Source maps: the names attribute is always empty

[thorn0]

Here is my isolated setup for the issue:

main.js

define(function() {
    var greeting = 'hi';
    console.log(greeting);
});

build.json

{
    "generateSourceMaps": true,
    "name": "main",
    "optimize": "uglify2",
    "out": "main-built.js",
    "preserveLicenseComments": false
}

That's how I run r.js: r.js.cmd -o build.json

And that's the source map I get in the end (formatted by me):

{
    "version": 3,
    "file": "main-built.js",
    "sources": [ "main.js" ],
    "names": [],
    "mappings": "AAAA,OAAA,UAAA,WACA,GAAA,GAAA,IACA,SAAA,IAAA",
    "sourcesContent": [ "define('main',[],function() {\r\n    var greeting = 'hi';\r\n    console.log(greeting);\r\n});\n" ]
}

Note that the names attribute is an empty array. This makes the source maps less usable than they could be as Chrome's debugger doesn't recognize the renamed variables in the mapped code, doesn't show their values on hover, etc.

For comparison, let's process the same main.js with Uglify:
uglifyjs main.js -o main-uglified.js -c -m --source-map main-uglified.js.map

Here is the source map. Note that the names are okay now.

{
    "version": 3,
    "file": "main-uglified.js",
    "sources": [ "main.js" ],
    "names": [ "define", "greeting", "console", "log" ],
    "mappings": "AAAAA,OAAO,WACH,GAAIC,GAAW,IACfC,SAAQC,IAAIF"
}

[jrburke]

For me, source map support in browsers is really rough, not very consistent. So it is hard for me to justify debugging these issues. I am open to someone else investigating them though and working out a pull request for it if it is possible. However, for this particular issue, it seems better if the browser is just smarter about the translation, as it has the mapping from source to running code in the source map.

Going to close this because I do not plan on working on it, but I am open to working on a merge if someone else does a pull request.