linter: Migrate prefer_conditional_assignment tests

Cq-Include-Trybots: luci.dart.try:flutter-analyze-try,analyzer-win-release-try,pkg-win-release-try
Change-Id: I0e09a9b51df81bad301cb7451534856afa7aea58
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/377727
Reviewed-by: Phil Quitslund <[email protected]>
Commit-Queue: Samuel Rawlins <[email protected]>

pkg/linter/test/rules/all.dart

@@ -162,6 +162,8 @@ import 'prefer_asserts_in_initializer_lists_test.dart'
     as prefer_asserts_in_initializer_lists;
 import 'prefer_asserts_with_message_test.dart' as prefer_asserts_with_message;
 import 'prefer_collection_literals_test.dart' as prefer_collection_literals;
+import 'prefer_conditional_assignment_test.dart'
+    as prefer_conditional_assignment;
 import 'prefer_const_constructors_in_immutables_test.dart'
     as prefer_const_constructors_in_immutables;
 import 'prefer_const_constructors_test.dart' as prefer_const_constructors;
@@ -408,6 +410,7 @@ void main() {
   prefer_asserts_in_initializer_lists.main();
   prefer_asserts_with_message.main();
   prefer_collection_literals.main();
+  prefer_conditional_assignment.main();
   prefer_const_constructors_in_immutables.main();
   prefer_const_constructors.main();
   prefer_const_declarations.main();

pkg/linter/test/rules/prefer_conditional_assignment_test.dart

@@ -0,0 +1,153 @@
+// Copyright (c) 2024, 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 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import '../rule_test_support.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(PreferConditionalAssignmentTest);
+  });
+}
+
+@reflectiveTest
+class PreferConditionalAssignmentTest extends LintRuleTest {
+  @override
+  String get lintRule => 'prefer_conditional_assignment';
+
+  test_field_ifEqNull() async {
+    await assertDiagnostics(r'''
+class C {
+  String? x;
+
+  void f(String s) {
+    if (x == null) {
+      x = s;
+    }
+  }
+}
+''', [
+      lint(49, 35),
+    ]);
+  }
+
+  test_field_ifEqNull_conditionWrappedInParens() async {
+    await assertDiagnostics(r'''
+class C {
+  String? x;
+  void f(String s) {
+    if ((x == null)) {
+      x = s;
+    }
+  }
+}
+''', [
+      lint(48, 37),
+    ]);
+  }
+
+  test_field_ifEqNull_eachWrappedInParens() async {
+    await assertDiagnostics(r'''
+class C {
+  String? x;
+  void f(String s) {
+    if ((x) == (null)) {
+      x = s;
+    }
+  }
+}
+''', [
+      lint(48, 39),
+    ]);
+  }
+
+  test_field_ifEqNull_statementBody() async {
+    await assertDiagnostics(r'''
+class C {
+  String? x;
+  String? f(String s) {
+    if (x == null)
+      x = s;
+    return x;
+  }
+}
+''', [
+      lint(51, 27),
+    ]);
+  }
+
+  test_field_ifHasElse() async {
+    await assertNoDiagnostics(r'''
+class C {
+  String? x;
+
+  void f() {
+    if (x == null) {
+      x = foo(this);
+    } else {}
+  }
+}
+
+String foo(C c) => '';
+''');
+  }
+
+  test_field_onOtherTarget() async {
+    await assertNoDiagnostics(r'''
+class C {
+  String? x;
+  void f(C a, C b) {
+    if (a.x == null) {
+      b.x = '';
+    }
+  }
+}
+''');
+  }
+
+  test_field_onSameTarget() async {
+    await assertDiagnostics(r'''
+class C {
+  String? x;
+  void f(C a) {
+    if (a.x == null) {
+      a.x = '';
+    }
+  }
+}
+''', [
+      lint(43, 40),
+    ]);
+  }
+
+  test_field_unrelatedAssignment() async {
+    await assertNoDiagnostics(r'''
+class C {
+  String? x;
+  var y = 1;
+  void f() {
+    if (x == null) {
+      y = 0;
+    }
+  }
+}
+''');
+  }
+
+  test_field_unrelatedAssignment_thenAssignment() async {
+    await assertNoDiagnostics(r'''
+class C {
+  String? x;
+  var y = 1;
+  void f() {
+    if (x == null) {
+      y = 0;
+      x = '';
+    }
+  }
+}
+''');
+  }
+}