Add quick assist to convert SwitchStatement (with patterns) into if-case chain.

Bug: https://github.com/dart-lang/sdk/issues/52068
Change-Id: Ia20b943dfc5212764f31cd94f4f8cce8755628bc
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/297140
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Phil Quitslund <pquitslund@google.com>

pkg/analysis_server/lib/src/services/correction/assist.dart

@@ -146,6 +146,11 @@ class DartAssistKind {
     DartAssistKindPriority.DEFAULT,
     "Convert to 'if-case' statement",
   );
+  static const CONVERT_TO_IF_CASE_STATEMENT_CHAIN = AssistKind(
+    'dart.assist.convert.ifCaseStatementChain',
+    DartAssistKindPriority.DEFAULT,
+    "Convert to 'if-case' statement chain",
+  );
   static const CONVERT_TO_IF_ELEMENT = AssistKind(
     'dart.assist.convert.toIfElement',
     DartAssistKindPriority.DEFAULT,

pkg/analysis_server/lib/src/services/correction/assist_internal.dart

@@ -31,6 +31,7 @@ import 'package:analysis_server/src/services/correction/dart/convert_to_expressi
 import 'package:analysis_server/src/services/correction/dart/convert_to_field_parameter.dart';
 import 'package:analysis_server/src/services/correction/dart/convert_to_generic_function_syntax.dart';
 import 'package:analysis_server/src/services/correction/dart/convert_to_if_case_statement.dart';
+import 'package:analysis_server/src/services/correction/dart/convert_to_if_case_statement_chain.dart';
 import 'package:analysis_server/src/services/correction/dart/convert_to_int_literal.dart';
 import 'package:analysis_server/src/services/correction/dart/convert_to_map_literal.dart';
 import 'package:analysis_server/src/services/correction/dart/convert_to_multiline_string.dart';
@@ -116,6 +117,7 @@ class AssistProcessor extends BaseProcessor {
     ConvertToFieldParameter.new,
     ConvertToGenericFunctionSyntax.new,
     ConvertToIfCaseStatement.new,
+    ConvertToIfCaseStatementChain.new,
     ConvertToIntLiteral.new,
     ConvertToMapLiteral.new,
     ConvertToMultilineString.new,

pkg/analysis_server/lib/src/services/correction/dart/convert_to_if_case_statement_chain.dart

@@ -0,0 +1,89 @@
+// Copyright (c) 2023, 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:analysis_server/src/services/correction/assist.dart';
+import 'package:analysis_server/src/services/correction/dart/abstract_producer.dart';
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer_plugin/utilities/assist/assist.dart';
+import 'package:analyzer_plugin/utilities/change_builder/change_builder_core.dart';
+import 'package:analyzer_plugin/utilities/change_builder/change_builder_dart.dart';
+import 'package:analyzer_plugin/utilities/range_factory.dart';
+
+class ConvertToIfCaseStatementChain extends CorrectionProducer {
+  @override
+  AssistKind get assistKind =>
+      DartAssistKind.CONVERT_TO_IF_CASE_STATEMENT_CHAIN;
+
+  @override
+  Future<void> compute(ChangeBuilder builder) async {
+    final switchStatement = node;
+    if (switchStatement is! SwitchStatement) {
+      return;
+    }
+
+    final ifIndent = utils.getLinePrefix(switchStatement.offset);
+    final expressionCode = utils.getNodeText(switchStatement.expression);
+
+    final switchPatternCases = <SwitchPatternCase>[];
+    SwitchDefault? defaultCase;
+    for (final member in switchStatement.members) {
+      switch (member) {
+        case SwitchPatternCase():
+          switchPatternCases.add(member);
+        case SwitchDefault():
+          defaultCase = member;
+        default:
+          return;
+      }
+    }
+
+    await builder.addDartFileEdit(file, (builder) {
+      builder.addReplacement(range.node(switchStatement), (builder) {
+        var isFirst = true;
+        for (final case_ in switchPatternCases) {
+          if (isFirst) {
+            isFirst = false;
+          } else {
+            builder.write(' else ');
+          }
+          final patternCode = utils.getNodeText(case_.guardedPattern);
+          builder.writeln('if ($expressionCode case $patternCode) {');
+          _writeStatements(
+            builder: builder,
+            blockIndent: ifIndent,
+            statements: case_.statements,
+          );
+          builder.write('$ifIndent}');
+        }
+        if (defaultCase case final defaultCase?) {
+          builder.writeln(' else {');
+          _writeStatements(
+            builder: builder,
+            blockIndent: ifIndent,
+            statements: defaultCase.statements,
+          );
+          builder.write('$ifIndent}');
+        }
+      });
+    });
+  }
+
+  void _writeStatements({
+    required DartEditBuilder builder,
+    required List<Statement> statements,
+    required String blockIndent,
+  }) {
+    final range = utils.getLinesRangeStatements(statements);
+
+    final firstIndent = utils.getLinePrefix(statements.first.offset);
+    final singleIndent = utils.getIndent(1);
+
+    final code = utils.replaceSourceRangeIndent(
+      range,
+      firstIndent,
+      blockIndent + singleIndent,
+    );
+    builder.write(code);
+  }
+}

