[ty] Add ty.inlayHints.variableTypes server option (#19780)

## Summary

This PR adds a new `ty.inlayHints.variableTypes` server setting to
configure ty to include / exclude inlay hints at variable position.

Currently, we only support inlay hints at this position so this option
basically translates to enabling / disabling inlay hints for now :)

The VS Code extension PR is
https://github.com/astral-sh/ty-vscode/pull/112.

closes: astral-sh/ty#472

## Test Plan

Add E2E tests.

crates/ty_ide/src/inlay_hints.rs

@@ -51,8 +51,13 @@ impl fmt::Display for DisplayInlayHint<'_, '_> {
     }
 }
 
-pub fn inlay_hints(db: &dyn Db, file: File, range: TextRange) -> Vec<InlayHint<'_>> {
-    let mut visitor = InlayHintVisitor::new(db, file, range);
+pub fn inlay_hints<'db>(
+    db: &'db dyn Db,
+    file: File,
+    range: TextRange,
+    settings: &InlayHintSettings,
+) -> Vec<InlayHint<'db>> {
+    let mut visitor = InlayHintVisitor::new(db, file, range, settings);
 
     let ast = parsed_module(db, file).load(db);
 
@@ -61,20 +66,34 @@ pub fn inlay_hints(db: &dyn Db, file: File, range: TextRange) -> Vec<InlayHint<'
     visitor.hints
 }
 
-struct InlayHintVisitor<'db> {
+/// Settings to control the behavior of inlay hints.
+#[derive(Clone, Default, Debug)]
+pub struct InlayHintSettings {
+    /// Whether to show variable type hints.
+    ///
+    /// For example, this would enable / disable hints like the ones quoted below:
+    /// ```python
+    /// x": Literal[1]" = 1
+    /// ```
+    pub variable_types: bool,
+}
+
+struct InlayHintVisitor<'a, 'db> {
     model: SemanticModel<'db>,
     hints: Vec<InlayHint<'db>>,
     in_assignment: bool,
     range: TextRange,
+    settings: &'a InlayHintSettings,
 }
 
-impl<'db> InlayHintVisitor<'db> {
-    fn new(db: &'db dyn Db, file: File, range: TextRange) -> Self {
+impl<'a, 'db> InlayHintVisitor<'a, 'db> {
+    fn new(db: &'db dyn Db, file: File, range: TextRange, settings: &'a InlayHintSettings) -> Self {
         Self {
             model: SemanticModel::new(db, file),
             hints: Vec::new(),
             in_assignment: false,
             range,
+            settings,
         }
     }
 
@@ -86,7 +105,7 @@ impl<'db> InlayHintVisitor<'db> {
     }
 }
 
-impl SourceOrderVisitor<'_> for InlayHintVisitor<'_> {
+impl SourceOrderVisitor<'_> for InlayHintVisitor<'_, '_> {
     fn enter_node(&mut self, node: AnyNodeRef<'_>) -> TraversalSignal {
         if self.range.intersect(node.range()).is_some() {
             TraversalSignal::Traverse
@@ -104,6 +123,10 @@ impl SourceOrderVisitor<'_> for InlayHintVisitor<'_> {
 
         match stmt {
             Stmt::Assign(assign) => {
+                if !self.settings.variable_types {
+                    return;
+                }
+
                 self.in_assignment = true;
                 for target in &assign.targets {
                     self.visit_expr(target);
@@ -213,8 +236,21 @@ mod tests {
     }
 
     impl InlayHintTest {
+        /// Returns the inlay hints for the given test case.
+        ///
+        /// All inlay hints are generated using the applicable settings. Use
+        /// [`inlay_hints_with_settings`] to generate hints with custom settings.
+        ///
+        /// [`inlay_hints_with_settings`]: Self::inlay_hints_with_settings
         fn inlay_hints(&self) -> String {
-            let hints = inlay_hints(&self.db, self.file, self.range);
+            self.inlay_hints_with_settings(&InlayHintSettings {
+                variable_types: true,
+            })
+        }
+
+        /// Returns the inlay hints for the given test case with custom settings.
+        fn inlay_hints_with_settings(&self, settings: &InlayHintSettings) -> String {
+            let hints = inlay_hints(&self.db, self.file, self.range, settings);
 
             let mut buf = source_text(&self.db, self.file).as_str().to_string();
 
