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Contributing

When contributing to this repository, please first discuss the change you wish to make via GitHub Discussions with the owners of this repository before submitting a Pull Request.

Please read our Code of Conduct and follow it in all your interactions with the project.

Local development

This project is configured in a monorepo, where one repository contains multiple npm packages. Dependencies are installed and managed with yarn, not npm CLI.

To get started, execute the following:

git clone https://github.com/vercel/vercel
cd vercel
corepack enable
yarn install
yarn bootstrap
yarn build
yarn lint
yarn test-unit

Make sure all the tests pass before making changes.

Verifying your change

Once you are done with your changes (we even suggest doing it along the way), make sure all the tests still pass by running:

yarn test-unit

from the root of the project.

If any test fails, make sure to fix it along with your changes. See Interpreting test errors for more information about how the tests are executed, especially the integration tests.

Pull Request Process

Once you are confident that your changes work properly, open a pull request on the main repository.

The pull request will be reviewed by the maintainers and the tests will be checked by our continuous integration platform.

Interpreting test errors

There are 2 kinds of tests in this repository – Unit tests and Integration tests.

Unit tests are run locally with jest and execute quickly because they are testing the smallest units of code.

Integration tests

Integration tests create deployments to your Vercel account using the test project name. After each test is deployed, the probes key is used to check if the response is the expected value. If the value doesn't match, you'll see a message explaining the difference. If the deployment failed to build, you'll see a more generic message like the following:

[Error: Fetched page https://test-8ashcdlew.vercel.app/root.js does not contain hello Root!. Instead it contains An error occurred with this application.

    NO_STATUS_CODE_FRO Response headers:
       cache-control=s-maxage=0
      connection=close
      content-type=text/plain; charset=utf-8
      date=Wed, 19 Jun 2019 18:01:37 GMT
      server=now
      strict-transport-security=max-age=63072000
      transfer-encoding=chunked
      x-now-id=iad1:hgtzj-1560967297876-44ae12559f95
      x-now-trace=iad1]

In such cases, you can visit the URL of the failed deployment and append /_logs to see the build error. In the case above, that would be https://test-8ashcdlew.vercel.app/_logs

The logs of this deployment will contain the actual error which may help you to understand what went wrong.

@vercel/nft

Some of the Builders use @vercel/nft to tree-shake files before deployment. If you suspect an error with this tree-shaking mechanism, you can create the following script in your project:

const { nodeFileTrace } = require('@vercel/nft');
nodeFileTrace(['path/to/entrypoint.js'], {
  ts: true,
  mixedModules: true,
})
  .then(o => console.log(o.fileList))
  .then(e => console.error(e));

When you run this script, you'll see all the imported files. If anything file is missing, the bug is in @vercel/nft and not the Builder.

Deploy a Builder with existing project

Sometimes you want to test changes to a Builder against an existing project, maybe with vercel dev or actual deployment. You can avoid publishing every Builder change to npm by uploading the Builder as a tarball.

  1. Change directory to the desired Builder cd ./packages/node
  2. Run yarn build to compile typescript and other build steps
  3. Run npm pack to create a tarball file
  4. Run vercel *.tgz to upload the tarball file and get a URL
  5. Edit any existing vercel.json project and replace use with the URL
  6. Run vercel or vercel dev to deploy with the experimental Builder