fix for prefer_expression_bodies

Change-Id: Ie1a76db4450f1b2447e8988e84f758d623810264
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/116360
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Phil Quitslund <pquitslund@google.com>

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

@@ -50,9 +50,7 @@ class DartAssistKind {
   static const CONVERT_INTO_BLOCK_BODY = const AssistKind(
       'dart.assist.convert.bodyToBlock', 30, "Convert to block body");
   static const CONVERT_INTO_EXPRESSION_BODY = const AssistKind(
-      'dart.assist.convert.bodyToExpression', 30, "Convert to expression body",
-      // todo (pq): migrate to (conditional) fix
-      associatedErrorCodes: <String>['prefer_expression_function_bodies']);
+      'dart.assist.convert.bodyToExpression', 30, "Convert to expression body");
   static const CONVERT_INTO_FINAL_FIELD = const AssistKind(
       'dart.assist.convert.getterToFinalField', 30, "Convert to final field",
       // todo (pq): migrate to (conditional) fix

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

@@ -78,7 +78,11 @@ class AssistProcessor extends BaseProcessor {
     await _addProposal_convertToAsyncFunctionBody();
     await _addProposal_convertToBlockFunctionBody();
     await _addProposal_convertToDoubleQuotedString();
-    await _addProposal_convertToExpressionFunctionBody();
+    if (!_containsErrorCode(
+      {LintNames.prefer_expression_function_bodies},
+    )) {
+      await _addProposal_convertToExpressionFunctionBody();
+    }
     await _addProposal_convertToFieldParameter();
     await _addProposal_convertToForIndexLoop();
     await _addProposal_convertToGenericFunctionSyntax();
@@ -175,39 +179,6 @@ class AssistProcessor extends BaseProcessor {
     return assists;
   }
 
-  FunctionBody getEnclosingFunctionBody() {
-    // TODO(brianwilkerson) Determine whether there is a reason why this method
-    // isn't just "return node.getAncestor((node) => node is FunctionBody);"
-    {
-      FunctionExpression function =
-          node.thisOrAncestorOfType<FunctionExpression>();
-      if (function != null) {
-        return function.body;
-      }
-    }
-    {
-      FunctionDeclaration function =
-          node.thisOrAncestorOfType<FunctionDeclaration>();
-      if (function != null) {
-        return function.functionExpression.body;
-      }
-    }
-    {
-      ConstructorDeclaration constructor =
-          node.thisOrAncestorOfType<ConstructorDeclaration>();
-      if (constructor != null) {
-        return constructor.body;
-      }
-    }
-    {
-      MethodDeclaration method = node.thisOrAncestorOfType<MethodDeclaration>();
-      if (method != null) {
-        return method.body;
-      }
-    }
-    return null;
-  }
-
   void _addAssistFromBuilder(DartChangeBuilder builder, AssistKind kind,
       {List args = null}) {
     if (builder == null) {
@@ -894,52 +865,7 @@ class AssistProcessor extends BaseProcessor {
   }
 
   Future<void> _addProposal_convertToExpressionFunctionBody() async {
-    // prepare current body
-    FunctionBody body = getEnclosingFunctionBody();
-    if (body is! BlockFunctionBody || body.isGenerator) {
-      _coverageMarker();
-      return;
-    }
-    // prepare return statement
-    List<Statement> statements = (body as BlockFunctionBody).block.statements;
-    if (statements.length != 1) {
-      _coverageMarker();
-      return;
-    }
-    Statement onlyStatement = statements.first;
-    // prepare returned expression
-    Expression returnExpression;
-    if (onlyStatement is ReturnStatement) {
-      returnExpression = onlyStatement.expression;
-    } else if (onlyStatement is ExpressionStatement) {
-      returnExpression = onlyStatement.expression;
-    }
-    if (returnExpression == null) {
-      _coverageMarker();
-      return;
-    }
-
-    // Return expressions can be quite large, e.g. Flutter build() methods.
-    // It is surprising to see this Quick Assist deep in the function body.
-    if (selectionOffset >= returnExpression.offset) {
-      _coverageMarker();
-      return;
-    }
-
-    var changeBuilder = _newDartChangeBuilder();
-    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
-      builder.addReplacement(range.node(body), (DartEditBuilder builder) {
-        if (body.isAsynchronous) {
-          builder.write('async ');
-        }
-        builder.write('=> ');
-        builder.write(_getNodeText(returnExpression));
-        if (body.parent is! FunctionExpression ||
-            body.parent.parent is FunctionDeclaration) {
-          builder.write(';');
-        }
-      });
-    });
+    final changeBuilder = await createBuilder_convertToExpressionFunctionBody();
     _addAssistFromBuilder(
         changeBuilder, DartAssistKind.CONVERT_INTO_EXPRESSION_BODY);
   }

