Clean up write_unit checks with guards

Author: alco

packages/sync-service/lib/electric/shapes/consumer.ex

@@ -279,7 +279,7 @@ defmodule Electric.Shapes.Consumer do
         {ShapeCache.Storage, :flushed, offset_in},
         %{write_unit: write_unit, pending_txn: pending_txn} = state
       )
-      when write_unit == :txn_fragment and not is_nil(pending_txn) do
+      when is_write_unit_txn_fragment(write_unit) and not is_nil(pending_txn) do
     state = notify_flushed_mappings(state, offset_in)
 
     # Save the flushed offset for the current pending txn.
@@ -584,7 +584,7 @@ defmodule Electric.Shapes.Consumer do
       # With write_unit=txn all fragments are buffered until the Commit change is seen. At that
       # point, a transaction struct is produced from the buffered fragments and is written to
       # storage.
-      state.write_unit == State.write_unit_txn() ->
+      is_write_unit_txn(state.write_unit) ->
         {txns, transaction_builder} =
           TransactionBuilder.build(txn_fragment, state.transaction_builder)
 

packages/sync-service/lib/electric/shapes/consumer/state.ex

@@ -398,6 +398,6 @@ defmodule Electric.Shapes.Consumer.State do
     ]
   end
 
-  def write_unit_txn, do: @write_unit_txn
-  def write_unit_txn_fragment, do: @write_unit_txn_fragment
+  defguard is_write_unit_txn(write_unit) when write_unit == @write_unit_txn
+  defguard is_write_unit_txn_fragment(write_unit) when write_unit == @write_unit_txn_fragment
 end