Merge remote-tracking branch 'origin/develop' into erikj/ss_room_store

13 files changed, 514 insertions, 33 deletions

diff --git a/CHANGES.md b/CHANGES.md
index 8279960b5b..0a2b816ed1 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,10 @@
+# Synapse 1.111.0 (2024-07-16)
+
+No significant changes since 1.111.0rc2.
+
+
+
+
 # Synapse 1.111.0rc2 (2024-07-10)
 
 ### Bugfixes
diff --git a/changelog.d/17435.bugfix b/changelog.d/17435.bugfix
new file mode 100644
index 0000000000..2d06a7c7fc
--- /dev/null
+++ b/changelog.d/17435.bugfix
@@ -0,0 +1 @@
+Order `heroes` by `stream_ordering` as the Matrix specification states (applies to `/sync`).
diff --git a/changelog.d/17451.doc b/changelog.d/17451.doc
new file mode 100644
index 0000000000..357ac2c906
--- /dev/null
+++ b/changelog.d/17451.doc
@@ -0,0 +1 @@
+Improve documentation for the [`default_power_level_content_override`](https://element-hq.github.io/synapse/latest/usage/configuration/config_documentation.html#default_power_level_content_override) config option.
diff --git a/changelog.d/17453.misc b/changelog.d/17453.misc
new file mode 100644
index 0000000000..2978a52477
--- /dev/null
+++ b/changelog.d/17453.misc
@@ -0,0 +1 @@
+Update experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint to bump room when it is created.
diff --git a/debian/changelog b/debian/changelog
index 0f3dcc64e6..0470e25f2d 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,9 @@
+matrix-synapse-py3 (1.111.0) stable; urgency=medium
+
+  * New Synapse release 1.111.0.
+
+ -- Synapse Packaging team <packages@matrix.org>  Tue, 16 Jul 2024 12:42:46 +0200
+
 matrix-synapse-py3 (1.111.0~rc2) stable; urgency=medium
 
   * New synapse release 1.111.0rc2.
diff --git a/docs/usage/configuration/config_documentation.md b/docs/usage/configuration/config_documentation.md
index 65b03ad0f8..38b24b5044 100644
--- a/docs/usage/configuration/config_documentation.md
+++ b/docs/usage/configuration/config_documentation.md
@@ -4134,6 +4134,38 @@ default_power_level_content_override:
    trusted_private_chat: null
    public_chat: null
 ```
+
+The default power levels for each preset are:
+```yaml
+"m.room.name": 50
+"m.room.power_levels": 100
+"m.room.history_visibility": 100
+"m.room.canonical_alias": 50
+"m.room.avatar": 50
+"m.room.tombstone": 100
+"m.room.server_acl": 100
+"m.room.encryption": 100
+```
+
+So a complete example where the default power-levels for a preset are maintained
+but the power level for a new key is set is:
+```yaml
+default_power_level_content_override:
+   private_chat:
+    events:
+      "com.example.foo": 0
+      "m.room.name": 50
+      "m.room.power_levels": 100
+      "m.room.history_visibility": 100
+      "m.room.canonical_alias": 50
+      "m.room.avatar": 50
+      "m.room.tombstone": 100
+      "m.room.server_acl": 100
+      "m.room.encryption": 100
+   trusted_private_chat: null
+   public_chat: null
+```
+
 ---
 ### `forget_rooms_on_leave`
 
diff --git a/poetry.lock b/poetry.lock
index 4092a41884..b3e45972f1 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -2504,18 +2504,19 @@ tests = ["coverage[toml] (>=5.0.2)", "pytest"]
 
 [[package]]
 name = "setuptools"
-version = "70.0.0"
+version = "67.6.0"
 description = "Easily download, build, install, upgrade, and uninstall Python packages"
 optional = false
-python-versions = ">=3.8"
+python-versions = ">=3.7"
 files = [
-    {file = "setuptools-70.0.0-py3-none-any.whl", hash = "sha256:54faa7f2e8d2d11bcd2c07bed282eef1046b5c080d1c32add737d7b5817b1ad4"},
