Attribute panics to the mdtests that cause them (#15241)

This updates the mdtest harness to catch any panics that occur during
type checking, and to display the panic message as an mdtest failure.
(We don't know which specific line causes the failure, so we attribute
panics to the first line of the test case.)

Author: dcreager

crates/red_knot_test/src/lib.rs

@@ -6,10 +6,11 @@ use red_knot_python_semantic::types::check_types;
 use red_knot_python_semantic::Program;
 use ruff_db::diagnostic::{Diagnostic, ParseDiagnostic};
 use ruff_db::files::{system_path_to_file, File, Files};
+use ruff_db::panic::catch_unwind;
 use ruff_db::parsed::parsed_module;
 use ruff_db::system::{DbWithTestSystem, SystemPathBuf};
 use ruff_db::testing::{setup_logging, setup_logging_with_filter};
-use ruff_source_file::LineIndex;
+use ruff_source_file::{LineIndex, OneIndexed};
 use ruff_text_size::TextSize;
 use salsa::Setter;
 
@@ -136,7 +137,20 @@ fn run_test(db: &mut db::Db, test: &parser::MarkdownTest) -> Result<(), Failures
                 })
                 .collect();
 
-            let type_diagnostics = check_types(db, test_file.file);
+            let type_diagnostics = match catch_unwind(|| check_types(db, test_file.file)) {
+                Ok(type_diagnostics) => type_diagnostics,
+                Err(info) => {
+                    let mut by_line = matcher::FailuresByLine::default();
+                    by_line.push(
+                        OneIndexed::from_zero_indexed(0),
+                        info.info.split('\n').map(String::from).collect(),
+                    );
+                    return Some(FileFailures {
+                        backtick_offset: test_file.backtick_offset,
+                        by_line,
+                    });
+                }
+            };
             diagnostics.extend(type_diagnostics.into_iter().map(|diagnostic| {
                 let diagnostic: Box<dyn Diagnostic> = Box::new((*diagnostic).clone());
                 diagnostic

crates/red_knot_test/src/matcher.rs

@@ -27,7 +27,7 @@ impl FailuresByLine {
         })
     }
 
-    fn push(&mut self, line_number: OneIndexed, messages: Vec<String>) {
+    pub(super) fn push(&mut self, line_number: OneIndexed, messages: Vec<String>) {
         let start = self.failures.len();
         self.failures.extend(messages);
         self.lines.push(LineFailures {

crates/ruff/src/commands/check.rs

@@ -11,6 +11,7 @@ use log::{debug, error, warn};
 use rayon::prelude::*;
 use rustc_hash::FxHashMap;
 
+use ruff_db::panic::catch_unwind;
 use ruff_diagnostics::Diagnostic;
 use ruff_linter::message::Message;
 use ruff_linter::package::PackageRoot;
@@ -27,7 +28,6 @@ use ruff_workspace::resolver::{
 use crate::args::ConfigArguments;
 use crate::cache::{Cache, PackageCacheMap, PackageCaches};
 use crate::diagnostics::Diagnostics;
-use crate::panic::catch_unwind;
 
 /// Run the linter over a collection of files.
 #[allow(clippy::too_many_arguments)]

crates/ruff/src/commands/format.rs

@@ -15,6 +15,7 @@ use rustc_hash::FxHashSet;
 use thiserror::Error;
 use tracing::debug;
 
+use ruff_db::panic::{catch_unwind, PanicError};
 use ruff_diagnostics::SourceMap;
 use ruff_linter::fs;
 use ruff_linter::logging::{DisplayParseError, LogLevel};
@@ -32,7 +33,6 @@ use ruff_workspace::FormatterSettings;
 
 use crate::args::{ConfigArguments, FormatArguments, FormatRange};
 use crate::cache::{Cache, FileCacheKey, PackageCacheMap, PackageCaches};
-use crate::panic::{catch_unwind, PanicError};
 use crate::resolve::resolve;
 use crate::{resolve_default_files, ExitStatus};
 

crates/ruff/src/lib.rs

@@ -29,7 +29,6 @@ pub mod args;
 mod cache;
 mod commands;
 mod diagnostics;
-mod panic;
 mod printer;
 pub mod resolve;
 mod stdin;

crates/ruff_db/src/lib.rs

@@ -10,6 +10,7 @@ pub mod diagnostic;
 pub mod display;
 pub mod file_revision;
 pub mod files;
+pub mod panic;
 pub mod parsed;
 pub mod source;
 pub mod system;

crates/ruff/src/panic.rs renamed to crates/ruff_db/src/panic.rs

@@ -1,7 +1,7 @@
 #[derive(Default, Debug)]
-pub(crate) struct PanicError {
-    pub(crate) info: String,
-    pub(crate) backtrace: Option<std::backtrace::Backtrace>,
+pub struct PanicError {
+    pub info: String,
+    pub backtrace: Option<std::backtrace::Backtrace>,
 }
 
 impl std::fmt::Display for PanicError {
@@ -21,7 +21,7 @@ thread_local! {
 
 /// [`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>
+pub fn catch_unwind<F, R>(f: F) -> Result<R, PanicError>
 where
     F: FnOnce() -> R + std::panic::UnwindSafe,
 {