@@ -276,4 +312,18 @@ mod tests {
         y = 2
         ");
     }
+
+    #[test]
+    fn disabled_variable_types() {
+        let test = inlay_hint_test("x = 1");
+
+        assert_snapshot!(
+            test.inlay_hints_with_settings(&InlayHintSettings {
+                variable_types: false,
+            }),
+            @r"
+        x = 1
+        "
+        );
+    }
 }

crates/ty_ide/src/lib.rs

@@ -27,7 +27,7 @@ pub use document_symbols::{document_symbols, document_symbols_with_options};
 pub use goto::{goto_declaration, goto_definition, goto_type_definition};
 pub use goto_references::goto_references;
 pub use hover::hover;
-pub use inlay_hints::inlay_hints;
+pub use inlay_hints::{InlayHintSettings, inlay_hints};
 pub use markup::MarkupKind;
 pub use references::ReferencesMode;
 pub use rename::{can_rename, rename};

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

@@ -47,7 +47,7 @@ impl BackgroundDocumentRequestHandler for InlayHintRequestHandler {
             .range
             .to_text_range(&source, &index, snapshot.encoding());
 
-        let inlay_hints = inlay_hints(db, file, range);
+        let inlay_hints = inlay_hints(db, file, range, snapshot.workspace_settings().inlay_hints());
 
         let inlay_hints = inlay_hints
             .into_iter()

crates/ty_server/src/session/options.rs

@@ -8,6 +8,7 @@ use serde::{Deserialize, Serialize};
 use serde_json::Value;
 
 use ty_combine::Combine;
+use ty_ide::InlayHintSettings;
 use ty_project::metadata::Options as TyOptions;
 use ty_project::metadata::options::ProjectOptionsOverrides;
 use ty_project::metadata::value::{RangedValue, RelativePathBuf};
@@ -106,6 +107,15 @@ impl ClientOptions {
         self
     }
 
+    #[must_use]
+    pub fn with_variable_types_inlay_hints(mut self, variable_types: bool) -> Self {
+        self.workspace
+            .inlay_hints
+            .get_or_insert_default()
+            .variable_types = Some(variable_types);
+        self
+    }
+
     #[must_use]
     pub fn with_experimental_rename(mut self, enabled: bool) -> Self {
         self.global.experimental.get_or_insert_default().rename = Some(enabled);
@@ -138,7 +148,7 @@ impl GlobalOptions {
         let experimental = self
             .experimental
             .map(|experimental| ExperimentalSettings {
-                rename: experimental.rename.unwrap_or_default(),
+                rename: experimental.rename.unwrap_or(true),
             })
             .unwrap_or_default();
 
@@ -158,6 +168,9 @@ pub(crate) struct WorkspaceOptions {
     /// Whether to disable language services like code completions, hover, etc.
     disable_language_services: Option<bool>,
 
+    /// Options to configure inlay hints.
+    inlay_hints: Option<InlayHintOptions>,
+
     /// Information about the currently active Python environment in the VS Code Python extension.
     ///
     /// This is relevant only for VS Code and is populated by the ty VS Code extension.
@@ -211,11 +224,29 @@ impl WorkspaceOptions {
 
         WorkspaceSettings {
             disable_language_services: self.disable_language_services.unwrap_or_default(),
+            inlay_hints: self
+                .inlay_hints
+                .map(InlayHintOptions::into_settings)
+                .unwrap_or_default(),
             overrides,
         }
     }
 }
 
