How to Contribute

Contributions are always welcome! And there is a multitude of ways in which you can help depending on what you like to do, or are good at. Anything from documentation, code cleanup, issue completion, new features, you name it, even filing issues is contributing and greatly appreciated!

Goals

There are a few goals of clap that I‘d like to maintain throughout contributions. If your proposed changes break, or go against any of these goals we’ll discuss the changes further before merging (but will not be ignored, all contributes are welcome!). These are by no means hard-and-fast rules, as I'm no expert and break them myself from time to time (even if by mistake or ignorance :P).

• Remain backwards compatible when possible
  • If backwards compatibility must be broken, use deprecation warnings if at all possible before removing legacy code
  • This does not apply for security concerns
• Parse arguments quickly
  • Parsing of arguments shouldn't slow down usage of the main program
  • This is also true of generating help and usage information (although slightly less stringent, as the program is about to exit)
• Try to be cognizant of memory usage
  • Once parsing is complete, the memory footprint of clap should be low since the main program is the star of the show
• panic! on developer error (e.g. apps and args), exit gracefully on end-user error

General Overview

Where to Start

• Discussions can be useful for getting help and brainstorming
• Issues work well discussing a need and how to solve it
  • Focus: requirements gathering and design discussions
  • Sometimes a branch or Draft PR might be used to demonstrate an idea
• PRs work well for when the solution has already been discussed as an Issue or there is little to no discussion (obvious bug or documentation fixes)
  • Focus: implementation discussions

Compatibility Expectations

Our releases fall into one of:

• Major releases which are reserved for breaking changes
  • Aspire to at least 6-9 months between releases
  • Remove all deprecated functionality
  • Changes in help/error output that could cause glaring inconsistencies in end-user applications
  • Try to minimize new breaking changes to ease user transition and reduce time “we go dark” (unreleased feature-branch)
  • Upon release, a minor release will be made for the previous major that enables deprecated feature by default
• Minor releases which are for minor compatibility changes
  • Aspire to at least 2 months between releases
  • Changes to MSRV
  • Wide-spread help/error output changes that would cause minor inconsistencies in end-user applications
  • Deprecating existing functionality (behind the deprecated feature flag)
  • Making the deprecated feature flag enabled-by-default (only on last planned minor release)
  • #[doc(hidden)] all deprecated items in the prior minor release
• Patch releases
  • One for every user-facing, user-contributed PR (i.e. release early, release often)
  • Changes in help/error output that are one-off or improving consistency so as to not increase inconsistency with end-user applications

If your change does not fit within a “patch” release, please coordinate with the clap maintainers for how to handle the situation.

Some practices to avoid breaking changes

• Duplicate functionality, with old functionality marked as “deprecated”
  • Common documentation pattern: /// Deprecated in [Issue #XXX](https://github.com/clap-rs/clap/issues/XXX), replaced with [intra-doc-link]
  • Common deprecation pattern: #[cfg_attr(feature = "deprecated", deprecated(since = "X.Y.Z", note = "Replaced with ITEM in Issue #XXX"))]
    • deprecated feature flag is to allow people to process them on their time table and allow us to process feedback from early adopters before requiring everyone to process them on the next major version.
  • Please keep API addition and deprecation in separate commits in a PR to make it easier to review
• Develop the feature behind an unstable-<name> feature flag with a stabilization tracking issue (e.g. Multicall Tracking issue)

Version Support Policy

As we work towards a more flexible architecture, we hope to support multiple major versions to help ease users through the upgrade churn.

Version	Status	Support	End-of-Life
v4	active	Features and bug fixes target master by default	TBD
v3	maintenance	Accepting trivial cherry-picks from master (i.e. minimal conflict resolution) by contributors and fixes for ecosystem-wide showstoppers	TBD
v2	deprecated	Only accepting fixes for ecosystem-wide showstoppers	TBD
v1	unsupported	-	-

Note: We have not yet determined the End-of-Life schedule for previous major versions. We will give at least a 2 month warning before changing the support status.

Verifying Changes

A common (sub)set of commands for verifying your change:

$ make test-full
$ make clippy-full
$ make doc

(If make is not available on your system, you can look up what these expand to in the Makefile)

Check out the Makefile for more commands run by CI.

Debugging Clap

A helpful technique is to see the clap debug output while developing features. In order to see the debug output while running the full test suite or individual tests, run:

$ cargo test --features debug

# Or for individual tests
$ cargo test --test <test_name> --features debug

Preparing the PR

As a heads up, we'll be running your PR through the following gauntlet:

• warnings turned to compile errors
• cargo test
• rustfmt
• clippy
• rustdoc
• committed as we use Conventional commit style
• typos to check spelling

Not everything can be checked automatically though.

We request that the commit history gets cleaned up. We ask that commits are atomic, meaning they are complete and have a single responsibility. PRs should tell a cohesive story, with test and refactor commits that keep the fix or feature commits simple and clear.

Specifically, we would encourage

• File renames be isolated into their own commit
• Add tests in a commit before their feature or fix, showing the current behavior. The diff for the feature/fix commit will then show how the behavior changed, making it clearer to reviewers and the community and showing people that the test is verifying the expected state.
  • e.g. clap#5520

Note that we are talking about ideals. We understand having a clean history requires more advanced git skills; feel free to ask us for help! We might even suggest where it would work to be lax. We also understand that editing some early commits may cause a lot of churn with merge conflicts which can make it not worth editing all of the history.

For code organization, we recommend

• Grouping impl blocks next to their type (or trait)
• Grouping private items after the pub item that uses them.
  • The intent is to help people quickly find the “relevant” details, allowing them to “dig deeper” as needed. Or put another way, the pub items serve as a table-of-contents.
  • The exact order is fuzzy; do what makes sense

Conditions for fulfilling a bounty:

1. You should make a pull request which fixes the issue the bounty was promised for
2. The pull request should be merged by one of the maintainers

Below are the steps to redeem a bounty:

1. Go to https://opencollective.com/clap/expenses/new.
2. Select Invoice.
3. Enter Expense Title as “Issue Bounty”.
4. In Description, link the issue you are redeeming (Ex: https://github.com/clap-rs/clap/issues/1464)
5. In Amount, write the amount that the issue promised (Ex: 10)
6. Fill payment information and submit
7. Wait for us to approve it

Can I forgo the bounty?

Yes, you can. In that case, you don't have to do anything except writing a comment on the issue saying that I do. The bounty will be reassigned to another issue.

Specific Tasks

Section-specific CONTRIBUTING

• Example CONTRIBUTING
• Tutorial (builder) CONTRIBUTING
• Tutorial (derive) CONTRIBUTING
• clap_derive CONTRIBUTING

Updating MSRV

Search for MSRV, for example

$ rg --hidden MSRV

And update all of the references