# Behavior traces — astral-sh/ruff

> Canonical page: https://codevetter.com/unpack/ruff/behavior-traces

# Behavior traces — astral-sh/ruff

Scanned commit c131cbad5a0f858ef2ba207e0260d76bb33069b1 (2026-09-22). Generated by codevetter codevetter 1.12.0 on 2026-09-22.

Three user-visible pipelines dominate: process startup for each binary, `ruff check` from arguments to printed diagnostics and cache, and `ty check` from project discovery through a cancellable Salsa main loop. Format and the Ruff language server are the same file pipeline entered from different adapters. Watch modes re-enter those pipelines on filesystem events instead of exiting.
- Ruff startup order: `main` enables Windows virtual terminal, expands args, `Args::parse_from`, `run`. `run` applies color, `ruff_db::set_program_version`, installs a panic hook that points at the GitHub issue URL, skips logging for `Command::Server`, then matches `Command` to `check`, `format`, `server`, `analyze_graph`, or the help commands. — [crates/ruff/src/main.rs#L30-L48](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ruff/src/main.rs#L30-L48) [crates/ruff/src/lib.rs#L128-L211](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ruff/src/lib.rs#L128-L211)
- `ruff check` order: `CheckCommand::partition` -> `resolve::resolve` -> optional `show_settings` / `show_files` -> compute `FixMode` -> if suppression flags, `commands::add_noqa::add_noqa` and return -> else build `Printer` -> if `--watch`, `recommended_watcher` and an initial `commands::check::check` -> otherwise the same `check` once. — [crates/ruff/src/lib.rs#L237-L403](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ruff/src/lib.rs#L237-L403)
- `commands::check::check` order: `project_files_in_path` -> retain Python and ruff/pyproject TOML -> `package_roots` -> `PackageCacheMap::init` if cache enabled -> `paths.par_iter` calling `lint_path` -> `catch_unwind` around `diagnostics::lint_path` -> fold/reduce diagnostics -> `sort_by(Diagnostic::ruff_start_ordering)` -> `caches.persist`. A panic becomes `create_panic_diagnostic` instead of aborting the process. — [crates/ruff/src/commands/check.rs#L34-L214](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ruff/src/commands/check.rs#L34-L214)
- `diagnostics::lint_path` order for Python: `FileCacheKey::from_path` and `cache.get` -> `settings.extension.get_source_type` -> `SourceKind::from_path` -> `lint_fix` or `lint_only` -> on `FixMode::Apply`, `transformed.write` to `File::create(path)`; on `Diff`, write `source_kind.diff` to stdout. TOML files branch earlier into `lint_fix_toml` / `lint_toml`. — [crates/ruff/src/diagnostics.rs#L191-L346](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ruff/src/diagnostics.rs#L191-L346)
- `lint_only` order: `settings.resolve_target_version` -> `ParseSource::into_parsed` -> `Locator::new` -> `Stylist::from_tokens` -> `Indexer::from_tokens` -> `directives::extract_directives` -> `Suppressions::from_tokens` -> `check_path`. `lint_fix` repeats that loop up to 100 iterations, tracking `FixTable`. — [crates/ruff_linter/src/linter.rs#L447-L570](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ruff_linter/src/linter.rs#L447-L570)
- `ruff format` order: `FormatCommand::partition` -> `resolve::resolve` -> `resolve_default_files` -> `project_files_in_path` -> `package_roots` -> optional `PackageCacheMap::init` -> parallel per-path format. Each file reaches `format_module_source` -> `parse` -> `format_module_ast` -> `Printed`. — [crates/ruff/src/lib.rs#L214-L221](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ruff/src/lib.rs#L214-L221) [crates/ruff/src/commands/format.rs#L70-L114](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ruff/src/commands/format.rs#L70-L114) [crates/ruff_python_formatter/src/lib.rs#L136-L154](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ruff_python_formatter/src/lib.rs#L136-L154)
- ty startup and check order: `main` -> `run` -> `setup_rayon` -> `Cli::parse_from` -> `run_check` -> `setup_tracing` -> resolve cwd/project/paths -> `UseUv::from_system` -> `ProjectMetadata::{from_config_file|discover_with_uv}` -> `ProjectDatabase::fallible` -> `MainLoop::new` -> `ctrlc::set_handler` -> `watch` or `run`. — [crates/ty/src/main.rs#L21-L23](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ty/src/main.rs#L21-L23) [crates/ty/src/lib.rs#L45-L77](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ty/src/lib.rs#L45-L77) [crates/ty/src/lib.rs#L95-L220](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ty/src/lib.rs#L95-L220)
- ty main-loop order: `synchronize_scripts` -> `request_check` -> biased select on uv sync wakeups, watcher messages, and check requests. `CheckWorkspace` defers while `has_pending_synchronizations`, else spawns `check_with_reporter` + `into_sorted_diagnostics`. `CheckCompleted` either `write_diagnostics` or `fix_all_diagnostics` / `suppress_all_diagnostics`. Ctrl+C calls `CancellationTokenSource::stop`. — [crates/ty/src/lib.rs#L304-L336](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ty/src/lib.rs#L304-L336) [crates/ty/src/lib.rs#L347-L476](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ty/src/lib.rs#L347-L476)
- Per-file ty order inside `check_file_impl`: if the file is a script without valid settings, return script settings diagnostics; else `ty_python_semantic::check_file`; then append script settings diagnostics and a dependency-metadata diagnostic. `check_file` itself loads `source_text`, returns `IOErrorDiagnostic` on read error, extends parse and unsupported-syntax diagnostics, extends `check_types`, and sorts by `rendering_sort_key`. — [crates/ty_project/src/lib.rs#L960-L996](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ty_project/src/lib.rs#L960-L996) [crates/ty_python_semantic/src/lib.rs#L204-L244](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ty_python_semantic/src/lib.rs#L204-L244)
- Ruff LSP diagnostic order: `publish_diagnostics_for_document` calls `generate_diagnostics`, which no-ops unless `client_settings().lint()`, otherwise `crate::lint::check` on the document snapshot, then `Client::send_notification` of `PublishDiagnosticsNotification` per URI with the document version. Server boot is `ConnectionInitializer::stdio` then `Server::new(...).run` and `io_threads.join`. — [crates/ruff_server/src/server/api/diagnostics.rs#L8-L39](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ruff_server/src/server/api/diagnostics.rs#L8-L39) [crates/ruff_server/src/lib.rs#L43-L63](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ruff_server/src/lib.rs#L43-L63)
- Cache persistence order on a dirty cache: `Cache::persist` -> `save` merges changes -> `tempfile_in(parent)` -> `rkyv::to_bytes` of `PackageCache` -> `write_all` -> `NamedTempFile::persist`. No-change caches return before opening a temp file. — [crates/ruff/src/cache.rs#L156-L197](https://github.com/astral-sh/ruff/blob/c131cbad5a0f858ef2ba207e0260d76bb33069b1/crates/ruff/src/cache.rs#L156-L197)

Every claim links to its cited files at the pinned commit. Citations identify source evidence; they do not establish runtime correctness. Independent CodeVetter scan — not reviewed by upstream maintainers.

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