Wire up source maps from transpiled languages

[jrburke]

perhaps just look for existing fileName.js.map file, then use that as the input source map to the next stage of the transform.

Prefer using fileName.js.map, with .js extension since it is conceivable down the road that there is a fileName.html.map, fileName.js.map. I suppose as a stopgap, also look for fileName.map assuming that it is the map to go into JS.

While that would work for "whole directory" optimizations, single file optimizations, where for example, maybe just out= is used (or in the browser out = function (){}), then it would be nice to pass the maps through the code flow without having to touch disk.

In requirejs/require-cs#42, @guybedford suggested perhaps something passed to load.fromText as a way to do this.

The "use existing .map" file change may be easy to support for 2.1.7, not sure about the other path yet.

[clavecoder]

We have this issue. We are coding in TypeScript and would like to use r.js to bundle/minify. However we lose the sourcemaps for debugging purposes. I've always been in the "old school" of generating "PDBs" even for production. There are bugs that only can be reproduced in production environments. If you lose the sourcemap support with release code, debugging becomes much harder.

+1 for sourcemap chaining.

[jrburke]

Ugh, bad commit comment. That commit is for #460.

[jrburke]

Ran out of time for this release window, but more thoughts on this:

1. load.fromText(text, opts), with opts.sourceMap being the source map. During dev, just tack it inline to the evaled code along with the sourceURL?
2. During a build, optimizer writes the sourceMap to the file system when multifile optimization. For single file optimization, hold on to it until the end, saved out separately(?). For out: function(){}, pass it in opts object as second arg, under sourceMap property.
3. Make sure loader plugin writeFile works out too.

[pelotom]

perhaps just look for existing fileName.js.map file, then use that as the input source map to the next stage of the transform.

Apologies if I'm misunderstanding something, but shouldn't it be possible to completely automatically figure out the source map for a given file? If it's a source-mapped file, then it has a comment saying where the source map is, no?

[codepunkt]

+1 for this issue!

I'm working with .coffee amd-modules, using a grunt task to compile those to .js amd-modules, each with their own .js to .coffee source-map.

Afterwards, i combine those amd-modules to components using r.js, each component being based on the dependency tree of a certain file. When using uglify2 and enabling sourcemap support, this results in a .js file and a sourcemap for each component - the sourcemap mapping the built .js file to the batch of .js files concatenated into it.

I was thinking about somehow using the uglify2 option in-source-map.
To clarify this - the required files are first concatenated using r.js and the resulting file is optimized afterwards using uglify/uglify2/closure?

[matthewwithanm]

Why is this necessary? Like @pelotom mentioned, the map filename should be in the compiled output, no?

[DrSammyD]

@matthewwithanm Nevermind, it is in the compiled output.

[matthewwithanm]

Neat! Seems to me that using that is much less fragile than making assumptions about filenames.

[DrSammyD]

There, now we check each js file for it's existing map instead of making assumptions about file names

            uglify2: function (fileName, fileContents, outFileName, keepLines, config) {
                var result, existingMap, resultMap, finalMap, sourceIndex,
                    uconfig = {},
                    existingMapPath = outFileName + '.map',
                    baseName = fileName && fileName.split('/').pop();

                config = config || {};
                var patt = new RegExp('\#.sourceMappingURL\=[a-zA-Z0-9\-\_\.]*');
                var filereg = patt.exec((fileContents.length)? fileContents : '' );
                existingMapPath = filereg? existingMapPath.split('/').slice(0,-1).join('/')+filereg[0].split('=')[1] : existingMapPath;

[codepunkt]

How does this help getting sourcemaps for transpiled languages?