Build engine binaries in post-submit on experimental branches. (#4710)

Closes flutter/flutter#169088.

Author: matanlurey

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

@@ -4,6 +4,7 @@
 
 import 'dart:convert';
 
+import 'package:cocoon_common/is_release_branch.dart';
 import 'package:collection/collection.dart';
 import 'package:github/github.dart';
 
@@ -210,29 +211,26 @@ class CiYaml {
   /// Pick targets out of the given [targets] list that should be run for the
   /// branch that's being tested.
   List<Target> _selectTargetsForBranch(List<Target> targets) {
-    final isReleaseBranch = branch.contains(RegExp('^flutter-'));
-
-    if (isReleaseBranch) {
-      // For release branches we don't want to run release targets or bringup
-      // targets because they are built outside of Cocoon. This applies in both
-      // fusion and non-fusion repos.
+    if (!isFusion) {
+      // Non-flutter/flutter repos run all targets in post-submit.
+      return targets;
+    } else if (isReleaseCandidateBranch(branchName: branch)) {
+      // For release branches:
+      // bringup: true         --> Always omitted.
+      // release_build: "true" --> Built by Linux flutter_release_builder.
       return [
         ...targets.where(
           (target) => !target.isReleaseBuild && !target.isBringup,
         ),
       ];
+    } else if (branch.contains('experimental')) {
+      // For experimental branches:
+      // Run all targets in post-submit.
+      // TODO(matanlurey): Codify this elsewhere once its proven.
+      return targets;
     } else {
-      // For non-release branches we also want to include bringup targets.
-      // However, there's a difference between fusion and non-fusion repos.
-      if (isFusion) {
-        // Fusion repos run release targets in the MQ, so we only need to
-        // schedule non-release targets in post-submit.
-        return [...targets.where((target) => !target.isReleaseBuild)];
-      } else {
-        // Non-fusion repos run all targets in post-submit. There's no MQ to run
-        // release builds prior to post-submit.
-        return targets;
-      }
+      // For flutter/flutter branches include "master".
+      return [...targets.where((target) => !target.isReleaseBuild)];
     }
   }
 

app_dart/lib/src/service/scheduler.dart

@@ -5,7 +5,6 @@
 import 'dart:convert';
 import 'dart:math';
 
-import 'package:cocoon_common/is_release_branch.dart';
 import 'package:cocoon_common/task_status.dart';
 import 'package:cocoon_server/logging.dart';
 import 'package:collection/collection.dart';
@@ -152,10 +151,10 @@ class Scheduler {
     }
 
     final _TaskCommitScheduling scheduling;
-    if (isReleaseCandidateBranch(branchName: commit.branch)) {
-      scheduling = _TaskCommitScheduling.releaseCandidateSkipTasksByDefault;
-    } else {
+    if (Config.defaultBranch(commit.slug) == commit.branch) {
       scheduling = _TaskCommitScheduling.defaultUseTargetSchedulingPolicy;
+    } else {
+      scheduling = _TaskCommitScheduling.nonDefaultBranchSkipTestsByDefault;
     }
 
     final ciYaml = await _ciYamlFetcher.getCiYamlByCommit(
@@ -178,7 +177,13 @@ class Scheduler {
     final toBeScheduled = <PendingTask>[];
     for (var target in targets) {
       final task = tasks.singleWhere((task) => task.taskName == target.name);
-      if (scheduling.skipPostsubmitTasks) {
+      // For flutter/flutter builds (non-master branch), we mark all builds that
+      // do not build the engine as "skipped" for later manual scheduling. Most
+      // branches won't have any release builds at this stage, but experimental
+      // branches *will*, which is why "!target.isReleaseBuild" is used.
+      //
+      // See https://github.com/flutter/flutter/issues/169088.
+      if (scheduling.skipPostsubmitTasks && !target.isReleaseBuild) {
         task.setStatus(TaskStatus.skipped);
         continue;
       }
@@ -1649,11 +1654,11 @@ enum _TaskCommitScheduling {
   /// Schedule according to how [Target.schedulerPolicy] is computed.
   defaultUseTargetSchedulingPolicy,
 
-  /// Release candidate where tasks are skipped to be manually run either.
-  releaseCandidateSkipTasksByDefault;
+  /// Non-default branches skip tests by default for later (manual) scheduling.
+  nonDefaultBranchSkipTestsByDefault;
 
   /// Whether postsubmit tasks should be initially skipped.
   bool get skipPostsubmitTasks {
-    return this == releaseCandidateSkipTasksByDefault;
+    return this == nonDefaultBranchSkipTestsByDefault;
   }
 }

app_dart/test/service/scheduler/ci_yaml_strings.dart

@@ -62,6 +62,7 @@ enabled_branches:
   - main
   - codefu
   - flutter-\d+\.\d+-candidate\.\d+
+  - ios-experimental
 targets:
   - name: Linux Z
     properties:

app_dart/test/service/scheduler_test.dart

@@ -409,7 +409,7 @@ void main() {
       });
 
       // Regression test for https://github.com/flutter/flutter/issues/168738.
-      test('marks all tasks as new for non-release/non-master', () async {
+      test('experimental branches build the engine, skip tests', () async {
         ciYamlFetcher.setCiYamlFrom(otherBranchCiYaml, engine: fusionCiYaml);
 
         final mergedPr = generatePullRequest(
@@ -436,7 +436,24 @@ void main() {
           firestore,
           existsInStorage(
             fs.Task.metadata,
-            everyElement(isTask.hasStatus(TaskStatus.waitingForBackfill)),
+            unorderedEquals([
+              // release_build: "true"
+              isTask
+                  .hasTaskName('Linux engine_build')
+                  .hasStatus(TaskStatus.waitingForBackfill),
+
+              // engine tests based on engine build
+              isTask
+                  .hasTaskName('Linux engine_presubmit')
+                  .hasStatus(TaskStatus.skipped),
+              isTask
+                  .hasTaskName('Linux runIf engine')
+                  .hasStatus(TaskStatus.skipped),
+              isTask.hasTaskName('Linux Z').hasStatus(TaskStatus.skipped),
+
+              // framework tests based on engine build
+              isTask.hasTaskName('Linux A').hasStatus(TaskStatus.skipped),
+            ]),
           ),
         );
       });