Merge pull request microsoft#3183 from Microsoft/marshalling_issue

perf: during file update request only changed portion of the text from the …

Author: vladima

src/services/services.ts

@@ -1829,7 +1829,34 @@ module ts {
  if (version !== sourceFile.version) {
  // Once incremental parsing is ready, then just call into this function.
  if (!disableIncrementalParsing) {
- let newSourceFile = updateSourceFile(sourceFile, scriptSnapshot.getText(0, scriptSnapshot.getLength()), textChangeRange, aggressiveChecks);
+ let newText: string;
+ 
+ // grab the fragment from the beginning of the original text to the beginning of the span
+ let prefix = textChangeRange.span.start !== 0
+ ? sourceFile.text.substr(0, textChangeRange.span.start)
+ : "";
+ 
+ // grab the fragment from the end of the span till the end of the original text
+ let suffix = textSpanEnd(textChangeRange.span) !== sourceFile.text.length
+ ? sourceFile.text.substr(textSpanEnd(textChangeRange.span))
+ : "";
+
+ if (textChangeRange.newLength === 0) {
+ // edit was a deletion - just combine prefix and suffix
+ newText = prefix && suffix ? prefix + suffix : prefix || suffix;
+ }
+ else {
+ // it was actual edit, fetch the fragment of new text that correspond to new span
+ let changedText = scriptSnapshot.getText(textChangeRange.span.start, textChangeRange.span.start + textChangeRange.newLength);
+ // combine prefix, changed text and suffix
+ newText = prefix && suffix 
+ ? prefix + changedText + suffix
+ : prefix
+ ? (prefix + changedText) 
+ : (changedText + suffix);
+ }
+
+ let newSourceFile = updateSourceFile(sourceFile, newText, textChangeRange, aggressiveChecks);
  setSourceFileFields(newSourceFile, scriptSnapshot, version);
  // after incremental parsing nameTable might not be up-to-date
  // drop it so it can be lazily recreated later