pnpm/patching/apply-patch/src/index.ts

import { PnpmError } from '@pnpm/error'
import { applyPatch } from '@pnpm/patch-package/dist/applyPatches'

export interface ApplyPatchToDirOpts {
  patchedDir: string
  patchFilePath: string
}

export function applyPatchToDir (opts: ApplyPatchToDirOpts): void {
  // 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)
  let success = false
  try {
    success = applyPatch({
      patchFilePath: opts.patchFilePath,
    })
  } 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) {
    throw new PnpmError('PATCH_FAILED', `Could not apply patch ${opts.patchFilePath} to ${opts.patchedDir}`)
  }
}