Support optional MSC3860 redirects

spec/unit/content-repo.spec.ts

@@ -37,6 +37,21 @@ describe("ContentRepo", function () {
             );
         });
 
+        it("should allow redirects when requested on download URLs", function () {
+            const mxcUri = "mxc://server.name/resourceid";
+            expect(getHttpUriForMxc(baseUrl, mxcUri, undefined, undefined, undefined, false, true)).toEqual(
+                baseUrl + "/_matrix/media/v3/download/server.name/resourceid?allow_redirect=true",
+            );
+        });
+
+        it("should allow redirects when requested on thumbnail URLs", function () {
+            const mxcUri = "mxc://server.name/resourceid";
+            expect(getHttpUriForMxc(baseUrl, mxcUri, 32, 32, "scale", false, true)).toEqual(
+                baseUrl +
+                    "/_matrix/media/v3/thumbnail/server.name/resourceid?width=32&height=32&method=scale&allow_redirect=true",
+            );
+        });
+
         it("should return the empty string for null input", function () {
             expect(getHttpUriForMxc(null as any, "")).toEqual("");
         });

spec/unit/matrix-client.spec.ts

@@ -55,6 +55,7 @@ import {
     RuleId,
     IPushRule,
     ConditionKind,
+    getHttpUriForMxc,
 } from "../../src";
 import { supportsMatrixCall } from "../../src/webrtc/call";
 import { makeBeaconEvent } from "../test-utils/beacon";
@@ -369,6 +370,21 @@ describe("MatrixClient", function () {
         client.stopClient();
     });
 
+    describe("mxcUrlToHttp", () => {
+        it("should call getHttpUriForMxc", () => {
+            const mxc = "mxc://server/example";
+            expect(client.mxcUrlToHttp(mxc)).toBe(getHttpUriForMxc(client.baseUrl, mxc));
+            expect(client.mxcUrlToHttp(mxc, 32)).toBe(getHttpUriForMxc(client.baseUrl, mxc, 32));
+            expect(client.mxcUrlToHttp(mxc, 32, 46)).toBe(getHttpUriForMxc(client.baseUrl, mxc, 32, 46));
+            expect(client.mxcUrlToHttp(mxc, 32, 46, "scale")).toBe(
+                getHttpUriForMxc(client.baseUrl, mxc, 32, 46, "scale"),
+            );
+            expect(client.mxcUrlToHttp(mxc, 32, 46, "scale", false, true)).toBe(
+                getHttpUriForMxc(client.baseUrl, mxc, 32, 46, "scale", false, true),
+            );
+        });
+    });
+
     describe("timestampToEvent", () => {
         const roomId = "!room:server.org";
         const eventId = "$eventId:example.org";

src/client.ts

@@ -5805,6 +5805,9 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      * @param allowDirectLinks - If true, return any non-mxc URLs
      * directly. Fetching such URLs will leak information about the user to
      * anyone they share a room with. If false, will return null for such URLs.
+     * @param allowRedirects - If true, the caller supports the URL being 307 or
+     * 308 redirected to another resource upon request. If false, redirects
+     * are not expected.
      * @returns the avatar URL or null.
      */
     public mxcUrlToHttp(
@@ -5813,8 +5816,9 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
         height?: number,
         resizeMethod?: string,
         allowDirectLinks?: boolean,
+        allowRedirects?: boolean,
     ): string | null {
-        return getHttpUriForMxc(this.baseUrl, mxcUrl, width, height, resizeMethod, allowDirectLinks);
+        return getHttpUriForMxc(this.baseUrl, mxcUrl, width, height, resizeMethod, allowDirectLinks, allowRedirects);
     }
 
     /**

src/content-repo.ts

@@ -28,6 +28,9 @@ import { encodeParams } from "./utils";
  * directly. Fetching such URLs will leak information about the user to
  * anyone they share a room with. If false, will return the emptry string
  * for such URLs.
+ * @param allowRedirects - If true, the caller supports the URL being 307 or
+ * 308 redirected to another resource upon request. If false, redirects
+ * are not expected.
  * @returns The complete URL to the content.
  */
 export function getHttpUriForMxc(
@@ -37,6 +40,7 @@ export function getHttpUriForMxc(
     height?: number,
     resizeMethod?: string,
     allowDirectLinks = false,
+    allowRedirects?: boolean,
 ): string {
     if (typeof mxc !== "string" || !mxc) {
         return "";
@@ -67,6 +71,11 @@ export function getHttpUriForMxc(
         prefix = "/_matrix/media/v3/thumbnail/";
     }
 
+    if (typeof allowRedirects === "boolean") {
+        // We add this after, so we don't convert everything to a thumbnail request.
+        params["allow_redirect"] = JSON.stringify(allowRedirects);
+    }
+
     const fragmentOffset = serverAndMediaId.indexOf("#");
     let fragment = "";
     if (fragmentOffset >= 0) {