Support for stable m.oauth UIA stage from MSC4312 (#31704)

* Support for stable m.oauth UIA stage from MSC4312

* Unit tests

* readonly props

src/components/structures/InteractiveAuth.tsx

@@ -117,6 +117,7 @@ export default class InteractiveAuthComponent<T> extends React.Component<Interac
                 AuthType.UnstableRegistrationToken,
                 AuthType.Sso,
                 AuthType.SsoUnstable,
+                AuthType.OAuth,
                 CustomAuthType.MasCrossSigningReset,
             ],
         });

src/components/views/auth/InteractiveAuthEntryComponents.tsx

@@ -951,7 +951,7 @@ export class FallbackAuthEntry<T extends object> extends React.Component<IAuthEn
 }
 
 export enum CustomAuthType {
-    // Workaround for MAS requiring non-UIA authentication for resetting cross-signing.
+    // This is the unstable value from MSC4312
     MasCrossSigningReset = "org.matrix.cross_signing_reset",
 }
 
@@ -960,7 +960,8 @@ export class MasUnlockCrossSigningAuthEntry extends FallbackAuthEntry<{
         url?: string;
     };
 }> {
-    public static LOGIN_TYPE = CustomAuthType.MasCrossSigningReset;
+    public static readonly LOGIN_TYPE = AuthType.OAuth;
+    public static readonly UNSTABLE_LOGIN_TYPE = CustomAuthType.MasCrossSigningReset;
 
     private onGoToAccountClick = (): void => {
         if (!this.props.stageParams?.url) return;
@@ -1017,6 +1018,7 @@ export interface IStageComponent extends React.ComponentClass<React.PropsWithRef
 
 export default function getEntryComponentForLoginType(loginType: AuthType | CustomAuthType): IStageComponent {
     switch (loginType) {
+        case AuthType.OAuth:
         case CustomAuthType.MasCrossSigningReset:
             return MasUnlockCrossSigningAuthEntry;
         case AuthType.Password:

test/unit-tests/components/views/auth/OAuthStage-test.tsx

@@ -0,0 +1,109 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import React from "react";
+import { fireEvent, render, type RenderResult } from "jest-matrix-react";
+
+import InteractiveAuthComponent from "../../../../../src/components/structures/InteractiveAuth";
+import { getMockClientWithEventEmitter, unmockClientPeg } from "../../../../test-utils";
+
+describe("InteractiveAuthComponent", function () {
+    const mockClient = getMockClientWithEventEmitter({
+        generateClientSecret: jest.fn().mockReturnValue("t35tcl1Ent5ECr3T"),
+        getDomain: jest.fn().mockReturnValue("test.local"),
+    });
+    const authUrl = "https://test.local/oauth?action=foo";
+    const onAuthFinished = jest.fn();
+    const makeRequest = jest.fn().mockResolvedValue({ a: 1 });
+
+    const defaultProps = {
+        matrixClient: mockClient,
+        makeRequest: jest.fn().mockResolvedValue(undefined),
+        onAuthFinished: jest.fn(),
+    };
+    const getComponent = (props = {}) => render(<InteractiveAuthComponent {...defaultProps} {...props} />);
+
+    beforeEach(function () {
+        jest.clearAllMocks();
+        jest.spyOn(global.window, "open").mockImplementation();
+    });
+
+    afterAll(() => {
+        unmockClientPeg();
+    });
+
+    const getSubmitButton = ({ container }: RenderResult) => container.querySelector(".mx_Dialog_nonDialogButton");
+
+    it("should use an m.oauth stage", async () => {
+        const authData = {
+            session: "sess",
+            flows: [{ stages: ["m.oauth"] }],
+            params: {
+                "m.oauth": {
+                    url: authUrl,
+                },
+            },
+        };
+
+        const wrapper = getComponent({ makeRequest, onAuthFinished, authData });
+
+        const submitNode = getSubmitButton(wrapper);
+        expect(submitNode).toBeTruthy();
+
+        // click button; should trigger the auth URL to be opened
+        fireEvent.click(submitNode!);
+
+        expect(global.window.open).toHaveBeenCalledWith(authUrl, "_blank");
+    });
+
+    it("should use an unstable org.matrix.cross_signing_reset stage", async () => {
+        const authData = {
+            session: "sess",
+            flows: [{ stages: ["org.matrix.cross_signing_reset"] }],
+            params: {
+                "org.matrix.cross_signing_reset": {
+                    url: authUrl,
+                },
+            },
+        };
+
+        const wrapper = getComponent({ makeRequest, onAuthFinished, authData });
+
+        const submitNode = getSubmitButton(wrapper);
+        expect(submitNode).toBeTruthy();
+
+        // click button; should trigger the auth URL to be opened
+        fireEvent.click(submitNode!);
+
+        expect(global.window.open).toHaveBeenCalledWith(authUrl, "_blank");
+    });
+
+    it("should use the first flow when both stable and unstable are present", async () => {
+        const authData = {
+            session: "sess",
+            flows: [{ stages: ["org.matrix.cross_signing_reset"] }, { stages: ["m.oauth"] }],
+            params: {
+                "org.matrix.cross_signing_reset": {
+                    url: authUrl,
+                },
+                "m.oauth": {
+                    url: "https://should.not.be/opened",
+                },
+            },
+        };
+
+        const wrapper = getComponent({ makeRequest, onAuthFinished, authData });
+
+        const submitNode = getSubmitButton(wrapper);
+        expect(submitNode).toBeTruthy();
+
+        // click button; should trigger the auth URL to be opened
+        fireEvent.click(submitNode!);
+
+        expect(global.window.open).toHaveBeenCalledWith(authUrl, "_blank");
+    });
+});