Gracefully handle lint panics (#3509)

crates/ruff_cli/src/commands/linter.rs

@@ -1,6 +1,6 @@
+use std::fmt::Write;
 use std::io;
 use std::io::BufWriter;
-use std::io::Write;
 
 use anyhow::Result;
 use itertools::Itertools;
@@ -41,7 +41,7 @@ pub fn linter(format: HelpFormat) -> Result<()> {
                         .join("/"),
                     prefix => prefix.to_string(),
                 };
-                output.push_str(&format!("{:>4} {}\n", prefix, linter.name()));
+                writeln!(output, "{:>4} {}", prefix, linter.name()).unwrap();
             }
         }
 
@@ -65,7 +65,7 @@ pub fn linter(format: HelpFormat) -> Result<()> {
         }
     }
 
-    write!(stdout, "{output}")?;
+    io::Write::write_fmt(&mut stdout, format_args!("{output}"))?;
 
     Ok(())
 }

crates/ruff_cli/src/commands/run.rs

@@ -1,24 +1,25 @@
 use std::io;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use std::time::Instant;
 
 use anyhow::Result;
 use colored::Colorize;
 use ignore::Error;
-use log::{debug, error};
+use log::{debug, error, warn};
 #[cfg(not(target_family = "wasm"))]
 use rayon::prelude::*;
 
+use crate::panic::catch_unwind;
 use ruff::message::{Location, Message};
 use ruff::registry::Rule;
 use ruff::resolver::PyprojectDiscovery;
-use ruff::settings::flags;
+use ruff::settings::{flags, AllSettings};
 use ruff::{fix, fs, packaging, resolver, warn_user_once, IOError, Range};
 use ruff_diagnostics::Diagnostic;
 
 use crate::args::Overrides;
 use crate::cache;
-use crate::diagnostics::{lint_path, Diagnostics};
+use crate::diagnostics::Diagnostics;
 
 /// Run the linter over a collection of files.
 pub fn run(
@@ -83,6 +84,7 @@ pub fn run(
                         .and_then(|parent| package_roots.get(parent))
                         .and_then(|package| *package);
                     let settings = resolver.resolve_all(path, pyproject_strategy);
+
                     lint_path(path, package, settings, cache, noqa, autofix)
                         .map_err(|e| (Some(path.to_owned()), e.to_string()))
                 }
@@ -135,3 +137,39 @@ pub fn run(
 
     Ok(diagnostics)
 }
+
+/// Wraps [`lint_path`](crate::diagnostics::lint_path) in a [`catch_unwind`](std::panic::catch_unwind) and emits
+/// a diagnostic if the linting the file panics.
+fn lint_path(
+    path: &Path,
+    package: Option<&Path>,
+    settings: &AllSettings,
+    cache: flags::Cache,
+    noqa: flags::Noqa,
+    autofix: fix::FixMode,
+) -> Result<Diagnostics> {
+    let result = catch_unwind(|| {
+        crate::diagnostics::lint_path(path, package, settings, cache, noqa, autofix)
+    });
+
+    match result {
+        Ok(inner) => inner,
+        Err(error) => {
+            let message = r#"This indicates a bug in `ruff`. If you could open an issue at:
+
+https://github.com/charliermarsh/ruff/issues/new?title=%5BLinter%20panic%5D
+
+with the relevant file contents, the `pyproject.toml` settings, and the following stack trace, we'd be very appreciative!
+"#;
+
+            warn!(
+                "{}{}{} {message}\n{error}",
+                "Linting panicked ".bold(),
+                fs::relativize_path(path).bold(),
+                ":".bold()
+            );
+
+            Ok(Diagnostics::default())
+        }
+    }
+}

crates/ruff_cli/src/lib.rs

@@ -18,6 +18,7 @@ pub mod args;
 mod cache;
 mod commands;
 mod diagnostics;
+mod panic;
 mod printer;
 mod resolve;
 
@@ -46,7 +47,6 @@ pub fn run(
         log_level_args,
     }: Args,
 ) -> Result<ExitStatus> {
-    #[cfg(not(debug_assertions))]
     {
         use colored::Colorize;
 

crates/ruff_cli/src/panic.rs

@@ -0,0 +1,46 @@
+#[derive(Default, Debug)]
+pub(crate) struct PanicError {
+    pub info: String,
+    pub backtrace: Option<std::backtrace::Backtrace>,
+}
+
+impl std::fmt::Display for PanicError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        writeln!(f, "{}", self.info)?;
+        if let Some(backtrace) = &self.backtrace {
+            writeln!(f, "Backtrace: {backtrace}")
+        } else {
+            Ok(())
+        }
+    }
+}
+
+thread_local! {
+    static LAST_PANIC: std::cell::Cell<Option<PanicError>> = std::cell::Cell::new(None);
+}
+
+/// [`catch_unwind`](std::panic::catch_unwind) wrapper that sets a custom [`set_hook`](std::panic::set_hook)
+/// to extract the backtrace. The original panic-hook gets restored before returning.
+pub(crate) fn catch_unwind<F, R>(f: F) -> Result<R, PanicError>
+where
+    F: FnOnce() -> R + std::panic::UnwindSafe,
+{
+    let prev = std::panic::take_hook();
+    std::panic::set_hook(Box::new(|info| {
+        let info = info.to_string();
+        let backtrace = std::backtrace::Backtrace::force_capture();
+        LAST_PANIC.with(|cell| {
+            cell.set(Some(PanicError {
+                info,
+                backtrace: Some(backtrace),
+            }));
+        });
+    }));
+
+    let result = std::panic::catch_unwind(f)
+        .map_err(|_| LAST_PANIC.with(std::cell::Cell::take).unwrap_or_default());
+
+    std::panic::set_hook(prev);
+
+    result
+}