295 lines
14 KiB
Markdown
295 lines
14 KiB
Markdown
# Contributing Quick Start
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Rust Analyzer is an ordinary Rust project, which is organized as a Cargo
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workspace, builds on stable and doesn't depend on C libraries. So, just
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```
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$ cargo test
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```
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should be enough to get you started!
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To learn more about how rust-analyzer works, see
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[./architecture.md](./architecture.md) document.
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We also publish rustdoc docs to pages:
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https://rust-analyzer.github.io/rust-analyzer/ide/
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Various organizational and process issues are discussed in this document.
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# Getting in Touch
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Rust Analyzer is a part of [RLS-2.0 working
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group](https://github.com/rust-lang/compiler-team/tree/6a769c13656c0a6959ebc09e7b1f7c09b86fb9c0/working-groups/rls-2.0).
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Discussion happens in this Zulip stream:
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https://rust-lang.zulipchat.com/#narrow/stream/185405-t-compiler.2Fwg-rls-2.2E0
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# Issue Labels
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* [good-first-issue](https://github.com/rust-analyzer/rust-analyzer/labels/good%20first%20issue)
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are good issues to get into the project.
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* [E-has-instructions](https://github.com/rust-analyzer/rust-analyzer/issues?q=is%3Aopen+is%3Aissue+label%3AE-has-instructions)
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issues have links to the code in question and tests.
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* [E-easy](https://github.com/rust-analyzer/rust-analyzer/issues?q=is%3Aopen+is%3Aissue+label%3AE-easy),
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[E-medium](https://github.com/rust-analyzer/rust-analyzer/issues?q=is%3Aopen+is%3Aissue+label%3AE-medium),
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[E-hard](https://github.com/rust-analyzer/rust-analyzer/issues?q=is%3Aopen+is%3Aissue+label%3AE-hard),
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[E-unknown](https://github.com/rust-analyzer/rust-analyzer/issues?q=is%3Aopen+is%3Aissue+label%3AE-unknown),
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labels are *estimates* for how hard would be to write a fix. Each triaged issue should have one of these labels.
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* [S-actionable](https://github.com/rust-analyzer/rust-analyzer/issues?q=is%3Aopen+is%3Aissue+label%3AS-actionable) and
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[S-unactionable](https://github.com/rust-analyzer/rust-analyzer/issues?q=is%3Aopen+is%3Aissue+label%3AS-unactionable)
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specify if there are concrete steps to resolve or advance an issue. Roughly, actionable issues need only work to be fixed,
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while unactionable ones are effectively wont-fix. Each triaged issue should have one of these labels.
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* [fun](https://github.com/rust-analyzer/rust-analyzer/issues?q=is%3Aopen+is%3Aissue+label%3Afun)
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is for cool, but probably hard stuff.
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# CI
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We use GitHub Actions for CI. Most of the things, including formatting, are checked by
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`cargo test` so, if `cargo test` passes locally, that's a good sign that CI will
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be green as well. The only exception is that some long-running tests are skipped locally by default.
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Use `env RUN_SLOW_TESTS=1 cargo test` to run the full suite.
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We use bors-ng to enforce the [not rocket science](https://graydon2.dreamwidth.org/1597.html) rule.
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You can run `cargo xtask install-pre-commit-hook` to install git-hook to run rustfmt on commit.
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# Launching rust-analyzer
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Debugging the language server can be tricky.
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LSP is rather chatty, so driving it from the command line is not really feasible, driving it via VS Code requires interacting with two processes.
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For this reason, the best way to see how rust-analyzer works is to find a relevant test and execute it.
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VS Code & Emacs include an action for running a single test.
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Launching a VS Code instance with a locally built language server is also possible.
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There's **"Run Extension (Debug Build)"** launch configuration for this in VS Code.
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In general, I use one of the following workflows for fixing bugs and implementing features:
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If the problem concerns only internal parts of rust-analyzer (i.e. I don't need to touch the `rust-analyzer` crate or TypeScript code), there is a unit-test for it.
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So, I use **Rust Analyzer: Run** action in VS Code to run this single test, and then just do printf-driven development/debugging.
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As a sanity check after I'm done, I use `cargo xtask install --server` and **Reload Window** action in VS Code to verify that the thing works as I expect.
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If the problem concerns only the VS Code extension, I use **Run Installed Extension** launch configuration from `launch.json`.
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Notably, this uses the usual `rust-analyzer` binary from `PATH`.