pkg/analysis_server/test/src/services/correction/assist/convert_to_if_case_statement_chain_test.dart

@@ -0,0 +1,69 @@
+// Copyright (c) 2023, 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:analysis_server/src/services/correction/assist.dart';
+import 'package:analyzer_plugin/utilities/assist/assist.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import 'assist_processor.dart';
+
+void main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(ConvertToIfCaseStatementChainTest);
+  });
+}
+
+@reflectiveTest
+class ConvertToIfCaseStatementChainTest extends AssistProcessorTest {
+  @override
+  AssistKind get kind => DartAssistKind.CONVERT_TO_IF_CASE_STATEMENT_CHAIN;
+
+  Future<void> test_noDefault() async {
+    await resolveTestCode('''
+void f(Object? x) {
+  switch (x) {
+    case int():
+      0;
+    case double():
+      1;
+  }
+}
+''');
+    await assertHasAssistAt('switch', '''
+void f(Object? x) {
+  if (x case int()) {
+    0;
+  } else if (x case double()) {
+    1;
+  }
+}
+''');
+  }
+
+  Future<void> test_withDefault() async {
+    await resolveTestCode('''
+void f(Object? x) {
+  switch (x) {
+    case int():
+      0;
+    case double():
+      1;
+    default:
+      2;
+  }
+}
+''');
+    await assertHasAssistAt('switch', '''
+void f(Object? x) {
+  if (x case int()) {
+    0;
+  } else if (x case double()) {
+    1;
+  } else {
+    2;
+  }
+}
+''');
+  }
+}

pkg/analysis_server/test/src/services/correction/assist/test_all.dart

@@ -30,6 +30,8 @@ import 'convert_to_double_quoted_string_test.dart'
     as convert_to_double_quoted_string;
 import 'convert_to_field_parameter_test.dart' as convert_to_field_parameter;
 import 'convert_to_for_element_test.dart' as convert_to_for_element;
+import 'convert_to_if_case_statement_chain_test.dart'
+    as convert_to_if_case_statement_chain;
 import 'convert_to_if_case_statement_test.dart' as convert_to_if_case_statement;
 import 'convert_to_if_element_test.dart' as convert_to_if_element;
 import 'convert_to_int_literal_test.dart' as convert_to_int_literal;
@@ -119,6 +121,7 @@ void main() {
     convert_to_double_quoted_string.main();
     convert_to_field_parameter.main();
     convert_to_for_element.main();
+    convert_to_if_case_statement_chain.main();
     convert_to_if_case_statement.main();
     convert_to_if_element.main();
     convert_to_int_literal.main();