Add tracing support to mdtest (#14935)

## Summary

This PR extends the mdtest configuration with a `log` setting that can
be any of:

* `true`: Enables tracing
* `false`: Disables tracing (default)
* String: An ENV_FILTER similar to `RED_KNOT_LOG`

```toml
log = true
```

Closes https://github.com/astral-sh/ruff/issues/13865

## Test Plan

I changed a test and tried `log=true`, `log=false`, and `log=INFO`

crates/red_knot_python_semantic/Cargo.toml

@@ -53,5 +53,9 @@ tempfile = { workspace = true }
 quickcheck = { version = "1.0.3", default-features = false }
 quickcheck_macros = { version = "1.0.0" }
 
+[features]
+serde = ["ruff_db/serde", "dep:serde"]
+
 [lints]
 workspace = true
+

crates/red_knot_python_semantic/src/python_version.rs

@@ -5,7 +5,6 @@ use std::fmt;
 /// Unlike the `TargetVersion` enums in the CLI crates,
 /// this does not necessarily represent a Python version that we actually support.
 #[derive(Debug, Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Hash)]
-#[cfg_attr(feature = "serde", derive(serde::Serialize))]
 pub struct PythonVersion {
     pub major: u8,
     pub minor: u8,
@@ -68,3 +67,42 @@ impl fmt::Display for PythonVersion {
         write!(f, "{major}.{minor}")
     }
 }
+
+#[cfg(feature = "serde")]
+impl<'de> serde::Deserialize<'de> for PythonVersion {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        let as_str = String::deserialize(deserializer)?;
+
+        if let Some((major, minor)) = as_str.split_once('.') {
+            let major = major
+                .parse()
+                .map_err(|err| serde::de::Error::custom(format!("invalid major version: {err}")))?;
+            let minor = minor
+                .parse()
+                .map_err(|err| serde::de::Error::custom(format!("invalid minor version: {err}")))?;
+
+            Ok((major, minor).into())
+        } else {
+            let major = as_str.parse().map_err(|err| {
+                serde::de::Error::custom(format!(
+                    "invalid python-version: {err}, expected: `major.minor`"
+                ))
+            })?;
+
+            Ok((major, 0).into())
+        }
+    }
+}
+
+#[cfg(feature = "serde")]
+impl serde::Serialize for PythonVersion {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        serializer.serialize_str(&self.to_string())
+    }
+}

crates/red_knot_test/Cargo.toml

@@ -11,9 +11,9 @@ authors.workspace = true
 license.workspace = true
 
 [dependencies]
-red_knot_python_semantic = { workspace = true }
+red_knot_python_semantic = { workspace = true, features = ["serde"] }
 red_knot_vendored = { workspace = true }
-ruff_db = { workspace = true }
+ruff_db = { workspace = true, features = ["testing"] }
 ruff_index = { workspace = true }
 ruff_python_trivia = { workspace = true }
 ruff_source_file = { workspace = true }
@@ -30,7 +30,5 @@ smallvec = { workspace = true }
 serde = { workspace = true }
 toml = { workspace = true }
 
-[dev-dependencies]
-
 [lints]
 workspace = true

crates/red_knot_test/README.md

@@ -241,6 +241,8 @@ python-version = "3.10"
 This configuration will apply to all tests in the same section, and all nested sections within that
 section. Nested sections can override configurations from their parent sections.
 
+See [`MarkdownTestConfig`](https://github.com/astral-sh/ruff/blob/main/crates/red_knot_test/src/config.rs) for the full list of supported configuration options.
+
 ## Documentation of tests
 
 Arbitrary Markdown syntax (including of course normal prose paragraphs) is permitted (and ignored by

crates/red_knot_test/src/config.rs

@@ -3,26 +3,45 @@
 //! following limited structure:
 //!
 //! ```toml
+//! log = true # or log = "red_knot=WARN"
 //! [environment]
 //! python-version = "3.10"
 //! ```
 
 use anyhow::Context;
+use red_knot_python_semantic::PythonVersion;
 use serde::Deserialize;
 
