[Amund211]

The ./compat/* wildcard export only declared a CJS default condition, so import get from "es-toolkit/compat/get" always resolved to a CommonJS stub even in fully-ESM graphs. Every other subpath already splits import/require; compat alone shipped CJS to ESM importers, costing interop wrappers and worse tree-shaking.

This was uncovered by a rolldown (vite 8) chunk-rendering bug where the dist require_* helper naming crashed production builds (rolldown#9653) — but that bug is now fixed upstream, so it is not the motivation here. The motivation is the independent, measurable cost of shipping CJS to ESM consumers, which stands regardless of any bundler.

Generate .mjs (ESM) stubs and .d.mts types alongside the existing .js/.d.ts in postbuild, and split ./compat/* into import / require conditions like every other subpath. ESM importers now resolve to pure-ESM .mjs (zero require( in the chain); require still gets CJS. attw node16 (from ESM) goes from "Incorrect default export" to "OK (ESM)".

Package size impact (measured via npm pack; dist/ is byte-identical between old and new — the ESM implementations already ship either way, this only adds tiny one-line re-export stubs):

    metric            OLD (CJS)   NEW (+ESM)   delta
    tarball (gzip)    645.5 KB    670.0 KB     +24.5 KB (+3.8%)
    unpacked          3.33 MB     3.37 MB      +0.04 MB (+1.2%)
    file count        3018        3612         +594 (297 fns x 2)

Smaller consumer bundles. Bundled small ESM apps that deep-import compat functions with esbuild (bundle + tree-shake + minify) against the old and new packages and compared output bytes:

    import set                       OLD (CJS)   NEW (ESM)   reduction
    get + maxBy                      11,602 B    8,122 B     -30.0%
    recharts 3's 11 deep-imports     21,526 B    15,193 B    -29.4%

Timeline:
2025-06-07 #1199 (f6e1ce3) added this exact change (.mjs/.d.mts
stubs + import/require split) to support ESM consumers.
2025-06-15 e6f6762 reverted it ("Provide compat/* in CommonJS
format by default") — direct push to main, no PR, no
rationale in the message.
2025-10-18 #1479 reported exports is not defined and proposed
this identical fix. Closed; maintainer rationale was
package size + "importing CJS from ESM is fine."
2026-06-05 #1756 filed. The triggering rolldown bug is fixed
upstream, but it surfaced that compat/* ships CJS to ESM
importers — independently worth fixing (size, resolution,
tree-shaking) per the measurements above.

Closes #1756

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Project	Deployment	Actions	Updated (UTC)
es-toolkit	Ready	Preview, Comment	Jun 6, 2026 9:50am

[Copilot]

Pull request overview

Note

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Updates the package’s ./compat/* exports to support separate ESM/CJS entrypoints (and corresponding TypeScript declaration outputs) and extends the post-build script to generate the additional compat wrapper files.

Changes:

• Adjust package.json conditional exports for ./compat/* to split import vs require with different types/default targets.
• Extend .scripts/postbuild.sh to generate compat/*.mjs and compat/*.d.mts wrappers alongside existing CJS and .d.ts wrappers.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
package.json	Adds conditional import/require mapping (including types) for ./compat/* exports.
.scripts/postbuild.sh	Generates additional ESM (.mjs) and ESM declaration (.d.mts) compat wrapper files during postbuild.

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[raon0211]

We originally held off on adding ESM exports for individual functions because (1) we already do some manual tree-shaking, and (2) it bloats our install size. But it looks like it still helps with bundle size, so let's go ahead and merge this. Thanks for the PR!