docs/qapidoc: factor out do_parse()

Factor out the compatibility parser helper into a base class, so it can
be shared by other directives.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240717021312.606116-3-jsnow@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

docs/sphinx/qapidoc.py

@@ -481,7 +481,25 @@ class QAPISchemaGenDepVisitor(QAPISchemaVisitor):
         super().visit_module(name)
 
 
-class QAPIDocDirective(Directive):
+class NestedDirective(Directive):
+    def run(self):
+        raise NotImplementedError
+
+    def do_parse(self, rstlist, node):
+        """
+        Parse rST source lines and add them to the specified node
+
+        Take the list of rST source lines rstlist, parse them as
+        rST, and add the resulting docutils nodes as children of node.
+        The nodes are parsed in a way that allows them to include
+        subheadings (titles) without confusing the rendering of
+        anything else.
+        """
+        with switch_source_input(self.state, rstlist):
+            nested_parse_with_titles(self.state, rstlist, node)
+
+
+class QAPIDocDirective(NestedDirective):
     """Extract documentation from the specified QAPI .json file"""
 
     required_argument = 1
@@ -519,18 +537,6 @@ class QAPIDocDirective(Directive):
             # so they are displayed nicely to the user
             raise ExtensionError(str(err)) from err
 
-    def do_parse(self, rstlist, node):
-        """Parse rST source lines and add them to the specified node
-
-        Take the list of rST source lines rstlist, parse them as
-        rST, and add the resulting docutils nodes as children of node.
-        The nodes are parsed in a way that allows them to include
-        subheadings (titles) without confusing the rendering of
-        anything else.
-        """
-        with switch_source_input(self.state, rstlist):
-            nested_parse_with_titles(self.state, rstlist, node)
-
 
 def setup(app):
     """Register qapi-doc directive with Sphinx"""