-    {file = "setuptools-70.0.0.tar.gz", hash = "sha256:f211a66637b8fa059bb28183da127d4e86396c991a942b028c6650d4319c3fd0"},
+    {file = "setuptools-67.6.0-py3-none-any.whl", hash = "sha256:b78aaa36f6b90a074c1fa651168723acbf45d14cb1196b6f02c0fd07f17623b2"},
+    {file = "setuptools-67.6.0.tar.gz", hash = "sha256:2ee892cd5f29f3373097f5a814697e397cf3ce313616df0af11231e2ad118077"},
 ]
 
 [package.extras]
-docs = ["furo", "jaraco.packaging (>=9.3)", "jaraco.tidelift (>=1.4)", "pygments-github-lexers (==0.0.5)", "pyproject-hooks (!=1.1)", "rst.linker (>=1.9)", "sphinx (>=3.5)", "sphinx-favicon", "sphinx-inline-tabs", "sphinx-lint", "sphinx-notfound-page (>=1,<2)", "sphinx-reredirects", "sphinxcontrib-towncrier"]
-testing = ["build[virtualenv] (>=1.0.3)", "filelock (>=3.4.0)", "importlib-metadata", "ini2toml[lite] (>=0.14)", "jaraco.develop (>=7.21)", "jaraco.envs (>=2.2)", "jaraco.path (>=3.2.0)", "mypy (==1.9)", "packaging (>=23.2)", "pip (>=19.1)", "pyproject-hooks (!=1.1)", "pytest (>=6,!=8.1.1)", "pytest-checkdocs (>=2.4)", "pytest-cov", "pytest-enabler (>=2.2)", "pytest-home (>=0.5)", "pytest-mypy", "pytest-perf", "pytest-ruff (>=0.2.1)", "pytest-subprocess", "pytest-timeout", "pytest-xdist (>=3)", "tomli", "tomli-w (>=1.0.0)", "virtualenv (>=13.0.0)", "wheel"]
+docs = ["furo", "jaraco.packaging (>=9)", "jaraco.tidelift (>=1.4)", "pygments-github-lexers (==0.0.5)", "rst.linker (>=1.9)", "sphinx (>=3.5)", "sphinx-favicon", "sphinx-hoverxref (<2)", "sphinx-inline-tabs", "sphinx-lint", "sphinx-notfound-page (==0.8.3)", "sphinx-reredirects", "sphinxcontrib-towncrier"]
+testing = ["build[virtualenv]", "filelock (>=3.4.0)", "flake8 (<5)", "flake8-2020", "ini2toml[lite] (>=0.9)", "jaraco.envs (>=2.2)", "jaraco.path (>=3.2.0)", "pip (>=19.1)", "pip-run (>=8.8)", "pytest (>=6)", "pytest-black (>=0.3.7)", "pytest-checkdocs (>=2.4)", "pytest-cov", "pytest-enabler (>=1.3)", "pytest-flake8", "pytest-mypy (>=0.9.1)", "pytest-perf", "pytest-timeout", "pytest-xdist", "tomli-w (>=1.0.0)", "virtualenv (>=13.0.0)", "wheel"]
+testing-integration = ["build[virtualenv]", "filelock (>=3.4.0)", "jaraco.envs (>=2.2)", "jaraco.path (>=3.2.0)", "pytest", "pytest-enabler", "pytest-xdist", "tomli", "virtualenv (>=13.0.0)", "wheel"]
 
 [[package]]
 name = "setuptools-rust"
diff --git a/pyproject.toml b/pyproject.toml
index 3df42ae448..1f9ee2b944 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -97,7 +97,7 @@ module-name = "synapse.synapse_rust"
 
 [tool.poetry]
 name = "matrix-synapse"
-version = "1.111.0rc2"
+version = "1.111.0"
 description = "Homeserver for the Matrix decentralised comms protocol"
 authors = ["Matrix.org Team and Contributors <packages@matrix.org>"]
 license = "AGPL-3.0-or-later"
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index 2302d283a7..262d9f4044 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -1188,6 +1188,8 @@ class RoomCreationHandler:
             )
             events_to_send.append((power_event, power_context))
         else:
+            # Please update the docs for `default_power_level_content_override` when
+            # updating the `events` dict below
             power_level_content: JsonDict = {
                 "users": {creator_id: 100},
                 "users_default": 0,
diff --git a/synapse/handlers/sliding_sync.py b/synapse/handlers/sliding_sync.py
index 75603b6f75..aef5bf7975 100644
--- a/synapse/handlers/sliding_sync.py
+++ b/synapse/handlers/sliding_sync.py
@@ -57,6 +57,7 @@ logger = logging.getLogger(__name__)
 
