CONTRIBUTING.md

Express Collaborator Guide

This document contains information for Collaborators of the express codemod regarding maintaining the code, documentation.

Getting Started

The steps below will give you a general idea of how to prepare your local environment for the express codemods and general steps for getting things done and landing your contribution.

1. Create an issue for the bug you want to fix or the feature that you want to add.
2. Create your own fork on GitHub
3. Clone your fork using SSH, GitHub CLI, or HTTPS.

git clone [email protected]:<YOUR_GITHUB_USERNAME>/codemod.git # SSH
git clone https://github.com/<YOUR_GITHUB_USERNAME>/codemod.git # HTTPS
gh repo clone <YOUR_GITHUB_USERNAME>/codemod # GitHub CLI

4. Change into the nodejs.org directory.

cd codemod

5. Create a remote to keep your fork and local clone up-to-date.

git remote add upstream [email protected]:expressjs/codemod.git # SSH
git remote add upstream https://github.com/expressjs/codemod.git # HTTPS
gh repo sync expressjs/codemod # GitHub CLI

6. Create a new branch for your work.

git checkout -b name-of-your-branch

7. Run the following to install the dependencies and start a local build of your work.

npm ci # installs this project's dependencies
npm run dev # starts a development environment

8. Perform your changes
9. Ensure your code is linted by running npm run lint -- fix any issue you see listed.
10. If the tests pass, you can commit your changes to your fork and then create a pull request from there. Make sure to reference your issue from the pull request comments by including the issue number e.g. #123.

How to add codemods

We use jscodeshift to create and run the codemods. To add a new codemod for Express, we follow the following process.

1. Create a new file in the transforms directory. For example, transforms/pluralized-methods.ts.

2. Write your codemod. Here's an example that pluralizes Express methods:

// filepath: codemod/transforms/pluralized-methods.ts
import type { API, FileInfo } from 'jscodeshift'
import { Identifier, identifier } from 'jscodeshift'
import { getParsedFile } from '../utils/parse'

export default function transformer(file: FileInfo, _api: API): string {
  const parsedFile = getParsedFile(file)

  const identifierNamesToReplace = ['acceptsLanguage', 'acceptsCharset', 'acceptsEncoding']

  for (const singular of identifierNamesToReplace) {
    const plural = `${singular}s`

    parsedFile
      .find(Identifier, {
        name: singular,
      })
      .replaceWith(() => identifier(plural))
  }

  return parsedFile.toSource()
}

3. Add tests to verify the functionality of the codemod

   • A new file is created in the /transforms/__test__ directory with the same name as the codemod with the following content

   // filepath: codemod/transforms/__test__/pluralized-methods.ts
   
   import { testSpecBuilder } from './util'
   
   testSpecBuilder('magic-redirect')

   • Two new files are created, name-codemod.input.ts and name_codemod.output.ts, inside the /transforms/__testfixtures__ directory
     • The files ending in .input.ts contain the content that should be changed by the codemod
     • The .output.ts files contain the content that should be present after the codemod has been correctly applied.

4. To make the codemod visible within the CLI, the config.ts file is modified, where a brief description of the codemod, its name, and the version of Express to which the migration should be applied are added.

Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

 (a) The contribution was created in whole or in part by me and I
     have the right to submit it under the open source license
     indicated in the file; or

 (b) The contribution is based upon previous work that, to the best
     of my knowledge, is covered under an appropriate open source
     license and I have the right under that license to submit that
     work with modifications, whether created in whole or in part
     by me, under the same open source license (unless I am
     permitted to submit under a different license), as indicated
     in the file; or

 (c) The contribution was provided directly to me by some other
     person who certified (a), (b) or (c) and I have not modified
     it.

 (d) I understand and agree that this project and the contribution
     are public and that a record of the contribution (including all
     personal information I submit with it, including my sign-off) is
     maintained indefinitely and may be redistributed consistent with
     this project or the open source license(s) involved.