dart2js: In minified mode shorter getter and setter names.

sdk/lib/_internal/compiler/implementation/js_backend/minify_namer.dart

 // Copyright (c) 2011, 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.
 
 part of js_backend;
 
 /**
  * Assigns JavaScript identifiers to Dart variables, class-names and members.
  */
 class MinifyNamer extends Namer {
   MinifyNamer(Compiler compiler) : super(compiler) {
     reserveBackendNames();
   }
 
   String get isolateName => 'I';
   String get isolatePropertiesName => 'p';
   bool get shouldMinify => true;
 
+  final String getterPrefix = 'g';
+  final String setterPrefix = 's';
+
   const ALPHABET_CHARACTERS = 52;  // a-zA-Z.
   const ALPHANUMERIC_CHARACTERS = 62;  // a-zA-Z0-9.
 
   // You can pass an invalid identifier to this and unlike its non-minifying
   // counterpart it will never return the proposedName as the new fresh name.
   String getFreshName(String proposedName,
                       Set<String> usedNames,
                       Map<String, String> suggestedNames,
                       {bool ensureSafe: true}) {
     var freshName;
@@ skipping 33 matching lines @@
         'Blob', 'blue', 'blur', 'BLUR', 'body', 'BOOL', 'BOTH', 'btoa', 'BYTE',
         'cite', 'clip', 'code', 'cols', 'cues', 'data', 'DECR', 'DONE', 'face',
         'file', 'File', 'fill', 'find', 'font', 'form', 'gain', 'hash', 'head',
         'high', 'hint', 'host', 'href', 'HRTF', 'IDLE', 'INCR', 'info', 'INIT',
         'isId', 'item', 'KEEP', 'kind', 'knee', 'lang', 'left', 'LESS', 'line',
         'link', 'list', 'load', 'loop', 'mode', 'name', 'Node', 'None', 'NONE',
         'only', 'open', 'OPEN', 'ping', 'play', 'port', 'rect', 'Rect', 'refX',
         'refY', 'RGBA', 'root', 'rows', 'save', 'seed', 'seek', 'self', 'send',
         'show', 'SINE', 'size', 'span', 'stat', 'step', 'stop', 'tags', 'text',
         'Text', 'time', 'type', 'view', 'warn', 'wrap', 'ZERO'];
+
     for (var name in reservedNativeProperties) {
       if (name.length < 2) {
         instanceNameMap[name] = name;
       }
       usedInstanceNames.add(name);
+      // Getter and setter names are autogenerated by prepending 'g' and 's' to
+      // field names.  Therefore there are some field names we don't want to
+      // use.
+      if (name.startsWith('g')) usedInstanceNames.add(name.substring(1));

[karlklose, 2013/02/12 14:41:19]

Can you use _hasBannedPrefix here?

[erikcorry, 2013/02/12 14:50:40]

Yes, but the substring(1) still retains implicit knowledge about what the prefix
is (or rather, its length).

+      if (name.startsWith('s')) usedInstanceNames.add(name.substring(1));
     }
 
     // This list of popular instance variable names generated with:
     // cat out.js |
     // perl -ne '$_=~s/(?<![^a-z0-9_\$]\$)\.([a-z0-9_\$]+)/print("$1\n")/gei' |
     // sort | uniq -c | sort -nr | head -40
     // Removed: html, call*, hasOwnProperty.
     _populateSuggestedNames(
         suggestedInstanceNames,
         usedInstanceNames,
@@ skipping 58 matching lines @@
     for (var n = 2; n <= 3; n++) {
       int h = hash;
       while (h > 10) {
         var codes = <int>[_letterNumber(h)];
         int h2 = h ~/ ALPHABET_CHARACTERS;
         for (var i = 1; i < n; i++) {
           codes.add(_alphaNumericNumber(h2));
           h2 ~/= ALPHANUMERIC_CHARACTERS;
         }
         final candidate = new String.fromCharCodes(codes);
-        if (!usedNames.contains(candidate) && !jsReserved.contains(candidate)) {
+        if (!usedNames.contains(candidate) &&
+            !jsReserved.contains(candidate) &&
+            !_hasBannedPrefix(candidate)) {
           return candidate;
         }
         // Try again with a slightly different hash.  After around 10 turns
         // around this loop h is zero and we try a longer name.
         h ~/= 7;
       }
     }
 
     // If we can't find a hash based name in the three-letter space, then base
     // the name on a letter and a counter.
     var startLetter = new String.fromCharCodes([_letterNumber(hash)]);
     var i = 0;
     while (usedNames.contains("$startLetter$i")) {
       i++;
     }
+    // We don't need to check for banned prefix because the name is in the form
+    // xnnn, where nnn is a number.  There can be no getter or setter called
+    // gnnn since that would imply a numeric field name.
     return "$startLetter$i";
   }
 
+  // Instance members starting with g and s are reserved for getters and

[karlklose, 2013/02/12 14:41:19]

Use /// to turn comment into dart doc.

[erikcorry, 2013/02/12 14:50:40]

Done.

+  // setters.
+  bool _hasBannedPrefix(String name) {
+    int code = name.codeUnitAt(0);
+    if (code == $g || code == $s) return true;

[karlklose, 2013/02/12 14:41:19]

'return (code == $g || code == $s)'?

[erikcorry, 2013/02/12 14:50:40]

Done.

+    return false;
+  }
+
   int _calculateHash(String name) {
     int h = 0;
     for (int i = 0; i < name.length; i++) {
       h += name.charCodeAt(i);
       h &= 0xffffffff;
       h += h << 10;
       h &= 0xffffffff;
       h ^= h >> 6;
       h &= 0xffffffff;
     }
     return h;
   }
 
   int _letterNumber(int x) {
     if (x >= ALPHABET_CHARACTERS) x %= ALPHABET_CHARACTERS;
     if (x < 26) return $a + x;
     return $A + x - 26;
   }
 
   int _alphaNumericNumber(int x) {
     if (x >= ALPHANUMERIC_CHARACTERS) x %= ALPHANUMERIC_CHARACTERS;
     if (x < 26) return $a + x;
     if (x < 52) return $A + x - 26;
     return $0 + x - 52;
   }
 
 }