 # The event types that clients should consider as new activity.
 DEFAULT_BUMP_EVENT_TYPES = {
+    EventTypes.Create,
     EventTypes.Message,
     EventTypes.Encrypted,
     EventTypes.Sticker,
diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py
index 5d2fd08495..f62d9f705d 100644
--- a/synapse/storage/databases/main/roommember.py
+++ b/synapse/storage/databases/main/roommember.py
@@ -279,8 +279,19 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):
 
     @cached(max_entries=100000)  # type: ignore[synapse-@cached-mutable]
     async def get_room_summary(self, room_id: str) -> Mapping[str, MemberSummary]:
-        """Get the details of a room roughly suitable for use by the room
+        """
+        Get the details of a room roughly suitable for use by the room
         summary extension to /sync. Useful when lazy loading room members.
+
+        Returns the total count of members in the room by membership type, and a
+        truncated list of members (the heroes). This will be the first 6 members of the
+        room:
+        - We want 5 heroes plus 1, in case one of them is the
+        calling user.
+        - They are ordered by `stream_ordering`, which are joined or
+        invited. When no joined or invited members are available, this also includes
+        banned and left users.
+
         Args:
             room_id: The room ID to query
         Returns:
@@ -308,23 +319,36 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):
             for count, membership in txn:
                 res.setdefault(membership, MemberSummary([], count))
 
-            # we order by membership and then fairly arbitrarily by event_id so
-            # heroes are consistent
-            # Note, rejected events will have a null membership field, so
-            # we we manually filter them out.
+            # Order by membership (joins -> invites -> leave (former insiders) ->
+            # everything else (outsiders like bans/knocks), then by `stream_ordering` so
+            # the first members in the room show up first and to make the sort stable
+            # (consistent heroes).
+            #
+            # Note: rejected events will have a null membership field, so we we manually
+            # filter them out.
             sql = """
                 SELECT state_key, membership, event_id
                 FROM current_state_events
                 WHERE type = 'm.room.member' AND room_id = ?
                     AND membership IS NOT NULL
                 ORDER BY
-                    CASE membership WHEN ? THEN 1 WHEN ? THEN 2 ELSE 3 END ASC,
-                    event_id ASC
+                    CASE membership WHEN ? THEN 1 WHEN ? THEN 2 WHEN ? THEN 3 ELSE 4 END ASC,
+                    event_stream_ordering ASC
                 LIMIT ?
             """
 
-            # 6 is 5 (number of heroes) plus 1, in case one of them is the calling user.
-            txn.execute(sql, (room_id, Membership.JOIN, Membership.INVITE, 6))
+            txn.execute(
+                sql,
+                (
+                    room_id,
+                    # Sort order
+                    Membership.JOIN,
+                    Membership.INVITE,
+                    Membership.LEAVE,
+                    # 6 is 5 (number of heroes) plus 1, in case one of them is the calling user.
+                    6,
+                ),
+            )
             for user_id, membership, event_id in txn:
                 summary = res[membership]
                 # we will always have a summary for this membership type at this
@@ -1509,10 +1533,19 @@ def extract_heroes_from_room_summary(
 ) -> List[str]:
     """Determine the users that represent a room, from the perspective of the `me` user.
 
+    This function expects `MemberSummary.members` to already be sorted by
+    `stream_ordering` like the results from `get_room_summary(...)`.
+
     The rules which say which users we select are specified in the "Room Summary"
     section of
     https://spec.matrix.org/v1.4/client-server-api/#get_matrixclientv3sync
 
+
+    Args:
+        details: Mapping from membership type to member summary. We expect
+            `MemberSummary.members` to already be sorted by `stream_ordering`.
+        me: The user for whom we are determining the heroes for.
+
     Returns a list (possibly empty) of heroes' mxids.