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For this, it is important to have the following in your `settings.json` file:
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```json
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{
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"rust-analyzer.serverPath": "rust-analyzer"
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}
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```
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After I am done with the fix, I use `cargo xtask install --client` to try the new extension for real.
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If I need to fix something in the `rust-analyzer` crate, I feel sad because it's on the boundary between the two processes, and working there is slow.
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I usually just `cargo xtask install --server` and poke changes from my live environment.
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Note that this uses `--release`, which is usually faster overall, because loading stdlib into debug version of rust-analyzer takes a lot of time.
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To speed things up, sometimes I open a temporary hello-world project which has `"rust-analyzer.withSysroot": false` in `.code/settings.json`.
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This flag causes rust-analyzer to skip loading the sysroot, which greatly reduces the amount of things rust-analyzer needs to do, and makes printf's more useful.
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Note that you should only use the `eprint!` family of macros for debugging: stdout is used for LSP communication, and `print!` would break it.
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If I need to fix something simultaneously in the server and in the client, I feel even more sad.
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I don't have a specific workflow for this case.
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Additionally, I use `cargo run --release -p rust-analyzer -- analysis-stats path/to/some/rust/crate` to run a batch analysis.
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This is primarily useful for performance optimizations, or for bug minimization.
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## Parser Tests
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Tests for the parser (`parser`) live in the `syntax` crate (see `test_data` directory).
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There are two kinds of tests:
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* Manually written test cases in `parser/ok` and `parser/err`
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* "Inline" tests in `parser/inline` (these are generated) from comments in `parser` crate.
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The purpose of inline tests is not to achieve full coverage by test cases, but to explain to the reader of the code what each particular `if` and `match` is responsible for.
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If you are tempted to add a large inline test, it might be a good idea to leave only the simplest example in place, and move the test to a manual `parser/ok` test.
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To update test data, run with `UPDATE_EXPECT` variable:
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```bash
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env UPDATE_EXPECT=1 cargo qt
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```
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After adding a new inline test you need to run `cargo xtest codegen` and also update the test data as described above.
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## TypeScript Tests
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If you change files under `editors/code` and would like to run the tests and linter, install npm and run:
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```bash
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cd editors/code
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npm ci
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npm run lint
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```
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# Code organization
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All Rust code lives in the `crates` top-level directory, and is organized as a single Cargo workspace.
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The `editors` top-level directory contains code for integrating with editors.
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Currently, it contains the plugin for VS Code (in TypeScript).
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The `docs` top-level directory contains both developer and user documentation.
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We have some automation infra in Rust in the `xtask` package.
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It contains stuff like formatting checking, code generation and powers `cargo xtask install`.
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The latter syntax is achieved with the help of cargo aliases (see `.cargo` directory).
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# Architecture Invariants
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This section tries to document high-level design constraints, which are not
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always obvious from the low-level code.
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## Incomplete syntax trees
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Syntax trees are by design incomplete and do not enforce well-formedness.
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If an AST method returns an `Option`, it *can* be `None` at runtime, even if this is forbidden by the grammar.
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## LSP independence
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rust-analyzer is independent from LSP.
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It provides features for a hypothetical perfect Rust-specific IDE client.
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Internal representations are lowered to LSP in the `rust-analyzer` crate (the only crate which is allowed to use LSP types).
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## IDE/Compiler split
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There's a semi-hard split between "compiler" and "IDE", at the `hir` crate.
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Compiler derives new facts about source code.
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It explicitly acknowledges that not all info is available (i.e. you can't look at types during name resolution).
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IDE assumes that all information is available at all times.
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IDE should use only types from `hir`, and should not depend on the underling compiler types.
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`hir` is a facade.
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## IDE API
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The main IDE crate (`ide`) uses "Plain Old Data" for the API.
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Rather than talking in definitions and references, it talks in Strings and textual offsets.
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In general, API is centered around UI concerns -- the result of the call is what the user sees in the editor, and not what the compiler sees underneath.
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The results are 100% Rust specific though.
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Shout outs to LSP developers for popularizing the idea that "UI" is a good place to draw a boundary at.
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## LSP is stateless
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The protocol is implemented in the mostly stateless way.
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A good mental model is HTTP, which doesn't store per-client state, and instead relies on devices like cookies to maintain an illusion of state.
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If some action requires multi-step protocol, each step should be self-contained.
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A good example here is code action resolving process.
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TO display the lightbulb, we compute the list of code actions without computing edits.
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Figuring out the edit is done in a separate `codeAction/resolve` call.
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Rather than storing some `lazy_edit: Box<dyn FnOnce() -> Edit>` somewhere, we use a string ID of action to re-compute the list of actions during the resolve process.
