feat(python): Add ty and select the Python language server (#121)

ty (`ty server`) joins basedpyright and Pyright as a Python language server (fallback, gets the project venv like the others, installable from Tools). Settings › Language Servers gets a Python language server picker: Automatic (first available), basedpyright, Pyright, ty or None, written through the per-server enabled settings (null globally / true in a project for enabled, false for disabled); other combinations show as Custom combination. Picker text is translated; the hint sits on its own line.

Claude-Session: https://claude.ai/code/session_01VUYsdXA2nkF5v6zsC93dpn
Co-authored-by: zzxzz12345 <[email protected]>

crates/ide-language/src/registry.rs

@@ -518,12 +518,14 @@ mod tests {
     #[test]
     fn alternative_servers_are_fallbacks() {
         let reg = reg();
-        for (lang, servers) in
-            [("python", ["basedpyright", "pyright"]), ("typescript", ["vtsls", "typescript-language-server"])]
-        {
+        for (lang, servers) in [
+            ("python", vec!["basedpyright", "pyright", "ty"]),
+            ("typescript", vec!["vtsls", "typescript-language-server"]),
+        ] {
             let cfg = reg.get(&LanguageId::new(lang)).unwrap();
             let got: Vec<(&str, bool)> = cfg.language_servers.iter().map(|s| (s.name.as_str(), s.fallback)).collect();
-            assert_eq!(got, [(servers[0], false), (servers[1], true)]);
+            let expected: Vec<(&str, bool)> = servers.iter().enumerate().map(|(i, name)| (*name, i > 0)).collect();
+            assert_eq!(got, expected);
         }
     }
 

crates/ide-lsp/tests/real_servers.rs

@@ -105,6 +105,44 @@ fn main() {
 }
 ";
 
+#[tokio::test(flavor = "multi_thread")]
+#[ignore = "requires ty on PATH"]
+async fn ty_python_end_to_end() {
+    let dir = tempfile::tempdir().unwrap();
+    let root = dir.path().canonicalize().unwrap();
+    let path = root.join("example.py");
+    let source = "def greet(name: str) -> str:\n    return name\n\nresult = greet('Ada')\nbad: int = 'wrong'\n";
+    std::fs::write(&path, source).unwrap();
+    let mut python = LanguageRegistry::load(None).unwrap().get(&LanguageId::new("python")).unwrap();
+    python.language_servers.retain(|server| server.name == "ty");
+    assert_eq!(python.language_servers.len(), 1);
+    let (mgr, events) = manager(&root, LanguageRegistry::from_configs(vec![python]));
+    let doc = DocId::next();
+    mgr.did_open(doc, &path, &LanguageId::new("python"), 1, source);
+    retry("ty ready", Duration::from_secs(30), || {
+        let status = last_status(&events, "ty");
+        if let Some((ServerStatus::Crashed | ServerStatus::Missing | ServerStatus::Misconfigured, msg)) = &status {
+            panic!("ty failed: {msg:?}");
+        }
+        async move { matches!(status, Some((ServerStatus::Ready | ServerStatus::Busy, _))).then_some(()) }
+    })
+    .await;
+    let defs = retry("ty definition", Duration::from_secs(30), || {
+        let mgr = mgr.clone();
+        async move { mgr.goto(doc, Pos::new(3, 10), GotoKind::Definition).await.ok().filter(|d| !d.is_empty()) }
+    })
+    .await;
+    assert_eq!(defs[0].path, path);
+    assert_eq!(defs[0].range.start.line, 0);
+    retry("ty diagnostics", Duration::from_secs(30), || {
+        let found = events.lock().iter().any(
+            |event| matches!(event, IdeEvent::Diagnostics { source, items, .. } if source == "ty" && !items.is_empty()),
+        );
+        async move { found.then_some(()) }
+    })
+    .await;
+}
+
 #[tokio::test(flavor = "multi_thread")]
 #[ignore = "requires rust-analyzer"]
 async fn rust_analyzer_end_to_end() {

crates/ide-sdk/src/apply.rs

@@ -134,7 +134,7 @@ pub fn tsdk(root: &Path, s: &Settings) -> Option<PathBuf> {
     }
 }
 
-const PYTHON_SERVERS: [&str; 5] = ["basedpyright", "pyright", "pylsp", "jedi-language-server", "ruff"];
+const PYTHON_SERVERS: [&str; 6] = ["basedpyright", "pyright", "ty", "pylsp", "jedi-language-server", "ruff"];
 
 fn merge(base: &mut Value, layer: Value) {
     match (base, layer) {

crates/ide-tools/src/registry.rs

@@ -167,6 +167,16 @@ pub static TOOLS: &[ToolSpec] = &[
         homepage: "https://docs.basedpyright.com",
         needs: &[],
     },
+    ToolSpec {
+        name: "ty",
+        display: "ty (Python)",
+        kind: LanguageServer,
+        commands: &["ty"],
+        method: Method::PipVenv { package: "ty" },
+        version: ver("ty"),
+        homepage: "https://docs.astral.sh/ty/",
+        needs: &[],
+    },
     ToolSpec {
         name: "bash-language-server",
         display: "Bash Language Server",

