Recalculate mentions of forwarded messages

src/components/views/dialogs/ForwardDialog.tsx

@@ -58,6 +58,10 @@ import { getKeyBindingsManager } from "../../../KeyBindingsManager";
 import { KeyBindingAction } from "../../../accessibility/KeyboardShortcuts";
 import { OverflowTileView } from "../rooms/OverflowTileView";
 import { attachMentions } from "../../../utils/messages";
+import { CommandPartCreator } from "../../../editor/parts";
+import SettingsStore from "../../../settings/SettingsStore";
+import { parseEvent } from "../../../editor/deserialize";
+import EditorModel from "../../../editor/model";
 
 const AVATAR_SIZE = 30;
 
@@ -184,13 +188,13 @@ const Entry: React.FC<IEntryProps<any>> = ({ room, type, content, matrixClient:
  * 1. Strip all relations.
  * 2. Convert location events into a static pin-drop location share,
  *    and remove description from self-location shares.
- * 3. Pass through attachMentions() to strip mentions (as no EditorModel is present to recalculate from).
+ * 3. Parse the event back into an EditorModel and recalculate mentions.
  *
  * @param event - The MatrixEvent to transform.
- * @param userId - Current user MXID (passed through to attachMentions()).
+ * @param cli - The MatrixClient (used for recalculation of mentions).
  * @returns The transformed event type and content.
  */
-const transformEvent = (event: MatrixEvent, userId: string): { type: string; content: IContent } => {
+const transformEvent = (event: MatrixEvent, cli: MatrixClient): { type: string; content: IContent } => {
     const {
         // eslint-disable-next-line @typescript-eslint/no-unused-vars
         "m.relates_to": _, // strip relations - in future we will attach a relation pointing at the original event
@@ -225,12 +229,17 @@ const transformEvent = (event: MatrixEvent, userId: string): { type: string; con
         };
     }
 
-    // Mentions can leak information about the context of the original message,
-    // so pass through attachMentions() to recalculate mentions.
-    // Currently, this strips all mentions (forces an empty m.mentions),
-    // as there is no EditorModel to parse pills from.
-    // Future improvements could actually recalculate mentions based on the message body.
-    attachMentions(userId, content, null, undefined);
+    // Mentions can leak information about the context of the original message, so:
+    // 1. Parse the event's message body back into an EditorModel, then
+    // 2. Pass through attachMentions() to recalculate mentions.
+    const room = cli.getRoom(event.getRoomId())!;
+    const partCreator = new CommandPartCreator(room, cli);
+    const parts = parseEvent(event, partCreator, {
+        shouldEscape: SettingsStore.getValue("MessageComposerInput.useMarkdown"),
+    });
+    const model = new EditorModel(parts, partCreator); // Temporary EditorModel to pass through
+    const userId = cli.getSafeUserId();
+    attachMentions(userId, content, model, undefined);
 
     return { type, content };
 };
@@ -242,7 +251,7 @@ const ForwardDialog: React.FC<IProps> = ({ matrixClient: cli, event, permalinkCr
         cli.getProfileInfo(userId).then((info) => setProfileInfo(info));
     }, [cli, userId]);
 
-    const { type, content } = transformEvent(event, userId);
+    const { type, content } = transformEvent(event, cli);
 
     // For the message preview we fake the sender as ourselves
     const mockEvent = new MatrixEvent({

test/unit-tests/components/views/dialogs/ForwardDialog-test.tsx

@@ -249,34 +249,56 @@ describe("ForwardDialog", () => {
         expect(secondButton.getAttribute("aria-disabled")).toBeFalsy();
     });
 
-    it("strips mentions from forwarded messages", async () => {
-        const messageWithMention = mkEvent({
-            type: "m.room.message",
-            room: sourceRoom,
-            user: "@bob:example.org",
-            content: {
-                "msgtype": "m.text",
-                "body": "Hi @alice:example.org",
-                "m.mentions": {
-                    user_ids: ["@alice:example.org"],
-                },
-            },
-            event: true,
-        });
-
-        const { container } = mountForwardDialog(messageWithMention);
+    describe("Mention recalculation", () => {
         const roomId = "a";
+        const sendClick = (container: HTMLElement): void =>
+            act(() => {
+                const sendButton = container.querySelector(".mx_ForwardList_sendButton");
+                fireEvent.click(sendButton!);
+            });
+        const makeMessage = (body: string, mentions: object, formattedBody?: string) => {
+            return mkEvent({
+                type: "m.room.message",
+                room: sourceRoom,
+                user: "@bob:example.org",
+                content: {
+                    "msgtype": "m.text",
+                    "body": body,
+                    "m.mentions": mentions,
+                    ...(formattedBody && {
+                        format: "org.matrix.custom.html",
+                        formatted_body: formattedBody,
+                    }),
+                },
+                event: true,
+            });
+        };
 
-        // Click the send button.
-        act(() => {
-            const sendButton = container.querySelector(".mx_ForwardList_sendButton");
-            fireEvent.click(sendButton!);
+        it("strips extra mentions", async () => {
+            const message = makeMessage("Hi Alice", { user_ids: [aliceId] });
+            const { container } = mountForwardDialog(message);
+            sendClick(container);
+            // Expected content should have mentions empty.
+            expect(mockClient.sendEvent).toHaveBeenCalledWith(roomId, message.getType(), {
+                ...message.getContent(),
+                "m.mentions": {},
+            });
         });
 
-        // Expected content should have mentions empty.
-        expect(mockClient.sendEvent).toHaveBeenCalledWith(roomId, messageWithMention.getType(), {
-            ...messageWithMention.getContent(),
-            "m.mentions": {},
+        // TODO: mock room membership
+        it("recalculates mention pills", async () => {
+            const message = makeMessage(
+                "Hi Alice",
+                { user_ids: [aliceId] },
+                `Hi <a href="https://matrix.to/#/${aliceId}">Alice</a>`,
+            );
+            const { container } = mountForwardDialog(message);
+            sendClick(container);
+            // Expected content should have mentions empty.
+            expect(mockClient.sendEvent).toHaveBeenCalledWith(roomId, message.getType(), {
+                ...message.getContent(),
+                "m.mentions": { user_ids: [aliceId] },
+            });
         });
     });