-#[derive(Deserialize)]
+#[derive(Deserialize, Debug, Default, Clone)]
+#[serde(rename_all = "kebab-case", deny_unknown_fields)]
 pub(crate) struct MarkdownTestConfig {
-    pub(crate) environment: Environment,
+    pub(crate) environment: Option<Environment>,
+
+    pub(crate) log: Option<Log>,
 }
 
 impl MarkdownTestConfig {
     pub(crate) fn from_str(s: &str) -> anyhow::Result<Self> {
         toml::from_str(s).context("Error while parsing Markdown TOML config")
     }
+
+    pub(crate) fn python_version(&self) -> Option<PythonVersion> {
+        self.environment.as_ref().and_then(|env| env.python_version)
+    }
 }
 
-#[derive(Deserialize)]
-#[serde(rename_all = "kebab-case")]
+#[derive(Deserialize, Debug, Default, Clone)]
+#[serde(rename_all = "kebab-case", deny_unknown_fields)]
 pub(crate) struct Environment {
-    pub(crate) python_version: String,
+    /// Python version to assume when resolving types.
+    pub(crate) python_version: Option<PythonVersion>,
+}
+
+#[derive(Deserialize, Debug, Clone)]
+#[serde(untagged)]
+pub(crate) enum Log {
+    /// Enable logging with tracing when `true`.
+    Bool(bool),
+    /// Enable logging and only show filters that match the given [env-filter](https://docs.rs/tracing-subscriber/latest/tracing_subscriber/filter/struct.EnvFilter.html)
+    Filter(String),
 }

crates/red_knot_test/src/lib.rs

@@ -1,3 +1,4 @@
+use crate::config::Log;
 use camino::Utf8Path;
 use colored::Colorize;
 use parser as test_parser;
@@ -7,6 +8,7 @@ use ruff_db::diagnostic::{Diagnostic, ParseDiagnostic};
 use ruff_db::files::{system_path_to_file, File, Files};
 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_text_size::TextSize;
 use salsa::Setter;
@@ -42,9 +44,14 @@ pub fn run(path: &Utf8Path, long_title: &str, short_title: &str, test_name: &str
             continue;
         }
 
+        let _tracing = test.configuration().log.as_ref().and_then(|log| match log {
+            Log::Bool(enabled) => enabled.then(setup_logging),
+            Log::Filter(filter) => setup_logging_with_filter(filter),
+        });
+
         Program::get(&db)
             .set_python_version(&mut db)
-            .to(test.python_version());
+            .to(test.configuration().python_version().unwrap_or_default());
 
         // Remove all files so that the db is in a "fresh" state.
         db.memory_file_system().remove_all();

crates/red_knot_test/src/parser.rs

@@ -1,8 +1,7 @@
 use std::sync::LazyLock;
 
-use anyhow::{bail, Context};
+use anyhow::bail;
 use memchr::memchr2;
-use red_knot_python_semantic::PythonVersion;
 use regex::{Captures, Match, Regex};
 use rustc_hash::{FxHashMap, FxHashSet};
 
@@ -74,8 +73,8 @@ impl<'m, 's> MarkdownTest<'m, 's> {
         self.files.iter()
     }
 
-    pub(crate) fn python_version(&self) -> PythonVersion {
-        self.section.python_version
+    pub(crate) fn configuration(&self) -> &MarkdownTestConfig {
+        &self.section.config
     }
 }
 
@@ -125,7 +124,7 @@ struct Section<'s> {
     title: &'s str,
     level: u8,
     parent_id: Option<SectionId>,
-    python_version: PythonVersion,
+    config: MarkdownTestConfig,
 }
 
 #[newtype_index]
@@ -222,7 +221,7 @@ impl<'s> Parser<'s> {
             title,
             level: 0,
             parent_id: None,
-            python_version: PythonVersion::default(),
+            config: MarkdownTestConfig::default(),
         });
         Self {
             sections,
@@ -305,7 +304,7 @@ impl<'s> Parser<'s> {
             title,
             level: header_level.try_into()?,
             parent_id: Some(parent),
-            python_version: self.sections[parent].python_version,
+            config: self.sections[parent].config.clone(),
         };
 
         if self.current_section_files.is_some() {
@@ -398,23 +397,8 @@ impl<'s> Parser<'s> {
             bail!("Multiple TOML configuration blocks in the same section are not allowed.");
         }
 
