From 28c9eed57abe57a0a0cb0c908356a288dc73440c Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
Date: Thu, 2 Jul 2026 15:48:16 +0100
Subject: [PATCH] Document incompatibility between playwright fixtures and MAS
 (#34101)

* Document incompatibility between playwright fixtures and MAS

* another comment
---
 .../playwright-common/src/fixtures/user.ts    | 20 ++++++++++++++++++-
 .../playwright-common/src/utils/context.ts    |  2 ++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/packages/playwright-common/src/fixtures/user.ts b/packages/playwright-common/src/fixtures/user.ts
index 03a4b55845..a60a28cba9 100644
--- a/packages/playwright-common/src/fixtures/user.ts
+++ b/packages/playwright-common/src/fixtures/user.ts
@@ -15,7 +15,11 @@ import { sample, uniqueId } from "lodash-es";
 import { test as base } from "./panel.js";
 import { type Credentials } from "../utils/api.js";
 
-/** Adds an initScript to the given page which will populate localStorage appropriately so that Element will use the given credentials. */
+/**
+ * Adds an initScript to the given page which will populate localStorage appropriately so that Element will use the given credentials.
+ *
+ * Warning: this is an incomplete implementation, particularly in MAS environments: for example, a logout operation will not work correctly.
+ */
 export async function populateLocalStorageWithCredentials(page: Page, credentials: Credentials) {
     await page.addInitScript(
         ({ credentials }) => {
@@ -27,6 +31,14 @@ export async function populateLocalStorageWithCredentials(page: Page, credential
             window.localStorage.setItem("mx_has_pickle_key", "false");
             window.localStorage.setItem("mx_has_access_token", "true");
 
+            // XXX: If the homeserver is using MAS, then Element uses additional localstorage settings to store more
+            // data. The fact that we don't populate them means that, for example, when you hit "Remove this device" in
+            // the app, it attempts to hit the legacy `/logout` endpoint, which returns a 40x error, which is silently
+            // ignored.
+            //
+            // If you fix this, (1) yay! (2) please remember to update the warning on the doc-comments of this method
+            // and its callers.
+
             window.localStorage.setItem(
                 "mx_local_settings",
                 JSON.stringify({
@@ -61,6 +73,9 @@ export interface TestFixtures {
      * but adds an initScript which will populate localStorage with the user's details from
      * {@link #credentials} and {@link #homeserver}.
      *
+     * Warning: this is an incomplete implementation, particularly in MAS environments: for example, a logout operation
+     * will not work correctly.
+     *
      * Similar to {@link #user}, but doesn't load the app.
      */
     pageWithCredentials: Page;
@@ -69,6 +84,9 @@ export interface TestFixtures {
      * A (rather poorly-named) test fixture which registers a user per {@link #credentials}, stores
      * the credentials into localStorage per {@link #pageWithCredentials}, and then loads the front page of the
      * app.
+     *
+     * Warning: the user credentials are an incomplete implementation, particularly in MAS environments: for example, a logout operation
+     * will not work correctly.
      */
     user: Credentials;
 }
diff --git a/packages/playwright-common/src/utils/context.ts b/packages/playwright-common/src/utils/context.ts
index c11477fe9c..3c8df55459 100644
--- a/packages/playwright-common/src/utils/context.ts
+++ b/packages/playwright-common/src/utils/context.ts
@@ -14,6 +14,8 @@ import { routeConfigJson } from "./config_json.js";
 import { populateLocalStorageWithCredentials } from "../fixtures/user.js";
 
 /** Create a new instance of the application, in a separate browser context, using the given credentials.
+ *
+ * Warning: `populateLocalStorageWithCredentials` is an incomplete implementation, particularly in MAS environments: for example, a logout operation will not work correctly.
  *
  * @param browser - the browser to use
  * @param credentials - the credentials to use for the new instance