fix: fast ssr access to globals should be allowed ouside of a request…

… after adding RequestStorageManager middleware (microsoft#6318)

* Updated installDOMShim logic so original global values are returned from getter if not in request scope

* Change files

* After install DOM Shim, globals will now return the original global instead of the shimmed version in async local storage if code is not in storage scope.

* Update change/@microsoft-fast-ssr-e107db57-9534-4ac4-bd65-157d5b40a79f.json

Co-authored-by: Rob Eisenberg <EisenbergEffect@users.noreply.github.com>

Co-authored-by: Rob Eisenberg <EisenbergEffect@users.noreply.github.com>

change/@microsoft-fast-ssr-e107db57-9534-4ac4-bd65-157d5b40a79f.json

@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "After install DOM Shim, globals will now return the original global instead of the shimmed version in async local storage if code is not in storage scope.",
+  "packageName": "@microsoft/fast-ssr",
+  "email": "erhuan@microsoft.com",
+  "dependentChangeType": "prerelease"
+}

packages/web-components/fast-ssr/src/request-storage.spec.ts

@@ -51,6 +51,29 @@ test.describe("RequestStorageManager", () => {
         expect(captured).toBe("world");
         expect(() => RequestStorage.get("hello")).toThrow(noStorageError);
     });
+
+    test("can get value from global without being in a storage scope", () => {
+        // window is part of perRequestGlobals setup by installDOMShim
+        (window as any)["hello"] = "world";
+        RequestStorageManager.installDOMShim();
+
+        expect((window as any)["hello"]).toBe("world");
+    });
+
+    test("can get different value from global in a storage scope", () => {
+
+        // window is part of perRequestGlobals setup by installDOMShim
+        (window as any)["hello"] = "world";
+        RequestStorageManager.installDOMShim();
+
+        let captured;
+        const storage = RequestStorageManager.createStorage();
+        RequestStorageManager.run(storage, () => {
+            captured = (window as any)["hello"];
+        });
+
+        expect(captured).not.toBe("world");
+    });
 });
 
 test.describe("RequestStorage", () => {

packages/web-components/fast-ssr/src/request-storage.ts

@@ -134,9 +134,12 @@ export const RequestStorageManager = Object.freeze({
      */
     installDOMShim(): void {
         for (const key of perRequestGlobals) {
+            const original = (globalThis as any)[key];
             Reflect.defineProperty(globalThis, key, {
                 get() {
-                    return RequestStorage.get("window")[key];
+                    // Return original global variable if currently not in the storage scope
+                    const store = asyncLocalStorage.getStore() as Map<string, any>;
+                    return store ? store.get("window")[key] : original;
                 },
             });
         }