Refactor the Name classifier and use to retain dunder names

crates/ty_ide/src/completion.rs

@@ -5,7 +5,7 @@ use ruff_db::parsed::{ParsedModuleRef, parsed_module};
 use ruff_python_ast as ast;
 use ruff_python_parser::{Token, TokenAt, TokenKind};
 use ruff_text_size::{Ranged, TextRange, TextSize};
-use ty_python_semantic::{Completion, SemanticModel};
+use ty_python_semantic::{Completion, NameKind, SemanticModel};
 
 use crate::Db;
 use crate::find_node::covering_node;
@@ -325,38 +325,7 @@ fn import_from_tokens(tokens: &[Token]) -> Option<&Token> {
 /// This has the effect of putting all dunder attributes after "normal"
 /// attributes, and all single-underscore attributes after dunder attributes.
 fn compare_suggestions(c1: &Completion, c2: &Completion) -> Ordering {
-    /// A helper type for sorting completions based only on name.
-    ///
-    /// This sorts "normal" names first, then dunder names and finally
-    /// single-underscore names. This matches the order of the variants defined for
-    /// this enum, which is in turn picked up by the derived trait implementation
-    /// for `Ord`.
-    #[derive(Clone, Copy, Eq, PartialEq, PartialOrd, Ord)]
-    enum Kind {
-        Normal,
-        Dunder,
-        Sunder,
-    }
-
-    impl Kind {
-        fn classify(c: &Completion) -> Kind {
-            // Dunder needs a prefix and suffix double underscore.
-            // When there's only a prefix double underscore, this
-            // results in explicit name mangling. We let that be
-            // classified as-if they were single underscore names.
-            //
-            // Ref: <https://docs.python.org/3/reference/lexical_analysis.html#reserved-classes-of-identifiers>
-            if c.name.starts_with("__") && c.name.ends_with("__") {
-                Kind::Dunder
-            } else if c.name.starts_with('_') {
-                Kind::Sunder
-            } else {
-                Kind::Normal
-            }
-        }
-    }
-
-    let (kind1, kind2) = (Kind::classify(c1), Kind::classify(c2));
+    let (kind1, kind2) = (NameKind::classify(&c1.name), NameKind::classify(&c2.name));
     kind1.cmp(&kind2).then_with(|| c1.name.cmp(&c2.name))
 }
 
@@ -472,8 +441,10 @@ mod tests {
 ",
         );
         test.assert_completions_include("filter");
+        // Sunder items should be filtered out
         test.assert_completions_do_not_include("_T");
-        test.assert_completions_do_not_include("__annotations__");
+        // Dunder attributes should not be stripped
+        test.assert_completions_include("__annotations__");
     }
 
     #[test]

crates/ty_python_semantic/src/lib.rs

@@ -15,7 +15,7 @@ pub use program::{
     PythonVersionWithSource, SearchPathSettings,
 };
 pub use python_platform::PythonPlatform;
-pub use semantic_model::{Completion, HasType, SemanticModel};
+pub use semantic_model::{Completion, HasType, NameKind, SemanticModel};
 pub use site_packages::{PythonEnvironment, SitePackagesPaths, SysPrefixPathOrigin};
 pub use util::diagnostics::add_inferred_python_version_hint_to_diagnostic;
 

crates/ty_python_semantic/src/semantic_model.rs

@@ -73,7 +73,7 @@ impl<'db> SemanticModel<'db> {
         crate::types::all_members(self.db, ty)
             .into_iter()
             // Filter out private members from `builtins`
-            .filter(|name| !builtin || !name.starts_with('_'))
+            .filter(|name| !(builtin && matches!(NameKind::classify(name), NameKind::Sunder)))
             .map(|name| Completion { name, builtin })
             .collect()
     }
@@ -131,6 +131,39 @@ impl<'db> SemanticModel<'db> {
     }
 }
 
+/// A classification for completion names.
+///
+/// The ordering here is used for sorting completions based only on name.
+///
+/// This sorts "normal" names first, then dunder names and finally
+/// single-underscore names. This matches the order of the variants defined for
+/// this enum, which is in turn picked up by the derived trait implementation
+/// for `Ord`.
+#[derive(Clone, Copy, Eq, PartialEq, PartialOrd, Ord)]
+pub enum NameKind {
+    Normal,
+    Dunder,
+    Sunder,
+}
+
+impl NameKind {
+    pub fn classify(name: &Name) -> NameKind {
+        // Dunder needs a prefix and suffix double underscore.
+        // When there's only a prefix double underscore, this
+        // results in explicit name mangling. We let that be
+        // classified as-if they were single underscore names.
+        //
+        // Ref: <https://docs.python.org/3/reference/lexical_analysis.html#reserved-classes-of-identifiers>
+        if name.starts_with("__") && name.ends_with("__") {
+            NameKind::Dunder
+        } else if name.starts_with('_') {
+            NameKind::Sunder
+        } else {
+            NameKind::Normal
+        }
+    }
+}
+
 /// A suggestion for code completion.
 #[derive(Clone, Debug)]
 pub struct Completion {