-        let config = MarkdownTestConfig::from_str(code)?;
-        let python_version = config.environment.python_version;
-
-        let parts = python_version
-            .split('.')
-            .map(str::parse)
-            .collect::<Result<Vec<_>, _>>()
-            .context(format!(
-                "Invalid 'python-version' component: '{python_version}'"
-            ))?;
-
-        if parts.len() != 2 {
-            bail!("Invalid 'python-version': expected MAJOR.MINOR, got '{python_version}'.",);
-        }
-
         let current_section = &mut self.sections[self.stack.top()];
-        current_section.python_version = PythonVersion::from((parts[0], parts[1]));
+        current_section.config = MarkdownTestConfig::from_str(code)?;
 
         self.current_section_has_config = true;
 

crates/red_knot_workspace/src/workspace/snapshots/red_knot_workspace__workspace__metadata__tests__member_pattern_matching_file.snap

@@ -22,10 +22,7 @@ WorkspaceMetadata(
   ],
   settings: WorkspaceSettings(
     program: ProgramSettings(
-      python_version: PythonVersion(
-        major: 3,
-        minor: 9,
-      ),
+      python_version: "3.9",
       search_paths: SearchPathSettings(
         extra_paths: [],
         src_root: "/app",

crates/red_knot_workspace/src/workspace/snapshots/red_knot_workspace__workspace__metadata__tests__member_pattern_matching_hidden_folder.snap

@@ -22,10 +22,7 @@ WorkspaceMetadata(
   ],
   settings: WorkspaceSettings(
     program: ProgramSettings(
-      python_version: PythonVersion(
-        major: 3,
-        minor: 9,
-      ),
+      python_version: "3.9",
       search_paths: SearchPathSettings(
         extra_paths: [],
         src_root: "/app",

crates/red_knot_workspace/src/workspace/snapshots/red_knot_workspace__workspace__metadata__tests__package_without_pyproject.snap

@@ -22,10 +22,7 @@ WorkspaceMetadata(
   ],
   settings: WorkspaceSettings(
     program: ProgramSettings(
-      python_version: PythonVersion(
-        major: 3,
-        minor: 9,
-      ),
+      python_version: "3.9",
       search_paths: SearchPathSettings(
         extra_paths: [],
         src_root: "/app",

crates/red_knot_workspace/src/workspace/snapshots/red_knot_workspace__workspace__metadata__tests__single_package.snap

@@ -22,10 +22,7 @@ WorkspaceMetadata(
   ],
   settings: WorkspaceSettings(
     program: ProgramSettings(
-      python_version: PythonVersion(
-        major: 3,
-        minor: 9,
-      ),
+      python_version: "3.9",
       search_paths: SearchPathSettings(
         extra_paths: [],
         src_root: "/app",

crates/red_knot_workspace/src/workspace/snapshots/red_knot_workspace__workspace__metadata__tests__workspace_excluded.snap

@@ -35,10 +35,7 @@ WorkspaceMetadata(
   ],
   settings: WorkspaceSettings(
     program: ProgramSettings(
-      python_version: PythonVersion(
-        major: 3,
-        minor: 9,
-      ),
+      python_version: "3.9",
       search_paths: SearchPathSettings(
         extra_paths: [],
         src_root: "/app",

crates/red_knot_workspace/src/workspace/snapshots/red_knot_workspace__workspace__metadata__tests__workspace_members.snap

@@ -48,10 +48,7 @@ WorkspaceMetadata(
   ],
   settings: WorkspaceSettings(
     program: ProgramSettings(
-      python_version: PythonVersion(
-        major: 3,
-        minor: 9,
-      ),
+      python_version: "3.9",
       search_paths: SearchPathSettings(
         extra_paths: [],
         src_root: "/app",

crates/ruff_db/src/testing.rs

@@ -158,7 +158,7 @@ impl LoggingBuilder {
                         .parse()
                         .expect("Hardcoded directive to be valid"),
                 ),
-            hierarchical: true,
+            hierarchical: false,
         }
     }
 
@@ -167,7 +167,7 @@ impl LoggingBuilder {
 
         Some(Self {
             filter,
-            hierarchical: true,
+            hierarchical: false,
         })
     }