Contributing.md

Contributing to Meteor

Thank you for contributing to the Meteor project! Please read the guidelines below or it might be hard for us to help you with your issue.

We are excited to have your help building Meteor — both the platform and the community behind it — and share in the rewards of getting in early on something great. Here's how you can help with bug reports and new code.

Reporting a bug in Meteor

We welcome clear bug reports. If you've found a bug in Meteor that isn't a security risk, please file a report in our issue tracker.

There is a separate procedure for security-related issues. If the issue you've found contains sensitive information or raises a security concern, email security@meteor.com instead, which will page the security team.

A Meteor app has many moving parts, and it's often difficult to reproduce a bug based on just a few lines of code. So your report should include a reproduction recipe. By making it as easy as possible for others to reproduce your bug, you make it easier for your bug to be fixed. We may not be able to tackle an issue opened without a reproduction recipe. If we can't, we'll close them with a pointer to this wiki section and a request for more information.

A single code snippet is not a reproduction recipe.

A reproduction recipe works like this:

• Create a new Meteor app that displays the bug with as little code as possible. Try to delete any code that is unrelated to the precise bug you're reporting, including extraneous Atmosphere packages. Ideally, try to use as few source files as possible so that it's easy to see the whole reproduction on one screen, rather than making a large number of small files, even if that's not how you'd choose to structure an app.

• Create a new GitHub repository with a name like meteor-reactivity-bug (or if you're adding a new reproduction recipe to an existing issue, meteor-issue-321) and push your code to it. (Make sure to include the .meteor/packages and .meteor/release files!)

• Reproduce the bug from scratch, starting with a git clone command. Copy and paste the entire command-line input and output, starting with the git clone command, into the issue description of a new GitHub issue. Also describe any web browser interaction you need to do.

• If you reproduced the issue using a checkout of Meteor instead of using a released version that was pinned with a .meteor/release file, specify what commit in the Meteor repository was checked out.

• Mention what operating system you're using and what browser (if any).

If you want to submit a pull request that fixes your bug, that's even better. We love getting bugfix pull requests. Just make sure they're written to the MDG style guide and come with tests. Read further down for more details on proposing changes to core code.

Feature requests

As of January 2015, we do use GitHub to track feature requests from our community. Feature request issues get the feature label, as well as a label corresponding to the Meteor subproject that they are a part of.

Meteor is a big project with many subprojects. Right now, the project doesn't have as many core developers (we're hiring!) as subprojects, so we're not able to work on every single subproject every month. We use our roadmap to communicate what we're actually working on now, and what things we might be working on soon.

Every additional feature adds a maintenance cost in addition to its value. This cost starts with the work of writing the feature or reviewing a community pull request. In addition to the core code change, attention needs to be paid to documentation, tests, maintability, how the feature interacts with existing and speculative Meteor features, cross-browser/platform support, user experience/API considerations, etc. Once the feature is shipped, it then becomes the core team's responsibility to fix future bugs related to the feature.

We're happy to see pull requests for Meteor feature requests on GitHub. Even if they don't get merged quickly, they can be helpful to other users who can use them as temporary workarounds, and community members can help each other iterate on making better pull requests.

But as described above, actually evaluating and merging them is real work that always has to be weighed against other work that Meteor users need. So don't be surprised if feature requests and their corresponding pull requests don't get acted on for a while or ever, especially if they contain API changes or don't contain tests.

That said, feature requests on GitHub are still a good place for the community to express their desires around features. We now organize issues using subproject labels, so it's easier for a core developer to find all the feature requests for a subproject and think of ways to holistically address multiple feature requests.

(We will close feature requests that are entire new subprojects that are already on the roadmap; discuss them on the roadmap! Many of these projects can be achieved (or at least prototyped) as non-core packages; the best way to influence the future of Meteor core on these future projects is to build a package that implements it yourself.)

In general, if a feature can be implemented as an external Atmosphere package by our community, that's better than building it in to core, since future changes can be made directly by the community users who directly depend on the feature.

Adding new packages to Meteor

If you have an idea for something new in Meteor, usually the best option is to publish it as an Atmosphere package. We want to keep the core as small as possible, with just the parts that most apps will need. If there's a way to do something as an Atmosphere package, we'll steer you in that direction.

Publishing your code as a separate package decouples your change from Meteor's core release cycle so you can maintain the code independently. It gives you and others in the community freedom to explore different variations of your idea. And it lets developers "vote with their feet" to find the best way to solve a problem or add a capability. For example, the popular iron:router package is an evolution of two earlier routing solutions that were both already available in Atmosphere.

For historical reasons, some packages that really ought to be in Atmosphere are currently in core, like less and coffeescript. We welcome PRs against these packages but they may not get the highest priority. If a community-supported package providing access to the same tool becomes popular, we'll likely start recommending that users use that instead and deprecate these core packages, as we already have with a few.

It's probably a good idea to write your packages to the MDG style guide. You can read more about that in the next section. In particular, two things you can get a head start on are:

• Your package should have tests. See the iron:router test suite as an example.

