
+      [],
+      experiments: ['records'],
+      generateBuildScript: () async {
+        return '''
+              // @dart=3.0
+              import 'dart:io';
+              import 'dart:isolate';
+
+              void main(List<String> _, SendPort sendPort) {
+                var x = (1, 2);
+                sendPort.send(x.\$2);
+              }
+              ''';
+      },
+      logger: logger,
+    );
+    expect(exitCode, 2);
+  });
+}

build_runner/test/build_script_generate/experiments_test.dart

@@ -101,7 +101,8 @@ main() {
 
   Future<void> _startDaemon(
       {BuildMode buildMode = BuildMode.Auto,
-      List<String> options = const []}) async {
+      List<String> options = const [],
+      bool expectFailure = false}) async {
     var args = [
       'build_runner',
       'daemon',
@@ -126,7 +127,11 @@ main() {
     unawaited(daemon.exitCode.then((exitCode) {
       printOnFailure('GOT EXIT CODE: $exitCode');
     }));
-    expect(await stdoutLines!.contains(readyToConnectLog), isTrue);
+    if (expectFailure) {
+      expect(await daemon.exitCode, isNot(0));
+    } else {
+      expect(await stdoutLines!.contains(readyToConnectLog), isTrue);
+    }
   }
 
   group('Build Daemon', () {
@@ -152,17 +157,10 @@ main() {
     }, skip: 'https://github.com/dart-lang/build/issues/3438');
 
     test('supports --enable-experiment option', () async {
-      await _startDaemon(options: ['--enable-experiment=fake-experiment']);
-      var client =
-          await _startClient(options: ['--enable-experiment=fake-experiment'])
-            ..registerBuildTarget(webTarget)
-            ..startBuild();
-      clients.add(client);
-      await expectLater(
-          client.buildResults,
-          // TODO: Check for specific message about a bad experiment
-          emitsThrough((BuildResults b) =>
-              b.results.first.status == BuildStatus.failed));
+      // TODO: Check for specific message about a bad experiment
+      await _startDaemon(
+          options: ['--enable-experiment=fake-experiment'],
+          expectFailure: true);
     });
 
     test('does not shut down down on build script change when configured',