Turn on sourcemaps in built dist

[schneidmaster]

Hi there! Just a suggested improvement, feel free to ignore if you intentionally don't want sourcemaps for whatever reason 😄

I originally got here from this issue. Webpack's source-map-loader allows webpack to ingest sourcemaps from your dependencies and bundle them into the sourcemap for your application itself -- which is nice for debugging in general because if an error comes from within a library you can instantly trace it to the source instead of having to parse through minified output. However, with react-json-view installed, the source-map-loader logs an annoying warning.

Turns out the warning is because of this -- style-loader has a conditional to add a sourceMappingURL if the sourceMap configuration option is set. Note that the entire addStyles.js source is bundled into the dist when you're using style-loader (i.e. you can't just turn off the sourceMap config option -- it's actually off-by-default anyway -- because the whole conditional that checks whether it's on or off is inlined.) The source-map-loader picks up the sourceMappingUrl text out of this conditional and thinks it's an actual sourcemap comment, not code to maybe add a sourcemap comment.

The folks working on source-map-loader have seen this issue before -- here's an issue and here's the PR that came out of it. Their solution was to change source-map-loader to only parse the last sourceMappingURL found in the file (rather than all of them). This helps for most cases, but it doesn't actually help here because react-json-view doesn't have sourcemaps enabled in the built dist at all, so the last/only sourceMappingURL is the false positive from style-loader.

So, I propose that we turn on sourcemaps in the built dist. This is a double improvement for people who want to use source-map-loader -- they get sourcemaps out of react-json-view and they also get no annoying warning. It shouldn't really have much impact on anyone else since all it does is add a comment to the end of the built output (and include a sourcemap file adjacent to it in the dist directory).

I also removed the new webpack.optimize.UglifyJsPlugin() line because it's redundant (the --optimize-minimize in the package.json script adds it anyway) and was causing me some issues getting the build to work right with the sourcemaps.

Let me know what you think 😄

[josefernandez1]

Hi @schneidmaster , I'm having the same problem, as the PR is still open, did you find a work around to make the warning not appear?
Everything seems to work fine, but the error is there and it's a bit annoying.

[schneidmaster]

@josefernandez1 Yes, to work around it I added an exclude line to my webpack config:

{
  test: /\.js$/,
  exclude: /react-json-view/,
  use: ['source-map-loader'],
  enforce: 'pre',
},