Mistakes when mangle top-level names

[gdh1995]

Bug report

Uglify version (uglifyjs -V)

uglify-js@3.4.9

JavaScript input

"use strict";
// test.js
var uglify = require('uglify-js');
var options = {
  nameCache: { vars: {}, props: {} },
  mangle: {
    toplevel: true
  }
};

var dist1 = uglify.minify({
  "1.js": "var extend = function() {}; function A() {};"
}, options);

var dist2 = uglify.minify({
  "2.js": "var B = (function (super) { function B() {}; extend(B, super); return B; })(A);"
}, options);

console.log(dist1);
console.log(dist2);

The uglifyjs CLI command executed or minify() options used.

$ npm install uglify-js
$ node test.js

JavaScript output

{ code: 'var n=function(){};function c(){}' }
{ code: 'var t=function(n){function t(){}return n(t,n),t}(c);' }

What is the mistake

• The global variable extend is renamed to n
• the name super in the second input is also renamed to n
• uglifyJS replaces extend in the second input with n, which collides with super
• if runs the test output, the real n(t, n) will call super(B, super)
  • then for more complicated code, it will throw.

[kzc]

Have you tried terser to see whether it exhibits the same toplevel name cache collision?

[gdh1995]

Have you tried terser to see whether it exhibits the same toplevel name cache collision?

After renaming super into super1, the terser works well:

{ code: 'var n=function(){};function c(){}' }
{ code: 'var t=function(t){function e(){}return n(e,t),e}(c);' }

I also tested complex 2.js and terser did skip the global name n when renaming local variables.

[kzc]

FWIW, this mangle regression occurred in f40f5eb.
This commit was not merged to Terser.

[gdh1995]

Thanks!