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

@@ -155,6 +155,93 @@ abstract class BaseProcessor {
     return validChange ? changeBuilder : null;
   }
 
+  Future<ChangeBuilder> createBuilder_convertToExpressionFunctionBody() async {
+    // prepare current body
+    FunctionBody body = getEnclosingFunctionBody();
+    if (body is! BlockFunctionBody || body.isGenerator) {
+      _coverageMarker();
+      return null;
+    }
+    // prepare return statement
+    List<Statement> statements = (body as BlockFunctionBody).block.statements;
+    if (statements.length != 1) {
+      _coverageMarker();
+      return null;
+    }
+    Statement onlyStatement = statements.first;
+    // prepare returned expression
+    Expression returnExpression;
+    if (onlyStatement is ReturnStatement) {
+      returnExpression = onlyStatement.expression;
+    } else if (onlyStatement is ExpressionStatement) {
+      returnExpression = onlyStatement.expression;
+    }
+    if (returnExpression == null) {
+      _coverageMarker();
+      return null;
+    }
+
+    // Return expressions can be quite large, e.g. Flutter build() methods.
+    // It is surprising to see this Quick Assist deep in the function body.
+    if (selectionOffset >= returnExpression.offset) {
+      _coverageMarker();
+      return null;
+    }
+
+    var changeBuilder = _newDartChangeBuilder();
+    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
+      builder.addReplacement(range.node(body), (DartEditBuilder builder) {
+        if (body.isAsynchronous) {
+          builder.write('async ');
+        }
+        builder.write('=> ');
+        builder.write(_getNodeText(returnExpression));
+        if (body.parent is! FunctionExpression ||
+            body.parent.parent is FunctionDeclaration) {
+          builder.write(';');
+        }
+      });
+    });
+    return changeBuilder;
+  }
+
+  /// Returns the text of the given node in the unit.
+  String /* TODO (pq): make visible */ _getNodeText(AstNode node) =>
+      utils.getNodeText(node);
+
+  FunctionBody getEnclosingFunctionBody() {
+    // TODO(brianwilkerson) Determine whether there is a reason why this method
+    // isn't just "return node.getAncestor((node) => node is FunctionBody);"
+    {
+      FunctionExpression function =
+          node.thisOrAncestorOfType<FunctionExpression>();
+      if (function != null) {
+        return function.body;
+      }
+    }
+    {
+      FunctionDeclaration function =
+          node.thisOrAncestorOfType<FunctionDeclaration>();
+      if (function != null) {
+        return function.functionExpression.body;
+      }
+    }
+    {
+      ConstructorDeclaration constructor =
+          node.thisOrAncestorOfType<ConstructorDeclaration>();
+      if (constructor != null) {
+        return constructor.body;
+      }
+    }
+    {
+      MethodDeclaration method = node.thisOrAncestorOfType<MethodDeclaration>();
+      if (method != null) {
+        return method.body;
+      }
+    }
+    return null;
+  }
+
   Future<ChangeBuilder>
       createBuilder_addTypeAnnotation_VariableDeclaration() async {
     AstNode node = this.node;

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

@@ -185,6 +185,8 @@ class DartFixKind {
       const FixKind('CONVERT_FLUTTER_CHILD', 50, "Convert to children:");
   static const CONVERT_FLUTTER_CHILDREN =
       const FixKind('CONVERT_FLUTTER_CHILDREN', 50, "Convert to child:");
+  static const CONVERT_INTO_EXPRESSION_BODY = const FixKind(
+      'CONVERT_INTO_EXPRESSION_BODY', 50, "Convert to expression body");
   static const CONVERT_TO_FOR_ELEMENT =
       const FixKind('CONVERT_TO_FOR_ELEMENT', 50, "Convert to a 'for' element");
   static const CONVERT_TO_IF_ELEMENT =

