Add a server flag onlyUseTipOfTreeTargetsExistenceToFilterTargets.

app_dart/bin/gae_server.dart

@@ -84,7 +84,11 @@ Future<void> main() async {
     /// Github checks api service used to provide luci test execution status on the Github UI.
     final githubChecksService = GithubChecksService(config);
 
-    final ciYamlFetcher = CiYamlFetcher(cache: cache, firestore: firestore);
+    final ciYamlFetcher = CiYamlFetcher(
+      config: config,
+      cache: cache,
+      firestore: firestore,
+    );
 
     /// Cocoon scheduler service to manage validating commits in presubmit and postsubmit.
     final scheduler = Scheduler(

app_dart/config.yaml

@@ -5,6 +5,8 @@
 
 backfillerCommitLimit: 50
 
+onlyUseTipOfTreeTargetsExistenceToFilterTargets: true
+
 contentAwareHashing:
   # This will cause PRs that enter the merge queue to wait on CAH hashing
   # to happen before scheduling builds.

app_dart/lib/src/model/ci_yaml/ci_yaml.dart

@@ -39,6 +39,8 @@ final class CiYamlSet {
     required this.slug,
     required this.branch,
     required Map<CiType, pb.SchedulerConfig> yamls,
+    bool onlyUseTipOfTreeTargetsExistenceToFilterTargets =
+        Config.kOnlyUseTipOfTreeTargetsExistenceToFilterTargets,
     CiYamlSet? totConfig,
     bool validate = false,
   }) {
@@ -50,6 +52,8 @@ final class CiYamlSet {
         type: type,
         validate: validate,
         totConfig: totConfig?.configs[type],
+        onlyUseTipOfTreeTargetsExistenceToFilterTargets:
+            onlyUseTipOfTreeTargetsExistenceToFilterTargets,
       );
     }
   }
@@ -117,7 +121,8 @@ class CiYaml {
     required this.branch,
     required this.config,
     required this.type,
-    this.onlyUseTipOfTreeTargetsExistenceToFilterTargets = false,
+    this.onlyUseTipOfTreeTargetsExistenceToFilterTargets =
+        Config.kOnlyUseTipOfTreeTargetsExistenceToFilterTargets,
     CiYaml? totConfig,
     bool validate = false,
   }) {

app_dart/lib/src/service/config.dart

@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+/// @docImport '../model/ci_yaml/ci_yaml.dart';
+library;
+
 import 'dart:convert';
 import 'dart:math' show Random;
 import 'dart:typed_data';
@@ -31,12 +34,18 @@ const String kDefaultBranchName = 'master';
 
 interface class Config {
   /// Creates and returns a [Config] instance.
-  Config(this._cache, this._secrets, {required DynamicConfig dynamicConfig})
-    : _dynamicConfig = dynamicConfig;
+  Config(
+    this._cache, //
+    this._secrets, {
+    required DynamicConfig dynamicConfig,
+  }) : _dynamicConfig = dynamicConfig;
 
   /// Access dynamically configured flags.
   DynamicConfig get flags => _dynamicConfig;
 
+  /// See [CiYaml.onlyUseTipOfTreeTargetsExistenceToFilterTargets].
+  static const bool kOnlyUseTipOfTreeTargetsExistenceToFilterTargets = false;
+
   /// When present on a pull request, instructs Cocoon to submit it
   /// automatically as soon as all the required checks pass.
   ///
@@ -514,9 +523,19 @@ final class DynamicConfig {
 
   final ContentAwareHashingJson contentAwareHashing;
 
+  /// Whether to _only_ use the existence of a target at tip-of-tree to filter
+  /// out targets on other branches.
+  ///
+  /// See [CiYaml.onlyUseTipOfTreeTargetsExistenceToFilterTargets].
+  @JsonKey(
+    defaultValue: Config.kOnlyUseTipOfTreeTargetsExistenceToFilterTargets,
+  )
+  final bool onlyUseTipOfTreeTargetsExistenceToFilterTargets;
+
   DynamicConfig({
     required this.backfillerCommitLimit,
     required this.contentAwareHashing,
+    required this.onlyUseTipOfTreeTargetsExistenceToFilterTargets,
   });
 
