[PATCH v2 12/62] docs/qapi-domain: add QAPIObject class

[John Snow <jsnow@redhat.com>]

Signed-off-by: John Snow <jsnow@redhat.com>
---
 docs/sphinx/qapi_domain.py | 95 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)

diff --git a/docs/sphinx/qapi_domain.py b/docs/sphinx/qapi_domain.py
index a445150ae59..183d9a2766f 100644
--- a/docs/sphinx/qapi_domain.py
+++ b/docs/sphinx/qapi_domain.py
@@ -18,7 +18,9 @@
 )
 
 from docutils import nodes
+from docutils.parsers.rst import directives
 
+from compat import KeywordNode, SpaceNode
 from sphinx import addnodes
 from sphinx.addnodes import desc_signature, pending_xref
 from sphinx.directives import ObjectDescription
@@ -40,6 +42,7 @@
     from sphinx.application import Sphinx
     from sphinx.builders import Builder
     from sphinx.environment import BuildEnvironment
+    from sphinx.util.typing import OptionSpec
 
 logger = logging.getLogger(__name__)
 
@@ -99,6 +102,8 @@ def process_link(
         return title, target
 
 
+# Alias for the return of handle_signature(), which is used in several places.
+# (In the Python domain, this is Tuple[str, str] instead.)
 Signature = str
 
 
@@ -158,6 +163,96 @@ def add_target_and_index(
                 )
 
 
+class QAPIObject(QAPIDescription):
+    """
+    Description of a generic QAPI object.
+
+    It's not used directly, but is instead subclassed by specific directives.
+    """
+
+    # Inherit some standard options from Sphinx's ObjectDescription
+    option_spec: OptionSpec = (  # type:ignore[misc]
+        ObjectDescription.option_spec.copy()
+    )
+    option_spec.update(
+        {
+            # Borrowed from the Python domain:
+            "module": directives.unchanged,  # Override contextual module name
+        }
+    )
+
+    def get_signature_prefix(self) -> List[nodes.Node]:
+        """Returns a prefix to put before the object name in the signature."""
+        assert self.objtype
+        return [
+            KeywordNode("", self.objtype.title()),
+            SpaceNode(" "),
+        ]
+
+    def get_signature_suffix(self) -> List[nodes.Node]:
+        """Returns a suffix to put after the object name in the signature."""
+        return []
+
+    def handle_signature(self, sig: str, signode: desc_signature) -> Signature:
+        """
+        Transform a QAPI definition name into RST nodes.
+
+        This method was originally intended for handling function
+        signatures. In the QAPI domain, however, we only pass the
+        definition name as the directive argument and handle everything
+        else in the content body with field lists.
+
+        As such, the only argument here is "sig", which is just the QAPI
+        definition name.
+        """
+        modname = self.options.get(
+            "module", self.env.ref_context.get("qapi:module")
+        )
+
+        signode["fullname"] = sig
+        signode["module"] = modname
+        sig_prefix = self.get_signature_prefix()
+        if sig_prefix:
+            signode += addnodes.desc_annotation(
+                str(sig_prefix), "", *sig_prefix
+            )
+        signode += addnodes.desc_name(sig, sig)
+        signode += self.get_signature_suffix()
+
+        return sig
+
+    def _object_hierarchy_parts(
+        self, sig_node: desc_signature
+    ) -> Tuple[str, ...]:
+        if "fullname" not in sig_node:
+            return ()
+        modname = sig_node.get("module")
+        fullname = sig_node["fullname"]
+
+        if modname:
+            return (modname, *fullname.split("."))
+
+        return tuple(fullname.split("."))
+
+    def _toc_entry_name(self, sig_node: desc_signature) -> str:
+        # This controls the name in the TOC and on the sidebar.
+
+        # This is the return type of _object_hierarchy_parts().
+        toc_parts = cast(Tuple[str, ...], sig_node.get("_toc_parts", ()))
+        if not toc_parts:
+            return ""
+
+        config = self.env.app.config
+        *parents, name = toc_parts
+        if config.toc_object_entries_show_parents == "domain":
+            return sig_node.get("fullname", name)
+        if config.toc_object_entries_show_parents == "hide":
+            return name
+        if config.toc_object_entries_show_parents == "all":
+            return ".".join(parents + [name])
+        return ""
+
+
 class QAPIModule(QAPIDescription):
     """
     Directive to mark description of a new module.
-- 
2.48.1