fix: shim non-existent source

[trappar]

PNPM has this long-standing issue where pnpm install fails when a package defines a bin that must be compiled first: pnpm/pnpm#1801

In this case the file can't be read and so a shebang can't be determined, and execution fails with error code ENOENT. This seems easily solvable. cmd-shim can still fall back to determining the program by using the extensionToProgramMap.

This PR is probably incomplete. Not being terribly familiar with the code, I've done my best, but the test is probably incomplete at the very least.

[zkochan]

I guess we can use this approach.

[trappar]

I've rebased the PR on the recent changes to main. Not sure what's going on with the broken tests. Seems like the checks run on Windows, so I tried running it locally. I've run it on Windows 11 with both Node 14 and 18 and all tests pass for me. Any chance you might be willing to help push this across the finish line? Probably a lot easier for you given that you're more familiar with the code 😅

Currently I'm working around this by adding the following to my monorepo's root package.json

"scripts": {
  "pnpm:devPreinstall": "scripts/createBinStubs"
},

Which runs this script:

#!/usr/bin/env node
const { writeFileSync, mkdirSync, existsSync } = require("fs");
const { dirname } = require("path");

const shims = [
  "packages/[redacted]/dist/index.js",
];

const fileContent = `/*
 * Temp file generated by scripts/createBinStubs.js
 * This file is created as a temporary workaround for this issue: https://github.com/pnpm/pnpm/issues/1801
 * Currently PNPM fails to create a bin while installing sub-packages when the source for that bin is missing while running pnpm install.
 * This is the case for any package with a bin that is built after install. By creating this temporary file, PNPM is able to link to it.
 * Once the actual bin is built, everything works.
*/`;

shims.forEach((shim) => {
  const shimDir = dirname(shim);
  if (!existsSync(shimDir)) {
    mkdirSync(shimDir, { recursive: true });
  }
  if (!existsSync(shim)) {
    writeFileSync(shim, fileContent);
  }
});

I'd love to remove this hacky workaround from my code!

[Copilot]

Pull Request Overview

This pull request addresses a PNPM issue where installations fail if a package’s bin file does not exist and cannot provide a shebang, by falling back on the extensionToProgramMap.

• Added a new test case for the scenario when the source file is missing.
• Modified the searchScriptRuntime function to handle ENOENT errors on Windows by checking for an alternative executable extension.

Reviewed Changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated no comments.

File	Description
test/test.js	Added a "no src file" test to cover the fallback behavior when the source file is missing.
src/index.ts	Refactored the shebang extraction and error handling logic to support the new fallback scenario.

Files not reviewed (1)

• test/snapshots/test.js.snap: Language not supported

Comments suppressed due to low confidence (2)

test/test.js:22

• Consider adding explicit assertions within the 'no src file' test case to verify that cmdShim correctly falls back to using the extensionToProgramMap when the source file is missing.

describe('no src file', () => {

src/index.ts:274

• Ensure that the fallback behavior when encountering an ENOENT error on Windows is fully intended – specifically, verify that relying on fs_.stat to check for an executable version aligns with the overall design, and consider adding a clarifying comment if needed.

if (isWindows() && err.code === 'ENOENT') {

[KSXGitHub]

The operation to compare err.code to ENOENT could be executed twice on Windows. You can optimize it by moving if (err.code !== 'ENOENT') throw err up to right under catch.