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Contributing to QIIME

QIIME is an open source software package, and we welcome community contributions. You can find the source code and test code for QIIME under public revision control in the QIIME git repository on GitHub. While we have a core development group, we very much welcome contributions from other users.

This document covers what you should do to get started with contributing to QIIME. You should read this whole document before considering submitting code to QIIME. This will save time for both you and the QIIME developers.

To get help with using QIIME, please visit http://help.qiime.org.

Type of Submissions

Some of the types of contributions we're interested in are new features (big or small, but for big ones it's generally a good idea to ask us if we're interested in including it before starting development), bug fixes, and documentation updates, additions, and fixes.

When considering submitting a new feature to QIIME, you should begin by posting an issue to the QIIME issue tracker. The information that you include in that post will differ based on the type of contribution. Your contribution will also need to be fully tested (discussed further below).

  • For new features, you'll want to describe why the functionality that you are proposing to add is relevant. For it to be relevant, it should be demonstrably useful to QIIME users. This typically means that a new analytic method is implemented (you should describe why it's useful, ideally including a link to a paper that uses this method), or an existing method is enhanced (your implementation matches the performance of the pre-existing method while reducing runtime, memory consumption, etc, or it improves performance over the pre-existing method). We will request benchmark results comparing your method to the pre-existing methods (which would also be required for publication of your method) so pointing to a paper or other document containing benchmark results, or including benchmark results in your issue, will speed up the process.

  • For bug fixes, you should provide a detailed description of the bug so other developers can reproduce it. We take bugs in QIIME very seriously. Bugs can be related to errors in code, documentation, or tests. Errors in documentation or tests are usually updated in the next major release of QIIME. Errors in code that could result in incorrect results or inability to access certain functionality may result in a new minor release of QIIME.

You should include the following information in your bug report:

  1. The exact command or function call that you issue to create the bug.
  2. A link to all necessary input files for reproducing the bug. These files should only be as large as necessary to create the bug. For example, if you have an input file with 10,000 fasta-formatted sequences but the error only arises due to one of the sequences, create a new fasta file with only that sequence, run the command that was giving you problems, and verify that you still get an error. Then post that command and link to the trimmed fasta file. This is extremely useful to other developers, and it is likely that if you don't provide this information you'll get a response asking for it. Often this process helps you to better understand the bug as well.
  • For documentation additions, you should first post an issue describing what you propose to add, where you'd like to add it in the documentation, and a description of why you think it's an important addition. For documentation improvements and fixes, you should post an issue describing what is currently wrong or missing, and how you propose to address it.

When you post your issue, the QIIME developers will respond to let you know if we agree with the addition or change. It's very important that you go through this step to avoid wasting time working on a feature that we are not interested in including in QIIME.

Getting started: "quick fixes"

Some of our issues are labeled as quick fix. Working on these issues is a good way to get started with contributing to QIIME. These are usually small bugs or documentation errors that will only require one or a few lines of code to fix. Getting started by working on one of these issues will allow you to familiarize yourself with our development process before committing to a large amount of work (e.g., adding a new feature to QIIME). If you're interested in working on one of these issues, you should comment on the issue requesting that it be assigned to you.

Code Review

When you submit code to QIIME, it will be reviewed by one or more QIIME developers. These reviews are intended to confirm a few points:

  • Your code is sufficiently well-tested (see Testing Guidelines below).
  • Your code adheres to our Coding Guidelines (see Coding Guidelines below).
  • Your code is sufficiently well-documented (see Coding Guidelines below).
  • Your code provides relevant changes or additions to QIIME (Type of Submissions above).

This process is designed to ensure the quality of QIIME, and can be a very useful experience for new developers.

Particularly for big changes, if you'd like feedback on your code in the form of a code review as you work, you should request help in the issue that you created and one of the QIIME developers will work with you to perform regular code reviews. This can greatly reduce development time (and frustration) so we highly recommend that new developers take advantage of this rather than submitting a pull request with a massive amount of code in one chunk. That can lead to frustration when the developer thinks they are done, but the reviewer requests large amounts of changes, and it is also very hard to review.

