src: pass the headerfile as jinja extra data

This removes another special handling of the C bindings from the
scanner.

meson.build

@@ -84,7 +84,8 @@ ei_proto_headers = custom_target('ei-proto-headers',
 ei_proto_sources = custom_target('ei-proto-sources',
                                  input: protocol_xml,
                                  output: ['ei-proto.c'],
-                                 command: [scanner, '--component=ei', '--output=@OUTPUT@', '@INPUT@', proto_c_template])
+                                 command: [scanner, '--component=ei', '--output=@OUTPUT@', '@INPUT@',
+                                           '--jinja-extra-data={"headerfile": "ei-proto.h"}', proto_c_template])
 src_libei = files(
     'src/brei-shared.c',
     'src/libei.c',
@@ -137,7 +138,8 @@ eis_proto_headers = custom_target('eis-proto-headers',
 eis_proto_sources = custom_target('eis-proto-sources',
                                   input: protocol_xml,
                                   output: ['eis-proto.c'],
-                                  command: [scanner, '--component=eis', '--output=@OUTPUT@', '@INPUT@', proto_c_template])
+                                  command: [scanner, '--component=eis', '--output=@OUTPUT@', '@INPUT@',
+                                           '--jinja-extra-data={"headerfile": "eis-proto.h"}', proto_c_template])
 
 src_libeis = files(
     'src/brei-shared.c',

proto/ei-scanner

@@ -738,7 +738,7 @@ def parse(protofile: Path, component: str) -> Protocol:
 
 
 def generate_source(
-    proto: Protocol, headerfile: Optional[str], template: Path, component: str, extra_data: Optional[dict]
+    proto: Protocol, template: Path, component: str, extra_data: Optional[dict]
 ) -> jinja2.environment.TemplateStream:
     assert component in ["ei", "eis", "brei"]
 
@@ -746,8 +746,6 @@ def generate_source(
     data["component"] = component
     data["interfaces"] = proto.interfaces
     data["extra"] = extra_data
-    if headerfile:
-        data["headerfile"] = headerfile
 
     env = jinja2.Environment(
         loader=jinja2.FileSystemLoader(os.fspath(template.parent)),
@@ -848,8 +846,6 @@ def main() -> None:
         print(f"Protocol XML error: {e}", file=sys.stderr)
         raise SystemExit(1)
 
-    headerfile = f"{Path(ns.output).stem}.h" if ns.output != "-" else None
-
     if ns.jinja_extra_data is not None:
         import json
 
@@ -874,7 +870,7 @@ def main() -> None:
         extra_data = None
 
     stream = generate_source(
-        proto=proto, headerfile=headerfile, template=ns.template, component=ns.component, extra_data=extra_data
+        proto=proto, template=ns.template, component=ns.component, extra_data=extra_data
     )
 
     file = sys.stdout if ns.output == "-" else open(ns.output, "w")

src/ei-proto.c.tmpl

@@ -31,8 +31,8 @@
 #include "brei-shared.h"
 #include "brei-proto.h"
 
-{% if headerfile %}
-#include "{{headerfile}}"
+{% if extra.headerfile %}
+#include "{{extra.headerfile}}"
 {% endif %}
 
 /**