     """
     empty_ms = MemberSummary([], 0)
@@ -1527,11 +1560,11 @@ def extract_heroes_from_room_summary(
         r[0] for r in details.get(Membership.LEAVE, empty_ms).members if r[0] != me
     ] + [r[0] for r in details.get(Membership.BAN, empty_ms).members if r[0] != me]
 
-    # FIXME: order by stream ordering rather than as returned by SQL
+    # We expect `MemberSummary.members` to already be sorted by `stream_ordering`
     if joined_user_ids or invited_user_ids:
-        return sorted(joined_user_ids + invited_user_ids)[0:5]
+        return (joined_user_ids + invited_user_ids)[0:5]
     else:
-        return sorted(gone_user_ids)[0:5]
+        return gone_user_ids[0:5]
 
 
 @attr.s(slots=True, auto_attribs=True)
diff --git a/tests/rest/client/test_sync.py b/tests/rest/client/test_sync.py
index 8ab72c48a3..80c7bfdca7 100644
--- a/tests/rest/client/test_sync.py
+++ b/tests/rest/client/test_sync.py
@@ -2167,18 +2167,15 @@ class SlidingSyncTestCase(unittest.HomeserverTestCase):
 
         # Room2 doesn't have a name so we should see `heroes` populated
         self.assertIsNone(channel.json_body["rooms"][room_id1].get("name"))
-        # FIXME: Remove this basic assertion and uncomment the better assertion below
-        # after https://github.com/element-hq/synapse/pull/17435 merges
-        self.assertEqual(len(channel.json_body["rooms"][room_id1].get("heroes", [])), 5)
-        # self.assertCountEqual(
-        #     [
-        #         hero["user_id"]
-        #         for hero in channel.json_body["rooms"][room_id1].get("heroes", [])
-        #     ],
-        #     # Heroes should be the first 5 users in the room (excluding the user
-        #     # themselves, we shouldn't see `user1`)
-        #     [user2_id, user3_id, user4_id, user5_id, user6_id],
-        # )
+        self.assertCountEqual(
+            [
+                hero["user_id"]
+                for hero in channel.json_body["rooms"][room_id1].get("heroes", [])
+            ],
+            # Heroes should be the first 5 users in the room (excluding the user
+            # themselves, we shouldn't see `user1`)
+            [user2_id, user3_id, user4_id, user5_id, user6_id],
+        )
         self.assertEqual(
             channel.json_body["rooms"][room_id1]["joined_count"],
             7,
diff --git a/tests/storage/test_roommember.py b/tests/storage/test_roommember.py
index 882f3bbbdc..418b556108 100644
--- a/tests/storage/test_roommember.py
+++ b/tests/storage/test_roommember.py
@@ -19,20 +19,28 @@
 # [This file includes modifications made by New Vector Limited]
 #
 #
+import logging
 from typing import List, Optional, Tuple, cast
 
 from twisted.test.proto_helpers import MemoryReactor
 
-from synapse.api.constants import Membership
+from synapse.api.constants import EventTypes, JoinRules, Membership
+from synapse.api.room_versions import RoomVersions
+from synapse.rest import admin
 from synapse.rest.admin import register_servlets_for_client_rest_resource
-from synapse.rest.client import login, room
+from synapse.rest.client import knock, login, room
 from synapse.server import HomeServer
+from synapse.storage.databases.main.roommember import extract_heroes_from_room_summary
+from synapse.storage.roommember import MemberSummary
 from synapse.types import UserID, create_requester
 from synapse.util import Clock
 
 from tests import unittest
 from tests.server import TestHomeServer
 from tests.test_utils import event_injection
+from tests.unittest import skip_unless
+
+logger = logging.getLogger(__name__)
 
 
 class RoomMemberStoreTestCase(unittest.HomeserverTestCase):
@@ -240,6 +248,397 @@ class RoomMemberStoreTestCase(unittest.HomeserverTestCase):
         )
 
 
+class RoomSummaryTestCase(unittest.HomeserverTestCase):
+    """
+    Test `/sync` room summary related logic like `get_room_summary(...)` and
+    `extract_heroes_from_room_summary(...)`
+    """
+
+    servlets = [
+        admin.register_servlets,
+        knock.register_servlets,
+        login.register_servlets,
+        room.register_servlets,
+    ]
+
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
+        self.sliding_sync_handler = self.hs.get_sliding_sync_handler()
+        self.store = self.hs.get_datastores().main
+
+    def _assert_member_summary(
+        self,
+        actual_member_summary: MemberSummary,
+        expected_member_list: List[str],
+        *,
+        expected_member_count: Optional[int] = None,
+    ) -> None:
+        """
+        Assert that the `MemberSummary` object has the expected members.
