Persist esbuild.mangleCache between builds

[hades343]

Description

When using Vite with esbuild minifier with property mangling, there’s no way to persist esbuild’s mangleCache across builds. esbuild returns an updated mangleCache on the result object. Vite doesn’t expose that result to userland and doesn’t mutate the object passed in via config. Outcome: the user-provided mangleCache stays empty/unchanged, making cross-build consistency impossible. Practically, mangleCache is useless in this flow right now.

Repro

import { defineConfig } from "vite";

const __cache__ = {};
export default defineConfig({
  plugins: [
    {
      name: "repro",
      apply: "build",
      closeBundle() {
        console.log(structuredClone(__cache__)); // always empty object since esbuild doesn't mutate args
      },
    },
  ],
  build: {
    minify: "esbuild",
  },
  esbuild: {
    minifyIdentifiers: true,
    mangleCache: __cache__,
    mangleProps: /.+/, // since this matches all props, __cache__ shouldn't be empty
    mangleQuoted: true,
  },
});

Suggested solution

Vite exposes esbuild’s returned mangleCache so userland can persist it.

Alternative

Vite ensures the provided mangleCache object is updated (mutated) with esbuild’s results.

Additional context

The whole point of mangleCache is cross-build determinism and compatibility across separately built chunks/packages. Without persistence, property mangling can break consumers or produce inconsistent artifacts.

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[sapphi-red]

Vite calls esbuild for each output chunk concurrently, so I'm not sure if this is feasible.

[hades343]

As temp solution I patched vite:esbuild plugin, after transformWIthEsbuild call i do:

if (options.mangleCache && result.mangleCache && JSON.stringify(result.mangleCache) !== "{}") {
    console.log("[vite:esbuild] extending mangle cache");
    Object.assign(options.mangleCache, result.mangleCache);
}

This isn’t a general solution because Vite minifies output chunks concurrently. It’s safe in my case (single-file IIFE bundle), but for multi-chunk builds it may introduce data race.