Built JS code not fully minified when dynamic import is used

[mdickopp]

Describe the bug

Generated JS files that use dynamic imports are not fully minified. For example, when building the reproduction repository, a file dist/assets/index-q-SMFOy6.js is generated that contains some minified code, followed by the following code that is not minified:

function __vite__mapDeps(indexes) {
  if (!__vite__mapDeps.viteFileDeps) {
    __vite__mapDeps.viteFileDeps = []
  }
  return indexes.map((i) => __vite__mapDeps.viteFileDeps[i])
}

I would have expected that everything in this file is minified, including the __vite__mapDeps function.

Reproduction

https://github.com/mdickopp/vite-minification-issue

Steps to reproduce

1. Clone the reproduction repository
2. Change into the cloned directory
3. Run npm install
4. Run npm run build

System Info

System:
    OS: Linux 6.5 Debian GNU/Linux trixie/sid
    CPU: (16) x64 Intel(R) Core(TM) i9-9900K CPU @ 3.60GHz
    Memory: 27.93 GB / 31.28 GB
    Container: Yes
    Shell: 5.2.21 - /bin/bash
  Binaries:
    Node: 18.19.0 - /usr/bin/node
    npm: 10.2.5 - ~/.npm/bin/npm
  Browsers:
    Chromium: 120.0.6099.71
  npmPackages:
    vite: ^5.0.7 => 5.0.7

Used Package Manager

npm

Logs

No response

Validations

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• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Make sure this is a Vite issue and not a framework-specific issue. For example, if it's a Vue SFC related bug, it should likely be reported to vuejs/core instead.
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• The provided reproduction is a minimal reproducible example of the bug.

[bluwy]

At the moment, this is intentional. The __vite__mapDeps code can only be injected post minification

[acid-chicken]

On the other hand, at the moment there still seems to be room for optimization. For example, __vite__mapDeps([]) can safely be replaced by []. And, it is possible to minify the declaration body of __vite__mapDeps in advance.

[bluwy]

I think circling back on this, I'm definitely open to minifying the injected util code a bit so it's shorter (though complete minification is still not the goal). Fixing the empty array case would be nice as you mentioned. About the __vite__mapDeps function name, it should probably still be kept still as a marker, though it currently appears thrice and I'm not sure of any other tricks to avoid that.

[DiFuks]

With this, there is another issue: I use the plugin @rollup/plugin-babel for transpiling to legacy browsers using the getBabelOutputPlugin mode. The code that Vite adds (__vite__mapDeps) is the only thing that doesn't get transpiled by this plugin because the addition occurs after the execution of the output plugins in Rollup.