Formatter selection preservation support.

pkg/analyzer_experimental/lib/src/services/formatter_impl.dart

 // Copyright (c) 2013, 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 formatter_impl;
 
 import 'dart:math';
 
 import 'package:analyzer_experimental/analyzer.dart';
 import 'package:analyzer_experimental/src/generated/parser.dart';
@@ skipping 75 matching lines @@
 /// Source selection state information.
 class Selection {
   
   /// The offset of the source selection.
   final int offset;
   
   /// The length of the selection.
   final int length;
   
   Selection(this.offset, this.length);
+  
+  String toString() => 'Selection (offset: $offset, length: $length)';
 }
 
 /// Formatted source.
 class FormattedSource {
   
   /// Selection state or null if unspecified.
   final Selection selection;
   
   /// Formatted source string.
   final String source;
@@ skipping 15 matching lines @@
 
   FormattedSource format(CodeKind kind, String source, {int offset, int end,
       int indentationLevel: 0, Selection selection: null}) {
 
     var startToken = tokenize(source);
     checkForErrors();
 
     var node = parse(kind, startToken);
     checkForErrors();
 
-    var formatter = new SourceVisitor(options, lineInfo);
+    var formatter = new SourceVisitor(options, lineInfo, selection);
     node.accept(formatter);
 
     var formattedSource = formatter.writer.toString();
     
     checkTokenStreams(startToken, tokenize(formattedSource));
 
-    return new FormattedSource(formattedSource);
+    return new FormattedSource(formattedSource, formatter.selection);
   }
 
   checkTokenStreams(Token t1, Token t2) =>
       new TokenStreamComparator(lineInfo, t1, t2).verifyEquals();
 
   ASTNode parse(CodeKind kind, Token start) {
 
     var parser = new Parser(null, this);
 
     switch (kind) {
@@ skipping 153 matching lines @@
   LineInfo lineInfo;
 
   /// Cached previous token for calculating preceding whitespace.
   Token previousToken;
 
   /// A flag to indicate that a newline should be emitted before the next token.
   bool needsNewline = false;
 
   /// Used for matching EOL comments
   final twoSlashes = new RegExp(r'//[^/]');
+  
+  /// Original pre-format selection information (may be null).
+  final Selection preSelection;
+  
+  /// Post format selection information.
+  Selection selection;
 
   /// Initialize a newly created visitor to write source code representing
   /// the visited nodes to the given [writer].
-  SourceVisitor(FormatterOptions options, this.lineInfo) :
+  SourceVisitor(FormatterOptions options, this.lineInfo, this.preSelection) :
       writer = new SourceWriter(indentCount: options.initialIndentationLevel,
                                 lineSeparator: options.lineSeparator);
 
   visitAdjacentStrings(AdjacentStrings node) {
     visitNodes(node.strings, separatedBy: space);
   }
 
   visitAnnotation(Annotation node) {
     token(node.atSign);
     visit(node.name);
@@ skipping 876 matching lines @@
       if (needsNewline) {
         minNewlines = max(1, minNewlines);
       }
       var emitted = emitPrecedingCommentsAndNewlines(token, min: minNewlines);
       if (emitted > 0) {
         needsNewline = false;
       }
       if (precededBy != null) {
         precededBy();
       }
+      checkForSelectionUpdate(token);
       append(token.lexeme);
       if (followedBy != null) {
         followedBy();
       }
       previousToken = token;
     }
   }
+  
+  checkForSelectionUpdate(Token token) {
+    // Cache the first token on or AFTER the selection offset
+    if (preSelection != null && selection == null) {
+      // Check for overshots
+      var overshot = token.offset - preSelection.offset;
+      if (overshot >= 0) {
+        //TODO(pquitslund): update length (may need truncating)
+        selection = new Selection(writer.toString().length - overshot, 
+            preSelection.length);
+      }
+    }
+  }
 
   commaSeperator() {
     comma();
     space();
   }
 
   comma() {
     append(',');
   }
 
@@ skipping 156 matching lines @@
     var lastLine =
         lineInfo.getLocation(lastOffset).lineNumber;
     var currentLine =
         lineInfo.getLocation(currentOffset).lineNumber;
     return currentLine - lastLine;
   }
 
   String toString() => writer.toString();
 
 }