From 830e3a1df3a73bc194e9d05be9865131cf3120e4 Mon Sep 17 00:00:00 2001
From: Half-Shot <will@half-shot.uk>
Date: Mon, 28 Oct 2024 12:04:59 +0000
Subject: [PATCH] Stablize MSC2409

---
 synapse/appservice/__init__.py |  2 ++
 synapse/appservice/api.py      | 11 ++++++++++-
 synapse/config/appservice.py   | 10 +++++++++-
 synapse/config/experimental.py |  4 +++-
 synapse/handlers/appservice.py |  7 +++----
 5 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/synapse/appservice/__init__.py b/synapse/appservice/__init__.py
index a96cdbf1e7..51e046d59d 100644
--- a/synapse/appservice/__init__.py
+++ b/synapse/appservice/__init__.py
@@ -86,6 +86,7 @@ class ApplicationService:
         rate_limited: bool = True,
         ip_range_whitelist: Optional[IPSet] = None,
         supports_ephemeral: bool = False,
+        supports_ephemeral_legacy: bool = False,
         msc3202_transaction_extensions: bool = False,
     ):
         self.token = token
@@ -99,6 +100,7 @@ class ApplicationService:
         self.id = id
         self.ip_range_whitelist = ip_range_whitelist
         self.supports_ephemeral = supports_ephemeral
+        self.supports_ephemeral_legacy = supports_ephemeral_legacy
         self.msc3202_transaction_extensions = msc3202_transaction_extensions
 
         if "|" in self.id:
diff --git a/synapse/appservice/api.py b/synapse/appservice/api.py
index 19322471dc..1b3ff6a083 100644
--- a/synapse/appservice/api.py
+++ b/synapse/appservice/api.py
@@ -353,7 +353,16 @@ class ApplicationServiceApi(SimpleHttpClient):
         if service.supports_ephemeral:
             body.update(
                 {
-                    # TODO: Update to stable prefixes once MSC2409 completes FCP merge.
+                    "ephemeral": ephemeral,
+                    # NOTE: This is actually https://github.com/matrix-org/matrix-spec-proposals/blob/tulir/appservice-to-device/proposals/4203-appservice-to-device.md
+                    # but for legacy reasons uses an older MSC number.
+                    "de.sorunome.msc2409.to_device": to_device_messages,
+                }
+            )
+        elif service.supports_ephemeral_legacy:
+            # Support to be removed in a future spec version.
+            body.update(
+                {
                     "de.sorunome.msc2409.ephemeral": ephemeral,
                     "de.sorunome.msc2409.to_device": to_device_messages,
                 }
diff --git a/synapse/config/appservice.py b/synapse/config/appservice.py
index 6ff00e1ff8..9a744ef363 100644
--- a/synapse/config/appservice.py
+++ b/synapse/config/appservice.py
@@ -170,7 +170,14 @@ def _load_appservice(
     if as_info.get("ip_range_whitelist"):
         ip_range_whitelist = IPSet(as_info.get("ip_range_whitelist"))
 
-    supports_ephemeral = as_info.get("de.sorunome.msc2409.push_ephemeral", False)
+    supports_ephemeral = as_info.get("receive_ephemeral", False)
+
+    # For ASes that haven't transitioned to the stable fields yet
+    supports_ephemeral_legacy = False
+    if not supports_ephemeral:
+        supports_ephemeral_legacy = as_info.get(
+            "de.sorunome.msc2409.push_ephemeral", False
+        )
 
     # Opt-in flag for the MSC3202-specific transactional behaviour.
     # When enabled, appservice transactions contain the following information:
@@ -194,5 +201,6 @@ def _load_appservice(
         rate_limited=rate_limited,
         ip_range_whitelist=ip_range_whitelist,
         supports_ephemeral=supports_ephemeral,
+        supports_ephemeral_legacy=supports_ephemeral_legacy,
         msc3202_transaction_extensions=msc3202_transaction_extensions,
     )
diff --git a/synapse/config/experimental.py b/synapse/config/experimental.py
index fd14db0d02..2c1daea213 100644
--- a/synapse/config/experimental.py
+++ b/synapse/config/experimental.py
@@ -294,7 +294,9 @@ class ExperimentalConfig(Config):
         # MSC3266 (room summary api)
         self.msc3266_enabled: bool = experimental.get("msc3266_enabled", False)
 
-        # MSC2409 (this setting only relates to optionally sending to-device messages).
+        # MSC4203 (Sending to-device events to appservices).
+        # NOTE: This used to be used to be part of MSC2409 but was split out, hence the config
+        # key not matching the MSC.
         # Presence, typing and read receipt EDUs are already sent to application services that
         # have opted in to receive them. If enabled, this adds to-device messages to that list.
         self.msc2409_to_device_messages_enabled: bool = experimental.get(
diff --git a/synapse/handlers/appservice.py b/synapse/handlers/appservice.py
index 4b33e1330d..143d19e6c5 100644
--- a/synapse/handlers/appservice.py
+++ b/synapse/handlers/appservice.py
@@ -242,9 +242,8 @@ class ApplicationServicesHandler:
                 will cause this function to return early.
 
                 Ephemeral events will only be pushed to appservices that have opted into
-                receiving them by setting `push_ephemeral` to true in their registration
-                file. Note that while MSC2409 is experimental, this option is called
-                `de.sorunome.msc2409.push_ephemeral`.
+                receiving them by setting `recieve_ephemeral` to true in their registration
+                file.
 
                 Appservices will only receive ephemeral events that fall within their
                 registered user and room namespaces.
@@ -588,7 +587,7 @@ class ApplicationServicesHandler:
             new_token,
         )
 
-        # According to MSC2409, we'll need to add 'to_user_id' and 'to_device_id' fields
+        # According to MSC4203, we'll need to add 'to_user_id' and 'to_device_id' fields
         # to the event JSON so that the application service will know which user/device
         # combination this messages was intended for.
         #