Add SourceMaps to minified JS

[maennchen]

As discussed in https://groups.google.com/g/phoenix-core/c/Dk2AbXVnzeg

When running npm run build, this will:

• Add a comment to priv/static/phoenix.js pointing to the sourcemap
• Add a new file priv/static/phoenix.js.map

I have verified that when using webpack in your application, it will incorporate this sourcemap and therefore create better error stacktraces.

[gcauchon]

I'm not a Webpack expert, but should we also adapt thewebpack.config.js template to include a sourcemap in the production bundle too?

https://github.com/phoenixframework/phoenix/blob/master/installer/templates/phx_assets/webpack.config.js#L27

    devtool: devMode ? 'eval-cheap-module-source-map' : 'source-map',

[maennchen]

@gcauchon I don't think so. The reason is that this is a decision that the user of the framework should make:

• Open Source Applications: Shoud probably have it
• Closed Source Applications: Most companies do not want to expose their unminified JS. If using Sentry for example a hidden-source-map can be used and uploaded instead.

[rktjmp]

I am a moron.

Same: #4265

[maennchen]

@rktjmp I don't think so. The linked PR is for the phoenix generator. This PR only looks at the JS packaged with phoenix.

[maennchen]

Rebased to current master

[maennchen]

Rebased to current master

[maennchen]

Amended compiled JS & Source Maps as discussed with @bcardarella

[bcardarella]

I believe if you add to this block

phoenix/installer/lib/phx_new/single.ex

Lines 89 to 97 in dcc9398

	template :static, [
	{:text, "phx_static/app.js", :web, "priv/static/js/app.js"},
	{:text, "phx_static/app.css", :web, "priv/static/css/app.css"},
	{:text, "phx_static/phoenix.css", :web, "priv/static/css/phoenix.css"},
	{:text, "phx_static/robots.txt", :web, "priv/static/robots.txt"},
	{:text, "phx_static/phoenix.js", :web, "priv/static/js/phoenix.js"},
	{:text, "phx_static/phoenix.png", :web, "priv/static/images/phoenix.png"},
	{:text, "phx_static/favicon.ico", :web, "priv/static/favicon.ico"}
	]

to ensure the new sourcemap file is being copied in for --no-webpack projects this PR should be ready to merge.

[chrismccord]

❤️❤️❤️🐥🔥