crates/ide-tools/src/tests.rs

@@ -67,6 +67,11 @@ fn everything_missing_on_an_empty_system() {
     let vtsls = find(&list, "vtsls");
     assert!(vtsls.languages.iter().any(|l| l == "TypeScript"));
     assert!(vtsls.unavailable_reason.as_deref().unwrap().contains("npm"));
+    let ty = find(&list, "ty");
+    assert_eq!(ty.status, ToolStatus::Missing);
+    assert_eq!(ty.command, "ty");
+    assert_eq!(ty.install_method.as_deref(), Some("pip (virtualenv)"));
+    assert!(ty.languages.iter().any(|language| language == "Python"));
     // Servers without an installer are listed with their manual hint.
     let hls = find(&list, "haskell-language-server");
     assert_eq!(hls.install_method, None);

languages/python.toml

@@ -32,6 +32,14 @@ args = ["--stdio"]
 root-markers = ["pyproject.toml", "setup.py", "setup.cfg", "requirements.txt", "Pipfile", "pyrightconfig.json"]
 install-hint = "npm i -g pyright (or: pip install pyright)"
 
+[[language-servers]]
+name = "ty"
+fallback = true
+command = "ty"
+args = ["server"]
+root-markers = ["ty.toml", "pyproject.toml", "setup.py", "setup.cfg", "requirements.txt", "Pipfile"]
+install-hint = "uv tool install ty (or: pip install ty)"
+
 [debugger]
 adapter = "debugpy"
 command = "python3"

src/features/tools/LanguageServersPage.module.css

@@ -11,6 +11,21 @@
   max-width: 680px;
   color: var(--fg-secondary);
 }
+.pythonAnalyzer {
+  display: flex;
+  flex-direction: column;
+  gap: 4px;
+}
+.pythonAnalyzerRow {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+}
+.pythonAnalyzerHint {
+  margin: 0;
+  color: var(--fg-secondary);
+  font-size: var(--fs-small);
+}
 .body {
   display: flex;
   flex: 1;

src/features/tools/LanguageServersPage.tsx

@@ -8,7 +8,7 @@
 import { useEffect, useMemo, useState, type KeyboardEvent } from "react";
 import clsx from "clsx";
 import type { ToolInfo } from "@/bindings";
-import { Badge, Button, EmptyState, IconButton, ProgressBar, SearchField, Spinner, T } from "@/ui";
+import { Badge, Button, EmptyState, IconButton, ProgressBar, SearchField, Select, Spinner, T } from "@/ui";
 import { onIdeEvent } from "@/platform/ipc";
 import { useProject } from "@/platform/project";
 import { useSettingsForm } from "@/workbench/contributions";
@@ -28,6 +28,25 @@ import { tx } from "@/platform/i18n";
 
 type Filter = "all" | "missing" | "installed";
 
+const PYTHON_ANALYZERS = ["basedpyright", "pyright", "ty"] as const;
+type PythonAnalyzer = (typeof PYTHON_ANALYZERS)[number] | "auto" | "none" | "custom";
+
+function selectedPythonAnalyzer(servers: Record<string, ServerEntry>): PythonAnalyzer {
+  const enabled = PYTHON_ANALYZERS.filter((name) => servers[name]?.enabled !== false);
+  if (enabled.length === PYTHON_ANALYZERS.length) return "auto";
+  if (enabled.length === 0) return "none";
+  return enabled.length === 1 ? enabled[0]! : "custom";
+}
+
+const PYTHON_ANALYZER_OPTIONS: ReadonlyArray<{ value: PythonAnalyzer; label: string; disabled?: boolean }> = [
+  { value: "auto", label: "Automatic (first available)" },
+  { value: "basedpyright", label: "basedpyright" },
+  { value: "pyright", label: "Pyright" },
+  { value: "ty", label: "ty" },
+  { value: "none", label: "None" },
+  { value: "custom", label: "Custom combination", disabled: true },
+];
+
 const STATUS_TONE: Record<ToolInfo["status"], "success" | "accent" | "warning"> = {
   installed: "success",
   onPath: "accent",
@@ -317,6 +336,29 @@ export function LanguageServersPage() {
           "Language servers and debug adapters used by the IDE. Missing tools can be installed into the IDE's own tools folder; nothing is downloaded until you click Install.",
         )}
       </p>
+      <div className={styles.pythonAnalyzer}>
+        <div className={styles.pythonAnalyzerRow}>
+          <span>
+            <T>Python language server</T>
+          </span>
+          <Select
+            aria-label="Python language server"
+            value={selectedPythonAnalyzer(servers)}
+            options={PYTHON_ANALYZER_OPTIONS}
+            onChange={(selected) => {
+              if (selected === "custom") return;
+              for (const name of PYTHON_ANALYZERS) {
+                const on = selected === "auto" || selected === name;
+                // Same as each server's own checkbox: on is the default, so only a project spells it out.
+                form.set(serverKey(name, "enabled"), on ? (form.scope === "project" ? true : null) : false);
+              }
+            }}
+          />
+        </div>
+        <p className={styles.pythonAnalyzerHint}>
+          <T>Only one of these built-in Python analyzers runs at a time.</T>
+        </p>
+      </div>
       {error && (
         <div className={styles.error} role="alert">
           {error}

src/features/tools/__tests__/serverSettings.test.tsx

@@ -73,6 +73,46 @@ describe("Language Servers page settings", () => {
 
   afterEach(() => setToolsBackend(null));
 
