[ty] Make auto-import completions opt-in via an experimental option

Instead of waiting to land auto-import until it is "ready
for users," it'd be nicer to get incremental progress merged
to `main`. By making it an experimental opt-in, we avoid making
the default completion experience worse but permit developers
and motivated users to try it.

crates/ty_server/src/server/api/requests/completion.rs

@@ -7,7 +7,7 @@ use lsp_types::{
 };
 use ruff_db::source::{line_index, source_text};
 use ruff_source_file::OneIndexed;
-use ty_ide::completion;
+use ty_ide::{CompletionSettings, completion};
 use ty_project::ProjectDatabase;
 use ty_python_semantic::CompletionKind;
 
@@ -55,7 +55,10 @@ impl BackgroundDocumentRequestHandler for CompletionRequestHandler {
             &line_index,
             snapshot.encoding(),
         );
-        let completions = completion(db, file, offset);
+        let settings = CompletionSettings {
+            auto_import: snapshot.global_settings().is_auto_import_enabled(),
+        };
+        let completions = completion(db, &settings, file, offset);
         if completions.is_empty() {
             return Ok(None);
         }

crates/ty_server/src/session.rs

@@ -826,6 +826,7 @@ impl Session {
             .map_err(DocumentQueryError::InvalidUrl);
         DocumentSnapshot {
             resolved_client_capabilities: self.resolved_client_capabilities,
+            global_settings: self.global_settings.clone(),
             workspace_settings: key
                 .as_ref()
                 .ok()
@@ -1000,6 +1001,7 @@ impl Drop for MutIndexGuard<'_> {
 #[derive(Debug)]
 pub(crate) struct DocumentSnapshot {
     resolved_client_capabilities: ResolvedClientCapabilities,
+    global_settings: Arc<GlobalSettings>,
     workspace_settings: Arc<WorkspaceSettings>,
     position_encoding: PositionEncoding,
     document_query_result: Result<DocumentQuery, DocumentQueryError>,
@@ -1016,6 +1018,11 @@ impl DocumentSnapshot {
         self.position_encoding
     }
 
+    /// Returns the client settings for all workspaces.
+    pub(crate) fn global_settings(&self) -> &GlobalSettings {
+        &self.global_settings
+    }
+
     /// Returns the client settings for the workspace that this document belongs to.
     pub(crate) fn workspace_settings(&self) -> &WorkspaceSettings {
         &self.workspace_settings

crates/ty_server/src/session/options.rs

@@ -122,6 +122,12 @@ impl ClientOptions {
         self
     }
 
+    #[must_use]
+    pub fn with_experimental_auto_import(mut self, enabled: bool) -> Self {
+        self.global.experimental.get_or_insert_default().auto_import = Some(enabled);
+        self
+    }
+
     #[must_use]
     pub fn with_unknown(mut self, unknown: HashMap<String, Value>) -> Self {
         self.unknown = unknown;
@@ -149,6 +155,7 @@ impl GlobalOptions {
             .experimental
             .map(|experimental| ExperimentalSettings {
                 rename: experimental.rename.unwrap_or(true),
+                auto_import: experimental.auto_import.unwrap_or(false),
             })
             .unwrap_or_default();
 
@@ -293,6 +300,12 @@ impl Combine for DiagnosticMode {
 pub(crate) struct Experimental {
     /// Whether to enable the experimental symbol rename feature.
     pub(crate) rename: Option<bool>,
+    /// Whether to enable the experimental "auto-import" feature.
+    ///
+    /// At time of writing (2025-08-29), this feature is still
+    /// under active development. It may not work right or may be
+    /// incomplete.
+    pub(crate) auto_import: Option<bool>,
 }
 
 #[derive(Clone, Debug, Serialize, Deserialize, Default)]

crates/ty_server/src/session/settings.rs

@@ -14,6 +14,10 @@ impl GlobalSettings {
     pub(crate) fn is_rename_enabled(&self) -> bool {
         self.experimental.rename
     }
+
+    pub(crate) fn is_auto_import_enabled(&self) -> bool {
+        self.experimental.auto_import
+    }
 }
 
 impl GlobalSettings {
@@ -25,6 +29,7 @@ impl GlobalSettings {
 #[derive(Clone, Default, Debug, PartialEq)]
 pub(crate) struct ExperimentalSettings {
     pub(super) rename: bool,
+    pub(super) auto_import: bool,
 }
 
 /// Resolved client settings for a specific workspace.