asolimando commented on code in PR #24051: URL: https://github.com/apache/datafusion/pull/24051#discussion_r3719301633
########## docs/source/contributor-guide/pr_review.md: ########## @@ -0,0 +1,223 @@ +<!--- + Licensed to the Apache Software Foundation (ASF) under one + or more contributor license agreements. See the NOTICE file + distributed with this work for additional information + regarding copyright ownership. The ASF licenses this file + to you under the Apache License, Version 2.0 (the + "License"); you may not use this file except in compliance + with the License. You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, + software distributed under the License is distributed on an + "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + KIND, either express or implied. See the License for the + specific language governing permissions and limitations + under the License. +--> + +# Reviewing Pull Requests + +When reviewing PRs, our primary goal is to improve DataFusion and its community +together. PR feedback should be constructive and help improve the code as well +as the understanding of the contributor. + +Review bandwidth is currently our most limited resource, and reviews from the +broader community are both welcomed and encouraged. Reviewing PRs is a great way +to learn the codebase, and you do not need to be a committer to leave valuable +review feedback. In fact one of the best ways to become a committer is to +thoughtfully review other PRs. + +Please ensure any comments you leave contain a rationale and suggested +alternative -- it is frustrating to be told "don't do it this way" without any +clear reason or alternate provided. + +The criteria in this guide are also a useful checklist when preparing your own +PR for review. + +## PR Review Mechanics + +Some helpful links: + +- [PRs Waiting for Review] on GitHub +- [Approved PRs Waiting for Merge] on GitHub + +[prs waiting for review]: https://github.com/apache/datafusion/pulls?q=is%3Apr+is%3Aopen+-review%3Aapproved+-is%3Adraft+ +[approved prs waiting for merge]: https://github.com/apache/datafusion/pulls?q=is%3Apr+is%3Aopen+review%3Aapproved+-is%3Adraft + +The overall PR lifecycle (CI triggering, approval, the 24 hour rule for +"major" PRs, and merging) is described in the +[Pull Request Overview](index.md#pull-request-overview) section of the +contributor guide. + +Practical tips: + +1. Check out the changes locally to explore them in your IDE or with an + agent, e.g. `gh pr checkout <PR number>` using the [GitHub CLI]. +2. There is normally no need to rerun tests locally that CI has already run. +3. Leave comments on specific lines of the diff where possible, so the + discussion has context. +4. If you review a PR but don't feel confident approving it, leaving comments + is still valuable: a partial review (e.g. "I reviewed the tests and they + look good") helps the next reviewer focus their time. +5. Anything that does not need to block the current PR can be noted as a + potential follow up (ideally by filing a ticket), keeping the PR focused + and quick to merge. + +[github cli]: https://cli.github.com/ + +## Review the PR Description + +The PR description is often what users and contributors will find when they run +`git log` / `git blame` and ask "why is the code like this?". + +Check that the description: + +1. Concisely describes the **problem being solved from the user's point of + view**. + +2. Follows the [PR template], and answers the template's questions. + +3. Accurately describes what the PR actually does. + +4. Explicitly calls out any user-facing or API changes (see + [Review the Code](#review-the-code) below). + +[pr template]: https://github.com/apache/datafusion/blob/main/.github/pull_request_template.md + +## Review the Code Comments + +Well written code comments are what makes the codebase understandable to the +next contributor. + +Check that: + +1. The code has adequate comments, and that the comments focus on the + **rationale** for any non-obvious change (the "why"), not a restatement of + what the code does (the "what"), which is typically clear from reading the + code itself. +2. Comments do not narrate irrelevant internal implementation details or the + history of how the change was developed (this is common in LLM-assisted + code, e.g. "// changed to use a HashMap" or "// this handles the case + mentioned above"). Such comments become irrelevant as soon as the PR merges. +3. When comments refer to other structs, functions, or modules, they should use + [rustdoc intra-doc links] (e.g. `` [`SessionContext`] ``) rather than plain + text names, so that `cargo doc` link checking ensures the references stay + valid as the code evolves. +4. New public APIs have doc comments, including examples where appropriate + (doc examples are also tested by CI, so they double as test coverage). + +[rustdoc intra-doc links]: https://doc.rust-lang.org/rustdoc/write-documentation/linking-to-items-by-name.html + +## Review the Test Coverage + +Check that the feature or fix is covered sufficiently with tests (see the +[Testing](testing.md) guide for more details): the PR should include tests for +any new functionality, and a bug fix should include a test that reproduces the +reported problem. + +Guidelines for evaluating tests: + +1. Prefer `sqllogictest` (`.slt`) tests or DataFrame API tests where + possible, as they exercise **user visible behavior** and are less coupled + to internal implementation details than unit tests. +2. Verify test coverage of changed code using the `codecov` check on the PR + or run [`cargo llvm-cov`] locally for an HTML report. Use judgement about + any uncovered lines (e.g. error paths that are hard to trigger may be + fine) -- the goal is confidence in the change, not slavishly hitting some + coverage number. +3. Avoid tests with lots of repeated boilerplate: when many tests share + near-identical setup, it is hard to understand what is different + (and thus what is actually being tested) between them. Make the _difference_ + between cases obvious. +4. Check that tests assert on specific expected values or plans (e.g. via + `insta` snapshots or `.slt` expected output) rather than merely checking + "no error occurred". + +[`cargo llvm-cov`]: https://github.com/taiki-e/cargo-llvm-cov + +## Review the Code Review Comment: > When creating new functions or tests, be intentional on their placement, try to keep related code close by. > > Non-exhaustive examples: > - introducing a new function/test related to a given functionality, co-locate it with other functions/tests covering the same functionality (e.g., grouping sets for aggregations) > - if you introduce a helper function, keep it close to where it is used > - if you introduce an SLT test, look for the closest `.slt` file by argument Here is an example of how I would phrase it, I think this framing could help both human reviewers and AI-tools alike (the latter also for code generation). When I manually inspect code it helps me to find related code together, and I also suspect (no data point to prove) that AI tools might benefit as well. WDYT? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
