mangle now receives a callback to be called when a name should be renamed or not

Author: joaosamouco

lib/esshorten.js

@@ -85,6 +85,8 @@
     const run = (scope, options) => {
         let generator = new NameGenerator(scope, options);
 
+        const shouldRename = options && options.shouldRename || () => true;
+
         if (scope.isStatic()) {
             let name = '9';
 
@@ -116,12 +118,16 @@
 
                 for (let def of variable.identifiers) {
                     // change definition's name
-                    def.name = name;
+                    if (shouldRename(def.name)) {
+                        def.name = name;
+                    }
                 }
 
                 for (let ref of variable.references) {
                     // change reference's name
-                    ref.identifier.name = name;
+                    if (shouldRename(ref.identifier.name)) {
+                        ref.identifier.name = name;
+                    }
                 }
             }
         }

test/mangle.coffee

@@ -161,3 +161,26 @@ describe 'mangle:', ->
                 distinguishFunctionExpressionScope: yes
             expect(result.body[0].expression.id.name).to.equal 'a'
             expect(result.body[0].expression.body.body[0].declarations[0].id.name).to.equal 'a'
+
+    describe '`shouldRename` option:', ->
+        it 'renames by default', ->
+            program = esprima.parse '(function name() { var foo, bar, baz; });'
+            result = esshorten.mangle program
+
+            expect(result.body[0].expression.id.name).to.equal 'a'
+
+        it 'renames if it returns `true`', ->
+            program = esprima.parse '(function name() { var foo, bar, baz; });'
+            result = esshorten.mangle program,
+                shouldRename: (id) ->
+                    return id == 'name'
+
+            expect(result.body[0].expression.id.name).to.equal 'a'
+
+        it 'does not rename if it returns `false`', ->
+            program = esprima.parse '(function name() { var foo, bar, baz; });'
+            result = esshorten.mangle program,
+                shouldRename: (id) ->
+                    return id != 'name'
+
+            expect(result.body[0].expression.id.name).to.equal 'name'