Refactor Rust lint test structure to use RuffTestFixture (#20689)

Co-authored-by: Micha Reiser <micha@reiser.io>

Cargo.lock

@@ -2777,6 +2777,7 @@ dependencies = [
  "ruff_python_ast",
  "ruff_python_formatter",
  "ruff_python_parser",
+ "ruff_python_trivia",
  "ruff_server",
  "ruff_source_file",
  "ruff_text_size",

crates/ruff/Cargo.toml

@@ -72,6 +72,7 @@ dunce = { workspace = true }
 indoc = { workspace = true }
 insta = { workspace = true, features = ["filters", "json"] }
 insta-cmd = { workspace = true }
+ruff_python_trivia = { workspace = true }
 tempfile = { workspace = true }
 test-case = { workspace = true }
 

crates/ruff/tests/cli/main.rs

@@ -0,0 +1,177 @@
+//! Test fixture utilities for ruff CLI tests
+//!
+//! The core concept is borrowed from ty/tests/cli/main.rs and can be extended
+//! with more functionality from there in the future if needed.
+
+#![cfg(not(target_family = "wasm"))]
+
+use anyhow::{Context as _, Result};
+use insta::internals::SettingsBindDropGuard;
+use insta_cmd::get_cargo_bin;
+use std::{
+    fs,
+    path::{Path, PathBuf},
+    process::Command,
+};
+use tempfile::TempDir;
+
+mod lint;
+
+const BIN_NAME: &str = "ruff";
+
+/// Creates a regex filter for replacing temporary directory paths in snapshots
+pub(crate) fn tempdir_filter(path: impl AsRef<str>) -> String {
+    format!(r"{}[\\/]?", regex::escape(path.as_ref()))
+}
+
+/// A test fixture for running ruff CLI tests with temporary directories and files.
+///
+/// This fixture provides:
+/// - Temporary directory management
+/// - File creation utilities
+/// - Proper snapshot filtering for cross-platform compatibility
+/// - Pre-configured ruff command creation
+///
+/// # Example
+///
+/// ```rust,no_run
+/// use crate::common::RuffTestFixture;
+///
+/// let fixture = RuffTestFixture::with_file("ruff.toml", "select = ['E']")?;
+/// let output = fixture.command().args(["check", "."]).output()?;
+/// ```
+pub(crate) struct CliTest {
+    _temp_dir: TempDir,
+    _settings_scope: SettingsBindDropGuard,
+    project_dir: PathBuf,
+}
+
+impl CliTest {
+    /// Creates a new test fixture with an empty temporary directory.
+    ///
+    /// This sets up:
+    /// - A temporary directory that's automatically cleaned up
+    /// - Insta snapshot filters for cross-platform path compatibility
+    /// - Environment isolation for consistent test behavior
+    pub(crate) fn new() -> Result<Self> {
+        Self::with_settings(|_, settings| settings)
+    }
+
+    pub(crate) fn with_settings(
+        setup_settings: impl FnOnce(&Path, insta::Settings) -> insta::Settings,
+    ) -> Result<Self> {
+        let temp_dir = TempDir::new()?;
+
+        // Canonicalize the tempdir path because macOS uses symlinks for tempdirs
+        // and that doesn't play well with our snapshot filtering.
+        // Simplify with dunce because otherwise we get UNC paths on Windows.
+        let project_dir = dunce::simplified(
+            &temp_dir
+                .path()
+                .canonicalize()
+                .context("Failed to canonicalize project path")?,
+        )
+        .to_path_buf();
+
+        let mut settings = setup_settings(&project_dir, insta::Settings::clone_current());
+
+        settings.add_filter(&tempdir_filter(project_dir.to_str().unwrap()), "[TMP]/");
+        settings.add_filter(r#"\\([\w&&[^nr"]]\w|\s|\.)"#, "/$1");
+        settings.add_filter(r"(Panicked at) [^:]+:\d+:\d+", "$1 <location>");
+        settings.add_filter(ruff_linter::VERSION, "[VERSION]");
+        settings.add_filter(
+            r#"The system cannot find the file specified."#,
+            "No such file or directory",
+        );
+
+        let settings_scope = settings.bind_to_scope();
+
+        Ok(Self {
+            project_dir,
+            _temp_dir: temp_dir,
+            _settings_scope: settings_scope,
+        })
+    }
+
+    /// Creates a test fixture with a single file.
+    ///
+    /// # Arguments
+    ///
+    /// * `path` - The relative path for the file
+    /// * `content` - The content to write to the file
+    ///
+    /// # Example
+    ///
+    /// ```rust,no_run
+    /// let fixture = RuffTestFixture::with_file("ruff.toml", "select = ['E']")?;
+    /// ```
+    pub(crate) fn with_file(path: impl AsRef<Path>, content: &str) -> Result<Self> {
+        let fixture = Self::new()?;
+        fixture.write_file(path, content)?;
+        Ok(fixture)
+    }
+
+    /// Ensures that the parent directory of a path exists.
+    fn ensure_parent_directory(path: &Path) -> Result<()> {
+        if let Some(parent) = path.parent() {
+            fs::create_dir_all(parent)
+                .with_context(|| format!("Failed to create directory `{}`", parent.display()))?;
+        }
+        Ok(())
+    }
+
+    /// Writes a file to the test directory.
+    ///
+    /// Parent directories are created automatically if they don't exist.
+    /// Content is dedented to remove common leading whitespace for cleaner test code.
+    ///
+    /// # Arguments
+    ///
+    /// * `path` - The relative path for the file
+    /// * `content` - The content to write to the file
+    pub(crate) fn write_file(&self, path: impl AsRef<Path>, content: &str) -> Result<()> {
+        let path = path.as_ref();
+        let file_path = self.project_dir.join(path);
+
+        Self::ensure_parent_directory(&file_path)?;
+
+        let content = ruff_python_trivia::textwrap::dedent(content);
+        fs::write(&file_path, content.as_ref())
+            .with_context(|| format!("Failed to write file `{}`", file_path.display()))?;
+
+        Ok(())
+    }
+
+    /// Returns the path to the test directory root.
+    pub(crate) fn root(&self) -> &Path {
+        &self.project_dir
+    }
+
+    /// Creates a pre-configured ruff command for testing.
+    ///
+    /// The command is set up with:
+    /// - The correct ruff binary path
+    /// - Working directory set to the test directory
+    /// - Clean environment variables for consistent behavior
+    ///
+    /// You can chain additional arguments and options as needed.
+    ///
+    /// # Example
+    ///
+    /// ```rust,no_run
+    /// let output = fixture
+    ///     .command()
+    ///     .args(["check", "--select", "E"])
+    ///     .arg(".")
+    ///     .output()?;
+    /// ```
+    pub(crate) fn command(&self) -> Command {
+        let mut command = Command::new(get_cargo_bin(BIN_NAME));
+        command.current_dir(&self.project_dir);
+
+        // Unset all environment variables because they can affect test behavior.
+        command.env_clear();
+
+        command
+    }
+}

crates/ruff/tests/cli/snapshots/cli__lint__output_format_sarif.snap

@@ -1,5 +1,5 @@
 ---
-source: crates/ruff/tests/lint.rs
+source: crates/ruff/tests/cli/lint.rs
 info:
   program: ruff
   args:
@@ -12,6 +12,7 @@ info:
     - "--target-version"
     - py39
     - input.py
+snapshot_kind: text
 ---
 success: false
 exit_code: 1