Cable message encoding

* Introduce a connection coder responsible for encoding Cable messages
  as WebSocket messages, defaulting to `ActiveSupport::JSON` and duck-
  typing to any object responding to `#encode` and `#decode`.
* Consolidate encoding responsibility to the connection. No longer
  explicitly JSON-encode from channels or other sources. Pass Cable
  messages as Hashes to `#transmit` and rely on it to encode.
* Introduce stream encoders responsible for decoding pubsub messages.
  Preserve the currently raw encoding, but make it easy to use JSON.
  Same duck type as the connection encoder.
* Revert recent data normalization/quoting (#23649) which treated
  `identifier` and `data` values as nested JSON objects rather than as
  opaque JSON-encoded strings. That dealt us an awkward hand where we'd
  decode JSON strings… or not, but always encode as JSON. Embedding
  JSON object values directly is preferably, no extra JSON encoding,
  but that should be a purposeful protocol version change rather than
  ambiguously, inadvertently supporting multiple message formats.

1 files changed, 10 insertions, 5 deletions

diff --git a/actioncable/CHANGELOG.md b/actioncable/CHANGELOG.md
index 1ea862b389..d59e48e00c 100644
--- a/actioncable/CHANGELOG.md
+++ b/actioncable/CHANGELOG.md
@@ -1,11 +1,16 @@
-*  Add ActiveSupport::Notifications to ActionCable::Channel.
+*   Pubsub: automatic stream decoding.
 
-   *Matthew Wear*
+        stream_for @room, coder: ActiveSupport::JSON do |message|
+          # `message` is a Ruby hash here instead of a JSON string
 
-*   Allow channel identifiers with no backslahes/escaping to be accepted
-    by the subscription storer.
+    The `coder` must respond to `#decode`. Defaults to `coder: nil`
+    which skips decoding entirely.
 
-    *Jon Moss*
+    *Jeremy Daer*
+
+*   Add ActiveSupport::Notifications to ActionCable::Channel.
+
+    *Matthew Wear*
 
 *   Safely support autoloading and class unloading, by preventing concurrent
     loads, and disconnecting all cables during reload.