From 30f13d54fbd8ab6f988b1cb126c02cab965e1531 Mon Sep 17 00:00:00 2001
From: David Morgan <davidmorgan@google.com>
Date: Fri, 14 Nov 2025 16:24:01 +0100
Subject: [PATCH] Fix build_modules for AOT.

---
 build_modules/CHANGELOG.md                    |  4 +++
 build_modules/lib/src/scratch_space.dart      | 25 ++++++++++++++++++-
 build_modules/pubspec.yaml                    |  2 +-
 .../integration_tests/web_compilers_test.dart |  8 +++++-
 4 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/build_modules/CHANGELOG.md b/build_modules/CHANGELOG.md
index af5747707..cc7b971f6 100644
--- a/build_modules/CHANGELOG.md
+++ b/build_modules/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 5.1.2
+
+- Make compatible with `dart run build_runner build --force-aot`.
+
 ## 5.1.1
 
 - Fix re-add `multiRootScheme` to build_modules exports.
diff --git a/build_modules/lib/src/scratch_space.dart b/build_modules/lib/src/scratch_space.dart
index 6c8bf35f3..f0b72f3d1 100644
--- a/build_modules/lib/src/scratch_space.dart
+++ b/build_modules/lib/src/scratch_space.dart
@@ -33,7 +33,7 @@ final scratchSpaceResource = Resource<ScratchSpace>(
       p.join(scratchSpace.tempDir.path, '.dart_tool', 'package_config.json'),
     );
     if (!packageConfigFile.existsSync()) {
-      final originalConfigFile = File.fromUri((await Isolate.packageConfig)!);
+      final originalConfigFile = await _findPackageConfig();
       final packageConfigContents = _scratchSpacePackageConfig(
         originalConfigFile.readAsStringSync(),
         originalConfigFile.absolute.uri,
@@ -134,3 +134,26 @@ String _scratchSpacePackageConfig(String rootConfig, Uri packageConfigUri) {
 }
 
 final Uri _currentDirUri = Directory.current.uri;
+
+/// Returns [Isolate.packageConfig], or finds the file if it's `null`.
+///
+/// The `null` case is hit when the builder is AOT compiled. The build runs
+/// within the package being built, so search upwards for the package config.
+Future<File> _findPackageConfig() async {
+  final result = await Isolate.packageConfig;
+  if (result != null) return File(result.toFilePath());
+  var directory = Directory.current;
+  while (true) {
+    final packageConfigFile = File(
+      p.join(directory.path, '.dart_tool', 'package_config.json'),
+    );
+    if (packageConfigFile.existsSync()) {
+      return packageConfigFile;
+    }
+    final parent = directory.parent;
+    if (parent.path == directory.path) {
+      throw StateError('Failed to find package_config.json.');
+    }
+    directory = parent;
+  }
+}
diff --git a/build_modules/pubspec.yaml b/build_modules/pubspec.yaml
index 3f2510fc5..257d5b96c 100644
--- a/build_modules/pubspec.yaml
+++ b/build_modules/pubspec.yaml
@@ -1,5 +1,5 @@
 name: build_modules
-version: 5.1.1
+version: 5.1.2
 description: >-
   Builders to analyze and split Dart code into individually compilable modules
   based on imports.
diff --git a/build_runner/test/integration_tests/web_compilers_test.dart b/build_runner/test/integration_tests/web_compilers_test.dart
index d906f3d41..5e144d4e3 100644
--- a/build_runner/test/integration_tests/web_compilers_test.dart
+++ b/build_runner/test/integration_tests/web_compilers_test.dart
@@ -10,7 +10,7 @@ import 'package:test/test.dart';
 
 import '../common/common.dart';
 
-const defaultTimeout = Timeout(Duration(seconds: 90));
+const defaultTimeout = Timeout(Duration(minutes: 3));
 
 void main() async {
   test('web compilers', () async {
@@ -55,6 +55,12 @@ void main() {
       },
     );
 
+    // Initial build AOT.
+    await tester.run(
+      'root_pkg',
+      'dart run build_runner build --output web:build --force-aot',
+    );
+
     // Initial build.
     await tester.run(
       'root_pkg',