type: ignore[codes] and knot: ignore (#15078)

Author: MichaReiser

Cargo.lock

@@ -20,6 +20,7 @@ ruff_python_stdlib = { workspace = true }
 ruff_source_file = { workspace = true }
 ruff_text_size = { workspace = true }
 ruff_python_literal = { workspace = true }
+ruff_python_trivia = { workspace = true }
 
 anyhow = { workspace = true }
 bitflags = { workspace = true }

crates/red_knot_python_semantic/Cargo.toml

@@ -0,0 +1,120 @@
+# Suppressing errors with `knot: ignore`
+
+Type check errors can be suppressed by a `knot: ignore` comment on the same line as the violation.
+
+## Simple `knot: ignore`
+
+```py
+a = 4 + test  # knot: ignore
+```
+
+## Suppressing a specific code
+
+```py
+a = 4 + test  # knot: ignore[unresolved-reference]
+```
+
+## Useless suppression
+
+TODO: Red Knot should emit an `unused-suppression` diagnostic for the
+`possibly-unresolved-reference` suppression.
+
+```py
+test = 10
+a = test + 3  # knot: ignore[possibly-unresolved-reference]
+```
+
+## Useless suppression if the error codes don't match
+
+TODO: Red Knot should emit a `unused-suppression` diagnostic for the `possibly-unresolved-reference`
+suppression because it doesn't match the actual `unresolved-reference` diagnostic.
+
+```py
+# error: [unresolved-reference]
+a = test + 3  # knot: ignore[possibly-unresolved-reference]
+```
+
+## Multiple suppressions
+
+```py
+# fmt: off
+def test(a: f"f-string type annotation", b: b"byte-string-type-annotation"): ...  # knot: ignore[fstring-type-annotation, byte-string-type-annotation]
+```
+
+## Can't suppress syntax errors
+
+<!-- blacken-docs:off -->
+
+```py
+# error: [invalid-syntax]
+def test(  # knot: ignore
+```
+
+<!-- blacken-docs:on -->
+
+## Can't suppress `revealed-type` diagnostics
+
+```py
+a = 10
+# revealed: Literal[10]
+reveal_type(a)  # knot: ignore
+```
+
+## Extra whitespace in type ignore comments is allowed
+
+```py
+a = 10 / 0  # knot   :   ignore
+a = 10 / 0  # knot: ignore  [    division-by-zero   ]
+```
+
+## Whitespace is optional
+
+```py
+# fmt: off
+a = 10 / 0  #knot:ignore[division-by-zero]
+```
+
+## Trailing codes comma
+
+Trailing commas in the codes section are allowed:
+
+```py
+a = 10 / 0  # knot: ignore[division-by-zero,]
+```
+
+## Invalid characters in codes
+
+```py
+# error: [division-by-zero]
+a = 10 / 0  # knot: ignore[*-*]
+```
+
+## Trailing whitespace
+
+<!-- blacken-docs:off -->
+
+```py
+a = 10 / 0  # knot: ignore[division-by-zero]      
+            #                               ^^^^^^ trailing whitespace
+```
+
+<!-- blacken-docs:on -->
+
+## Missing comma
+
+A missing comma results in an invalid suppression comment. We may want to recover from this in the
+future.
+
+```py
+# error: [unresolved-reference]
+a = x / 0  # knot: ignore[division-by-zero unresolved-reference]
+```
+
+## Empty codes
+
+An empty codes array suppresses no-diagnostics and is always useless
+
+```py
+# error: [division-by-zero]
+a = 4 / 0  # knot: ignore[]
+```

crates/red_knot_python_semantic/resources/mdtest/suppressions/knot-ignore.md

@@ -95,12 +95,8 @@ a = test  # type: ignore[name-defined]
 
 ## Nested comments
 
-TODO: We should support this for better interopability with other suppression comments.
-
 ```py
 # fmt: off
-# TODO this error should be suppressed
-# error: [unresolved-reference]
 a = test \
   + 2  # fmt: skip # type: ignore
 

crates/red_knot_python_semantic/resources/mdtest/suppressions/type-ignore.md

@@ -1,4 +1,4 @@
-use crate::lint::RuleSelection;
+use crate::lint::{LintRegistry, RuleSelection};
 use ruff_db::files::File;
 use ruff_db::{Db as SourceDb, Upcast};
 
@@ -8,6 +8,8 @@ pub trait Db: SourceDb + Upcast<dyn SourceDb> {
     fn is_file_open(&self, file: File) -> bool;
 
     fn rule_selection(&self) -> &RuleSelection;
+
+    fn lint_registry(&self) -> &LintRegistry;
 }
 
 #[cfg(test)]
@@ -19,7 +21,7 @@ pub(crate) mod tests {
     use crate::{default_lint_registry, ProgramSettings, PythonPlatform};
 
     use super::Db;
-    use crate::lint::RuleSelection;
+    use crate::lint::{LintRegistry, RuleSelection};
     use anyhow::Context;
     use ruff_db::files::{File, Files};
     use ruff_db::system::{DbWithTestSystem, System, SystemPathBuf, TestSystem};
@@ -45,7 +47,7 @@ pub(crate) mod tests {
                 vendored: red_knot_vendored::file_system().clone(),
                 events: Arc::default(),
                 files: Files::default(),
-                rule_selection: Arc::new(RuleSelection::from_registry(&default_lint_registry())),
+                rule_selection: Arc::new(RuleSelection::from_registry(default_lint_registry())),
             }
         }
 
@@ -112,6 +114,10 @@ pub(crate) mod tests {
         fn rule_selection(&self) -> &RuleSelection {
             &self.rule_selection
         }
+
+        fn lint_registry(&self) -> &LintRegistry {
+            default_lint_registry()
+        }
     }
 
     #[salsa::db]

crates/red_knot_python_semantic/src/db.rs

@@ -33,11 +33,15 @@ mod visibility_constraints;
 
 type FxOrderSet<V> = ordermap::set::OrderSet<V, BuildHasherDefault<FxHasher>>;
 
-/// Creates a new registry with all known semantic lints.
-pub fn default_lint_registry() -> LintRegistry {
-    let mut registry = LintRegistryBuilder::default();
-    register_lints(&mut registry);
-    registry.build()
+/// Returns the default registry with all known semantic lints.
+pub fn default_lint_registry() -> &'static LintRegistry {
+    static REGISTRY: std::sync::LazyLock<LintRegistry> = std::sync::LazyLock::new(|| {
+        let mut registry = LintRegistryBuilder::default();
+        register_lints(&mut registry);
+        registry.build()
+    });
+
+    &REGISTRY
 }
 
 /// Register all known semantic lints.

crates/red_knot_python_semantic/src/lib.rs

@@ -321,7 +321,7 @@ impl LintRegistryBuilder {
     }
 }
 
-#[derive(Default, Debug)]
+#[derive(Default, Debug, Clone)]
 pub struct LintRegistry {
     lints: Vec<LintId>,
     by_name: FxHashMap<&'static str, LintEntry>,
@@ -385,7 +385,7 @@ pub enum GetLintError {
     Unknown(String),
 }
 
-#[derive(Debug, PartialEq, Eq)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
 pub enum LintEntry {
     /// An existing lint rule. Can be in preview, stable or deprecated.
     Lint(LintId),