Submitting code to QIIME

QIIME is hosted on GitHub, and we use GitHub's Pull Request mechanism for accepting submissions. You should go through the following steps to submit code to QIIME.

  1. Begin by creating an issue describing your proposed change. This should include a description of your proposed change (is it a new feature, a bug fix, etc.), and note in the issue description that you want to work on it. If you'll be modifying existing QIIME file(s), you'll want to get input from the developer responsible for the relevant file(s) via a discussion on the issue tracker to let them know you what you'd like to do. The developer responsible for the code is named in the __maintainer__ variable at the top of the file. Once you hear back that it is OK to make changes (i.e., they don't have local edits, they agree with the change you'd like to make, and they're comfortable with you editing their code), we will assign the issue to you on GitHub.

  2. Fork the QIIME repository on the GitHub website to your GitHub account.

  3. Clone your forked repository to the system where you'll be developing with git clone.

  4. Ensure that you have the latest version of all files (especially important if you cloned a long time ago, but you'll need to do this before submitting changes regardless). You should do this by adding QIIME as a remote repository and then pulling from that repository. You'll only need to run the git remote step one time:

git checkout master
git remote add upstream https://github.com/qiime/qiime.git
git pull upstream master
  1. Create a new topic branch that you will make your changes in with git checkout -b:
git checkout -b my-topic-branch

  1. Run qiime/tests/all_tests.py to confirm that the tests pass before you make any changes. You may get some failures, for example if you don't have an external application (e.g., RDP Classifier) installed. It is acceptable to continue if the failing tests are unrelated to the the code your working with. However, if you want to make changes to assign_taxonomy.py and test_assign_taxonomy.py is failing because of missing external applications, you should not proceed until you have installed the external applications and all tests pass.

  2. Make your changes, add them (with git add), and commit them (with git commit). Don't forget to update associated scripts and tests as necessary. You should make incremental commits, rather than one massive commit at the end. Write descriptive commit messages to accompany each commit.

  3. When you think you're ready to submit your code, again ensure that you have the latest version of all files in case some changed while you were working on your edits. You can do this by merging master into your topic branch:

git checkout my-topic-branch
git pull upstream master

  1. Run qiime/tests/all_tests.py to ensure that your changes did not cause anything unexpected to break. Note that some tests may fail again because you do not have external applications installed. This is why it is important that you run all_tests.py prior to making changes: if the same tests fail, then you should be OK.

  2. Once the tests pass, you should push your changes to your forked repository on GitHub using:

git push origin my-topic-branch
  1. Issue a pull request on the GitHub website to request that we merge your branch's changes into QIIME's master branch. One of the QIIME developers will review your code at this stage. If we request changes (which is very common), don't issue a new pull request. You should make changes on your topic branch, and commit and push them to GitHub. Your pull request will update automatically.

Coding Guidelines

We adhere to the PEP 8 python coding guidelines for code and documentation standards. Before submitting any code to QIIME, you should read these carefully and apply the guidelines in your code.

On reviewing QIIME, you will notice that all of our code isn't up to PEP 8 standards. This is something that we're striving toward, and as such all new contributions must adhere.

Testing Guidelines

All code that is added to QIIME must be unit tested, and the unit test code must be submitted in the same pull request as the library code that you are submitting. We will not merge code that is not unit tested. The PyCogent Coding Guidelines describe our expectations for unit tests. You should review the unit test section before working on your test code.

Because (at this time) our user interface is entirely command-line-based, we have developed a script interface testing framework to ensure that future changes to scripts don't break the command line interface. If you are developing or extending a QIIME script, you should review the PyCogent script guidelines and the script interface testing documentation.

Getting help with git

If you're new to git, you'll probably find gitref.org helpful.