[ty] Use dedicated collector for completions

This is a small refactor that helps centralize the
logic for how we gather, convert and possibly filter
completions.

Some of this logic was spread out before, which
motivated this refactor. Moreover, as part of other
refactoring, I found myself chaffing against the
lack of this abstraction.

crates/ty_ide/src/all_symbols.rs

@@ -8,13 +8,12 @@ use crate::symbols::{QueryPattern, SymbolInfo, symbols_for_file_global_only};
 ///
 /// Returns symbols from all files in the workspace and dependencies, filtered
 /// by the query.
-pub fn all_symbols<'db>(db: &'db dyn Db, query: &str) -> Vec<AllSymbolInfo<'db>> {
+pub fn all_symbols<'db>(db: &'db dyn Db, query: &QueryPattern) -> Vec<AllSymbolInfo<'db>> {
     // If the query is empty, return immediately to avoid expensive file scanning
-    if query.is_empty() {
+    if query.will_match_everything() {
         return Vec::new();
     }
 
-    let query = QueryPattern::new(query);
     let results = std::sync::Mutex::new(Vec::new());
     {
         let modules = all_modules(db);
@@ -144,7 +143,7 @@ ABCDEFGHIJKLMNOP = 'https://api.example.com'
 
     impl CursorTest {
         fn all_symbols(&self, query: &str) -> String {
-            let symbols = all_symbols(&self.db, query);
+            let symbols = all_symbols(&self.db, &QueryPattern::new(query));
 
             if symbols.is_empty() {
                 return "No symbols found".to_string();

crates/ty_ide/src/completion.rs

@@ -21,6 +21,91 @@ use crate::importer::{ImportRequest, Importer};
 use crate::symbols::QueryPattern;
 use crate::{Db, all_symbols};
 
+/// A collection of completions built up from various sources.
+#[derive(Clone)]
+struct Completions<'db> {
+    db: &'db dyn Db,
+    items: Vec<Completion<'db>>,
+    query: QueryPattern,
+}
+
+impl<'db> Completions<'db> {
+    /// Create a new empty collection of completions.
+    ///
+    /// The given typed text should correspond to what we believe
+    /// the user has typed as part of the next symbol they are writing.
+    /// This collection will treat it as a query when present, and only
+    /// add completions that match it.
+    fn new(db: &'db dyn Db, typed: Option<&str>) -> Completions<'db> {
+        let query = typed
+            .map(QueryPattern::new)
+            .unwrap_or_else(QueryPattern::matches_all_symbols);
+        Completions {
+            db,
+            items: vec![],
+            query,
+        }
+    }
+
+    /// Convert this collection into a simple
+    /// sequence of completions.
+    fn into_completions(mut self) -> Vec<Completion<'db>> {
+        self.items.sort_by(compare_suggestions);
+        self.items
+            .dedup_by(|c1, c2| (&c1.name, c1.module_name) == (&c2.name, c2.module_name));
+        self.items
+    }
+
+    /// Attempts to adds the given completion to this collection.
+    ///
+    /// When added, `true` is returned.
+    ///
+    /// This might not add the completion for a variety of reasons.
+    /// For example, if the symbol name does not match this collection's
+    /// query.
+    fn try_add(&mut self, completion: Completion<'db>) -> bool {
+        if !self.query.is_match_symbol_name(completion.name.as_str()) {
+            return false;
+        }
+        self.force_add(completion);
+        true
+    }
+
+    /// Attempts to adds the given semantic completion to this collection.
+    ///
+    /// When added, `true` is returned.
+    fn try_add_semantic(&mut self, completion: SemanticCompletion<'db>) -> bool {
+        self.try_add(Completion::from_semantic_completion(self.db, completion))
+    }
+
+    /// Always adds the given completion to this collection.
+    fn force_add(&mut self, completion: Completion<'db>) {
+        self.items.push(completion);
+    }
+}
+
+impl<'db> Extend<SemanticCompletion<'db>> for Completions<'db> {
+    fn extend<T>(&mut self, it: T)
+    where
+        T: IntoIterator<Item = SemanticCompletion<'db>>,
+    {
+        for c in it {
+            self.try_add_semantic(c);
+        }
+    }
+}
+
+impl<'db> Extend<Completion<'db>> for Completions<'db> {
+    fn extend<T>(&mut self, it: T)
+    where
+        T: IntoIterator<Item = Completion<'db>>,
+    {
+        for c in it {
+            self.try_add(c);
+        }
+    }
+}
+
 #[derive(Clone, Debug)]
 pub struct Completion<'db> {
     /// The label shown to the user for this suggestion.
@@ -251,11 +336,6 @@ pub fn completion<'db>(
         return vec![completions];
     }
 
