Thanks for being interested in contributing to pub! Contributing to a new project can be hard: there‘s a lot of new code and practices to learn. This document is intended to get you up and running as quickly as possible. If you’re looking for documentation on using pub, try pub.dartlang.org.
The first step towards contributing is to contact the pub dev team and let us know what you‘re working on, so we can be sure not to start working on the same thing at the same time. Just send an email to misc@dartlang.org letting us know that you’re interested in contributing and what you plan on working on. This will also let us give you specific advice about where to start.
Pub isn‘t a package, but it’s organized like one. It has four top-level directories:
lib/ contains the implementation of pub. Currently, it's all in lib/src/, since there are no libraries intended for public consumption.
test/ contains the tests for pub.
bin/ contains pub.dart, the entrypoint script that's run whenever a user types “pub” on the command line or runs it in the Dart editor. This is usually run through shell scripts in sdk/bin at the root of the Dart repository.
resource/ contains static resource files that pub uses. They're automatically distributed in the Dart SDK.
It's probably easiest to start diving into the codebase by looking at a particular pub command. Each command is encapsulated in files in lib/src/command/.
To run pub from the Dart repository, first build Dart. From the root of the repo:
./tools/build.py -m release
You'll need to re-build whenever you sync the repository, but not when you modify pub or any packages it depends on. To run pub, just run sdk/bin/pub (or sdk/bin/pub.bat on Windows).
Before any change is made to pub, all tests should pass. To run all the pub tests, run this from the root of the Dart repository:
./tools/test.py -m release pub
Changes to pub should be accompanied by one or more tests that exercise the new functionality. When adding a test, the best strategy is to find a similar test in test/ and follow the same patterns. Note that pub makes wide use of the scheduled_test package in its tests, so it's usually important to be familiar with that when adding tests.
Pub tests come in two basic forms. The first, which is usually used to unit test classes and libraries internal to pub, has many tests in a single file. This is used when each test will take a short time to run. For example, test/version_test.dart contains unit tests for pub's Version class.
The other form, used by most pub tests, is usually used for integration tests of user-visible pub commands. Each test has a file to itself, which is named after the test description. This is used when tests can take a long time to run to avoid having the tests time out when running on the build bots. For example, tests/get/hosted/get_transitive_test.dart tests the resolution of transitive hosted dependencies when using pub get.
When testing new functionality, it's often useful to run a single test rather than the entire test suite. You can do this by appending the path to the test file to the test command. For example, to run get/relative_symlink_test.dart:
./tools/test.py -m release pub/get/relative_symlink_test
All patches to the Dart repo, including to pub, need to undergo code review before they're submitted. The full process for putting up your patch for review is documented elsewhere.