• Meteor minifies all JS/CSS. Packages should include only the original JS/CSS files, not the minified versions.

Making changes to Meteor core

Eventually you may want to change something in a core Meteor package, or in the meteor command line tool. These changes have the highest standards for API design, for the names of symbols, for documentation, and for the code itself. Be prepared for a lot of work!

It may take some study to get comfortable with Meteor's core architecture. Each core package is designed to stand separately. At the same time, all the parts of core fit together to make the distinctive Meteor development experience. Core APIs should be consistent between the client and the server (not always workable; we don't have fibers on the client or a DOM on the server). We prefer synchronous APIs wherever possible: you can use Meteor.wrapAsync on the server to wrap async APIs that take a callback.

Above all, we are concerned with two design requirements when evaluating any change to a core package:

1. Nothing in Meteor should harm the experience of a new Meteor developer. That can be a difficult standard to reach, because we're concerned here with the entire experience of developing and deploying an application. For example, we work hard to make sure that the Meteor docs don't force new users to understand advanced concepts before they need them. And we think a great deal about making our APIs as intuitive as possible, so that you can figure out a lot of Meteor without first having a long reading session with the docs.

2. Nothing in Meteor should preclude an expert from doing what they want. The low-level DDP API maps closely to the DDP wire protocol, for example, so that when the need arises you can control exactly what data gets sent to a client. It's okay to write syntactic sugar that makes the easy stuff easy, but if your change harms the experience of an expert then we'll probably prefer a different approach.

We have found that writing software to meet both these standards at the same time is hard but incredibly rewarding. We hope you come to feel the same way.

Proposing your change

You'll have the best chance of getting a change into core if you can build consensus in the community for it and eventually get a core developer on board. It is very unlikely that we'll take a patch that adds a feature without seeing some initial discussion about it. Probably the best way to get consensus is to discuss it on Meteor Forums, search the archives for anything relevant, and then post your proposal there. It's okay to post an idea to Meteor Forums without having a design or some initial code — others may be interested in helping.

Another option is to come to Devshop in San Francisco, where you can sit with a core developer and work out some of the design in person.

Most non-trivial changes need more discussion than comfortably fits inside GitHub's issue tracker, so that is not a good place to propose a new idea. We will probably close most "surprise" PRs that we find there with a note to start a discussion on Meteor Forums.

Small changes, especially if they don't affect APIs or documentation, may not really need a thread on Meteor Forums first. But a new feature that's small enough not to need discussion probably isn't super valuable. It may not get the highest priority from the core team, or we may just close it.

Submitting pull requests

Once you've hammered out a good design and gotten at least one core developer on board, go ahead and submit a pull request. Please follow these guidelines:

• Sign the contributor's agreement.

• Base all your work off of the devel branch. The devel branch is where active development happens. We do not merge patches directly into master.

• Name your branch to match the feature/bug fix that you are submitting.

• Limit yourself to one feature or bug fix per pull request.

• Include tests that prove your code works.

• Follow the MDG style guide for code and commit messages.

• Be sure your author field in git is properly filled out with your full name and email address so we can credit you.

Need help with your pull request?

Meteor now has groups defined to cover different areas of the codebase. If you need help getting acceptance on certain pull requests with an area of focus listed below, you can address the appropriate people in the pull request:

• Meteor Data Team - This includes DDP, tracker, mongo, accounts, etc. You can mention @data in the PR.
• Blaze - This includes Spacebars, Blaze, etc. You can mention @view-layer in the PR.
• Build tools - This includes modules, build tool changes, etc. You can memtion @platform in the PR.
• Mobile integration - This includes Cordova, React Native, etc. You can mention @mobile in the PR.
• Documentation - This includes the Guide, the Docs, and any supporting material. You can mention @guide in the PR.

Including the people above is no guarantee that you will get a response, or ultimately that your pull request will be accepted. This section exists to give some minor guidance on internal Meteor Development Group team structures.

Running tests on Meteor core

When you are working with code in the core Meteor packages, you will want to make sure you run the full test-suite (including the tests you added) to ensure you haven't broken anything in Meteor. The test-packages command will do just that for you.

The test packages command will start up a Meteor app with TinyTest setup, just connect to http://localhost:3000 or your specified port, like you would do with a normal meteor app.

Run against your local meteor copy

When running test-packages, be sure that you use the current directory copy of Meteor instead of the installed version. Here is the INCORRECT way: meteor test-packages.

The CORRECT way is to use ./meteor test-packages to run the full test suite against the branch you are on.

This is important because you want to make sure you are running the test-packages command against the Meteor code on the branch you have pulled from GitHub, rather than the stable Meteor release you have installed on your computer.

Running a subset of tests

You can also just run a subset of tests from one package to speed up testing time. Let's say for example that you just want to run the Spacebars test suite. Just simple do ./meteor test-packages ./packages/spacebars-tests and it will just run the test files from that one package. You can examine the package.js file for the onTest block, it outlines all the test files that should be run.

How we respond to issues

You might be interesting in reading this guide for core developers about responding to issues.