Feat: detect changes also in configuration files (#4169)

crates/ruff_cli/src/lib.rs

@@ -43,6 +43,36 @@ impl From<ExitStatus> for ExitCode {
     }
 }
 
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+enum ChangeKind {
+    Configuration,
+    SourceFile,
+}
+
+/// Return the [`ChangeKind`] based on the list of modified file paths.
+///
+/// Returns `None` if no relevant changes were detected.
+fn change_detected(paths: &[PathBuf]) -> Option<ChangeKind> {
+    // If any `.toml` files were modified, return `ChangeKind::Configuration`. Otherwise, return
+    // `ChangeKind::SourceFile` if any `.py`, `.pyi`, or `.pyw` files were modified.
+    let mut source_file = false;
+    for path in paths {
+        if let Some(suffix) = path.extension() {
+            match suffix.to_str() {
+                Some("toml") => {
+                    return Some(ChangeKind::Configuration);
+                }
+                Some("py" | "pyi" | "pyw") => source_file = true,
+                _ => {}
+            }
+        }
+    }
+    if source_file {
+        return Some(ChangeKind::SourceFile);
+    }
+    None
+}
+
 pub fn run(
     Args {
         command,
@@ -207,30 +237,41 @@ fn check(args: CheckArgs, log_level: LogLevel) -> Result<ExitStatus> {
         for file in &cli.files {
             watcher.watch(file, RecursiveMode::Recursive)?;
         }
+        if let Some(file) = pyproject_config.path.as_ref() {
+            watcher.watch(file, RecursiveMode::Recursive)?;
+        }
+
+        // In watch mode, we may need to re-resolve the configuration.
+        // TODO(charlie): Re-compute other derivative values, like the `printer`.
+        let mut pyproject_config = pyproject_config;
 
         loop {
             match rx.recv() {
                 Ok(event) => {
-                    let paths = event?.paths;
-                    let py_changed = paths.iter().any(|path| {
-                        path.extension()
-                            .map(|ext| ext == "py" || ext == "pyi")
-                            .unwrap_or_default()
-                    });
-                    if py_changed {
-                        Printer::clear_screen()?;
-                        printer.write_to_user("File change detected...\n");
-
-                        let messages = commands::run::run(
-                            &cli.files,
-                            &pyproject_config,
+                    let Some(change_kind) = change_detected(&event?.paths) else {
+                        continue;
+                    };
+
+                    if matches!(change_kind, ChangeKind::Configuration) {
+                        pyproject_config = resolve::resolve(
+                            cli.isolated,
+                            cli.config.as_deref(),
                             &overrides,
-                            cache.into(),
-                            noqa.into(),
-                            autofix,
+                            cli.stdin_filename.as_deref(),
                         )?;
-                        printer.write_continuously(&messages)?;
                     }
+                    Printer::clear_screen()?;
+                    printer.write_to_user("File change detected...\n");
+
+                    let messages = commands::run::run(
+                        &cli.files,
+                        &pyproject_config,
+                        &overrides,
+                        cache.into(),
+                        noqa.into(),
+                        autofix,
+                    )?;
+                    printer.write_continuously(&messages)?;
                 }
                 Err(err) => return Err(err.into()),
             }
@@ -311,3 +352,83 @@ fn check(args: CheckArgs, log_level: LogLevel) -> Result<ExitStatus> {
     }
     Ok(ExitStatus::Success)
 }
+
+#[cfg(test)]
+mod test_file_change_detector {
+    use crate::{change_detected, ChangeKind};
+    use std::path::PathBuf;
+
+    #[test]
+    fn detect_correct_file_change() {
+        assert_eq!(
+            Some(ChangeKind::Configuration),
+            change_detected(&[
+                PathBuf::from("tmp/pyproject.toml"),
+                PathBuf::from("tmp/bin/ruff.rs"),
+            ]),
+        );
+        assert_eq!(
+            Some(ChangeKind::Configuration),
+            change_detected(&[
+                PathBuf::from("pyproject.toml"),
+                PathBuf::from("tmp/bin/ruff.rs"),
+            ]),
+        );
+        assert_eq!(
+            Some(ChangeKind::Configuration),
+            change_detected(&[
+                PathBuf::from("tmp1/tmp2/tmp3/pyproject.toml"),
+                PathBuf::from("tmp/bin/ruff.rs"),
+            ]),
+        );
+        assert_eq!(
+            Some(ChangeKind::Configuration),
+            change_detected(&[
+                PathBuf::from("tmp/ruff.toml"),
+                PathBuf::from("tmp/bin/ruff.rs"),
+            ]),
+        );
+        assert_eq!(
+            Some(ChangeKind::Configuration),
+            change_detected(&[
+                PathBuf::from("tmp/.ruff.toml"),
+                PathBuf::from("tmp/bin/ruff.rs"),
+            ]),
+        );
+        assert_eq!(
+            Some(ChangeKind::SourceFile),
+            change_detected(&[
+                PathBuf::from("tmp/rule.py"),
+                PathBuf::from("tmp/bin/ruff.rs"),
+            ]),
+        );
+        assert_eq!(
+            Some(ChangeKind::SourceFile),
+            change_detected(&[
+                PathBuf::from("tmp/rule.pyi"),
+                PathBuf::from("tmp/bin/ruff.rs"),
+            ]),
+        );
+        assert_eq!(
+            Some(ChangeKind::Configuration),
+            change_detected(&[
+                PathBuf::from("pyproject.toml"),
+                PathBuf::from("tmp/rule.py"),
+            ]),
+        );
+        assert_eq!(
+            Some(ChangeKind::Configuration),
+            change_detected(&[
+                PathBuf::from("tmp/rule.py"),
+                PathBuf::from("pyproject.toml"),
+            ]),
+        );
+        assert_eq!(
+            None,
+            change_detected(&[
+                PathBuf::from("tmp/rule.js"),
+                PathBuf::from("tmp/bin/ruff.rs"),
+            ]),
+        );
+    }
+}