[playground] fix Python Emitter module loading for playground

.chronus/changes/python-module-loading-2026-3-29-14-53-8.md

@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/http-client-python"
+---
+
+Update Python emitter browser behavior to only load Pyodide once instead of on every emit

packages/http-client-python/emitter/src/emitter.ts

@@ -235,11 +235,21 @@ async function onEmitMain(context: EmitContext<PythonEmitterOptions>) {
 
   if (typeof window !== "undefined") {
     // Running in browser with Pyodide - fileURLToPath and other filesystem operations are browser-incompatible
-    const pyodide = await setupPyodideCallBrowser();
+    const pyodide = await browserPyodidePromise;
+
+    if (!pyodide) {
+      reportDiagnostic(program, {
+        code: "browser-runtime-load-failed",
+        target: NoTarget,
+        format: { details: "" },
+      });
+      return;
+    }
 
     const yamlFilePath = "/yaml/python-yaml-path.yaml";
     pyodide.FS.mkdirTree("/yaml");
     pyodide.FS.mkdirTree("/output");
+    clearMemfsDirectory(pyodide, "/output");
     pyodide.FS.writeFile(yamlFilePath, jsyaml.dump(parsedYamlMap));
 
     await runPyodideGeneration(pyodide, "/output", yamlFilePath, commandArgs);
@@ -325,6 +335,25 @@ async function onEmitMain(context: EmitContext<PythonEmitterOptions>) {
   }
 }
 
+const browserPyodidePromise: Promise<PyodideInterface> | null =
+  typeof window !== "undefined" ? setupPyodideCallBrowser() : null;
+
+function clearMemfsDirectory(pyodide: PyodideInterface, dir: string): void {
+  const entries: string[] = pyodide.FS.readdir(dir).filter(
+    (entry: string) => entry !== "." && entry !== "..",
+  );
+  for (const entry of entries) {
+    const fullPath = `${dir}/${entry}`;
+    const stats = pyodide.FS.stat(fullPath);
+    if (pyodide.FS.isDir(stats.mode)) {
+      clearMemfsDirectory(pyodide, fullPath);
+      pyodide.FS.rmdir(fullPath);
+    } else {
+      pyodide.FS.unlink(fullPath);
+    }
+  }
+}
+
 async function setupPyodideCallBrowser() {
   const pyodide = await loadPyodide({
     indexURL: `https://cdn.jsdelivr.net/pyodide/v${PYODIDE_VERSION}/full/`,

website/src/components/playground-component/playground.tsx

@@ -37,7 +37,7 @@ export const WebsitePlayground = ({ versionData }: WebsitePlaygroundProps) => {
       libraries={imports}
       emitterViewers={{ "@typespec/openapi3": [SwaggerUIViewer] }}
       emitterOptions={{
-        "@typespec/http-client-python": { debounce: 500 },
+        "@typespec/http-client-python": { debounce: 1000 },
         "@typespec/http-client-csharp": { debounce: 500 },
       }}
       importConfig={{ useShim: true }}