JS minify failed on public/javascripts/app.js: TypeError: Cannot assign to read only property 'except' of [object Object]

[rtruong]

When using uglify-js-brunch with the following configuration (from config.coffee):

exports.config =
  plugins:
    uglify:
      mangle:
        except: [ "require" ]

With the following command line:

brunch build --optimize

I get the following error.

error: JS minify failed on public/javascripts/app.js: TypeError: Cannot assign to read only property 'except' of [object Object]

I'm using node v0.10.5, brunch 1.6.3, and uglify-js-brunch 1.5.1.

[paulmillr]

does uglify works if you do it w/o brunch with these params?

[rtruong]

If I invoke uglifyjs with the following command line:

uglifyjs -m -c -r "require" public/javascripts/app.js

It works just fine.

[paulmillr]

ah, indeed this is the issue, just checked code.

@es128 seems it’s from your changes

[es128]

I believe I'm just passing through the config parameters as-is. Perhaps these are malformed for what the ugiify API expects? You sure except is a configurable param and expects an array?

[rtruong]

If you look at the uglifyjs source, except is configurable and expected to be an array:

https://github.com/mishoo/UglifyJS2/blob/master/bin/uglifyjs#L130
https://github.com/mishoo/UglifyJS2/blob/master/lib/scope.js#L340

[es128]

The issue is definitely happening within Uglify, though, and you're trying to use the config options in an undocumented way. The only documented usage I can see via the node API is mangle: false. You might need to take your issue over there.

[rtruong]

It is not undocumented. Uglify's command line allows for reserved identifiers:

https://github.com/mishoo/UglifyJS2#usage (see -r/--reserved)

And grunt's uglify plugin uses the very same except array:

https://github.com/gruntjs/grunt-contrib-uglify/blob/master/README.md#reserved-identifiers

[rtruong]

Moreover, if I hack my own object into uglify-js-brunch/lib/index.js:

  optimized = uglify.minify(data, {
    fromString: true,
    mangle: {
      except: ["require"]
    }
  }).code;

That works just fine. For whatever reason, the config object as it is in the source is causing "TypeError: Cannot assign to read only property"

[es128]

It's undocumented in terms of the Uglify.minify API method, but yes you've proven your point. I'm glad you were able to isolate the issue further. I'll see if I can figure it out.

[es128]

Ok, looks like I found the source of the issue and a solution. PR on its way.

@paulmillr Brunch's freeze/deepFreeze stuff has turned out to have lots of side effects. This issue for one, but most notably the watching/changing of config.coffee. How important is it to keep doing that?

[rtruong]

Works fine, now. Thanks for the quick turnaround!

[paulmillr]

whats up with plugins like that -- sass etc?

[es128]

I'll check, but for the most part I don't think they just copy the whole object from config like this one.

[rtruong]

Has this issue resurfaced? When using uglify-js-brunch 1.7.4, it works just fine. When I upgrade to 1.7.6, I get the same error I originally reported.

[paulmillr]

Any points on how can this be reproduced?

[es128]

Looks like 7b1610a dropped the clone function in favor of a shallow extend. The config object went through deepFreeze, so extend doesn't cut it for solving the same problem as before of uglify attempting to mutate something in the config object that was passed in to it.

[paulmillr]

extend right now basically copies all properties from config to a new empty object. What's wrong here?

We don't have any nested objects so it should not matter. clone(obj) === extend({}, obj).

[es128]

We don't have any nested objects

Sure we do. Isn't that the whole source of the problem?

[paulmillr]

I see. There are arrays. Should be fixed now. @rtruong try master please

[rtruong]

Works fine, now. Thanks for the quick turnaround!