fix for UNUSED_LOCAL_VARIABLE

see: https://github.com/dart-lang/sdk/issues/38361

Change-Id: I5329067d6f132393efd9194886713c30e1dafbfc
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/117205
Commit-Queue: Phil Quitslund <pquitslund@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

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

@@ -323,6 +323,8 @@ class DartFixKind {
       appliedTogetherMessage: "Remove all unused imports in this file");
   static const REMOVE_UNUSED_LABEL =
       const FixKind('REMOVE_UNUSED_LABEL', 50, "Remove unused label");
+  static const REMOVE_UNUSED_LOCAL_VARIABLE = const FixKind(
+      'REMOVE_UNUSED_LOCAL_VARIABLE', 50, "Remove unused local variable");
   static const RENAME_TO_CAMEL_CASE =
       const FixKind('RENAME_TO_CAMEL_CASE', 50, "Rename to '{0}'");
   static const REPLACE_BOOLEAN_WITH_BOOL = const FixKind(

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

@@ -376,11 +376,9 @@ class FixProcessor extends BaseProcessor {
     if (errorCode == HintCode.UNUSED_LABEL) {
       await _addFix_removeUnusedLabel();
     }
-    // TODO(brianwilkerson) Add a fix to remove the local variable, either with
-    //  or without the initialization code.
-//    if (errorCode == HintCode.UNUSED_LOCAL_VARIABLE) {
-//      await _addFix_removeUnusedLocalVariable();
-//    }
+    if (errorCode == HintCode.UNUSED_LOCAL_VARIABLE) {
+      await _addFix_removeUnusedLocalVariable();
+    }
     if (errorCode == HintCode.UNUSED_SHOWN_NAME) {
       await _addFix_removeNameFromCombinator();
     }
@@ -3536,6 +3534,50 @@ class FixProcessor extends BaseProcessor {
     }
   }
 
+  Future<void> _addFix_removeUnusedLocalVariable() async {
+    final declaration = node.parent;
+    if (!(declaration is VariableDeclaration && declaration.name == node)) {
+      return;
+    }
+
+    Element element = (declaration as VariableDeclaration).declaredElement;
+    if (element is LocalElement) {
+      final functionBody = declaration.thisOrAncestorOfType<FunctionBody>();
+      final references = findLocalElementReferences(functionBody, element);
+      final changeBuilder = _newDartChangeBuilder();
+      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
+        for (var reference in references) {
+          final node = reference.thisOrAncestorMatching((node) =>
+              node is VariableDeclaration || node is AssignmentExpression);
+          var sourceRange;
+          if (node is VariableDeclaration) {
+            VariableDeclarationList parent = node.parent;
+            if (parent.variables.length == 1) {
+              sourceRange = range.node(parent.parent);
+            } else {
+              sourceRange =
+                  range.endEnd(node.beginToken.previous, node.endToken.next);
+            }
+          } else if (node is AssignmentExpression) {
+            // todo (pq): consider node.parent is! ExpressionStatement to handle
+            // assignments in parens, etc.
+            if (node.parent is ArgumentList) {
+              sourceRange =
+                  range.endStart(node.beginToken.previous, node.operator.next);
+            } else {
+              sourceRange = range.node(node.parent);
+            }
+          } else {
+            return;
+          }
+          builder.addDeletion(utils.getLinesRange(sourceRange));
+        }
+      });
+      _addFixFromBuilder(
+          changeBuilder, DartFixKind.REMOVE_UNUSED_LOCAL_VARIABLE);
+    }
+  }
+
   Future<void> _addFix_renameToCamelCase() async {
     if (node is! SimpleIdentifier) {
       return;

pkg/analysis_server/test/edit/fixes_test.dart

@@ -37,6 +37,7 @@ class FixesTest extends AbstractAnalysisTest {
     addTestFile('''
 main() {
   Completer<String> x = null;
+  print(x);
 }
 ''');
     await waitForTasksFinished();

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

@@ -0,0 +1,82 @@
+// 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:analyzer/src/error/codes.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(RemoveUnusedLocalVariableTest);
+  });
+}
+
+@reflectiveTest
+class RemoveUnusedLocalVariableTest extends FixProcessorTest {
+  @override
+  FixKind get kind => DartFixKind.REMOVE_UNUSED_LOCAL_VARIABLE;
+
+  test_inArgumentList() async {
+    await resolveTestUnit(r'''
+main() {
+  var v = 1;
+  print(v = 2);
+}
+''');
+    await assertHasFix(r'''
+main() {
+  print(2);
+}
+''');
+  }
+
+  test_inDeclarationList() async {
+    await resolveTestUnit(r'''
+main() {
+  var v = 1, v2 = 3;
+  v = 2;
+  print(v2);
+}
+''');
+    await assertHasFix(r'''
+main() {
+  var v2 = 3;
+  print(v2);
+}
+''');
+  }
+
+  test_withReferences() async {
+    await resolveTestUnit(r'''
+main() {
+  var v = 1;
+  v = 2;
+}
+''');
+    await assertHasFix(r'''
+main() {
+}
+''');
+  }
+
+  test_withReferences_beforeDeclaration() async {
+    // CompileTimeErrorCode.REFERENCED_BEFORE_DECLARATION
+    verifyNoTestUnitErrors = false;
+    await resolveTestUnit(r'''
+main() {
+  v = 2;
+  var v = 1;
+}
+''');
+    await assertHasFix(r'''
+main() {
+}
+''',
+        errorFilter: (e) =>
+            e.errorCode != CompileTimeErrorCode.REFERENCED_BEFORE_DECLARATION);
+  }
+}

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

@@ -104,6 +104,7 @@ import 'remove_unused_catch_clause_test.dart' as remove_unused_catch_clause;
 import 'remove_unused_catch_stack_test.dart' as remove_unused_catch_stack;
 import 'remove_unused_import_test.dart' as remove_unused_import;
 import 'remove_unused_label_test.dart' as remove_unused_label;
+import 'remove_unused_local_variable_test.dart' as remove_unused_local_variable;
 import 'rename_to_camel_case_test.dart' as rename_to_camel_case;
 import 'replace_boolean_with_bool_test.dart' as replace_boolean_with_bool;
 import 'replace_colon_with_equals_test.dart' as replace_colon_with_equals;
@@ -221,6 +222,7 @@ main() {
     remove_unused_catch_stack.main();
     remove_unused_import.main();
     remove_unused_label.main();
+    remove_unused_local_variable.main();
     rename_to_camel_case.main();
     replace_boolean_with_bool.main();
     replace_colon_with_equals.main();