Issue 21233. Improve inlining strings into string interpolations.

pkg/analysis_server/lib/src/services/refactoring/inline_local.dart

 // Copyright (c) 2014, 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.
 
 library services.src.refactoring.inline_local;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/protocol_server.dart' hide Element;
+import 'package:analysis_server/src/services/correction/source_range.dart';
 import 'package:analysis_server/src/services/correction/status.dart';
 import 'package:analysis_server/src/services/correction/util.dart';
 import 'package:analysis_server/src/services/refactoring/refactoring.dart';
 import 'package:analysis_server/src/services/refactoring/refactoring_internal.dart';
 import 'package:analysis_server/src/services/search/search_engine.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/java_core.dart';
 import 'package:analyzer/src/generated/scanner.dart';
 import 'package:analyzer/src/generated/source.dart';
@@ skipping 108 matching lines @@
       Statement declarationStatement =
           _variableNode.getAncestor((node) => node is VariableDeclarationStatement);
       SourceRange range = utils.getLinesRangeStatements([declarationStatement]);
       doSourceChange_addElementEdit(
           change,
           unitElement,
           newSourceEdit_range(range, ''));
     }
     // prepare initializer
     Expression initializer = _variableNode.initializer;
-    String initializerSource = utils.getNodeText(initializer);
+    String initializerCode = utils.getNodeText(initializer);
     int initializerPrecedence = getExpressionPrecedence(initializer);
     // replace references
     for (SearchMatch reference in _references) {
       SourceRange range = reference.sourceRange;
-      String sourceForReference =
-          _getSourceForReference(range, initializerSource, initializerPrecedence);
+      // prepare context
+      int offset = range.offset;
+      AstNode node = utils.findNode(offset);
+      AstNode parent = node.parent;
+      // prepare code
+      String codeForReference;
+      if (parent is InterpolationExpression) {
+        StringInterpolation target = parent.parent;
+        if (initializer is SingleStringLiteral &&
+            !initializer.isRaw &&
+            initializer.isSingleQuoted == target.isSingleQuoted &&
+            (!initializer.isMultiline || target.isMultiline)) {
+          range = rangeNode(parent);
+          // unwrap the literal being inlined
+          int initOffset = initializer.contentsOffset;
+          int initLength = initializer.contentsEnd - initOffset;
+          codeForReference = utils.getText(initOffset, initLength);
+          // drop leading multiline EOL
+          if (initializer.isMultiline) {
+            if (codeForReference.startsWith('\n')) {
+              codeForReference = codeForReference.substring(1);
+            } else if (codeForReference.startsWith('\r\n')) {
+              codeForReference = codeForReference.substring(2);
+            }
+          }
+        } else if (_shouldBeExpressionInterpolation(parent, initializer)) {
+          codeForReference = '{$initializerCode}';
+        } else {
+          codeForReference = initializerCode;
+        }
+      } else if (initializerPrecedence < getExpressionParentPrecedence(node)) {
+        codeForReference = '($initializerCode)';
+      } else {
+        codeForReference = initializerCode;
+      }
+      // do replace
       doSourceChange_addElementEdit(
           change,
           unitElement,
-          newSourceEdit_range(range, sourceForReference));
+          newSourceEdit_range(range, codeForReference));
     }
     // done
     return new Future.value(change);
   }
 
   @override
   bool requiresPreview() => false;
 
-  /**
-   * Returns the source which should be used to replace the reference with the
-   * given [SourceRange].
-   *
-   * [range] - the [SourceRange] of the reference.
-   * [source] - the source of the initializer, to be inserted at [range].
-   * [precedence] - the precedence of the initializer [source].
-   */
-  String _getSourceForReference(SourceRange range, String source,
-      int precedence) {
-    int offset = range.offset;
-    AstNode node = utils.findNode(offset);
-    AstNode parent = node.parent;
-    if (_isIdentifierStringInterpolation(parent)) {
-      return '{${source}}';
-    }
-    if (precedence < getExpressionParentPrecedence(node)) {
-      return '(${source})';
-    }
-    return source;
-  }
-
-  /**
-   * Checks if the given node is a string interpolation in form `$name`.
-   */
-  bool _isIdentifierStringInterpolation(AstNode parent) {
-    if (parent is InterpolationExpression) {
-      InterpolationExpression element = parent;
-      return element.beginToken.type ==
-          TokenType.STRING_INTERPOLATION_IDENTIFIER;
-    }
-    return false;
+  static bool _shouldBeExpressionInterpolation(InterpolationExpression target,
+      Expression expression) {
+    TokenType targetType = target.beginToken.type;
+    return targetType == TokenType.STRING_INTERPOLATION_IDENTIFIER &&
+        expression is! SimpleIdentifier;
   }
 }