+  it("selects exactly one Python analyzer and restores automatic fallback without writing defaults", async () => {
+    const user = userEvent.setup();
+    renderPage();
+    const picker = screen.getByRole("button", { name: "Python language server" });
+    expect(picker).toHaveTextContent("Automatic");
+    await user.click(picker);
+    await user.click(screen.getByRole("option", { name: "ty" }));
+    expect(stagedFor("languageServers.basedpyright.enabled")).toBe(false);
+    expect(stagedFor("languageServers.pyright.enabled")).toBe(false);
+    expect(stagedFor("languageServers.ty.enabled")).toBeNull();
+    expect(picker).toHaveTextContent("ty");
+    await user.click(picker);
+    await user.click(screen.getByRole("option", { name: /Automatic/ }));
+    for (const name of ["basedpyright", "pyright", "ty"]) {
+      expect(stagedFor(`languageServers.${name}.enabled`)).toBeNull();
+      expect(useTestForm.getState().values).not.toHaveProperty(`languageServers.${name}.enabled`);
+    }
+  });
+
+  it("spells out the chosen Python analyzer in project settings", async () => {
+    const user = userEvent.setup();
+    render(
+      <TestSettingsForm scope="project">
+        <LanguageServersPage />
+      </TestSettingsForm>,
+    );
+    const picker = screen.getByRole("button", { name: "Python language server" });
+    await user.click(picker);
+    await user.click(screen.getByRole("option", { name: "Pyright" }));
+    expect(stagedFor("languageServers.basedpyright.enabled")).toBe(false);
+    expect(stagedFor("languageServers.pyright.enabled")).toBe(true);
+    expect(stagedFor("languageServers.ty.enabled")).toBe(false);
+    expect(picker).toHaveTextContent("Pyright");
+    await user.click(picker);
+    await user.click(screen.getByRole("option", { name: /Automatic/ }));
+    for (const name of ["basedpyright", "pyright", "ty"]) {
+      expect(stagedFor(`languageServers.${name}.enabled`)).toBe(true);
+    }
+  });
+
   it("stages startup options, showing the defaults they replace", async () => {
     const user = userEvent.setup();
     renderPage();

src/features/tools/__tests__/settingsForm.tsx

@@ -34,15 +34,21 @@ export function stagedFor(key: string): unknown {
   return useTestForm.getState().staged.findLast(([k]) => k === key)?.[1];
 }
 
-export function TestSettingsForm({ children }: { children: ReactNode }) {
+export function TestSettingsForm({
+  children,
+  scope = "global",
+}: {
+  children: ReactNode;
+  scope?: SettingsForm["scope"];
+}) {
   const form = useMemo<SettingsForm>(
     () => ({
-      scope: "global",
+      scope,
       useValue: (key) => useTestForm((s) => getAt(s.values, key)),
       set: (key, value) =>
         useTestForm.setState((s) => ({ values: putAt(s.values, key, value), staged: [...s.staged, [key, value]] })),
     }),
-    [],
+    [scope],
   );
   return <SettingsFormContext.Provider value={form}>{children}</SettingsFormContext.Provider>;
 }

src/platform/locales/text/zh.json

@@ -4473,5 +4473,9 @@
   "Renamed": "已重命名",
   "Unversioned": "未跟踪",
   "Merge conflict": "合并冲突",
-  "by {author}": "由 {author} 创建"
+  "by {author}": "由 {author} 创建",
+  "Automatic (first available)": "自动（第一个可用的）",
+  "Custom combination": "自定义组合",
+  "Python language server": "Python 语言服务器",
+  "Only one of these built-in Python analyzers runs at a time.": "这些内置 Python 分析器同一时间只运行一个。"
 }

src/platform/locales/textCatalog.test.ts

@@ -88,6 +88,7 @@ const UNTRANSLATED = new Set<string>([
   // Products, tools and formats
   "Amazon Aurora MySQL",
   "Amazon Redshift",
+  "basedpyright",
   "Cargo Check",
   "Clippy",
   "CockroachDB",
@@ -123,6 +124,7 @@ const UNTRANSLATED = new Set<string>([
   "npm",
   "OpenIDEA",
   "PostgreSQL",
+  "Pyright",
   "Rust",
   "Rustfmt",
   "SingleStore",
@@ -131,6 +133,7 @@ const UNTRANSLATED = new Set<string>([
   "TiDB",
   "TimescaleDB",
   "TSV",
+  "ty",
   "TypeScript",
   "Vim",
   "YugabyteDB",