fix(streaming): address Greptile review of the RetroArch state core

A broker too old to name its core also doesn't refuse a pushed state from
another core, so hydration with no core filter now only sends a newest
state that has no recorded core, and otherwise sends nothing.

backend/handler/streaming/states.py

@@ -599,6 +599,10 @@ async def hydrate_states_to_broker(
         return 0
 
     newest = states[0]
+    # A broker that can't name its core doesn't refuse another core's state.
+    if state_core is None and newest.core is not None:
+        log.info("not hydrating a %s state into an unnamed core", newest.core)
+        return 0
     try:
         content = await fs_asset_handler.read_file(
             f"{newest.file_path}/{newest.file_name}"

backend/tests/endpoints/test_streaming.py

@@ -4943,14 +4943,27 @@ def test_hydrate_pushes_nothing_when_no_state_matches(rom: Rom, admin_user: User
     push.assert_not_called()
 
 
-def test_hydrate_filters_nothing_when_the_core_is_unknown(rom: Rom, admin_user: User):
+def test_hydrate_pushes_an_unrecorded_state_when_the_core_is_unknown(
+    rom: Rom, admin_user: User
+):
     """No configured core and a broker that can't name its default is how every
     RetroArch launch ran before cores were recorded."""
-    _core_state(rom, admin_user, "Game.state", "whatever")
+    _core_state(rom, admin_user, "Game.state", None)
     push = _hydrate_core(rom, admin_user, "retroarch", None)
     assert push.call_args.args[1:] == ("Game.state", b"state-bytes", None)
 
 
+def test_hydrate_pushes_nothing_recorded_when_the_core_is_unknown(
+    rom: Rom, admin_user: User
+):
+    """A broker too old to name its core doesn't refuse another core's state
+    either, so a newest state with a recorded core stays home."""
+    _core_state(rom, admin_user, "Old.state", None)
+    _core_state(rom, admin_user, "New.state", "bsnes")
+    push = _hydrate_core(rom, admin_user, "retroarch", None)
+    push.assert_not_called()
+
+
 def test_hydrate_pushes_nothing_into_a_configured_core_it_cannot_match(
     rom: Rom, admin_user: User
 ):