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How to Contribute
First of all, thank you for your interest in Puppeteer! We'd love to accept your patches and contributions!
Contributor License Agreement
Contributions to this project must be accompanied by a Contributor License Agreement. You (or your employer) retain the copyright to your contribution, this simply gives us permission to use and redistribute your contributions as part of the project. Head over to https://cla.developers.google.com/ to see your current agreements on file or to sign a new one.
You generally only need to submit a CLA once, so if you've already submitted one (even if it was for a different project), you probably don't need to do it again.
Getting Code
- Clone this repository
git clone https://github.com/puppeteer/puppeteer
cd puppeteer
- Install dependencies
npm install
- Run Puppeteer tests locally. For more information about tests, read Running & Writing Tests.
npm run unit
Code reviews
All submissions, including submissions by project members, require review. We use GitHub pull requests for this purpose. Consult GitHub Help for more information on using pull requests.
Code Style
- Coding style is fully defined in
.eslintrc
and we automatically format our code with Prettier. - It's recommended to set-up Prettier into your editor, or you can run
npm run eslint-fix
to automatically format any files. - If you're working in a JS file, code should be annotated with closure annotations.
- If you're working in a TS file, you should explicitly type all variables and return types. You'll get ESLint warnings if you don't so if you're not sure use them as guidelines, and feel free to ask us for help!
To run ESLint, use:
npm run eslint
You can check your code (both JS & TS) type-checks by running:
npm run tsc
TypeScript guidelines
- Try to avoid the use of
any
when possible. Considerunknown
as a better alternative. You are able to useany
if needbe, but it will generate an ESLint warning.
API guidelines
When authoring new API methods, consider the following:
- Expose as little information as needed. When in doubt, don’t expose new information.
- Methods are used in favor of getters/setters.
- The only exception is namespaces, e.g.
page.keyboard
andpage.coverage
- The only exception is namespaces, e.g.
- All string literals must be small case. This includes event names and option values.
- Avoid adding "sugar" API (API that is trivially implementable in user-space) unless they're very demanded.
Commit Messages
Commit messages should follow the Semantic Commit Messages format:
label(namespace): title
description
footer
- label is one of the following:
fix
- puppeteer bug fixes.feat
- puppeteer features.docs
- changes to docs, e.g.docs(api.md): ..
to change documentation.test
- changes to puppeteer tests infrastructure.style
- puppeteer code style: spaces/alignment/wrapping etc.chore
- build-related work, e.g. doclint changes / travis / appveyor.
- namespace is put in parenthesis after label and is optional. Must be lowercase.
- title is a brief summary of changes.
- description is optional, new-line separated from title and is in present tense.
- footer is optional, new-line separated from description and contains "fixes" / "references" attribution to github issues.
- footer should also include "BREAKING CHANGE" if current API clients will break due to this change. It should explain what changed and how to get the old behavior.
Example:
fix(page): fix page.pizza method
This patch fixes page.pizza so that it works with iframes.
Fixes #123, Fixes #234
BREAKING CHANGE: page.pizza now delivers pizza at home by default.
To deliver to a different location, use "deliver" option:
`page.pizza({deliver: 'work'})`.
Writing Documentation
All public API should have a descriptive entry in docs/api.md
. There's a documentation linter which makes sure documentation is aligned with the codebase.
To run the documentation linter, use:
npm run doc
Adding New Dependencies
For all dependencies (both installation and development):
- Do not add a dependency if the desired functionality is easily implementable.
- If adding a dependency, it should be well-maintained and trustworthy.
A barrier for introducing new installation dependencies is especially high:
- Do not add installation dependency unless it's critical to project success.
Running & Writing Tests
- Every feature should be accompanied by a test.
- Every public api event/method should be accompanied by a test.
- Tests should not depend on external services.
- Tests should work on all three platforms: Mac, Linux and Win. This is especially important for screenshot tests.
Puppeteer tests are located in the test directory (test
and are written using Mocha. See test/README.md
for more details.
Despite being named 'unit', these are integration tests, making sure public API methods and events work as expected.
- To run all tests:
npm run unit
- To run a specific test, substitute the
it
withit.only
:
...
it.only('should work', async function({server, page}) {
const response = await page.goto(server.EMPTY_PAGE);
expect(response.ok).toBe(true);
});
- To disable a specific test, substitute the
it
withxit
(mnemonic rule: 'cross it'):
...
// Using "xit" to skip specific test
xit('should work', async function({server, page}) {
const response = await page.goto(server.EMPTY_PAGE);
expect(response.ok).toBe(true);
});
- To run tests in non-headless mode:
HEADLESS=false npm run unit
- To run Firefox tests, firstly ensure you have Firefox installed locally (you only need to do this once, not on every test run) and then you can run the tests:
PUPPETEER_PRODUCT=firefox node install.js
PUPPETEER_PRODUCT=firefox npm run unit
- To run tests with custom browser executable:
BINARY=<path-to-executable> npm run unit
Public API Coverage
Every public API method or event should be called at least once in tests. To ensure this, there's a coverage
command which tracks calls to public API and reports back if some methods/events were not called.
Run coverage:
npm run coverage
Debugging Puppeteer
See Debugging Tips in the readme.
For Project Maintainers
Releasing to npm
Releasing to npm consists of the following phases:
- Source Code: mark a release.
- Bump
package.json
version following the SEMVER rules. - Run
npm run doc
to update the docs accordingly. - Update the “Releases per Chromium Version” list in
docs/api.md
to include the new version. Note: only do this when the Chrome revision is different from the previous release. - Send a PR titled
'chore: mark version vXXX.YYY.ZZZ'
(example). - Make sure the PR passes all checks.
- WHY: there are linters in place that help to avoid unnecessary errors, e.g. like this
- Merge the PR.
- Once merged, publish the release notes using GitHub's “draft new release tag” option.
- NOTE: tag names are prefixed with
'v'
, e.g. for version1.4.0
the tag isv1.4.0
. - For the “raw notes” section, use
git log --pretty="%h - %s" v2.0.0..HEAD
.
- NOTE: tag names are prefixed with
- Bump
- Publish
puppeteer
to npm.- On your local machine, pull from upstream and make sure the last commit is the one just merged.
- Run
git status
and make sure there are no untracked files.- WHY: this is to avoid adding unnecessary files to the npm package.
- Run
npx pkgfiles
to make sure you don't publish anything unnecessary. - Run
npm publish
. This publishes thepuppeteer
package.
- Publish
puppeteer-core
to npm.- Run
./utils/prepare_puppeteer_core.js
. The script changes the name insidepackage.json
topuppeteer-core
. - Run
npm publish
. This publishes thepuppeteer-core
package. - Run
git reset --hard
to reset the changes topackage.json
.
- Run
- Source Code: mark post-release.
- Bump
package.json
version to-post
version, runnpm run doc
to update the “released APIs” section at the top ofdocs/api.md
accordingly, and send a PR titled'chore: bump version to vXXX.YYY.ZZZ-post'
(example)- NOTE: no other commits should be landed in-between release commit and bump commit.
- Bump
Updating npm dist tags
For both puppeteer
and puppeteer-core
we maintain chrome-*
npm dist tags, e.g. chrome-75
and so on. These tags match the Puppeteer version that corresponds to the chrome-*
release.
These tags are updated on every Puppeteer release.
Managing tags 101:
# List tags
$ npm dist-tag ls puppeteer
# Add tags
$ npm dist-tag add puppeteer@3.0.0 chrome-81
$ npm dist-tag add puppeteer-core@3.0.0 chrome-81