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| <h1 id="rust-analyzer"><a class="header" href="#rust-analyzer">Rust Analyzer</a></h1> |
| <p><code>rules_rust</code> ships a one-shot installer that configures |
| <a href="https://rust-analyzer.github.io/">rust-analyzer</a> to use the project's Bazel |
| toolchain. After setup, rust-analyzer, the proc-macro server, and rustfmt |
| all come from Bazel — no host Rust install required.</p> |
| <h2 id="quick-start"><a class="header" href="#quick-start">Quick start</a></h2> |
| <p>Pick your editor below. Each runs the same <code>setup</code> tool with a different |
| subcommand — <code>setup</code> is re-runnable any time.</p> |
| <h3 id="vscode"><a class="header" href="#vscode">VSCode</a></h3> |
| <ol> |
| <li>Install the |
| <a href="https://marketplace.visualstudio.com/items?itemName=rust-lang.rust-analyzer">rust-analyzer extension</a>.</li> |
| <li> |
| <pre><code>bazel run @rules_rust//tools/rust_analyzer:setup -- vscode |
| </code></pre> |
| </li> |
| <li>Reload the VSCode window.</li> |
| </ol> |
| <p><code>.vscode/settings.json</code> is always written; a <code>*.code-workspace</code> at |
| the workspace root is picked up too. Existing user keys and comments |
| survive re-runs, so <code>.vscode/settings.json</code> and <code>.code-workspace</code> are |
| safe to commit.</p> |
| <p>Add the launcher dir to <code>.gitignore</code>:</p> |
| <pre><code>.vscode/.rules_rust_analyzer/ |
| </code></pre> |
| <p>Re-run <code>setup</code> after a toolchain change (rustup update, <code>MODULE.bazel</code> |
| edit, <code>bazel clean --expunge</code>).</p> |
| <h3 id="neovim"><a class="header" href="#neovim">Neovim</a></h3> |
| <pre><code>bazel run @rules_rust//tools/rust_analyzer:setup -- neovim |
| </code></pre> |
| <p>Prints an <code>nvim-lspconfig</code> Lua snippet to stdout. Paste it into your |
| <code>init.lua</code> (or pipe to a file you <code>require</code>). Restart Neovim.</p> |
| <p>For <a href="https://github.com/mrcjkb/rustaceanvim"><code>rustaceanvim</code></a> users: |
| pass the printed <code>cmd</code> and <code>settings</code> table through its <code>server</code> |
| option (<code>vim.g.rustaceanvim = { server = { cmd = ..., settings = ... } }</code>).</p> |
| <h3 id="helix"><a class="header" href="#helix">Helix</a></h3> |
| <pre><code>bazel run @rules_rust//tools/rust_analyzer:setup -- helix |
| </code></pre> |
| <p>Prints a <code>languages.toml</code> snippet. Paste it into |
| <code><workspace>/.helix/languages.toml</code>. Restart Helix.</p> |
| <h3 id="other-editors-cocnvim-vim-lsp-ale-etc"><a class="header" href="#other-editors-cocnvim-vim-lsp-ale-etc">Other editors (<code>coc.nvim</code>, <code>vim-lsp</code>, ALE, etc.)</a></h3> |
| <pre><code>bazel run @rules_rust//tools/rust_analyzer:setup -- print |
| </code></pre> |
| <p>Prints a generic JSON snippet using the <code>rust-analyzer.*</code> keys VSCode |
| uses. <code>coc.nvim</code> reads them via <code>coc-settings.json</code> (open with |
| <code>:CocConfig</code>); <code>vim-lsp</code> / ALE / <code>LanguageClient-neovim</code> accept the |
| same keys via plugin-specific config files.</p> |
| <h2 id="flags"><a class="header" href="#flags">Flags</a></h2> |
| <p>Re-runnable at any time. Global flags work on any subcommand.</p> |
| <div class="table-wrapper"><table><thead><tr><th>Flag</th><th>Effect</th></tr></thead><tbody> |
| <tr><td><code>--skip-proc-macro-server</code></td><td>Don't manage the proc-macro key.</td></tr> |
| <tr><td><code>--skip-rustfmt</code></td><td>Don't manage the formatter key (use host rustfmt).</td></tr> |
| <tr><td><code>--per-package-workspaces</code> / <code>--no-per-package-workspaces</code></td><td>Opt this developer in/out of per-package workspace splitting (see below).</td></tr> |
| <tr><td><code>--clippy</code> / <code>--no-clippy</code></td><td>Opt this developer in/out of running clippy on save and streaming its diagnostics alongside rustc's.</td></tr> |
| <tr><td><code>--clean</code></td><td>Delete <code><launcher-dir>/cache/</code> before running the rest of setup. See Troubleshooting.</td></tr> |
| </tbody></table> |
| </div> |
| <p>The <code>--clippy</code> and <code>--per-package-workspaces</code> toggles are <strong>per-user</strong>: they mutate <code><launcher-dir>/user_config.json</code> (gitignored) instead of the shared committed settings file. Two developers on the same workspace can hold different preferences without touching the checked-in configuration. Editing <code>user_config.json</code> by hand works too.</p> |
| <p>The <code>vscode</code> subcommand adds:</p> |
| <div class="table-wrapper"><table><thead><tr><th>Flag</th><th>Effect</th></tr></thead><tbody> |
| <tr><td><code>--settings-json <path></code></td><td>Override the settings.json output. Defaults to <code><workspace>/.vscode/settings.json</code>.</td></tr> |
