Add property name mangler

We only touch properties that are present in an object literal, or which are
assigned to.  Example:

    x = { foo: 1 };
    x.bar = 2;
    x["baz"] = 3;
    x[cond ? "qwe" : "asd"] = 4;
    console.log(x.stuff);

The names "foo", "bar", "baz", "qwe" and "asd" will be mangled, and the
resulting mangled names will be used for the same properties throughout the
code.  The "stuff" will not be, since it's just referenced but never
assigned to.

This *will* break most of the code out there, but could work on carefully
written code: do not use eval, do not define methods or properties by
walking an array of names, etc.  Also, a comprehensive list of exclusions
needs to be passed, to avoid mangling properties that are standard in
JavaScript, DOM, used in external libraries etc.

bin/uglifyjs

@@ -67,6 +67,9 @@ You need to pass an argument to this option to specify the name that your module
     .describe("bare-returns", "Allow return outside of functions.  Useful when minifying CommonJS modules.")
     .describe("keep-fnames", "Do not mangle/drop function names.  Useful for code relying on Function.prototype.name.")
     .describe("quotes", "Quote style (0 - auto, 1 - single, 2 - double, 3 - original)")
+    .describe("reserved-file", "File containing reserved names")
+    .describe("mangle-props", "Mangle property names")
+    .describe("prop-cache", "File to hold mangled properties mapping")
 
     .alias("p", "prefix")
     .alias("o", "output")
@@ -91,6 +94,8 @@ You need to pass an argument to this option to specify the name that your module
     .string("comments")
     .string("wrap")
     .string("p")
+    .string("reserved-file")
+    .string("prop-cache")
 
     .boolean("expr")
     .boolean("source-map-include-sources")
@@ -106,6 +111,7 @@ You need to pass an argument to this option to specify the name that your module
     .boolean("noerr")
     .boolean("bare-returns")
     .boolean("keep-fnames")
+    .boolean("mangle-props")
 
     .wrap(80)
 
@@ -153,6 +159,16 @@ if (ARGS.r) {
     if (MANGLE) MANGLE.except = ARGS.r.replace(/^\s+|\s+$/g).split(/\s*,+\s*/);
 }
 
+if (ARGS.reserved_file) (function(){
+    var data = fs.readFileSync(ARGS.reserved_file, "utf8");
+    RESERVED = data = JSON.parse(data);
+    if (data.vars) {
+        MANGLE.except = MANGLE.except
+            ? MANGLE.except.concat(data.vars)
+            : data.vars;
+    }
+})();
+
 if (ARGS.quotes === true) {
     ARGS.quotes = 3;
 }
@@ -242,6 +258,7 @@ var OUTPUT_FILE = ARGS.o;
 var TOPLEVEL = null;
 var P_RELATIVE = ARGS.p && ARGS.p == "relative";
 var SOURCES_CONTENT = {};
+var RESERVED = null;
 
 var SOURCE_MAP = ARGS.source_map ? UglifyJS.SourceMap({
     file: P_RELATIVE ? path.relative(path.dirname(ARGS.source_map), OUTPUT_FILE) : OUTPUT_FILE,
@@ -334,6 +351,33 @@ async.eachLimit(files, 1, function (file, cb) {
         TOPLEVEL = TOPLEVEL.wrap_enclose(arg_parameter_list);
     }
 
+    if (ARGS.mangle_props) (function(){
+        var reserved = RESERVED ? RESERVED.props : null;
+        var cache = null;
+        if (ARGS.prop_cache) {
+            try {
+                cache = fs.readFileSync(ARGS.prop_cache, "utf8");
+                cache = JSON.parse(cache);
+                cache.props = UglifyJS.Dictionary.fromObject(cache.props);
+            } catch(ex) {
+                cache = {
+                    cname: -1,
+                    props: new UglifyJS.Dictionary()
+                };
+            }
+        }
+        TOPLEVEL = UglifyJS.mangle_properties(TOPLEVEL, {
+            reserved: reserved,
+            cache: cache
+        });
+        if (ARGS.prop_cache) {
+            fs.writeFileSync(ARGS.prop_cache, JSON.stringify({
+                cname: cache.cname,
+                props: cache.props.toObject()
+            }, null, 2), "utf8");
+        }
+    })();
+
     var SCOPE_IS_NEEDED = COMPRESS || MANGLE || ARGS.lint;
 