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(See [this post](https://rust-analyzer.github.io/blog/2020/09/28/how-to-make-a-light-bulb.html) for more details.)
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The benefit here is that, generally speaking, the state of the world might change between `codeAction` and `codeAction` resolve requests, so any closure we store might become invalid.
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While we don't currently implement any complicated refactors with complex GUI, I imagine we'd use the same techniques for refactors.
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After clicking each "Next" button during refactor, the client would send all the info which server needs to re-recreate the context from scratch.
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## CI
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CI does not test rust-analyzer, CI is a core part of rust-analyzer, and is maintained with above average standard of quality.
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CI is reproducible -- it can only be broken by changes to files in this repository, any dependence on externalities is a bug.
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# Code Style & Review Process
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Do see [./style.md](./style.md).
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# Logging
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Logging is done by both rust-analyzer and VS Code, so it might be tricky to
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figure out where logs go.
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Inside rust-analyzer, we use the standard `log` crate for logging, and
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`env_logger` for logging frontend. By default, log goes to stderr, but the
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stderr itself is processed by VS Code.
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To see stderr in the running VS Code instance, go to the "Output" tab of the
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panel and select `rust-analyzer`. This shows `eprintln!` as well. Note that
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`stdout` is used for the actual protocol, so `println!` will break things.
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To log all communication between the server and the client, there are two choices:
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* you can log on the server side, by running something like
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```
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env RA_LOG=gen_lsp_server=trace code .
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```
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* you can log on the client side, by enabling `"rust-analyzer.trace.server":
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"verbose"` workspace setting. These logs are shown in a separate tab in the
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output and could be used with LSP inspector. Kudos to
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[@DJMcNab](https://github.com/DJMcNab) for setting this awesome infra up!
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There are also two VS Code commands which might be of interest:
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* `Rust Analyzer: Status` shows some memory-usage statistics.
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* `Rust Analyzer: Syntax Tree` shows syntax tree of the current file/selection.
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You can hover over syntax nodes in the opened text file to see the appropriate
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rust code that it refers to and the rust editor will also highlight the proper
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text range.
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If you trigger Go to Definition in the inspected Rust source file,
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the syntax tree read-only editor should scroll to and select the
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appropriate syntax node token.
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# Profiling
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We have a built-in hierarchical profiler, you can enable it by using `RA_PROFILE` env-var:
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```
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RA_PROFILE=* // dump everything
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RA_PROFILE=foo|bar|baz // enabled only selected entries
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RA_PROFILE=*@3>10 // dump everything, up to depth 3, if it takes more than 10 ms
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```
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In particular, I have `export RA_PROFILE='*>10'` in my shell profile.
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To measure time for from-scratch analysis, use something like this:
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```
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$ cargo run --release -p rust-analyzer -- analysis-stats ../chalk/
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```
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For measuring time of incremental analysis, use either of these:
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```
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$ cargo run --release -p rust-analyzer -- analysis-bench ../chalk/ --highlight ../chalk/chalk-engine/src/logic.rs
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$ cargo run --release -p rust-analyzer -- analysis-bench ../chalk/ --complete ../chalk/chalk-engine/src/logic.rs:94:0
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```
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# Release Process
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Release process is handled by `release`, `dist` and `promote` xtasks, `release` being the main one.
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`release` assumes that you have checkouts of `rust-analyzer`, `rust-analyzer.github.io`, and `rust-lang/rust` in the same directory:
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```
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./rust-analyzer
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./rust-analyzer.github.io
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./rust-rust-analyzer # Note the name!
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```
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Additionally, it assumes that remote for `rust-analyzer` is called `upstream` (I use `origin` to point to my fork).
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Release steps:
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1. Inside rust-analyzer, run `cargo xtask release`. This will:
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* checkout the `release` branch
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* reset it to `upstream/nightly`
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* push it to `upstream`. This triggers GitHub Actions which:
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* runs `cargo xtask dist` to package binaries and VS Code extension
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* makes a GitHub release
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* pushes VS Code extension to the marketplace
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* create new changelog in `rust-analyzer.github.io`
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* create `rust-analyzer.github.io/git.log` file with the log of merge commits since last release
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2. While the release is in progress, fill-in the changelog using `git.log`
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3. Commit & push the changelog
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4. Tweet
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5. Inside `rust-analyzer`, run `cargo xtask promote` -- this will create a PR to rust-lang/rust updating rust-analyzer's submodule.
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Self-approve the PR.
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