Disambiguate displaynames (#2918)

* Disambigute displaynames

* Add test

* fixup test functions

* prettier

* lint

* Split displayname utils into own file and add tests.

* Split out fixtures

* Add more testcases for displayname calculation.

* lint

* Also listen for displayname changes. (I stand corrected!)

* fix missing media tiles on missing member

src/utils/displayname.test.ts

@@ -0,0 +1,118 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only
+Please see LICENSE in the repository root for full details.
+*/
+
+import { describe, expect, test } from "vitest";
+
+import { calculateDisplayName, shouldDisambiguate } from "./displayname";
+import {
+  alice,
+  aliceDoppelganger,
+  aliceDoppelgangerRtcMember,
+  aliceRtcMember,
+  bob,
+  bobRtcMember,
+  bobZeroWidthSpace,
+  bobZeroWidthSpaceRtcMember,
+  daveRTL,
+} from "./test-fixtures";
+import { mockMatrixRoom } from "./test";
+
+describe("shouldDisambiguate", () => {
+  test("should not disambiguate a solo member", () => {
+    const room = mockMatrixRoom({});
+    expect(shouldDisambiguate(alice, [], room)).toEqual(false);
+  });
+  test("should not disambiguate a member with an empty displayname", () => {
+    const room = mockMatrixRoom({
+      getMember: (u) =>
+        [alice, aliceDoppelganger].find((m) => m.userId === u) ?? null,
+    });
+    expect(
+      shouldDisambiguate(
+        { rawDisplayName: "", userId: alice.userId },
+        [aliceRtcMember, aliceDoppelgangerRtcMember],
+        room,
+      ),
+    ).toEqual(false);
+  });
+  test("should disambiguate a member with RTL characters", () => {
+    const room = mockMatrixRoom({});
+    expect(shouldDisambiguate(daveRTL, [], room)).toEqual(true);
+  });
+  test("should disambiguate a member with a matching displayname", () => {
+    const room = mockMatrixRoom({
+      getMember: (u) =>
+        [alice, aliceDoppelganger].find((m) => m.userId === u) ?? null,
+    });
+    expect(
+      shouldDisambiguate(
+        alice,
+        [aliceRtcMember, aliceDoppelgangerRtcMember],
+        room,
+      ),
+    ).toEqual(true);
+    expect(
+      shouldDisambiguate(
+        aliceDoppelganger,
+        [aliceRtcMember, aliceDoppelgangerRtcMember],
+        room,
+      ),
+    ).toEqual(true);
+  });
+  test("should disambiguate a member with a matching displayname with hidden spaces", () => {
+    const room = mockMatrixRoom({
+      getMember: (u) =>
+        [bob, bobZeroWidthSpace].find((m) => m.userId === u) ?? null,
+    });
+    expect(
+      shouldDisambiguate(bob, [bobRtcMember, bobZeroWidthSpaceRtcMember], room),
+    ).toEqual(true);
+    expect(
+      shouldDisambiguate(
+        bobZeroWidthSpace,
+        [bobRtcMember, bobZeroWidthSpaceRtcMember],
+        room,
+      ),
+    ).toEqual(true);
+  });
+  test.for(["Alice @foo:bar", "@foo:b", "A@foo:lice", "A @f oo: ba r"])(
+    "should disambiguate a member with a displayname containing a mxid-like string '%s'",
+    (rawDisplayName) => {
+      const room = mockMatrixRoom({
+        getMember: (u) =>
+          [alice, aliceDoppelganger].find((m) => m.userId === u) ?? null,
+      });
+      expect(
+        shouldDisambiguate({ rawDisplayName, userId: alice.userId }, [], room),
+      ).toEqual(true);
+    },
+  );
+});
+
+describe("calculateDisplayName", () => {
+  test.for<[{ rawDisplayName?: string; userId: string }, boolean, string]>([
+    [alice, false, alice.rawDisplayName],
+    [alice, true, `${alice.rawDisplayName} (${alice.userId})`],
+    [alice, false, alice.rawDisplayName],
+    [{ rawDisplayName: "", userId: alice.userId }, false, alice.userId],
+    [
+      { rawDisplayName: alice.userId, userId: alice.userId },
+      false,
+      alice.userId,
+    ],
+    [bobZeroWidthSpace, false, "Bob"],
+    [
+      { rawDisplayName: "\u200b\u200b\u200b", userId: alice.userId },
+      false,
+      alice.userId,
+    ],
+    [daveRTL, false, "evaD"],
+    [daveRTL, true, `evaD (${daveRTL.userId})`],
+  ])("correctly calculates displayname", ([member, disambiguate, result]) =>
+    expect(calculateDisplayName(member, disambiguate)).toEqual(result),
+  );
+});