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

@@ -621,6 +621,9 @@ class FixProcessor extends BaseProcessor {
       if (errorCode.name == LintNames.prefer_const_declarations) {
         await _addFix_replaceFinalWithConst();
       }
+      if (errorCode.name == LintNames.prefer_expression_function_bodies) {
+        await _addFix_convertToExpressionBody();
+      }
       if (errorCode.name == LintNames.prefer_for_elements_to_map_fromIterable) {
         await _addFix_convertMapFromIterableToForLiteral();
       }
@@ -1357,6 +1360,11 @@ class FixProcessor extends BaseProcessor {
     _addFixFromBuilder(changeBuilder, DartFixKind.CONVERT_TO_FOR_ELEMENT);
   }
 
+  Future<void> _addFix_convertToExpressionBody() async {
+    final changeBuilder = await createBuilder_convertToExpressionFunctionBody();
+    _addFixFromBuilder(changeBuilder, DartFixKind.CONVERT_INTO_EXPRESSION_BODY);
+  }
+
   Future<void> _addFix_convertToIntLiteral() async {
     final changeBuilder = await createBuilder_convertToIntLiteral();
     _addFixFromBuilder(changeBuilder, DartFixKind.CONVERT_TO_INT_LITERAL);

pkg/analysis_server/lib/src/services/linter/lint_names.dart

@@ -33,6 +33,8 @@ class LintNames {
   static const String prefer_const_declarations = 'prefer_const_declarations';
   static const String prefer_equal_for_default_values =
       'prefer_equal_for_default_values';
+  static const String prefer_expression_function_bodies =
+      'prefer_expression_function_bodies';
   static const String prefer_final_fields = 'prefer_final_fields';
   static const String prefer_final_locals = 'prefer_final_locals';
   static const String prefer_for_elements_to_map_fromIterable =

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

@@ -3,6 +3,7 @@
 // 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/linter/lint_names.dart';
 import 'package:analyzer_plugin/utilities/assist/assist.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
@@ -41,6 +42,20 @@ class A {
 ''');
   }
 
+  test_async_noAssistWithLint() async {
+    createAnalysisOptionsFile(
+        lints: [LintNames.prefer_expression_function_bodies]);
+    verifyNoTestUnitErrors = false;
+    await resolveTestUnit('''
+class A {
+  mmm() async {
+    return 42;
+  }
+}
+''');
+    await assertNoAssist();
+  }
+
   test_closure() async {
     await resolveTestUnit('''
 setup(x) {}

pkg/analysis_server/test/src/services/correction/fix/convert_into_expression_body_test.dart

@@ -0,0 +1,41 @@
+// Copyright (c) 2019, 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/fix.dart';
+import 'package:analysis_server/src/services/linter/lint_names.dart';
+import 'package:analyzer_plugin/utilities/fixes/fixes.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import 'fix_processor.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(ConvertIntoExpressionBodyTest);
+  });
+}
+
+@reflectiveTest
+class ConvertIntoExpressionBodyTest extends FixProcessorLintTest {
+  @override
+  FixKind get kind => DartFixKind.CONVERT_INTO_EXPRESSION_BODY;
+
+  @override
+  String get lintCode => LintNames.prefer_expression_function_bodies;
+
+  /// More coverage in the `convert_into_expression_body_test.dart` assist test.
+  test_async() async {
+    await resolveTestUnit('''
+class A {
+  mmm() async { 
+    return 42; /*LINT*/
+  }
+}
+''');
+    await assertHasFix('''
+class A {
+  mmm() async => 42;
+}
+''');
+  }
+}

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

@@ -37,6 +37,7 @@ import 'convert_documentation_into_line_test.dart'
     as convert_documentation_into_line;
 import 'convert_flutter_child_test.dart' as convert_flutter_child;
 import 'convert_flutter_children_test.dart' as convert_flutter_children;
+import 'convert_into_expression_body_test.dart' as convert_into_expression_body;
 import 'convert_to_for_element_test.dart' as convert_to_for_element;
 import 'convert_to_if_element_test.dart' as convert_to_if_element;
 import 'convert_to_int_literal_test.dart' as convert_to_int_literal;
@@ -148,6 +149,7 @@ main() {
     convert_documentation_into_line.main();
     convert_flutter_child.main();
     convert_flutter_children.main();
+    convert_into_expression_body.main();
     convert_to_for_element.main();
     convert_to_if_element.main();
     convert_to_int_literal.main();