qapi/commands: Simplify command registry generation

QAPISchemaGenCommandVisitor.visit_command() needs to generate the
marshalling function into the current module, and also generate its
registration into the ./init system module.  The latter is done
somewhat awkwardly: .__init__() creates a QAPIGenCCode that will not
be written out, each .visit_command() adds its registration to it, and
.visit_end() copies its contents into the ./init module it creates.

Instead provide the means to temporarily switch to another module.
Create the ./init module in .visit_begin(), and generate its initial
part.  Add registrations to it in .visit_command().  Finish it in
.visit_end().

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
Message-Id: <20210201193747.2169670-14-jsnow@redhat.com>

scripts/qapi/commands.py

@@ -23,7 +23,6 @@
 from .common import c_name, mcgen
 from .gen import (
     QAPIGenC,
-    QAPIGenCCode,
     QAPISchemaModularCVisitor,
     build_params,
     ifcontext,
@@ -237,28 +236,11 @@ def gen_register_command(name: str,
     return ret
 
 
-def gen_registry(registry: str, prefix: str) -> str:
-    ret = mcgen('''
-
-void %(c_prefix)sqmp_init_marshal(QmpCommandList *cmds)
-{
-    QTAILQ_INIT(cmds);
-
-''',
-                c_prefix=c_name(prefix, protect=False))
-    ret += registry
-    ret += mcgen('''
-}
-''')
-    return ret
-
-
 class QAPISchemaGenCommandVisitor(QAPISchemaModularCVisitor):
     def __init__(self, prefix: str):
         super().__init__(
             prefix, 'qapi-commands',
             ' * Schema-defined QAPI/QMP commands', None, __doc__)
-        self._regy = QAPIGenCCode(None)
         self._visited_ret_types: Dict[QAPIGenC, Set[QAPISchemaType]] = {}
 
     def _begin_user_module(self, name: str) -> None:
@@ -285,7 +267,7 @@ def _begin_user_module(self, name: str) -> None:
 ''',
                              types=types))
 
-    def visit_end(self) -> None:
+    def visit_begin(self, schema: QAPISchema) -> None:
         self._add_module('./init', ' * QAPI Commands initialization')
         self._genh.add(mcgen('''
 #include "qapi/qmp/dispatch.h"
@@ -293,13 +275,24 @@ def visit_end(self) -> None:
 void %(c_prefix)sqmp_init_marshal(QmpCommandList *cmds);
 ''',
                              c_prefix=c_name(self._prefix, protect=False)))
-        self._genc.preamble_add(mcgen('''
+        self._genc.add(mcgen('''
 #include "qemu/osdep.h"
 #include "%(prefix)sqapi-commands.h"
 #include "%(prefix)sqapi-init-commands.h"
+
+void %(c_prefix)sqmp_init_marshal(QmpCommandList *cmds)
+{
+    QTAILQ_INIT(cmds);
+
 ''',
-                                      prefix=self._prefix))
-        self._genc.add(gen_registry(self._regy.get_content(), self._prefix))
+                             prefix=self._prefix,
+                             c_prefix=c_name(self._prefix, protect=False)))
+
+    def visit_end(self) -> None:
+        with self._temp_module('./init'):
+            self._genc.add(mcgen('''
+}
+'''))
 
     def visit_command(self,
                       name: str,
@@ -324,15 +317,17 @@ def visit_command(self,
         if ret_type and ret_type not in self._visited_ret_types[self._genc]:
             self._visited_ret_types[self._genc].add(ret_type)
             with ifcontext(ret_type.ifcond,
-                           self._genh, self._genc, self._regy):
+                           self._genh, self._genc):
                 self._genc.add(gen_marshal_output(ret_type))
-        with ifcontext(ifcond, self._genh, self._genc, self._regy):
+        with ifcontext(ifcond, self._genh, self._genc):
             self._genh.add(gen_command_decl(name, arg_type, boxed, ret_type))
             self._genh.add(gen_marshal_decl(name))
             self._genc.add(gen_marshal(name, arg_type, boxed, ret_type))
-            self._regy.add(gen_register_command(name, success_response,
-                                                allow_oob, allow_preconfig,
-                                                coroutine))
+        with self._temp_module('./init'):
+            with ifcontext(ifcond, self._genh, self._genc):
+                self._genc.add(gen_register_command(name, success_response,
+                                                    allow_oob, allow_preconfig,
+                                                    coroutine))
 
 
 def gen_commands(schema: QAPISchema,