[release/v1.7.0]: Revert "Remove connection_id from ViewContext (#3464)"

This reverts commit f8631cc.

Author: bfops

crates/bindings/src/lib.rs

@@ -805,6 +805,7 @@ pub struct AnonymousViewContext {
 /// Use this type if the view depends on the caller's identity.
 pub struct ViewContext {
     pub sender: Identity,
+    pub connection_id: Option<ConnectionId>,
     pub db: LocalReadOnly,
 }
 
@@ -941,6 +942,7 @@ impl ReducerContext {
     pub fn as_read_only(&self) -> ViewContext {
         ViewContext {
             sender: self.sender,
+            connection_id: self.connection_id,
             db: LocalReadOnly {},
         }
     }

crates/bindings/src/rt.rs

@@ -807,6 +807,8 @@ extern "C" fn __call_view__(
     sender_1: u64,
     sender_2: u64,
     sender_3: u64,
+    conn_id_0: u64,
+    conn_id_1: u64,
     args: BytesSource,
     sink: BytesSink,
 ) -> i16 {
@@ -815,12 +817,29 @@ extern "C" fn __call_view__(
     let sender: [u8; 32] = bytemuck::must_cast(sender);
     let sender = Identity::from_byte_array(sender); // The LITTLE-ENDIAN constructor.
 
+    // Piece together `conn_id_i` into a `ConnectionId`.
+    // The all-zeros `ConnectionId` (`ConnectionId::ZERO`) is interpreted as `None`.
+    let conn_id = [conn_id_0, conn_id_1];
+    let conn_id: [u8; 16] = bytemuck::must_cast(conn_id);
+    let conn_id = ConnectionId::from_le_byte_array(conn_id); // The LITTLE-ENDIAN constructor.
+    let conn_id = (conn_id != ConnectionId::ZERO).then_some(conn_id);
+
     let views = VIEWS.get().unwrap();
     let db = LocalReadOnly {};
+    let connection_id = conn_id;
 
     write_to_sink(
         sink,
-        &with_read_args(args, |args| views[id](ViewContext { sender, db }, args)),
+        &with_read_args(args, |args| {
+            views[id](
+                ViewContext {
+                    sender,
+                    connection_id,
+                    db,
+                },
+                args,
+            )
+        }),
     );
     0
 }