feat(pj_plugins): expose parser capability tags on the runtime catalog

pj_plugins/CMakeLists.txt

@@ -124,6 +124,16 @@ target_compile_features(mock_schema_parser_plugin PRIVATE cxx_std_20)
 target_compile_options(mock_schema_parser_plugin PRIVATE ${PJ_WARNING_FLAGS})
 target_link_libraries(mock_schema_parser_plugin PRIVATE pj_base)
 
+# ---------------------------------------------------------------------------
+# Mock Media Parser plugin (declares "object" capability — exercises the
+# dual-emit path: scalar `seq` field + opaque blob via objectWriteHost())
+# ---------------------------------------------------------------------------
+
+add_library(mock_media_parser_plugin SHARED examples/mock_media_parser.cpp)
+target_compile_features(mock_media_parser_plugin PRIVATE cxx_std_20)
+target_compile_options(mock_media_parser_plugin PRIVATE ${PJ_WARNING_FLAGS})
+target_link_libraries(mock_media_parser_plugin PRIVATE pj_base)
+
 endif() # PJ_BUILD_TESTS
 
 # ---------------------------------------------------------------------------

pj_plugins/examples/mock_media_parser.cpp

@@ -0,0 +1,50 @@
+#include <cstdint>
+#include <cstring>
+#include <string>
+#include <vector>
+
+#include "pj_base/sdk/message_parser_plugin_base.hpp"
+
+namespace {
+
+/// Example parser that exercises the dual-emit path: a scalar `seq` field
+/// alongside a raw blob written to the ObjectStore. Payload envelope:
+///   bytes [0..8)  → little-endian uint64 seq
+///   bytes [8..N)  → opaque blob (e.g. compressed frame, image, serialized msg)
+///
+/// The parser declares the `object` capability in its manifest, which signals
+/// the host runtime to register the optional `pj.parser_object_write.v1`
+/// service so `objectWriteHost()` is non-null inside parse().
+class MockMediaParser : public PJ::MessageParserPluginBase {
+ public:
+  PJ::Status parse(PJ::Timestamp timestamp_ns, PJ::Span<const uint8_t> payload) override {
+    if (!writeHostBound()) {
+      return PJ::unexpected(std::string("write host not bound"));
+    }
+    if (payload.size() < sizeof(uint64_t)) {
+      return PJ::unexpected(std::string("payload too small (need 8 bytes seq prefix)"));
+    }
+
+    uint64_t seq = 0;
+    std::memcpy(&seq, payload.data(), sizeof(uint64_t));
+    if (auto s = writeHost().appendRecord(
+            timestamp_ns, {{.name = "seq", .value = static_cast<uint64_t>(seq)}});
+        !s) {
+      return s;
+    }
+
+    if (auto* obj = objectWriteHost()) {
+      std::vector<uint8_t> body(payload.data() + sizeof(uint64_t), payload.data() + payload.size());
+      if (auto s = obj->pushOwned(timestamp_ns, std::move(body)); !s) {
+        return s;
+      }
+    }
+    return PJ::okStatus();
+  }
+};
+
+}  // namespace
+
+PJ_MESSAGE_PARSER_PLUGIN(
+    MockMediaParser,
+    R"({"id":"mock-media-parser","name":"Mock Media Parser","version":"1.0.0","encoding":["mock-media"],"capabilities":["object"]})")

pj_plugins/include/pj_plugins/host/plugin_runtime_catalog.hpp

@@ -33,6 +33,7 @@ struct RuntimeMessageParserPlugin {
   std::string id;
   std::string version;
   std::vector<std::string> encodings;
+  std::vector<std::string> capabilities;
   std::filesystem::file_time_type loaded_mtime;
 };
 

pj_plugins/src/plugin_runtime_catalog.cpp

@@ -223,6 +223,7 @@ bool PluginRuntimeCatalog::loadAndRegisterMessageParser(const PluginDescriptor&
   loaded.name = descriptor.name;
   loaded.version = descriptor.version;
   loaded.encodings.insert(loaded.encodings.end(), descriptor.encoding.begin(), descriptor.encoding.end());
+  loaded.capabilities = descriptor.capabilities;
 
   report(DiagnosticLevel::kInfo, loaded.id, "Loaded MessageParser " + loaded.name + " from " + loaded.path);
   message_parsers_.push_back(std::move(loaded));