feat: add detailed error handling for patch failures

[zardoy]

for pnpm/pnpm#5503

so in patching/apply-patch/src/index.ts we can do this:

const patchLogger = logger('patch')
//...

export function applyPatchToDir (opts: ApplyPatchToDirOpts): boolean {
  // Ideally, we would just run "patch" or "git apply".
  // However, "patch" is not available on Windows and "git apply" is hard to execute on a subdirectory of an existing repository
  const cwd = process.cwd()
  process.chdir(opts.patchedDir)
  patchLogger.debug({ message: 'Applying patch to directory', patchFilePath: opts.patchFilePath, patchedDir: opts.patchedDir, cwd })
  let success = false
  let applyPatchError: Error | undefined
  try {
    success = applyPatch({
      patchFilePath: opts.patchFilePath,
      onPatchError: (err: Error, context: { phase: 'apply' | 'reverse-dry-run' }) => {
        if (context.phase === 'apply') {
          applyPatchError = err
          patchLogger.debug({ message: 'Patch application error', error: err.message, phase: context.phase })
        }
      },
    })
  } catch (err: any) { // eslint-disable-line
    if (err.code === 'ENOENT') {
      throw new PnpmError('PATCH_NOT_FOUND', `Patch file not found: ${opts.patchFilePath}`)
    }
    throw new PnpmError('INVALID_PATCH', `Applying patch "${opts.patchFilePath}" failed: ${err.message as string}`)
  } finally {
    process.chdir(cwd)
  }
  if (!success) {
    const message = `Could not apply patch ${opts.patchFilePath} to ${opts.patchedDir}: ${applyPatchError?.message ?? 'Unknown error'}`
    if (opts.allowFailure) {
      globalWarn(message)
    } else {
      throw new PnpmError('PATCH_FAILED', message)
    }
  }
  return success
}

[dschmidt]

I'm trying to debug a patch applying issue, it would be nice to have this - is anything holding this back?

[zardoy]

I think it will never get merged because this is not pnpm repository…
You might want to check bun, they have a well maintained version of the patch functionality… (shrug)