Fix log stack overflow. (#4080)

Author: davidmorgan

build_test/CHANGELOG.md

@@ -1,5 +1,7 @@
 ## 3.3.0-wip
 
+- Bug fix: don't crash when a builder logs during a `testBuilder` or
+  `resolveSource` call outside a test.
 - Remove unused deps: `async`, `convert`.
 - Remove unused dev_deps: `collection`.
 

build_test/lib/src/test_builder.dart

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 import 'dart:async';
 import 'dart:convert';
+import 'dart:io';
 
 import 'package:build/build.dart';
 import 'package:build/experiments.dart';
@@ -233,7 +234,7 @@ Future<TestBuilderResult> testBuilders(
   TestReaderWriter? readerWriter,
   bool enableLowResourceMode = false,
 }) async {
-  onLog ??= _printOnFailureOrPrint;
+  onLog ??= _printOnFailureOrWrite;
 
   var inputIds = {
     for (var descriptor in sourceAssets.keys) makeAssetId(descriptor),
@@ -382,7 +383,7 @@ class TestBuilderResult {
   TestBuilderResult({required this.buildResult, required this.readerWriter});
 }
 
-void _printOnFailureOrPrint(LogRecord record) {
+void _printOnFailureOrWrite(LogRecord record) {
   final message =
       '$record'
       '${record.error == null ? '' : '  ${record.error}'}'
@@ -391,7 +392,8 @@ void _printOnFailureOrPrint(LogRecord record) {
     // This throws if a test is not currently running.
     printOnFailure(message);
   } catch (_) {
-    // Print instead.
-    print(message);
+    // Write instead. Don't `print` because that would hit the Zone print
+    // handler if logging from a builder.
+    stdout.writeln(message);
   }
 }

build_test/test/test_builder_test.dart

@@ -13,20 +13,8 @@ import 'package:test/test.dart';
 
 Future<void> main() async {
   // Default logging uses `printOnFailure` which crashes outside tests; check
-  // that it falls back to `print` outside tests.
-  final printed = <String>[];
-  await runZonedGuarded(
-    () async {
-      await testBuilder(TestBuilder(), {'a|lib/a.dart': ''}, rootPackage: 'a');
-    },
-    (_, _) {},
-    zoneSpecification: ZoneSpecification(
-      print: (_, _, _, string) {
-        printed.add(string);
-      },
-    ),
-  );
-  if (printed.isEmpty) throw StateError('Expected some prints.');
+  // that it falls back to something else outside tests.
+  await testBuilder(TestBuilder(), {'a|lib/a.dart': ''}, rootPackage: 'a');
 
   test('can glob files in the root package', () async {
     var assets = {