readme.md

Vercel Ignore Build Step Example

NOTE: I no longer use this script since the release of turbo-ignore (More details)

Example of a script called by vercel Ignored Build Step option to only build application in monorepo when changes have been detected.

---

node ../../scripts/ignore-step.js

More details available here

ignore-build-step-vercel.js

const childProcess = require("child_process");

// https://vercel.com/support/articles/how-do-i-use-the-ignored-build-step-field-on-vercel
const ABORT_BUILD_CODE = 0;
const CONTINUE_BUILD_CODE = 1;

const continueBuild = () => process.exit(CONTINUE_BUILD_CODE);
const abortBuild = () => process.exit(ABORT_BUILD_CODE);

const app = process.argv[2] || path.basename(path.resolve());

const stepCheck = () => {
  // no app name (directory) was passed in via args
  if (!app) {
    return abortBuild();
  }

  // get all file names changed in last commit
  const fileNameList = childProcess
    .execSync("git diff --name-only HEAD~1")
    .toString()
    .trim()
    .split("\n");

  // check if any files in the app, or in any shared packages have changed
  const shouldBuild = fileNameList.some(
    (file) => file.startsWith(`apps/${app}`) || file.startsWith("packages/")
  );

  if (shouldBuild) {
    return continueBuild();
  }

  return abortBuild();
};

stepCheck();

Thanks, this is just wat I was looking for, just one thing on line L25 the app is referenced but the variable is never set

  const app = process.argv[2];
  const shouldBuild = fileNameList.some(
    (file) => file.startsWith(`apps/${app}`) || file.startsWith("packages/")
  );

Ah yes, thanks @paul-vd ! I removed this by accident when generalizing this for the gist - I’ll get that fixed! But the intention is for the app var to be pulled from the command line as described in the README above.

Here is how I’m using this in my own monorepo:
https://github.com/tknickman/personal/blob/main/scripts/ignore-step.js

Amazing script, so useful!

Improved it a bit for my use case by just assuming the current folder name as app name if no argument provided:

const path = require('path');

const app = process.argv[2] || path.basename(path.resolve());

Great idea @IsraelOrtuno, updated!

NOTE: If using Turborepo (like I am in this repo) - you can now just use npx turbo-ignore as your ignored build step and it figures out if your app or any of it's dependencies have changed automatically:

https://vercel.com/changelog/intelligent-ignored-builds-using-turborepo

This modification checks against the previous successful deploy commit SHA, which is provided by vercel now. (https://vercel.com/docs/concepts/projects/environment-variables/system-environment-variables)

const fileNameList = childProcess
    .execSync(
      `git diff ${process.env.VERCEL_GIT_PREVIOUS_SHA} HEAD --name-only ./`
    )
    .toString()
    .trim()
    .split("\n");

Just wanted to say thank you!
and if you are using "type": "module", in your package.json file, then rename the file to ignore-step.cjs