fix(core): Handle undefined INIT_CWD in postinstall script for ARM builds

[Copilot]

Fixes #9283 where @swc/[email protected] fails to install on ARM64 systems with exit code 129.

Problem

The postinstall script crashes when process.env.INIT_CWD is undefined, which can happen on ARM systems or with certain package managers like Yarn PnP. The error occurs because path.resolve() receives undefined as its first argument:

The "paths[0]" argument must be of type string. Received undefined

This causes the installation to fail with exit code 129, breaking the build process on ARM platforms.

Root Cause

Two locations in packages/core/src/postinstall.ts used TypeScript's non-null assertion operator (!) with process.env.INIT_CWD!, assuming the environment variable would always be present:

1. Line 34: Package name validation
2. Line 123: Fallback wasm installation path resolution

When compiled to JavaScript, these became direct property accesses that could return undefined, causing path.resolve(undefined, ...) to throw.

Solution

Added proper null checks for process.env.INIT_CWD before using it:

1. Early return for package validation: Skip the check gracefully when INIT_CWD is missing since this can happen legitimately with some package managers
2. Descriptive error for wasm installation: Throw a clear error message explaining the requirement instead of letting path.resolve() fail cryptically

Changes

• Modified packages/core/src/postinstall.ts to add null checks
• Recompiled to update packages/core/postinstall.js
• Maintains full backward compatibility for environments where INIT_CWD is properly set

Testing

Verified that the fix:

• Prevents crashes when INIT_CWD is undefined (ARM/Yarn PnP scenario)
• Continues to work normally when INIT_CWD is set (standard npm scenario)
• Provides clear error messages instead of cryptic failures

This restores ARM64 build functionality that worked in v1.13.5 while maintaining all existing behavior for other platforms.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>v1.13.19 fails to build on ARM</issue_title>
<issue_description>### Describe the bug

The previous release v1.13.5 builds on both AMD64 and ARM64.

However the new release v1.13.19 builds on AMD64, but fails to build on ARM64.

Input code

Config

Link to the code that reproduces this issue

Not applicable

SWC Info output

No response

Expected behavior

Previous release works on ARM64.

# yarn add @swc/[email protected]
➤ YN0000: · Yarn 4.10.3
➤ YN0000: ┌ Resolution step
➤ YN0085: │ + @swc/core@npm:1.13.5, @swc/core-darwin-arm64@npm:1.13.5, @swc/core-darwin-x64@npm:1.13.5, and 9 more.
➤ YN0000: └ Completed in 0s 460ms
➤ YN0000: ┌ Fetch step
➤ YN0013: │ 3 packages were added to the project (+ 39.79 MiB).
➤ YN0000: └ Completed in 0s 980ms
➤ YN0000: ┌ Link step
➤ YN0000: │ ESM support for PnP uses the experimental loader API and is therefore experimental
➤ YN0007: │ @swc/core@npm:1.13.5 [89330] must be built because it never has been before or the last one failed
➤ YN0000: └ Completed in 0s 971ms
➤ YN0000: · Done with warnings in 2s 644ms

Actual behavior

New release fails on ARM64.

# yarn add @swc/[email protected]
➤ YN0000: · Yarn 4.10.3
➤ YN0000: ┌ Resolution step
➤ YN0085: │ + @swc/core@npm:1.13.19, @swc/core-darwin-arm64@npm:1.13.19, @swc/core-darwin-x64@npm:1.13.19, and 9 more.
➤ YN0000: └ Completed in 0s 486ms
➤ YN0000: ┌ Fetch step
➤ YN0013: │ 3 packages were added to the project (+ 39.33 MiB).
➤ YN0000: └ Completed in 0s 955ms
➤ YN0000: ┌ Link step
➤ YN0000: │ ESM support for PnP uses the experimental loader API and is therefore experimental
➤ YN0007: │ @swc/core@npm:1.13.19 [89330] must be built because it never has been before or the last one failed
➤ YN0009: │ @swc/core@npm:1.13.19 [89330] couldn't be built successfully (exit code 129, logs can be found here: /tmp/xfs-56708825/build.log)
➤ YN0000: └ Completed in 2s 743ms
➤ YN0000: · Failed with errors in 4s 298ms

build.log

# This file contains the result of Yarn building a package (@swc/core@virtual:89330598b4331d00a5582adce1d8ee73be9a2882b577f43d7a976fd7250e3eaec26d0c4161dbd30caedfcf07a2aee7f328a717ea0bd55f08ad9927c8db05d9e6#npm:1.13.19)
# Script name: postinstall

Version

v1.13.19

Additional context

Yarn v4.10.3 with PnP</issue_description>

Comments on the Issue (you are @copilot in this section)

@kdy1 cc @Brooooooklyn Can you take a look? @Brooooooklyn the error comes from the postinstall script in @swc/core @kdy1 cc @kwonoj Do you have any ideas? @kdy1 Can you just all wait? I’m already aware of the issue. Such comments disturbs issue resolution and does not help at all @kwonoj I just tried with creating an empty repo but couldn't repo. For the anyone seeing this issue, please

• create a minimal reproducible repo and share gh link
• share full logs for failure instead of yarn's output only

 ... (exit code 129, logs can be found here: /tmp/xfs-56708825/build.log) -> this

@kdy1 Does this still happen with `v1.13.20`? @kdy1 Nothing

Fixes #11120

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[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	cac@​6.7.14

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