export function generateDifferencePatch()

in packages/blueprints/blueprint/src/differences/differences.ts [6:39]

• 27 lines of code
• 7 McCabe index (conditional complexity)

export function generateDifferencePatch(intendedOldFile: string, intendedNewFile: string, destination: string): string {
  let oldFile = intendedOldFile;
  if (!fs.existsSync(oldFile)) {
    oldFile = '/dev/null';
  }

  let newFile = intendedNewFile;
  if (!fs.existsSync(newFile)) {
    newFile = '/dev/null';
  }

  // todo clean up in the future to use a stream
  const args = ['diff', '--binary', '--no-index', oldFile, newFile];
  const diffCommand = cp.spawnSync('git', args, { maxBuffer: 999_990_999_999 });
  if (diffCommand.error) {
    throw new Error(`git diff failed: ${diffCommand.error}`);
  }

  // git diff returns 0 if there is no diff and 1 if there is a diff. Otherwise, the status indicates an
  // error:
  if (diffCommand.status !== 0 && diffCommand.status !== 1) {
    throw new Error(`git diff failed: ${diffCommand.stderr.toString()}`);
  }

  let rawDiff = diffCommand.stdout.toString();
  if (rawDiff.length) {
    rawDiff = rawDiff.replace(/^(.*)$/m, `diff --git a/${destination} b/${destination}`);
    rawDiff = rawDiff.replace(`--- a${oldFile}`, `--- a/${destination}`);
    rawDiff = rawDiff.replace(`--- a/${oldFile}`, `--- a/${destination}`);
    rawDiff = rawDiff.replace(`+++ b${newFile}`, `+++ b/${destination}`);
    rawDiff = rawDiff.replace(`+++ b/${newFile}`, `+++ b/${destination}`);
  }
  return rawDiff;
}