     if (SCOPE_IS_NEEDED) {

lib/propmangle.js

@@ -0,0 +1,211 @@
+/***********************************************************************
+
+  A JavaScript tokenizer / parser / beautifier / compressor.
+  https://github.com/mishoo/UglifyJS2
+
+  -------------------------------- (C) ---------------------------------
+
+                           Author: Mihai Bazon
+                         <mihai.bazon@gmail.com>
+                       http://mihai.bazon.net/blog
+
+  Distributed under the BSD license:
+
+    Copyright 2012 (c) Mihai Bazon <mihai.bazon@gmail.com>
+
+    Redistribution and use in source and binary forms, with or without
+    modification, are permitted provided that the following conditions
+    are met:
+
+        * Redistributions of source code must retain the above
+          copyright notice, this list of conditions and the following
+          disclaimer.
+
+        * Redistributions in binary form must reproduce the above
+          copyright notice, this list of conditions and the following
+          disclaimer in the documentation and/or other materials
+          provided with the distribution.
+
+    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER “AS IS” AND ANY
+    EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+    PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE
+    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
+    OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
+    TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+    THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+    SUCH DAMAGE.
+
+ ***********************************************************************/
+
+"use strict";
+
+function find_builtins() {
+    var a = [];
+    [ Object, Array, Function, Number,
+      String, Boolean, Error, Math,
+      Date, RegExp
+    ].forEach(function(ctor){
+        Object.getOwnPropertyNames(ctor).map(add);
+        if (ctor.prototype) {
+            Object.getOwnPropertyNames(ctor.prototype).map(add);
+        }
+    });
+    function add(name) {
+        push_uniq(a, name);
+    }
+    return a;
+}
+
+function mangle_properties(ast, options) {
+    options = defaults(options, {
+        reserved : null,
+        cache : null
+    });
+
+    var reserved = options.reserved;
+    if (reserved == null)
+        reserved = find_builtins();
+
+    var cache = options.cache;
+    if (cache == null) {
+        cache = {
+            cname: -1,
+            props: new Dictionary()
+        };
+    }
+
+    var names_to_mangle = [];
+
+    // step 1: find candidates to mangle
+    ast.walk(new TreeWalker(function(node){
+        if (node instanceof AST_ObjectKeyVal) {
+            add(node.key);
+        }
+        else if (node instanceof AST_ObjectProperty) {
+            // setter or getter, since KeyVal is handled above
+            add(node.key.name);
+        }
+        else if (node instanceof AST_Dot) {
+            if (this.parent() instanceof AST_Assign) {
+                add(node.property);
+            }
+        }
+        else if (node instanceof AST_Sub) {
+            if (this.parent() instanceof AST_Assign) {
+                addStrings(node.property);
+            }
+        }
+    }));
+
+    // step 2: transform the tree, renaming properties
+    return ast.transform(new TreeTransformer(null, function(node){
+        if (node instanceof AST_ObjectKeyVal) {
+            if (should_mangle(node.key)) {
+                node.key = mangle(node.key);
+            }
+        }
+        else if (node instanceof AST_ObjectProperty) {
+            // setter or getter
+            if (should_mangle(node.key.name)) {
+                node.key.name = mangle(node.key.name);
+            }
+        }
+        else if (node instanceof AST_Dot) {
+            if (should_mangle(node.property)) {
+                node.property = mangle(node.property);
+            }
+        }
+        else if (node instanceof AST_Sub) {
+            node.property = mangleStrings(node.property);
+        }
+        // else if (node instanceof AST_String) {
+        //     if (should_mangle(node.value)) {
+        //         AST_Node.warn(
+        //             "Found \"{prop}\" property candidate for mangling in an arbitrary string [{file}:{line},{col}]", {
+        //                 file : node.start.file,
+        //                 line : node.start.line,
+        //                 col  : node.start.col,
+        //                 prop : node.value
+        //             }
+        //         );
+        //     }
+        // }
+    }));
+
+    // only function declarations after this line
+
+    function can_mangle(name) {
+        if (reserved.indexOf(name) >= 0) return false;
+        if (/^[0-9.]+$/.test(name)) return false;
+        return true;
+    }
+
+    function should_mangle(name) {
+        return names_to_mangle.indexOf(name) >= 0;
+    }
+
+    function add(name) {
+        if (can_mangle(name))
+            push_uniq(names_to_mangle, name);
+    }
+
+    function mangle(name) {
+        var mangled = cache.props.get(name);
+        if (!mangled) {
+            do {
+                mangled = base54(++cache.cname);
+            } while (!can_mangle(mangled));
+            cache.props.set(name, mangled);
+        }
+        return mangled;
+    }
+
+    function addStrings(node) {
+        var out = {};
+        try {
+            (function walk(node){
+                node.walk(new TreeWalker(function(node){
+                    if (node instanceof AST_Seq) {
+                        walk(node.cdr);
+                        return true;
+                    }
+                    if (node instanceof AST_String) {
+                        add(node.value);
+                        return true;
+                    }
+                    if (node instanceof AST_Conditional) {
+                        walk(node.consequent);
+                        walk(node.alternative);
+                        return true;
+                    }
+                    throw out;
+                }));
+            })(node);
+        } catch(ex) {
+            if (ex !== out) throw ex;
+        }
+    }
+
+    function mangleStrings(node) {
+        return node.transform(new TreeTransformer(function(node){
+            if (node instanceof AST_Seq) {
+                node.cdr = mangleStrings(node.cdr);
+            }
+            else if (node instanceof AST_String) {
+                if (should_mangle(node.value)) {
+                    node.value = mangle(node.value);
+                }
+            }
+            else if (node instanceof AST_Conditional) {
+                node.consequent = mangleStrings(node.consequent);
+                node.alternative = mangleStrings(node.alternative);
+            }
+            return node;
+        }));
+    }
+
+}

lib/utils.js

@@ -106,10 +106,12 @@ function defaults(args, defs, croak) {
 };
 
 function merge(obj, ext) {
+    var count = 0;
     for (var i in ext) if (ext.hasOwnProperty(i)) {
         obj[i] = ext[i];
+        count++;
     }
-    return obj;
+    return count;
 };
 
 function noop() {};
@@ -298,5 +300,11 @@ Dictionary.prototype = {
         for (var i in this._values)
             ret.push(f(this._values[i], i.substr(1)));
         return ret;
-    }
+    },
+    toObject: function() { return this._values }
+};
+Dictionary.fromObject = function(obj) {
+    var dict = new Dictionary();
+    dict._size = merge(dict._values, obj);
+    return dict;
 };

tools/node.js

@@ -33,7 +33,8 @@ var FILES = exports.FILES = [
     "../lib/output.js",
     "../lib/compress.js",
     "../lib/sourcemap.js",
-    "../lib/mozilla-ast.js"
+    "../lib/mozilla-ast.js",
+    "../lib/propmangle.js"
 ].map(function(file){
     return fs.realpathSync(path.join(path.dirname(__filename), file));
 });