+        """
+        self.assertListEqual(
+            [
+                user_id
+                for user_id, _membership_event_id in actual_member_summary.members
+            ],
+            expected_member_list,
+        )
+        self.assertEqual(
+            actual_member_summary.count,
+            (
+                expected_member_count
+                if expected_member_count is not None
+                else len(expected_member_list)
+            ),
+        )
+
+    def test_get_room_summary_membership(self) -> None:
+        """
+        Test that `get_room_summary(...)` gets every kind of membership when there
+        aren't that many members in the room.
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+        user3_id = self.register_user("user3", "pass")
+        _user3_tok = self.login(user3_id, "pass")
+        user4_id = self.register_user("user4", "pass")
+        user4_tok = self.login(user4_id, "pass")
+        user5_id = self.register_user("user5", "pass")
+        user5_tok = self.login(user5_id, "pass")
+
+        # Setup a room (user1 is the creator and is joined to the room)
+        room_id = self.helper.create_room_as(user1_id, tok=user1_tok)
+
+        # User2 is banned
+        self.helper.join(room_id, user2_id, tok=user2_tok)
+        self.helper.ban(room_id, src=user1_id, targ=user2_id, tok=user1_tok)
+
+        # User3 is invited by user1
+        self.helper.invite(room_id, targ=user3_id, tok=user1_tok)
+
+        # User4 leaves
+        self.helper.join(room_id, user4_id, tok=user4_tok)
+        self.helper.leave(room_id, user4_id, tok=user4_tok)
+
+        # User5 joins
+        self.helper.join(room_id, user5_id, tok=user5_tok)
+
+        room_membership_summary = self.get_success(self.store.get_room_summary(room_id))
+        empty_ms = MemberSummary([], 0)
+
+        self._assert_member_summary(
+            room_membership_summary.get(Membership.JOIN, empty_ms),
+            [user1_id, user5_id],
+        )
+        self._assert_member_summary(
+            room_membership_summary.get(Membership.INVITE, empty_ms), [user3_id]
+        )
+        self._assert_member_summary(
+            room_membership_summary.get(Membership.LEAVE, empty_ms), [user4_id]
+        )
+        self._assert_member_summary(
+            room_membership_summary.get(Membership.BAN, empty_ms), [user2_id]
+        )
+        self._assert_member_summary(
+            room_membership_summary.get(Membership.KNOCK, empty_ms),
+            [
+                # No one knocked
+            ],
+        )
+
+    def test_get_room_summary_membership_order(self) -> None:
+        """
+        Test that `get_room_summary(...)` stacks our limit of 6 in this order: joins ->
+        invites -> leave -> everything else (bans/knocks)
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+        user3_id = self.register_user("user3", "pass")
+        _user3_tok = self.login(user3_id, "pass")
+        user4_id = self.register_user("user4", "pass")
+        user4_tok = self.login(user4_id, "pass")
+        user5_id = self.register_user("user5", "pass")
+        user5_tok = self.login(user5_id, "pass")
+        user6_id = self.register_user("user6", "pass")
+        user6_tok = self.login(user6_id, "pass")
+        user7_id = self.register_user("user7", "pass")
+        user7_tok = self.login(user7_id, "pass")
+
+        # Setup the room (user1 is the creator and is joined to the room)
+        room_id = self.helper.create_room_as(user1_id, tok=user1_tok)
+
+        # We expect the order to be joins -> invites -> leave -> bans so setup the users
+        # *NOT* in that same order to make sure we're actually sorting them.
+
+        # User2 is banned
+        self.helper.join(room_id, user2_id, tok=user2_tok)
+        self.helper.ban(room_id, src=user1_id, targ=user2_id, tok=user1_tok)
+
+        # User3 is invited by user1
+        self.helper.invite(room_id, targ=user3_id, tok=user1_tok)
+
+        # User4 leaves
+        self.helper.join(room_id, user4_id, tok=user4_tok)
+        self.helper.leave(room_id, user4_id, tok=user4_tok)
+
+        # User5, User6, User7 joins
+        self.helper.join(room_id, user5_id, tok=user5_tok)
+        self.helper.join(room_id, user6_id, tok=user6_tok)
+        self.helper.join(room_id, user7_id, tok=user7_tok)
+
+        room_membership_summary = self.get_success(self.store.get_room_summary(room_id))
+        empty_ms = MemberSummary([], 0)
+
+        self._assert_member_summary(
+            room_membership_summary.get(Membership.JOIN, empty_ms),
+            [user1_id, user5_id, user6_id, user7_id],
+        )
+        self._assert_member_summary(
+            room_membership_summary.get(Membership.INVITE, empty_ms), [user3_id]
+        )
+        self._assert_member_summary(
+            room_membership_summary.get(Membership.LEAVE, empty_ms), [user4_id]
+        )
+        self._assert_member_summary(
+            room_membership_summary.get(Membership.BAN, empty_ms),
+            [
+                # The banned user is not in the summary because the summary can only fit
+                # 6 members and prefers everything else before bans
+                #
+                # user2_id
+            ],
+            # But we still see the count of banned users
+            expected_member_count=1,
+        )
+        self._assert_member_summary(
+            room_membership_summary.get(Membership.KNOCK, empty_ms),
+            [
+                # No one knocked
+            ],
+        )
+
+    def test_extract_heroes_from_room_summary_excludes_self(self) -> None:
+        """
+        Test that `extract_heroes_from_room_summary(...)` does not include the user
+        itself.