   /// Connect the generated [_$DynamicConfigFromJson] function to the `fromJson`

app_dart/lib/src/service/scheduler/ci_yaml_fetcher.dart

@@ -21,6 +21,7 @@ import '../firestore.dart';
 interface class CiYamlFetcher {
   /// Creates a [CiYamlFetcher] from the provided configuration.
   CiYamlFetcher({
+    required Config config,
     required CacheService cache,
     required FirestoreService firestore,
     HttpClientProvider httpClientProvider = Providers.freshHttpClient,
@@ -30,13 +31,15 @@ interface class CiYamlFetcher {
       delayFactor: Duration(seconds: 2),
       maxAttempts: 4,
     ),
-  }) : _cache = cache,
+  }) : _config = config,
+       _cache = cache,
        _cacheTtl = cacheTtl,
        _subcacheName = subcacheName,
        _retryOptions = retryOptions,
        _httpClientProvider = httpClientProvider,
        _firestore = firestore;
 
+  final Config _config;
   final CacheService _cache;
   final String _subcacheName;
   final Duration _cacheTtl;
@@ -127,6 +130,8 @@ interface class CiYamlFetcher {
       branch: commit.branch,
       totConfig: totCiYaml,
       validate: validate,
+      onlyUseTipOfTreeTargetsExistenceToFilterTargets:
+          _config.flags.onlyUseTipOfTreeTargetsExistenceToFilterTargets,
     );
   }
 

app_dart/test/service/scheduler/ci_yaml_fetcher_test.dart

@@ -17,6 +17,7 @@ import 'package:path/path.dart' as p;
 import 'package:retry/retry.dart';
 import 'package:test/test.dart';
 
+import '../../src/fake_config.dart';
 import '../../src/service/fake_firestore_service.dart';
 import '../../src/utilities/entity_generators.dart';
 
@@ -34,6 +35,7 @@ void main() {
   late CacheService cache;
   late MockClient httpClient;
   late FakeFirestoreService firestore;
+  late FakeConfig config;
 
   late CiYamlFetcher ciYamlFetcher;
 
@@ -46,6 +48,7 @@ void main() {
     firestore = FakeFirestoreService();
 
     ciYamlFetcher = CiYamlFetcher(
+      config: config = FakeConfig(),
       cache: cache,
       httpClientProvider: () => httpClient,
       retryOptions: const RetryOptions(maxAttempts: 1),
@@ -77,6 +80,27 @@ void main() {
     );
   }
 
+  // TODO(matanlurey): Remove after https://github.com/flutter/flutter/issues/169625.
+  test('passes flag onlyUseTipOfTreeTargetsExistenceToFilterTargets', () async {
+    config.dynamicConfig = DynamicConfig.fromJson({
+      'onlyUseTipOfTreeTargetsExistenceToFilterTargets': false,
+    });
+    mockFillFirestore(slug: Config.packagesSlug, branch: 'main');
+    httpClient = MockClient((request) async {
+      return http.Response(singleCiYaml, HttpStatus.ok);
+    });
+
+    final ciYaml = await ciYamlFetcher.getCiYamlByCommit(
+      CommitRef(slug: Config.packagesSlug, sha: currentSha, branch: 'main'),
+    );
+    expect(
+      ciYaml
+          .configs[CiType.any]
+          ?.onlyUseTipOfTreeTargetsExistenceToFilterTargets,
+      isFalse,
+    );
+  });
+
   test('fetches the root .ci.yaml for a repository (GitHub)', () async {
     httpClient = MockClient((request) async {
       if (request.url.host != 'raw.githubusercontent.com') {

app_dart/tool/local_server.dart

@@ -65,7 +65,11 @@ Future<void> main() async {
   /// Github checks api service used to provide luci test execution status on the Github UI.
   final githubChecksService = GithubChecksService(config);
 
-  final ciYamlFetcher = CiYamlFetcher(cache: cache, firestore: firestore);
+  final ciYamlFetcher = CiYamlFetcher(
+    config: config,
+    cache: cache,
+    firestore: firestore,
+  );
 
   /// Cocoon scheduler service to manage validating commits in presubmit and postsubmit.
   final scheduler = Scheduler(