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Contributing

Welcome to Nushell and thank you for considering contributing!

Table of contents

Other helpful resources

More resources can be found in the nascent developer documentation in this repo.

Tips for submitting PRs

Thank you for improving Nushell! We love to see other folks enthusiastic about Nushell, and we can help you work through the design or implementation of your PR. Come talk with us in Discord, or create a GitHub discussion or draft PR and we can help you work out the details from there.

Please talk to the core team before making major changes! See the proposing design changes for more details.

Release notes section

In our PR template, we have a "Release notes summary" section which will be included in our release notes for our blog. This section should include all information about your change which is relevant to a user of Nushell.

You should try to keep it brief and simple to understand, and focus on the ways your change directly impacts the user experience. Motivation, technical details, and any other information which isn't directly relevant to users should be put somewhere else -- either above or below the release notes section is fine.

The release notes summary section doesn't need to be filled until your PR is finalized. Feel free to leave it blank until the PR has undergone review already. Of course, this section can also be useful to demonstrate to reviewers how your proposed changed will work, so don't hesitate to fill in the section if it helps you explain your PR.

Please make sure to consider both the intended changes, such as additions or deliberate breaking changes and possible side effects that might change how users interact with a command or feature. It's important to think carefully about the ways that your PR might affect any aspect of the user experience, and to document these changes even if they seem minor or aren't directly related to the main purpose of the PR.

If you're not sure what to put here, or need some help, a core team member would be glad to help you out. We may also make some tweaks to your release notes section. Please don't take it personally, we just want to make sure our release notes are polished and easy to understand. Once the release notes section is finalized, we'll add the notes:ready label to indicate that your summary section is ready to be included in the actual release notes.

If you want to write the best possible release notes summary (we appreciate it!), we have a couple guides we use to make sure the release notes are up to our standards before marking them as ready. The how to prepare PRs for release notes explains the process we go through to make sure that PRs are properly labeled, and explains how formatting within the PR affects the generated release notes. The release notes summary style guide explains the conventions we follow in our release notes, and might help if you're not sure how to word your release notes summary.

Structuring your summary

For smaller changes, a simple one to two sentence explanation is sufficient. If that's all you need to explain the impact of the change, keep any further details out of the release notes summary. Summaries which are a single line will appear as a bullet point in our release notes.

For larger changes, you can use multiple lines to fully explain your change. We highly encourage adding examples and/or screenshots if this is the case.

Summaries which are multiple lines will appear under their own heading in the release notes. By default, the title for the heading will be the title of your PR. If you'd like to add a more user-friendly title, or your PR encompasses multiple changes that should appear in their own sections, you can manually add one or more third-level headings to your release notes summary section. For example:

## Release notes summary - What our users need to know

### Cool command

This change adds a cool new feature. Here's how you use it:

```nushell
my-cool-command
```

In the release notes, this will appear under a heading titled simply "Cool command". A concise title like this might be more appropriate than the PR title, which may have more info than is necessary for the release notes.

This section might not be relevant for all PRs. If your PR is a work in progress, feel free to write "WIP"/"TODO"/etc in this section. You can also write "N/A" or simply leave this section blank if this is a purely technical change which doesn't impact the user experience.

Tests and formatting checks

Our CI system automatically checks formatting and runs our tests. If you're running into an issue, or just want to make sure everything is ready to go before creating your PR, you can run the checks yourself:

use toolkit.nu # or use an `env_change` hook to activate it automatically
toolkit check pr

Furthermore, you can also runs these checks individually with the subcommands of toolkit, or run the underlying commands yourself:

  • cargo fmt --all -- --check to check standard code formatting (cargo fmt --all applies these changes)
  • cargo clippy --workspace -- -D warnings -D clippy::unwrap_used to check that you're using the standard code style
  • cargo test --workspace to check that all tests pass (on Windows make sure to enable developer mode)
  • cargo run -- -c "use toolkit.nu; toolkit test stdlib" to run the tests for the standard library

If the checks are passing on your local system, but CI just won't pass, feel free to ask for help from the core team.

Linking and mentioning issues

If your PR closes one or more issues, you can automatically link the PR with them by using one of the linking keywords:

  • This PR should close #xxxx
  • Fixes #xxxx

You can also mention related issues, PRs or discussions!

