option to exclude certain names from mangling

bin/uglifyjs2

@@ -19,6 +19,7 @@ For example -p 3 will drop 3 directories from file names and ensure they are rel
     .describe("o", "Output file (default STDOUT).")
     .describe("b", "Beautify output/specify output options.")
     .describe("m", "Mangle names/pass mangler options.")
+    .describe("r", "Reserved names to exclude from mangling.")
     .describe("c", "Enable compressor/pass compressor options. \
 Pass options like -c hoist_vars=false,if_return=false. \
 Use -c with no argument if you want to disable the squeezer entirely.")
@@ -34,6 +35,7 @@ Use -c with no argument if you want to disable the squeezer entirely.")
     .alias("m", "mangle")
     .alias("c", "compress")
     .alias("d", "define")
+    .alias("r", "reserved-names")
 
     .string("b")
     .string("m")
@@ -83,6 +85,10 @@ if (COMPRESS && ARGS.d) {
     COMPRESS.global_defs = getOptions("d");
 }
 
+if (MANGLE && ARGS.r) {
+    MANGLE.except = ARGS.r.replace(/^\s+|\s+$/g).split(/\s*,+\s*/);
+}
+
 var OUTPUT_OPTIONS = {
     beautify: BEAUTIFY ? true : false
 };

lib/scope.js

@@ -354,7 +354,8 @@ AST_LoopControl.DEFMETHOD("target", function(){
 
 AST_Toplevel.DEFMETHOD("mangle_names", function(options){
     options = defaults(options, {
-        sort: false
+        sort   : false,
+        except : []
     });
     // We only need to mangle declaration nodes.  Special logic wired
     // into the code generator will display the mangled name if it's
@@ -376,8 +377,11 @@ AST_Toplevel.DEFMETHOD("mangle_names", function(options){
             var a = node.variables;
             for (var i in a) if (HOP(a, i)) {
                 var symbol = a[i];
-                if (!(is_setget && symbol instanceof AST_SymbolLambda))
-                    to_mangle.push(symbol);
+                if (!(is_setget && symbol instanceof AST_SymbolLambda)) {
+                    if (options.except.indexOf(symbol.name) < 0) {
+                        to_mangle.push(symbol);
+                    }
+                }
             }
             return;
         }
@@ -385,7 +389,7 @@ AST_Toplevel.DEFMETHOD("mangle_names", function(options){
             var name;
             do name = base54(++lname); while (!is_identifier(name));
             node.mangled_name = name;
-            return;
+            return true;
         }
     });
     this.walk(tw);