Add a --debug flag for production builds which disables uglify

[KyleAMathews]

It's really hard to debug some problems (e.g. mismatches between SSR & client renders #3067) without this.

[m-allanson]

Could this initially be done as a plugin if someone wanted to work on it?

[KyleAMathews]

Yeah — but this seems like something that should be built in — not something people have to install and add/remove to their gatsby-config.

Let's perhaps not name it --debug though as that'll confuse people as the scope of the feature is small and debug seems expansive. Maybe be really specific e.g. --no-uglify.

It'd be a really easy PR to add.

[tsriram]

I'll give this a go.

[dandv]

If --no-uglify was necessary, am I to understand that gatsby build does uglify by default (or should uglify)?

I see code in clear, including comments, as a result of gatsby build, and you can see that in some big brand public sites:

I thought, maybe those sites are engineering-oriented and leave their code open for inspection, but then I looked at https://www.shopflamingo.com. Same story. https://impossiblefoods.com/ Same.

Does Gatsby actually no longer uglify when building?

[LekoArts]

Please don't open up year old issues, it's not really helping your cause. Thanks!

About your comment: You can see those things due to Webpack's "Sourcemaps" that get shipped with the build (you can disable this behavior manually if you want).