| <tr><td><code>--code-workspace <path></code></td><td><code>.code-workspace</code> file to also update. Required when the workspace root has more than one.</td></tr> |
| <tr><td><code>--no-code-workspace</code></td><td>Skip the <code>.code-workspace</code> write.</td></tr> |
| <tr><td><code>--settings-key <key></code></td><td>Nest managed keys under this key inside the <code>.code-workspace</code> (default: <code>settings</code>).</td></tr> |
| <tr><td><code>--dry-run</code></td><td>Print each would-be-written file to stdout.</td></tr> |
| <tr><td><code>--replace</code></td><td>Overwrite managed keys instead of merging. Sibling <code>folders</code> / <code>tasks</code> / <code>extensions</code> in a <code>.code-workspace</code> survive.</td></tr> |
| </tbody></table> |
| </div> |
| <h2 id="what-you-get"><a class="header" href="#what-you-get">What you get</a></h2> |
| <ul> |
| <li><strong><code>▶ Run Tests</code> / <code>▶ Run Test</code></strong> codelens on every <code>#[cfg(test)] mod</code> and |
| individual <code>#[test]</code>.</li> |
| <li><strong>On-save squiggles</strong> from rustc diagnostics. Matches <code>cargo check</code> — |
| errors anywhere in the dep graph surface at their actual file paths.</li> |
| <li><strong>Format-on-save</strong> via the Bazel-toolchain rustfmt.</li> |
| <li><strong>Workspace reload</strong> on watched <code>BUILD</code> / <code>MODULE.bazel</code> changes.</li> |
| </ul> |
| <h2 id="troubleshooting"><a class="header" href="#troubleshooting">Troubleshooting</a></h2> |
| <h3 id="symbols--deps-look-wrong"><a class="header" href="#symbols--deps-look-wrong">Symbols / deps look wrong</a></h3> |
| <p>Restart rust-analyzer (or save a <code>BUILD</code> file). If that doesn't fix |
| it, re-run setup with <code>--clean</code> to nuke the discovery cache:</p> |
| <pre><code>bazel run @rules_rust//tools/rust_analyzer:setup -- --clean vscode |
| </code></pre> |
| <p>Works with any subcommand (<code>vscode</code> / <code>neovim</code> / <code>helix</code> / <code>print</code>).</p> |
| <h3 id="diagnostics-stopped-appearing"><a class="header" href="#diagnostics-stopped-appearing">Diagnostics stopped appearing</a></h3> |
| <p>Check <code><workspace>/.rules_rust_analyzer/flycheck.log</code>.</p> |
| <h3 id="after-bazel-clean---expunge-or-toolchain-changes"><a class="header" href="#after-bazel-clean---expunge-or-toolchain-changes">After <code>bazel clean --expunge</code> or toolchain changes</a></h3> |
| <p>Re-run <code>setup</code>.</p> |
| <h3 id="noisy-cargo-metadata-errors-on-startup"><a class="header" href="#noisy-cargo-metadata-errors-on-startup">Noisy <code>cargo metadata</code> errors on startup</a></h3> |
| <p><code>setup</code> does not manage <code>rust-analyzer.files.excludeDirs</code>. If your |
| workspace has stub <code>Cargo.toml</code> files that aren't meant to be |
| auto-loaded (common in <code>rules_rust</code> itself under <code>examples/</code>, |
| <code>crate_universe/</code>, etc.), rust-analyzer still finds them and logs |
| errors. Silence them by adding the directory names to <code>settings.json</code> |
| yourself — your entries survive future <code>setup</code> runs:</p> |
| <pre><code>"rust-analyzer.files.excludeDirs": ["examples", "some_other_dir"] |
| </code></pre> |
| <p>Trade-off: <code>files.excludeDirs</code> also hides those sources from |
| rust-analyzer's virtual filesystem, so files under those directories |
| won't get IDE features even if they're part of a Bazel-discovered |
| crate. Only exclude directories whose sources you're willing to lose |
| IDE support on.</p> |
| <h2 id="workspace-splitting"><a class="header" href="#workspace-splitting">Workspace splitting</a></h2> |
| <p>By default the whole project is treated as a single workspace.</p> |
| <p>For monorepos where indexing the whole graph is too slow, pass |
| <code>--per-package-workspaces</code>. Discover then scopes to the saved file's |
| package + deps; rust-analyzer reloads when you jump to a different |
| package. Caveat: <em>dependents</em> of the package you're working on aren't |
| indexed, so "find usages" can miss callers in other packages.</p> |
| <p>Switch any time by re-running <code>setup</code> with or without the flag.</p> |
| <h2 id="debugging"><a class="header" href="#debugging">Debugging</a></h2> |
| <p>The <code>▶ Debug</code> codelens VSCode renders next to <code>#[test]</code> functions |
| <strong>does not work</strong> for Bazel projects. Use <code>.vscode/launch.json</code> + F5 |
| instead:</p> |
| <pre><code>bazel run @rules_rust//tools/vscode:gen_launch_json |
| </code></pre> |
| <p>Install |
| <a href="https://marketplace.visualstudio.com/items?itemName=vadimcn.vscode-lldb">CodeLLDB</a> |
| first. Set a breakpoint inside the test and run the target — one |
| launch config covers every test in that binary.</p> |
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