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Don't minify symbols in production builds #28881

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merged 1 commit into from
Apr 20, 2024

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@acdlite acdlite commented Apr 19, 2024

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.

@facebook-github-bot facebook-github-bot added CLA Signed React Core Team Opened by a member of the React Core Team labels Apr 19, 2024
@acdlite acdlite force-pushed the dont-minify-symbols branch 2 times, most recently from 9f02628 to c4f36e8 Compare April 19, 2024 19:40
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@acdlite acdlite marked this pull request as ready for review April 19, 2024 19:55
@acdlite acdlite force-pushed the dont-minify-symbols branch from c4f36e8 to 001602f Compare April 19, 2024 19:57
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 facebook#28827 and facebook#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.
@acdlite acdlite force-pushed the dont-minify-symbols branch from 001602f to e625cd8 Compare April 19, 2024 19:59
@acdlite acdlite merged commit 857ee8c into facebook:main Apr 20, 2024
38 checks passed
github-actions bot pushed a commit that referenced this pull request Apr 20, 2024
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.

DiffTrain build for [857ee8c](857ee8c)
unstubbable added a commit to unstubbable/next.js that referenced this pull request Apr 20, 2024
This can be reverted when a React canary version is used that
includes facebook/react#28881.
eps1lon added a commit to vercel/next.js that referenced this pull request Apr 21, 2024
commit ea37c04
Author: Hendrik Liebau <mail@hendrik-liebau.de>
Date:   Wed Apr 17 21:59:01 2024 +0200

    Fix vscode launch configs to allow setting breakpoints in the IDE

commit 47fe8e8
Author: Hendrik Liebau <mail@hendrik-liebau.de>
Date:   Sat Apr 20 21:23:37 2024 +0200

    Add and load React production source maps

    This can be reverted when a React canary version is used that
    includes facebook/react#28881.

commit c8f3798
Author: Hendrik Liebau <mail@hendrik-liebau.de>
Date:   Sat Apr 20 21:18:35 2024 +0200

    Inline Next.js sources content into source map files

    This avoids a `loadNetworkResource` error in Chrome DevTools when trying
    to set breakpoints in the Next.js sources, for both server and client.

commit c286c02
Author: Tim Neutkens <tim@timneutkens.nl>
Date:   Sat Apr 20 15:45:35 2024 +0200

    Disable ncc cache instead of cache cleaning (#64804)

    `ncc cache clean` is running each time we call `ncc-compiled`. This PR
    removes the cache cleaning and instead just always passes `cache: false`
    to disable the built-in ncc cache.

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    Closes NEXT-3174

commit b914ad8
Author: Zack Tanner <1939140+ztanner@users.noreply.github.com>
Date:   Fri Apr 19 18:11:32 2024 -0600

    fix interception route rewrite regex not supporting hyphenated segments (#64805)

    The function we use to generate a string with named parameters to pass
    into `path-to-regexp` currently doesn't properly handle non-word
    characters (namely, for the purposes of this bugfix, hyphens). As a
    result, `pathToRegexp` will convert something like `/foo/:bar-baz` into
    `/^\/foo(?:\/([^\/#\?]+?))-baz[\/#\?]?$/i`, effectively only treating
    the `:foo` as part of the regex capture group and leaving a dangling
    -baz.

    This means using an interception route within a dynamic segment (such as
    `/foo/[bar-baz]`) would not properly trigger the route interception

    Fixes #64766

commit 02e5f65
Author: vercel-release-bot <infra+release@vercel.com>
Date:   Fri Apr 19 23:23:22 2024 +0000

    v14.3.0-canary.13

commit c1ca6ac
Author: Jeffrey Zutt <jeffrey@hang-out.nl>
Date:   Sat Apr 20 01:13:58 2024 +0200

    fix: remove traceparent from cachekey should not remove traceparent from original object (#64727)

    I submitted PR #64499 , it got merged, but it contains a mistake.
    I'm terribly sorry about this!

    By removing the traceparent from the cachekey, we mistakenly removed the
    header from the original object.
    Causing the actual request to be executed without the traceparent
    header.

    Creating a cachekey should not alter the original object.

    Flip the arguments for Object.assign

    ---------

    Co-authored-by: Jeffrey <jeffrey@jeffreyzutt.nl>
    Co-authored-by: JJ Kasper <jj@jjsweb.site>

commit ea0f516
Author: Sean O'Neil <59893658+sean-rallycry@users.noreply.github.com>
Date:   Fri Apr 19 15:43:26 2024 -0500

    Update 06-bundle-analyzer.mdx (#64740)

    The[ existing code
    example](https://nextjs.org/docs/app/building-your-application/optimizing/bundle-analyzer)
    generates the following warning when using `--turbo` in the current
    latest version of NextJS (14.2.2):

    ⚠ Webpack is configured while Turbopack is not, which may cause
    problems.
     ⚠ See instructions if you need to configure Turbopack:
      https://nextjs.org/docs/app/api-reference/next-config-js/turbo

    This modification ensures that the bundle analyzer is only applied when
    the user intends to generate a report.

    Fixes # #64739

    ---------

    Co-authored-by: Lee Robinson <me@leerob.io>
    Co-authored-by: Maxim Svetlakov <maxim@ebookapplications.com>
    Co-authored-by: JJ Kasper <jj@jjsweb.site>

commit cf038a3
Author: Steven Primeaux <58159084+Auxdible@users.noreply.github.com>
Date:   Fri Apr 19 14:36:25 2024 -0400

    docs: "generateMetadata" to "generateViewport" in doc "generateViewport" (#64795)

    Changed "generateMetadata" to "generateViewport" in
    generate-viewport.mdx

    Co-authored-by: Sam Ko <sam@vercel.com>

commit a0f334c
Author: Kushagra Sharma <162145291+IAmKushagraSharma@users.noreply.github.com>
Date:   Sat Apr 20 00:04:21 2024 +0530

    Update index.mdx (#64794)

    Removed a type annotation from a code block

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commit bd6ab04
Author: Tim Neutkens <tim@timneutkens.nl>
Date:   Fri Apr 19 20:26:54 2024 +0200

    Upgrade Turborepo (#64767)

    Upgrade Turborepo to the latest version and enable the new terminal UI
    to dogfood: https://turbo.build/blog/turbo-1-13-0#new-terminal-ui.

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    Closes NEXT-3164
@markerikson
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markerikson commented Oct 16, 2024

Hey, @acdlite . Any chance of reconsidering shipping sourcemaps?

The main issue I'm seeing with looking at some of the prod artifacts is that all the Closure function inlining in the production artifacts is making it harder to actually understand what the original React code actually looked like, as well as things like constant flags being turned into integers.

Having the prod artifact be readable is a huge step in the right direction, but the optimized code deviates enough from the original source that it can still be pretty tricky to dig through.

@eps1lon
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eps1lon commented Oct 18, 2024

The main issue I'm seeing with looking at some of the prod artifacts is that all the Closure function inlining in the production artifacts is making it harder to actually understand what the original React code actually looked like

Sourcemaps don't help with inlined functions: tc39/ecma426#40

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