kafka: protocol code gen should take output paths

This changes makes the code generator easier to integrate into Meson
which wants to have far more control over output file paths than cmake.

Signed-off-by: Noah Watkins <noah@redpanda.com>

src/v/kafka/protocol/CMakeLists.txt

@@ -7,14 +7,14 @@ foreach(schema ${schemata})
   get_filename_component(msg_name ${schema} NAME_WE)
   set(schema_src ${CMAKE_CURRENT_SOURCE_DIR}/schemata/${schema})
   set(msg_dir "${CMAKE_CURRENT_BINARY_DIR}/schemata")
-  set(msg_srcs
-    "${msg_dir}/${msg_name}.h"
-    "${msg_dir}/${msg_name}.cc")
-  list(APPEND message_srcs ${msg_srcs})
+  set(msg_hdr "${msg_dir}/${msg_name}.h")
+  set(msg_src "${msg_dir}/${msg_name}.cc")
+  list(APPEND message_srcs ${msg_hdr})
+  list(APPEND message_srcs ${msg_src})
   add_custom_command(
-    OUTPUT ${msg_srcs}
+    OUTPUT ${msg_hdr} ${msg_src}
     COMMAND ${KAFKA_CODEGEN_VENV} ${message_gen}
-    ARGS ${msg_dir} ${schema_src}
+    ARGS ${schema_src} ${msg_hdr} ${msg_src}
     DEPENDS ${schema_src} ${message_gen} ${KAFKA_CODEGEN_VENV}
     COMMENT "Running kafka request codegen on ${schema_src}"
     VERBATIM)

src/v/kafka/protocol/schemata/generator.py

@@ -1,3 +1,5 @@
+#!/usr/bin/env python3
+#
 # Copyright 2020 Redpanda Data, Inc.
 #
 # Use of this software is governed by the Business Source License
@@ -1501,11 +1503,10 @@ def parse_flexible_versions(flex_version):
 
 
 if __name__ == "__main__":
-    assert len(sys.argv) == 3
-    outdir = pathlib.Path(sys.argv[1])
-    schema_path = pathlib.Path(sys.argv[2])
-    src = (outdir / schema_path.name).with_suffix(".cc")
-    hdr = (outdir / schema_path.name).with_suffix(".h")
+    assert len(sys.argv) == 4
+    schema_path = pathlib.Path(sys.argv[1])
+    hdr = pathlib.Path(sys.argv[2])
+    src = pathlib.Path(sys.argv[3])
 
     # remove comments from the json file. comments are a non-standard json
     # extension that is not supported by the python json parser.