Fix running dart_dev in mixed-version packages opted into null safety

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## [3.8.5](https://github.com/Workiva/dart_dev/compare/3.8.4...3.8.5)
+
+- Fix errors when running in mixed-version packages that have opted into null safety via pubspec.yaml.
+
 ## [3.8.4](https://github.com/Workiva/dart_dev/compare/3.8.3...3.8.4)
 - Replace deprecated CLI command.
 

lib/src/executable.dart

@@ -6,6 +6,7 @@ import 'package:args/command_runner.dart';
 import 'package:dart_dev/dart_dev.dart';
 import 'package:dart_dev/src/dart_dev_tool.dart';
 import 'package:dart_dev/src/utils/format_tool_builder.dart';
+import 'package:dart_dev/src/utils/get_dart_version_comment.dart';
 import 'package:dart_dev/src/utils/parse_flag_from_args.dart';
 import 'package:io/ansi.dart';
 import 'package:io/io.dart' show ExitCode;
@@ -114,9 +115,24 @@ bool get shouldWriteRunScript =>
     !_runScript.existsSync() ||
     _runScript.readAsStringSync() != buildDartDevRunScriptContents();
 
+/// Whether dart_dev itself has opted into null-safety.
+const _isDartDevNullSafe = false;
+
 String buildDartDevRunScriptContents() {
   final hasCustomToolDevDart = File(_configPath).existsSync();
+  // If the config has a dart version comment (e.g., if it opts out of null safety),
+  // copy it over to the entrypoint so the program is run in that language version.
+  var dartVersionComment = hasCustomToolDevDart
+      ? getDartVersionComment(File(_configPath).readAsStringSync())
+      : null;
+  // If dart_dev itself is not null-safe, opt the entrypoint out of null-safety
+  // so the entrypoint doesn't fail to run in packages that have opted into null-safety.
+  if (!_isDartDevNullSafe && dartVersionComment == null) {
+    dartVersionComment = '// @dart=2.9';
+  }
+
   return '''
+${dartVersionComment ?? ''}
 import 'dart:io';
 
 import 'package:dart_dev/src/core_config.dart';

lib/src/utils/get_dart_version_comment.dart

@@ -0,0 +1,6 @@
+/// Returns the Dart version comment contained in a given [source] file,
+/// or `null` if one does not exist.
+///
+/// Uses regex over the analyzer for performance.
+String getDartVersionComment(String source) =>
+    RegExp(r'^//\s*@dart\s*=.+$', multiLine: true).firstMatch(source)?.group(0);

test/functional/fixtures/null_safety/opted_in_custom_config/pubspec.yaml

@@ -0,0 +1,10 @@
+name: dart_dev_test_functional_null_safety_opted_in_custom_config_version_comment
+version: 0.0.0
+environment:
+ sdk: ">=2.12.0"
+dev_dependencies:
+  dart_dev:
+    path: ../../../../..
+
+workiva:
+  disable_core_checks: true

test/functional/fixtures/null_safety/opted_in_custom_config/tool/dart_dev/config.dart

@@ -0,0 +1,5 @@
+import 'package:dart_dev/dart_dev.dart';
+
+final config = {
+  ...coreConfig,
+};

test/functional/fixtures/null_safety/opted_in_custom_config_version_comment/pubspec.yaml

@@ -0,0 +1,10 @@
+name: dart_dev_test_functional_null_safety_opted_in_custom_config
+version: 0.0.0
+environment:
+ sdk: ">=2.12.0"
+dev_dependencies:
+  dart_dev:
+    path: ../../../../..
+
+workiva:
+  disable_core_checks: true

test/functional/fixtures/null_safety/opted_in_custom_config_version_comment/tool/dart_dev/config.dart

@@ -0,0 +1,6 @@
+// @dart=2.9
+import 'package:dart_dev/dart_dev.dart';
+
+final config = {
+  ...coreConfig,
+};

test/functional/fixtures/null_safety/opted_in_no_config/pubspec.yaml

@@ -0,0 +1,10 @@
+name: dart_dev_test_functional_null_safety_opted_in_no_config
+version: 0.0.0
+environment:
+ sdk: ">=2.12.0"
+dev_dependencies:
+  dart_dev:
+    path: ../../../../..
+
+workiva:
+  disable_core_checks: true

test/functional/null_safety_functional_test.dart

@@ -0,0 +1,27 @@
+@TestOn('vm')
+@Timeout(Duration(seconds: 20))
+import 'package:test/test.dart';
+
+import '../functional.dart';
+
+void main() {
+  group('runs properly in a project that has opted into null safety', () {
+    test('without any custom config', () async {
+      final process = await runDevToolFunctionalTest(
+          'analyze', 'test/functional/fixtures/null_safety/opted_in_no_config');
+      await process.shouldExit(0);
+    });
+
+    test('with a custom config', () async {
+      final process = await runDevToolFunctionalTest('analyze',
+          'test/functional/fixtures/null_safety/opted_in_custom_config');
+      await process.shouldExit(0);
+    });
+
+    test('with a custom config that has a language version comment', () async {
+      final process = await runDevToolFunctionalTest('analyze',
+          'test/functional/fixtures/null_safety/opted_in_custom_config_version_comment');
+      await process.shouldExit(0);
+    });
+  });
+}

test/utils/get_dart_version_comment_test.dart

@@ -0,0 +1,42 @@
+@TestOn('vm')
+import 'package:dart_dev/src/utils/get_dart_version_comment.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('getDartVersionComment returns the version comment in a Dart file', () {
+    test('', () {
+      expect(
+          getDartVersionComment([
+            '//@dart=2.9',
+            '',
+            'main() {}',
+          ].join('\n')),
+          '//@dart=2.9');
+    });
+
+    test('allowing for whitespace', () {
+      expect(getDartVersionComment('//@dart=2.9'), '//@dart=2.9');
+      expect(
+          getDartVersionComment('//  @dart  =  2.9  '), '//  @dart  =  2.9  ');
+    });
+
+    test('regardless of which line it appears on', () {
+      expect(getDartVersionComment('\n\n//@dart=2.9\n\n'), '//@dart=2.9');
+    });
+
+    test(
+        'ignores version comments that don\'t start at the beginning of the line',
+        () {
+      const wellFormedVersionComment = '//@dart=2.9';
+      expect(getDartVersionComment(wellFormedVersionComment), isNotNull,
+          reason: 'test setup check');
+
+      expect(getDartVersionComment(' $wellFormedVersionComment'), isNull);
+      expect(getDartVersionComment('"$wellFormedVersionComment"'), isNull);
+    });
+
+    test('ignores incomplete version comments', () {
+      expect(getDartVersionComment('//@dart='), isNull);
+    });
+  });
+}