-    let typed_query = typed
-        .as_deref()
-        .map(QueryPattern::new)
-        .unwrap_or_else(QueryPattern::matches_all_symbols);
-
     let Some(target_token) = CompletionTargetTokens::find(&parsed, offset) else {
         return vec![];
     };
@@ -282,14 +362,12 @@ pub fn completion<'db>(
             (model.scoped_completions(scoped.node), Some(scoped))
         }
     };
-    let mut completions: Vec<Completion<'_>> = semantic_completions
-        .into_iter()
-        .filter(|c| typed_query.is_match_symbol_name(c.name.as_str()))
-        .map(|c| Completion::from_semantic_completion(db, c))
-        .collect();
+
+    let mut completions = Completions::new(db, typed.as_deref());
+    completions.extend(semantic_completions);
 
     if scoped.is_some() {
-        add_keyword_completions(db, &typed_query, &mut completions);
+        add_keyword_completions(db, &mut completions);
     }
     if settings.auto_import {
         if let Some(scoped) = scoped {
@@ -303,9 +381,7 @@ pub fn completion<'db>(
             );
         }
     }
-    completions.sort_by(compare_suggestions);
-    completions.dedup_by(|c1, c2| (&c1.name, c1.module_name) == (&c2.name, c2.module_name));
-    completions
+    completions.into_completions()
 }
 
 /// Adds completions derived from keywords.
@@ -313,21 +389,14 @@ pub fn completion<'db>(
 /// This should generally only be used when offering "scoped" completions.
 /// This will include keywords corresponding to Python values (like `None`)
 /// and general language keywords (like `raise`).
-fn add_keyword_completions<'db>(
-    db: &'db dyn Db,
-    query: &QueryPattern,
-    completions: &mut Vec<Completion<'db>>,
-) {
+fn add_keyword_completions<'db>(db: &'db dyn Db, completions: &mut Completions<'db>) {
     let keyword_values = [
         ("None", Type::none(db)),
         ("True", Type::BooleanLiteral(true)),
         ("False", Type::BooleanLiteral(false)),
     ];
     for (name, ty) in keyword_values {
-        if !query.is_match_symbol_name(name) {
-            continue;
-        }
-        completions.push(Completion::value_keyword(name, ty));
+        completions.try_add(Completion::value_keyword(name, ty));
     }
 
     // Note that we specifically omit the `type` keyword here, since
@@ -343,10 +412,7 @@ fn add_keyword_completions<'db>(
         "yield", "case", "match",
     ];
     for name in keywords {
-        if !query.is_match_symbol_name(name) {
-            continue;
-        }
-        completions.push(Completion::keyword(name));
+        completions.try_add(Completion::keyword(name));
     }
 }
 
@@ -377,17 +443,22 @@ fn add_unimported_completions<'db>(
     parsed: &ParsedModuleRef,
     scoped: ScopedTarget<'_>,
     typed: Option<&str>,
-    completions: &mut Vec<Completion<'db>>,
+    completions: &mut Completions<'db>,
 ) {
-    let Some(typed) = typed else {
+    // This is redundant since `all_symbols` will also bail
+    // when the query can match everything. But we bail here
+    // to avoid building an `Importer` and other plausibly
+    // costly work when we know we won't use it.
+    if completions.query.will_match_everything() {
         return;
-    };
+    }
+
     let source = source_text(db, file);
     let stylist = Stylist::from_tokens(parsed.tokens(), source.as_str());
     let importer = Importer::new(db, &stylist, file, source.as_str(), parsed);
     let members = importer.members_in_scope_at(scoped.node, scoped.node.start());
 
-    for symbol in all_symbols(db, typed) {
+    for symbol in all_symbols(db, &completions.query) {
         if symbol.module.file(db) == Some(file) {
             continue;
         }
@@ -399,7 +470,7 @@ fn add_unimported_completions<'db>(
         // "fine," but it might mean that we import a symbol from the
         // "wrong" module.
         let import_action = importer.import(request, &members);
-        completions.push(Completion {
+        completions.add(Completion {
             name: ast::name::Name::new(&symbol.symbol.name),
             insert: Some(import_action.symbol_text().into()),
             ty: None,
@@ -975,6 +1046,8 @@ fn is_import_alias_incomplete(tokens: &[Token], typed: Option<&str>) -> bool {
 ///
 /// If there isn't any typed text or it could not otherwise be found,
 /// then `None` is returned.
+///
+/// When `Some` is returned, the string is guaranteed to be non-empty.
 fn find_typed_text(
     db: &dyn Db,
     file: File,
@@ -997,7 +1070,7 @@ fn find_typed_text(
     // been typed. This likely means there is whitespace
     // or something that isn't represented in the token
     // stream. So just give up.
-    if last.end() < offset {
+    if last.end() < offset || last.range().is_empty() {
         return None;
     }
     Some(source[last.range()].to_string())

crates/ty_ide/src/symbols.rs

@@ -67,6 +67,16 @@ impl QueryPattern {
             symbol_name.contains(&self.original)
         }
     }
+
+    /// Returns true when it is known that this pattern will return `true` for
+    /// all inputs given to `QueryPattern::is_match_symbol_name`.
+    ///
+    /// This will never return `true` incorrectly, but it may return `false`
+    /// incorrectly. That is, it's possible that this query will match all
+    /// inputs but this still returns `false`.
+    pub fn will_match_everything(&self) -> bool {
+        self.re.is_none()
+    }
 }
 
 impl From<&str> for QueryPattern {