feat(interpreters): add an existing Python virtual environment as an interpreter (#2076)

Refs #1907

Add Python Interpreter → Existing environment: Browse picks the environment folder, which is resolved right away (pyvenv.cfg, bin/python or Scripts\python.exe) and added to the interpreter list as "Python X.Y (<env name>)", then remembered. Picking the folder rather than the executable keeps the environment's identity, since the native file picker resolves the venv's python symlink to the base interpreter. Works for `python -m venv` and uv environments; a broken environment shows an error instead of being added. Probing runs off the command thread.

Co-authored-by: Inf1mum <[email protected]>

src/features/settings/languages/AddInterpreterDialog.tsx

@@ -5,7 +5,7 @@
 import { isCancelled } from "@/platform/ipc";
 import { useId, useMemo, useState } from "react";
 import { Dialog, IconButton, Input, Select, Spinner, type SelectOption, T } from "@/ui";
-import { choosePath, createVenv, rememberSdk, type VenvTool } from "./api";
+import { choosePath, createVenv, pythonInterpreter, rememberSdk, type Sdk, type VenvTool } from "./api";
 import { tildify, useDetected } from "./components";
 import styles from "./Sdk.module.css";
 import { tx } from "@/platform/i18n";
@@ -36,6 +36,7 @@ export function AddInterpreterDialog({
   const [base, setBase] = useState<string | null>(null);
   const [location, setLocation] = useState(`${root}/.venv`);
   const [existing, setExisting] = useState<string | null>(null);
+  const [browsed, setBrowsed] = useState<Sdk[]>([]);
   const [busy, setBusy] = useState<{ cancel: () => void } | null>(null);
   const [log, setLog] = useState<string[]>([]);
   const [error, setError] = useState<string | null>(null);
@@ -48,17 +49,46 @@ export function AddInterpreterDialog({
     detail: tildify(s.path),
   });
   const baseOptions = bases.map(toOption);
-  const existingOptions = useMemo(() => {
-    const opts = list.map(toOption);
-    if (existing && !opts.some((o) => o.value === existing))
-      opts.push({ value: existing, label: tildify(existing), detail: "custom" });
-    return opts;
-  }, [list, existing]);
+  const existingOptions = [...browsed, ...list.filter((s) => !browsed.some((b) => b.path === s.path))].map((s) => ({
+    value: s.path,
+    label: `${s.name} — ${tildify(s.path)}`,
+  }));
+
+  const checkExisting = (path: string, onResolved: (sdk: Sdk) => void) => {
+    setError(null);
+    let cancelled = false;
+    setBusy({
+      cancel: () => {
+        cancelled = true;
+        setBusy(null);
+      },
+    });
+    void pythonInterpreter(path)
+      .then((sdk) => {
+        if (cancelled) return;
+        if (!sdk) {
+          setError(tx("Cannot run this Python interpreter. Select a working Python executable or virtualenv folder."));
+          return;
+        }
+        onResolved(sdk);
+      })
+      .catch((e: unknown) => {
+        if (!cancelled) setError(String((e as Error)?.message ?? e));
+      })
+      .finally(() => {
+        if (!cancelled) setBusy(null);
+      });
+  };
 
   const ok = () => {
+    if (busy) return;
     setError(null);
     if (mode === "existing") {
-      if (existing) onAdded(existing);
+      if (existing)
+        checkExisting(existing, (sdk) => {
+          rememberSdk("python", sdk);
+          onAdded(sdk.path);
+        });
       return;
     }
     if (!baseValue || !location.trim()) return;
@@ -74,7 +104,7 @@ export function AddInterpreterDialog({
       .finally(() => setBusy(null));
   };
 
-  const canOk = mode === "new" ? !!baseValue && !!location.trim() && !busy : !!existing;
+  const canOk = !busy && (mode === "new" ? !!baseValue && !!location.trim() : !!existing?.trim());
   const note = {
     venv: tx("Runs “<base> -m venv <location>”; the new interpreter becomes the project interpreter."),
     conda: tx("Runs “conda create -p <location>”; the new interpreter becomes the project interpreter."),
@@ -91,7 +121,11 @@ export function AddInterpreterDialog({
       title="Add Python Interpreter"
       width={680}
       aria-label="Add Python Interpreter"
-      footerStart={busy && <Spinner size={14} label="Creating environment" />}
+      footerStart={
+        busy && (
+          <Spinner size={14} label={mode === "existing" ? tx("Checking interpreter") : tx("Creating environment")} />
+        )
+      }
       buttons={[
         { label: "OK", role: "default", disabled: !canOk, onClick: ok },
         { label: "Cancel", role: "cancel" },
@@ -103,6 +137,7 @@ export function AddInterpreterDialog({
             <li key={k.tool}>
               <button
                 type="button"
+                disabled={!!busy}
                 className={`${styles.kind} ${kind === k.tool ? styles.kindOn : ""}`}
                 aria-current={kind === k.tool || undefined}
                 onClick={() => {
@@ -118,11 +153,23 @@ export function AddInterpreterDialog({
         <div className={styles.form}>
           <div className={styles.radios} role="radiogroup" aria-label={tx("Environment")}>
             <label className={styles.radio}>
-              <input type="radio" name="env" checked={mode === "new"} onChange={() => setMode("new")} />{" "}
+              <input
+                type="radio"
+                name="env"
+                disabled={!!busy}
+                checked={mode === "new"}
+                onChange={() => setMode("new")}
+              />{" "}
               <T>New environment</T>
             </label>
             <label className={styles.radio}>
-              <input type="radio" name="env" checked={mode === "existing"} onChange={() => setMode("existing")} />{" "}
+              <input
+                type="radio"
+                name="env"
+                disabled={!!busy}
+                checked={mode === "existing"}
+                onChange={() => setMode("existing")}
+              />{" "}
               <T>Existing environment</T>
             </label>
           </div>
@@ -179,10 +226,12 @@ export function AddInterpreterDialog({
               <label htmlFor={ids.existing}>
                 <T>Interpreter:</T>
               </label>
-              <div className={styles.pathRow}>
+              <div className={`${styles.pathRow} ${styles.existingPathRow}`}>
                 <Select
+                  id={ids.existing}
                   className={styles.pathInput}
                   value={existing}
+                  disabled={!!busy}
                   options={existingOptions}
                   onChange={setExisting}
                   placeholder={loading ? "Detecting…" : "Select an interpreter"}
@@ -192,9 +241,18 @@ export function AddInterpreterDialog({
                   icon="folder-open"
                   size="small"
                   title="Browse…"
+                  disabled={!!busy}
                   onClick={async () => {
-                    const p = await choosePath({ directory: false, title: "Select Python Interpreter" });
-                    if (p) setExisting(p);
+                    const p = await choosePath({
+                      directory: true,
+                      title: "Select Python Environment Folder",
+                      defaultPath: root,
+                    });
+                    if (p)
+                      checkExisting(p, (sdk) => {
+                        setBrowsed((current) => [sdk, ...current.filter((s) => s.path !== sdk.path)]);
+                        setExisting(sdk.path);
+                      });
                   }}
                 />
               </div>