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+
+        # Setup the room (user1 is the creator and is joined to the room)
+        room_id = self.helper.create_room_as(user1_id, tok=user1_tok)
+
+        # User2 joins
+        self.helper.join(room_id, user2_id, tok=user2_tok)
+
+        room_membership_summary = self.get_success(self.store.get_room_summary(room_id))
+
+        # We first ask from the perspective of a random fake user
+        hero_user_ids = extract_heroes_from_room_summary(
+            room_membership_summary, me="@fakeuser"
+        )
+
+        # Make sure user1 is in the room (ensure our test setup is correct)
+        self.assertListEqual(hero_user_ids, [user1_id, user2_id])
+
+        # Now, we ask for the room summary from the perspective of user1
+        hero_user_ids = extract_heroes_from_room_summary(
+            room_membership_summary, me=user1_id
+        )
+
+        # User1 should not be included in the list of heroes because they are the one
+        # asking
+        self.assertListEqual(hero_user_ids, [user2_id])
+
+    def test_extract_heroes_from_room_summary_first_five_joins(self) -> None:
+        """
+        Test that `extract_heroes_from_room_summary(...)` returns the first 5 joins.
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+        user3_id = self.register_user("user3", "pass")
+        user3_tok = self.login(user3_id, "pass")
+        user4_id = self.register_user("user4", "pass")
+        user4_tok = self.login(user4_id, "pass")
+        user5_id = self.register_user("user5", "pass")
+        user5_tok = self.login(user5_id, "pass")
+        user6_id = self.register_user("user6", "pass")
+        user6_tok = self.login(user6_id, "pass")
+        user7_id = self.register_user("user7", "pass")
+        user7_tok = self.login(user7_id, "pass")
+
+        # Setup the room (user1 is the creator and is joined to the room)
+        room_id = self.helper.create_room_as(user1_id, tok=user1_tok)
+
+        # User2 -> User7 joins
+        self.helper.join(room_id, user2_id, tok=user2_tok)
+        self.helper.join(room_id, user3_id, tok=user3_tok)
+        self.helper.join(room_id, user4_id, tok=user4_tok)
+        self.helper.join(room_id, user5_id, tok=user5_tok)
+        self.helper.join(room_id, user6_id, tok=user6_tok)
+        self.helper.join(room_id, user7_id, tok=user7_tok)
+
+        room_membership_summary = self.get_success(self.store.get_room_summary(room_id))
+
+        hero_user_ids = extract_heroes_from_room_summary(
+            room_membership_summary, me="@fakuser"
+        )
+
+        # First 5 users to join the room
+        self.assertListEqual(
+            hero_user_ids, [user1_id, user2_id, user3_id, user4_id, user5_id]
+        )
+
+    def test_extract_heroes_from_room_summary_membership_order(self) -> None:
+        """
+        Test that `extract_heroes_from_room_summary(...)` prefers joins/invites over
+        everything else.
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+        user3_id = self.register_user("user3", "pass")
+        _user3_tok = self.login(user3_id, "pass")
+        user4_id = self.register_user("user4", "pass")
+        user4_tok = self.login(user4_id, "pass")
+        user5_id = self.register_user("user5", "pass")
+        user5_tok = self.login(user5_id, "pass")
+
+        # Setup the room (user1 is the creator and is joined to the room)
+        room_id = self.helper.create_room_as(user1_id, tok=user1_tok)
+
+        # We expect the order to be joins -> invites -> leave -> bans so setup the users
+        # *NOT* in that same order to make sure we're actually sorting them.