Proposing design changes

First of all, before diving into the code, if you want to create a new feature, change something significantly, and especially if the change is user-facing, it is a good practice to first get an approval from the core team before starting to work on it. This saves both your and our time if we realize the change needs to go another direction before spending time on it. So, please, reach out and tell us what you want to do. This will significantly increase the chance of your PR being accepted.

The review process can be summarized as follows:

  1. You want to make some change to Nushell that is more involved than simple bug-fixing.
  2. Go to Discord or a GitHub issue and chat with some core team members and/or other contributors about it.
  3. After getting a green light from the core team, implement the feature, open a pull request (PR) and write a concise but comprehensive description of the change.
  4. If your PR includes any user-facing features (such as adding a flag to a command), clearly list them in the PR description.
  5. Then, core team members and other regular contributors will review the PR and suggest changes.
  6. When we all agree, the PR will be merged.
  7. If your PR includes any user-facing features, make sure the changes are also reflected in the documentation after the PR is merged.
  8. Congratulate yourself, you just improved Nushell! :-)

Developing

Setup

Nushell requires a recent Rust toolchain and some dependencies; refer to the Nu Book for up-to-date requirements. After installing dependencies, you should be able to clone+build Nu like any other Rust project:

git clone https://github.com/nushell/nushell
cd nushell
cargo build

Tests

It is good practice to cover your changes with a test. Also, try to think about corner cases and various ways how your changes could break. Cover those in the tests as well.

Tests can be found in different places:

  • /tests
  • command examples
  • crate-specific tests

Most of the tests are built upon the nu-test-support crate. For testing specific features, such as running Nushell in a REPL mode, we have so called "testbins". For simple tests, you can find run_test() and fail_test() functions.

Useful Commands

As Nushell is built using a cargo workspace consisting of multiple crates keep in mind that you may need to pass additional flags compared to how you may be used to it from a single crate project. Read cargo's documentation for more details: https://doc.rust-lang.org/cargo/reference/workspaces.html

  • Build and run Nushell:

    cargo run

  • Run Clippy on Nushell:

    cargo clippy --workspace -- -D warnings -D clippy::unwrap_used

    or via the toolkit.nu command:

    use toolkit.nu clippy
clippy

  • Run all tests:

    cargo test --workspace

    or via the toolkit.nu command:

    use toolkit.nu test
test

  • Run all tests for a specific command

    cargo test --package nu-cli --test main -- commands::<command_name_here>

  • Check to see if there are code formatting issues

    cargo fmt --all -- --check

    or via the toolkit.nu command:

    use toolkit.nu fmt
fmt --check

  • Format the code in the project

    cargo fmt --all

    or via the toolkit.nu command:

    use toolkit.nu fmt
fmt

  • Set up git hooks to check formatting and run clippy before committing and pushing:

    use toolkit.nu setup-git-hooks
setup-git-hooks

    Unfortunately, this hook isn't available on Windows.

Debugging Tips

  • To view verbose logs when developing, enable the trace log level.

    cargo run --release -- --log-level trace

  • To redirect trace logs to a file, enable the --log-target file switch.

    cargo run --release -- --log-level trace --log-target file
open $"($nu.temp-dir)/nu-($nu.pid).log"

Experimental options

We sometimes add new behavior behind experimental options. These are opt-in (or opt-out) flags that let us try out changes without affecting everyone by default. Before introducing a new option, make sure the core team agrees roughly with that experimental option.

If you introduce a new experimental option, you must also:

  1. Open a tracking issue using the Experimental Option Tracking template.
  • Link the issue in your implementation using ExperimentalOptionMarker::ISSUE.

  1. Document the behavior in the tracking issue with a short description and before/after examples.

  2. Update the status in the tracking issue when the option moves forward (becomes default) or is discarded.

This ensures experimental options are discoverable, tracked properly, and easy to follow up on later.

Git etiquette

As nushell thrives on its broad base of volunteer contributors and maintainers with different backgrounds we have a few guidelines for how we best utilize git and GitHub for our contributions. We strive to balance three goals with those recommendations:

  1. The volunteer maintainers and contributors can easily follow the changes you propose, gauge the impact, and come to help you or make a decision.
  2. You as a contributor can focus most of your time on improving the quality of the nushell project and contributing your expertise to the code or documentation.
  3. Making sure we can trace back why decisions were made in the past. This includes discarded approaches. Also we want to quickly identify regressions and fix when something broke.

