[hooks_runner] Pass proxy environment variables to hook (#2821)

Author: simolus3

pkgs/hooks/example/build/download_asset/lib/src/hook_helpers/download.dart

@@ -27,7 +27,10 @@ Future<File> downloadAsset(
     createTargetName(targetOS.name, targetArchitecture.name, iOSSdk?.type),
   );
   final uri = downloadUri(targetName);
-  final request = await HttpClient().getUrl(uri);
+  final client = HttpClient()
+    // Respect the http(s)_proxy environment variables.
+    ..findProxy = HttpClient.findProxyFromEnvironment;
+  final request = await client.getUrl(uri);
   final response = await request.close();
   if (response.statusCode != 200) {
     throw ArgumentError('The request to $uri failed.');

pkgs/hooks_runner/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 1.0.2-wip
+
+- Pass `HTTP(S)_PROXY` and related environment variables to hooks.
+
 ## 1.0.1
 
 - Ensure build fails if a build hook does not produce an output file.

pkgs/hooks_runner/lib/src/build_runner/build_runner.dart

@@ -5,7 +5,7 @@
 import 'dart:async';
 import 'dart:convert';
 import 'dart:developer';
-import 'dart:io' show Platform;
+import 'dart:io' show HttpClient, Platform;
 
 import 'package:collection/collection.dart';
 import 'package:file/file.dart';
@@ -538,6 +538,19 @@ class NativeAssetsBuildRunner {
     ),
   );
 
+  /// Environment variables respected by [HttpClient.findProxyFromEnvironment].
+  ///
+  /// We forward them to allow hooks to make HTTP requests in environments where
+  /// a proxy is required.
+  static const _httpProxyEnvironmentVariables = {
+    'http_proxy',
+    'https_proxy',
+    'no_proxy',
+    'HTTP_PROXY',
+    'HTTPS_PROXY',
+    'NO_PROXY',
+  };
+
   /// Determines whether to allow an environment variable through
   /// if [hookEnvironment] is not passed in.
   ///
@@ -556,6 +569,7 @@ class NativeAssetsBuildRunner {
       'TMPDIR', // Needed for temp dirs in Dart process.
       'USERPROFILE', // Needed to find tools in default install locations.
       'WINDIR', // Needed for CMake.
+      ..._httpProxyEnvironmentVariables,
     };
     const variablePrefixesFilter = {
       'NIX_', // Needed for Nix-installed toolchains.

pkgs/hooks_runner/pubspec.yaml

@@ -2,7 +2,7 @@ name: hooks_runner
 description: >-
   This package is the backend that invokes build hooks.
 
-version: 1.0.1
+version: 1.0.2-wip
 
 repository: https://github.com/dart-lang/native/tree/main/pkgs/hooks_runner
 

pkgs/hooks_runner/test/build_runner/concurrency_shared_test_helper.dart renamed to pkgs/hooks_runner/test/build_runner/build_process_helper.dart

@@ -10,7 +10,10 @@ import 'package:logging/logging.dart';
 
 import '../helpers.dart';
 
-// Is invoked concurrently multiple times in separate processes.
+/// Runs the build process for a test package.
+///
+/// Extracted into a separate file so that this can be invoked as an independent
+/// process to patch environment variables or to test concurrency.
 void main(List<String> args) async {
   final packageUri = Uri.directory(args[0]);
   final packageName = packageUri.pathSegments.lastWhere((e) => e.isNotEmpty);

pkgs/hooks_runner/test/build_runner/concurrency_shared_test.dart

@@ -31,9 +31,7 @@ void main() async {
           executable: dartExecutable,
           arguments: [
             pkgNativeAssetsBuilderUri
-                .resolve(
-                  'test/build_runner/concurrency_shared_test_helper.dart',
-                )
+                .resolve('test/build_runner/build_process_helper.dart')
                 .toFilePath(),
             packageUri.toFilePath(),
             target.toString(),

pkgs/hooks_runner/test/build_runner/environment_filter_test.dart

@@ -0,0 +1,50 @@
+// Copyright (c) 2025, 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.
+
+import 'dart:io';
+
+import 'package:hooks_runner/hooks_runner.dart';
+import 'package:test/test.dart';
+
+import '../helpers.dart';
+import 'helpers.dart';
+
+void main() {
+  test('hooks have access to http proxy variable', () async {
+    final server = await HttpServer.bind(InternetAddress.anyIPv4, 0);
+    server.listen((request) async {
+      expect(request.headers.host, 'testing_proxy.dart.dev');
+      expect(request.uri.path, '/test_asset');
+
+      final response = request.response;
+      response.statusCode = 200;
+      response.writeln('test body response');
+      await response.close();
+    });
+
+    addTearDown(server.close);
+    final port = server.port;
+
+    await inTempDir((tempUri) async {
+      await copyTestProjects(targetUri: tempUri);
+      final packageUri = tempUri.resolve('download_assets/');
+      await runPubGet(workingDirectory: packageUri, logger: logger);
+
+      final result = await runProcess(
+        executable: dartExecutable,
+        arguments: [
+          pkgNativeAssetsBuilderUri
+              .resolve('test/build_runner/build_process_helper.dart')
+              .toFilePath(),
+          packageUri.toFilePath(),
+          Target.current.toString(),
+        ],
+        workingDirectory: packageUri,
+        logger: logger,
+        environment: {'HTTP_PROXY': 'localhost:$port'},
+      );
+      expect(result.exitCode, 0);
+    });
+  });
+}

pkgs/hooks_runner/test_data/download_assets/hook/build.dart

@@ -0,0 +1,25 @@
+import 'dart:io';
+
+import 'package:hooks/hooks.dart';
+
+void main(List<String> args) async {
+  await build(args, (input, output) async {
+    final file = File.fromUri(input.outputDirectory.resolve('testfile'));
+
+    final client = HttpClient()
+      ..findProxy = HttpClient.findProxyFromEnvironment;
+    // This request should fail outside of proxies.
+    final request = await client.get(
+      'testing_proxy.dart.dev',
+      80,
+      'test_asset',
+    );
+    final response = await request.close();
+
+    if (response.statusCode != 200) {
+      throw Exception('Could not fetch asset');
+    }
+
+    await response.pipe(file.openWrite());
+  });
+}

pkgs/hooks_runner/test_data/download_assets/pubspec.yaml

@@ -0,0 +1,13 @@
+name: download_assets
+description: Has a build hook downloading a code asset, used to verify proxy env variables working.
+version: 0.1.0
+
+publish_to: none
+
+resolution: workspace
+
+environment:
+  sdk: '>=3.9.0 <4.0.0'
+
+dependencies:
+  hooks: any

pkgs/hooks_runner/test_data/manifest.yaml

@@ -40,6 +40,8 @@
 - depend_on_fail_build_app/pubspec.yaml
 - dev_dependency_with_hook/pubspec.yaml
 - dev_dependency_with_hook/test/my_test.dart
+- download_assets/hook/build.dart
+- download_assets/pubspec.yaml
 - drop_dylib_link/bin/drop_dylib_link.dart
 - drop_dylib_link/hook/build.dart
 - drop_dylib_link/hook/link.dart