+
+        # User2 is banned
+        self.helper.join(room_id, user2_id, tok=user2_tok)
+        self.helper.ban(room_id, src=user1_id, targ=user2_id, tok=user1_tok)
+
+        # User3 is invited by user1
+        self.helper.invite(room_id, targ=user3_id, tok=user1_tok)
+
+        # User4 leaves
+        self.helper.join(room_id, user4_id, tok=user4_tok)
+        self.helper.leave(room_id, user4_id, tok=user4_tok)
+
+        # User5 joins
+        self.helper.join(room_id, user5_id, tok=user5_tok)
+
+        room_membership_summary = self.get_success(self.store.get_room_summary(room_id))
+
+        hero_user_ids = extract_heroes_from_room_summary(
+            room_membership_summary, me="@fakeuser"
+        )
+
+        # Prefer joins -> invites, over everything else
+        self.assertListEqual(
+            hero_user_ids,
+            [
+                # The joins
+                user1_id,
+                user5_id,
+                # The invites
+                user3_id,
+            ],
+        )
+
+    @skip_unless(
+        False,
+        "Test is not possible because when everyone leaves the room, "
+        + "the server is `no_longer_in_room` and we don't have any `current_state_events` to query",
+    )
+    def test_extract_heroes_from_room_summary_fallback_leave_ban(self) -> None:
+        """
+        Test that `extract_heroes_from_room_summary(...)` falls back to leave/ban if
+        there aren't any joins/invites.
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+        user3_id = self.register_user("user3", "pass")
+        user3_tok = self.login(user3_id, "pass")
+
+        # Setup the room (user1 is the creator and is joined to the room)
+        room_id = self.helper.create_room_as(user1_id, tok=user1_tok)
+
+        # User2 is banned
+        self.helper.join(room_id, user2_id, tok=user2_tok)
+        self.helper.ban(room_id, src=user1_id, targ=user2_id, tok=user1_tok)
+
+        # User3 leaves
+        self.helper.join(room_id, user3_id, tok=user3_tok)
+        self.helper.leave(room_id, user3_id, tok=user3_tok)
+
+        # User1 leaves (we're doing this last because they're the room creator)
+        self.helper.leave(room_id, user1_id, tok=user1_tok)
+
+        room_membership_summary = self.get_success(self.store.get_room_summary(room_id))
+
+        hero_user_ids = extract_heroes_from_room_summary(
+            room_membership_summary, me="@fakeuser"
+        )
+
+        # Fallback to people who left -> banned
+        self.assertListEqual(
+            hero_user_ids,
+            [user3_id, user1_id, user3_id],
+        )
+
+    def test_extract_heroes_from_room_summary_excludes_knocks(self) -> None:
+        """
+        People who knock on the room have (potentially) never been in the room before
+        and are total outsiders. Plus the spec doesn't mention them at all for heroes.
+        """
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+
+        # Setup the knock room (user1 is the creator and is joined to the room)
+        knock_room_id = self.helper.create_room_as(
+            user1_id, tok=user1_tok, room_version=RoomVersions.V7.identifier
+        )
+        self.helper.send_state(
+            knock_room_id,
+            EventTypes.JoinRules,
+            {"join_rule": JoinRules.KNOCK},
+            tok=user1_tok,
+        )
+
+        # User2 knocks on the room
+        knock_channel = self.make_request(
+            "POST",
+            "/_matrix/client/r0/knock/%s" % (knock_room_id,),
+            b"{}",
+            user2_tok,
+        )
+        self.assertEqual(knock_channel.code, 200, knock_channel.result)
+
+        room_membership_summary = self.get_success(
+            self.store.get_room_summary(knock_room_id)
+        )
+
+        hero_user_ids = extract_heroes_from_room_summary(
+            room_membership_summary, me="@fakeuser"
+        )
+
+        # user1 is the creator and is joined to the room (should show up as a hero)
+        # user2 is knocking on the room (should not show up as a hero)
+        self.assertListEqual(
+            hero_user_ids,
+            [user1_id],
+        )
+
+
 class CurrentStateMembershipUpdateTestCase(unittest.HomeserverTestCase):
     def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
         self.store = hs.get_datastores().main