qapi/gen: Replace ._begin_system_module()

QAPISchemaModularCVisitor._begin_system_module() is actually just for
the builtin module.  Rename it to ._begin_builtin_module() and drop
its useless @name parameter.

Clarify conditionals in visit_module to make this clear.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
Message-Id: <20210201193747.2169670-7-jsnow@redhat.com>

scripts/qapi/gen.py

@@ -295,23 +295,24 @@ def write(self, output_dir: str, opt_builtins: bool = False) -> None:
             genc.write(output_dir)
             genh.write(output_dir)
 
-    def _begin_system_module(self, name: None) -> None:
+    def _begin_builtin_module(self) -> None:
         pass
 
     def _begin_user_module(self, name: str) -> None:
         pass
 
     def visit_module(self, name: Optional[str]) -> None:
-        if name is None:
+        if QAPISchemaModule.is_builtin_module(name):
             if self._builtin_blurb:
-                self._add_system_module(None, self._builtin_blurb)
-                self._begin_system_module(name)
+                self._add_system_module(name, self._builtin_blurb)
+                self._begin_builtin_module()
             else:
                 # The built-in module has not been created.  No code may
                 # be generated.
                 self._genc = None
                 self._genh = None
         else:
+            assert QAPISchemaModule.is_user_module(name)
             self._add_user_module(name, self._user_blurb)
             self._begin_user_module(name)
 

scripts/qapi/types.py

@@ -271,7 +271,7 @@ def __init__(self, prefix: str):
             prefix, 'qapi-types', ' * Schema-defined QAPI types',
             ' * Built-in QAPI types', __doc__)
 
-    def _begin_system_module(self, name: None) -> None:
+    def _begin_builtin_module(self) -> None:
         self._genc.preamble_add(mcgen('''
 #include "qemu/osdep.h"
 #include "qapi/dealloc-visitor.h"

scripts/qapi/visit.py

@@ -305,7 +305,7 @@ def __init__(self, prefix: str):
             prefix, 'qapi-visit', ' * Schema-defined QAPI visitors',
             ' * Built-in QAPI visitors', __doc__)
 
-    def _begin_system_module(self, name: None) -> None:
+    def _begin_builtin_module(self) -> None:
         self._genc.preamble_add(mcgen('''
 #include "qemu/osdep.h"
 #include "qapi/error.h"