fed-sx-m1: Step 6c-schema-pure — pipeline:stage_schema/1,/2 with SchemaLookup callback + 14 tests

next/kernel/pipeline.erl

@@ -4,7 +4,8 @@
          inbound_stages/0, outbound_stages/0,
          stage_envelope/1,
          stage_signature/1, stage_signature/2,
-         stage_replay/1, stage_replay/2]).
+         stage_replay/1, stage_replay/2,
+         stage_schema/1, stage_schema/2]).
 
 %% Validation pipeline per design §14.
 %%
@@ -89,3 +90,46 @@ log_has_id(Id, [Act | Rest]) ->
         {ok, Id} -> true;
         _        -> log_has_id(Id, Rest)
     end.
+
+%% stage_schema/2 — validates the activity's :object against the
+%% schema registered for its :type. SchemaLookup is a caller-
+%% supplied fun (Type) -> {ok, SchemaFn} | not_found; SchemaFn is
+%% itself a fun (Object) -> bool. Returns:
+%%   ok                          when the schema accepts the object
+%%   {error, no_type}            when the activity has no :type
+%%   {error, schema_mismatch}    when SchemaFn returned false
+%%
+%% Open-world default: an unregistered Type returns ok so the
+%% pipeline doesn't block activities the kernel hasn't yet learned
+%% about. Tightening to strict-world happens later in milestone 2.
+%%
+%% Activities with no :object skip the schema check (some verbs
+%% legitimately carry no object).
+%%
+%% The Erlang-fun shape is the substrate-friendly stand-in for the
+%% SX-source :schema bodies stored in the genesis bundle. Once an
+%% SX-source eval bridge exists, the same stage shape will dispatch
+%% through it instead — no API change.
+stage_schema(Activity, SchemaLookup) ->
+    case envelope:get_field(type, Activity) of
+        not_found -> {error, no_type};
+        {ok, Type} ->
+            case SchemaLookup(Type) of
+                not_found -> ok;
+                {ok, SchemaFn} ->
+                    check_object_schema(Activity, SchemaFn)
+            end
+    end.
+
+check_object_schema(Activity, SchemaFn) ->
+    case envelope:get_field(object, Activity) of
+        not_found -> ok;
+        {ok, Obj} ->
+            case SchemaFn(Obj) of
+                true -> ok;
+                false -> {error, schema_mismatch}
+            end
+    end.
+
+stage_schema(SchemaLookup) ->
+    fun (Activity) -> stage_schema(Activity, SchemaLookup) end.