How we merge PRs

In general the maintainers squash all changes of your PR into a single commit when merging.

This keeps a clean enough linear history, while not forcing you to conform to a too strict style while iterating in your PR or fixing small problems. As an added benefit the commits on the main branch are tied to the discussion that happened in the PR through their #1234 issue number.

Note Pro advice: In some circumstances, we can agree on rebase-merging a particularly large but connected PR as a series of atomic commits onto the main branch to ensure we can more easily revert or bisect particular aspects.

A good PR makes a change!

As a result of this PR-centric strategy and the general goal that the reviewers should easily understand your change, the PR title and description matters a great deal!

Make sure your description is concise but contains all relevant information and context. This means demonstrating what changes, ideally through nushell code or output examples. Furthermore links to technical documentation or instructions for folks that want to play with your change make the review process much easier.

Note Try to follow the suggestions in our PR message template to make sure we can quickly focus on the technical merits and impact on the users.

A PR should limit itself to a single functional change or related set of same changes.

Mixing different changes in the same PR will make the review process much harder. A PR might get stuck on one aspect while we would actually like to land another change. Furthermore, if we are forced to revert a change, mixing and matching different aspects makes fixing bugs or regressions much harder.

Thus, please try to separate out unrelated changes! Don't mix unrelated refactors with a potentially contested change. Stylistic fixes and housekeeping can be bundled up into singular PRs.

Guidelines for the PR title

The PR title should be concise but contain everything for a contributor to know if they should help out in the review of this particular change.

DON'T

  • Update file/in/some/deeply/nested/path.rs
    • Why are you making this change?
  • Fix 2134
    • What has to be fixed?
    • Hard to follow when not online on GitHub.
  • Ignore `~` expansion
    • In what context should this change take effect?
  • [feature] refactor the whole parser and also make nushell indentation-sensitive, upgrade to using Cpython. Let me know what you think!
    • Be concise
    • Maybe break up into smaller commits or PRs if the title already appears too long?

DO

  • Mention the nushell feature or command that is affected.
    • Fix URL parsing in `http get` (issue #1234)
  • You can mention the issue number if other context is there.
    • In general, mention all related issues in the description to crosslink (e.g. Fixes #1234, Closes #6789)
  • For internal changes mention the area or symbols affected if it helps to clarify
    • Factor out `quote_string()` from parser to reuse in `explore`

Review process / Merge conflicts

Note Keep in mind that the maintainers are volunteers that need to allocate their attention to several different areas and active PRs. We will try to get back to you as soon as possible.

You can help us to make the review process a smooth experience:

  • Testing:
    • We generally review in detail after all the tests pass. Let us know if there is a problem you want to discuss to fix a test failure or forces us to accept a breaking change.
    • If you fix a bug, it is highly recommended that you add a test that reproduces the original issue/panic in a minimal form.
    • In general, added tests help us to understand which assumptions go into a particular addition/change.
    • Try to also test corner cases where those assumptions might break. This can be more valuable than simply adding many similar tests.
  • Commit history inside a PR during code review:
    • Good atomic commits can help follow larger changes, but we are not pedantic.
    • We don't shame fixup commits while you try to figure out a problem. They can help others see what you tried and what didn't work. (see our squash policy)
    • During active review constant force pushing just to amend changes can be confusing!
      • GitHub's UI presents reviewers with less options to compare diffs
      • fetched branches for experimentation become invalid!
      • the notification a maintainer receives has a low signal-to-noise ratio
    • Git pros can use their judgement to rebase/squash to clean up the history if it aids the understanding of a larger change during review
  • Merge conflicts:
    • In general you should take care of resolving merge conflicts.
      • Use your judgement whether to git merge main or to git rebase main
      • Choose what simplifies having confidence in the conflict resolution and the review. Merge commits in your branch are OK in the squash model.
    • Feel free to notify your reviewers or affected PR authors if your change might cause larger conflicts with another change.
    • During the rollup of multiple PRs, we may choose to resolve merge conflicts and CI failures ourselves. (Allow maintainers to push to your branch to enable us to do this quickly.)

License

We use the MIT License in all of our Nushell projects. If you are including or referencing a crate that uses the GPL License unfortunately we will not be able to accept your PR.