+#[derive(Clone, Combine, Debug, Serialize, Deserialize, Default)]
+#[serde(rename_all = "camelCase")]
+struct InlayHintOptions {
+    variable_types: Option<bool>,
+}
+
+impl InlayHintOptions {
+    fn into_settings(self) -> InlayHintSettings {
+        InlayHintSettings {
+            variable_types: self.variable_types.unwrap_or_default(),
+        }
+    }
+}
+
 /// Diagnostic mode for the language server.
 #[derive(Clone, Copy, Debug, Default, PartialEq, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]

crates/ty_server/src/session/settings.rs

@@ -1,5 +1,6 @@
 use super::options::DiagnosticMode;
 
+use ty_ide::InlayHintSettings;
 use ty_project::metadata::options::ProjectOptionsOverrides;
 
 /// Resolved client settings that are shared across all workspaces.
@@ -33,6 +34,7 @@ pub(crate) struct ExperimentalSettings {
 #[derive(Clone, Default, Debug)]
 pub(crate) struct WorkspaceSettings {
     pub(super) disable_language_services: bool,
+    pub(super) inlay_hints: InlayHintSettings,
     pub(super) overrides: Option<ProjectOptionsOverrides>,
 }
 
@@ -44,4 +46,8 @@ impl WorkspaceSettings {
     pub(crate) fn project_options_overrides(&self) -> Option<&ProjectOptionsOverrides> {
         self.overrides.as_ref()
     }
+
+    pub(crate) fn inlay_hints(&self) -> &InlayHintSettings {
+        &self.inlay_hints
+    }
 }

crates/ty_server/tests/e2e/inlay_hints.rs

@@ -0,0 +1,38 @@
+use anyhow::Result;
+use lsp_types::{Position, Range, notification::PublishDiagnostics};
+use ruff_db::system::SystemPath;
+use ty_server::ClientOptions;
+
+use crate::TestServerBuilder;
+
+/// Tests that disabling variable types inlay hints works correctly.
+#[test]
+fn variable_inlay_hints_disabled() -> Result<()> {
+    let workspace_root = SystemPath::new("src");
+    let foo = SystemPath::new("src/foo.py");
+    let foo_content = "x = 1";
+
+    let mut server = TestServerBuilder::new()?
+        .with_initialization_options(
+            ClientOptions::default().with_variable_types_inlay_hints(false),
+        )
+        .with_workspace(workspace_root, None)?
+        .with_file(foo, foo_content)?
+        .enable_inlay_hints(true)
+        .build()?
+        .wait_until_workspaces_are_initialized()?;
+
+    server.open_text_document(foo, &foo_content, 1);
+    let _ = server.await_notification::<PublishDiagnostics>()?;
+
+    let hints = server
+        .inlay_hints_request(foo, Range::new(Position::new(0, 0), Position::new(0, 5)))?
+        .unwrap();
+
+    assert!(
+        hints.is_empty(),
+        "Expected no inlay hints, but found: {hints:?}"
+    );
+
+    Ok(())
+}

crates/ty_server/tests/e2e/main.rs

@@ -28,6 +28,7 @@
 //! [`await_notification`]: TestServer::await_notification
 
 mod initialize;
+mod inlay_hints;
 mod publish_diagnostics;
 mod pull_diagnostics;
 
