This disables symbol renaming in production builds. The original
variable and function names are preserved. All other forms of
compression applied by Closure (dead code elimination, inlining, etc)
are unchanged — the final program is identical to what we were producing
before, just in a more readable form.
The motivation is to make it easier to debug React issues that only
occur in production — the same reason we decided to start shipping
sourcemaps in #28827 and #28827.
However, because most apps run their own minification step on their npm
dependencies, it's not necessary for us to minify the symbols before
publishing — it'll be handled the app, if desired.
This is the same strategy Meta has used to ship React for years. The
React build itself has unminified symbols, but they get minified as part
of Meta's regular build pipeline.
Even if an app does not minify their npm dependencies, gzip covers most
of the cost of symbol renaming anyway.
This saves us from having to ship sourcemaps, which means even apps that
don't have sourcemaps configured will be able to debug the React build
as easily as they would any other npm dependency.
The internal file ReactSharedSubset is what the `react` module resolves
to when imported from a Server Component environment. We gave it this
name because, originally, the idea was that Server Components can access
a subset of the APIs available on the client.
However, since then, we've also added APIs that can _only_ by accessed
on the server and not the client. In other words, it's no longer a
subset, it's a slightly different overlapping set.
So this commit renames ReactSharedSubet to ReactServer and updates all
the references. This does not affect the public API, only our internal
implementation.