@@ -48,20 +49,21 @@ use lsp_types::notification::{
     Initialized, Notification,
 };
 use lsp_types::request::{
-    DocumentDiagnosticRequest, HoverRequest, Initialize, Request, Shutdown, WorkspaceConfiguration,
-    WorkspaceDiagnosticRequest,
+    DocumentDiagnosticRequest, HoverRequest, Initialize, InlayHintRequest, Request, Shutdown,
+    WorkspaceConfiguration, WorkspaceDiagnosticRequest,
 };
 use lsp_types::{
     ClientCapabilities, ConfigurationParams, DiagnosticClientCapabilities,
     DidChangeTextDocumentParams, DidChangeWatchedFilesClientCapabilities,
     DidChangeWatchedFilesParams, DidCloseTextDocumentParams, DidOpenTextDocumentParams,
     DocumentDiagnosticParams, DocumentDiagnosticReportResult, FileEvent, Hover, HoverParams,
-    InitializeParams, InitializeResult, InitializedParams, NumberOrString, PartialResultParams,
-    Position, PreviousResultId, PublishDiagnosticsClientCapabilities,
-    TextDocumentClientCapabilities, TextDocumentContentChangeEvent, TextDocumentIdentifier,
-    TextDocumentItem, TextDocumentPositionParams, Url, VersionedTextDocumentIdentifier,
-    WorkDoneProgressParams, WorkspaceClientCapabilities, WorkspaceDiagnosticParams,
-    WorkspaceDiagnosticReportResult, WorkspaceFolder,
+    InitializeParams, InitializeResult, InitializedParams, InlayHint, InlayHintClientCapabilities,
+    InlayHintParams, NumberOrString, PartialResultParams, Position, PreviousResultId,
+    PublishDiagnosticsClientCapabilities, Range, TextDocumentClientCapabilities,
+    TextDocumentContentChangeEvent, TextDocumentIdentifier, TextDocumentItem,
+    TextDocumentPositionParams, Url, VersionedTextDocumentIdentifier, WorkDoneProgressParams,
+    WorkspaceClientCapabilities, WorkspaceDiagnosticParams, WorkspaceDiagnosticReportResult,
+    WorkspaceFolder,
 };
 use ruff_db::system::{OsSystem, SystemPath, SystemPathBuf, TestSystem};
 use rustc_hash::FxHashMap;
@@ -725,6 +727,23 @@ impl TestServer {
         let id = self.send_request::<HoverRequest>(params);
         self.await_response::<HoverRequest>(&id)
     }
+
+    /// Sends a `textDocument/inlayHint` request for the document at the given path and range.
+    pub(crate) fn inlay_hints_request(
+        &mut self,
+        path: impl AsRef<SystemPath>,
+        range: Range,
+    ) -> Result<Option<Vec<InlayHint>>> {
+        let params = InlayHintParams {
+            text_document: TextDocumentIdentifier {
+                uri: self.file_uri(path),
+            },
+            range,
+            work_done_progress_params: WorkDoneProgressParams::default(),
+        };
+        let id = self.send_request::<InlayHintRequest>(params);
+        self.await_response::<InlayHintRequest>(&id)
+    }
 }
 
 impl fmt::Debug for TestServer {
@@ -908,6 +927,19 @@ impl TestServerBuilder {
         self
     }
 
+    /// Enable or disable inlay hints capability
+    pub(crate) fn enable_inlay_hints(mut self, enabled: bool) -> Self {
+        self.client_capabilities
+            .text_document
+            .get_or_insert_default()
+            .inlay_hint = if enabled {
+            Some(InlayHintClientCapabilities::default())
+        } else {
+            None
+        };
+        self
+    }
+
     /// Enable or disable file watching capability
     #[expect(dead_code)]
     pub(crate) fn enable_did_change_watched_files(mut self, enabled: bool) -> Self {

crates/ty_wasm/src/lib.rs

@@ -16,8 +16,8 @@ use ruff_python_formatter::formatted_file;
 use ruff_source_file::{LineIndex, OneIndexed, SourceLocation};
 use ruff_text_size::{Ranged, TextSize};
 use ty_ide::{
-    MarkupKind, RangedValue, document_highlights, goto_declaration, goto_definition,
-    goto_references, goto_type_definition, hover, inlay_hints,
+    InlayHintSettings, MarkupKind, RangedValue, document_highlights, goto_declaration,
+    goto_definition, goto_references, goto_type_definition, hover, inlay_hints,
 };
 use ty_ide::{NavigationTargets, signature_help};
 use ty_project::metadata::options::Options;
@@ -435,6 +435,10 @@ impl Workspace {
             &self.db,
             file_id.file,
             range.to_text_range(&index, &source, self.position_encoding)?,
+            // TODO: Provide a way to configure this
+            &InlayHintSettings {
+                variable_types: true,
+            },
         );
 
         Ok(result