[PATCH 05/27] docs/qapi-domain: add resolve_any_xref()

[John Snow <jsnow@redhat.com>]

Add the ability to resolve cross-references using the `any`
cross-reference syntax. Adding QAPI-specific cross-reference roles will
be added in a forthcoming commit, and will share the same find_obj()
helper.

(There's less code needed for the generic cross-reference resolver, so
it comes first in this series.)

Once again, this code is based very heavily on sphinx.domains.python.

Signed-off-by: John Snow <jsnow@redhat.com>
---
 docs/qapi/index.rst        |  7 +++
 docs/sphinx/qapi-domain.py | 95 +++++++++++++++++++++++++++++++++++++-
 2 files changed, 101 insertions(+), 1 deletion(-)

diff --git a/docs/qapi/index.rst b/docs/qapi/index.rst
index 051dc6b3a37..39ad405fd93 100644
--- a/docs/qapi/index.rst
+++ b/docs/qapi/index.rst
@@ -40,3 +40,10 @@ QAPI Domain Test
 
    Modules will also be reported in the `qapi-index`, under the Modules
    category and in the alphabetical categories that follow.
+
+
+QAPI modules can now be cross-referenced using the ```any```
+cross-referencing syntax. Here's a link to `bar-module`, even though
+the actual output of that directive was suppressed. Here's a link to
+`block-core`. A link to ```foo-module``` won't resolve because of the
+``:no-index:`` option we used for that directive.
diff --git a/docs/sphinx/qapi-domain.py b/docs/sphinx/qapi-domain.py
index 65409786119..4758451ff0e 100644
--- a/docs/sphinx/qapi-domain.py
+++ b/docs/sphinx/qapi-domain.py
@@ -21,6 +21,7 @@
 from docutils.parsers.rst import directives
 
 from sphinx import addnodes
+from sphinx.addnodes import pending_xref
 from sphinx.domains import (
     Domain,
     Index,
@@ -30,13 +31,19 @@
 from sphinx.locale import _, __
 from sphinx.util import logging
 from sphinx.util.docutils import SphinxDirective, switch_source_input
-from sphinx.util.nodes import make_id, nested_parse_with_titles
+from sphinx.util.nodes import (
+    make_id,
+    make_refnode,
+    nested_parse_with_titles,
+)
 
 
 if TYPE_CHECKING:
     from docutils.nodes import Element, Node
 
     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__)
@@ -289,6 +296,92 @@ def merge_domaindata(self, docnames: List[str], otherdata: Dict[str, Any]) -> No
                 ), f"!?!? collision on merge? {fullname=} {obj=} {self.objects[fullname]=}"
                 self.objects[fullname] = obj
 
+    def find_obj(
+        self, modname: str, name: str, type: Optional[str]
+    ) -> list[tuple[str, ObjectEntry]]:
+        """
+        Find a QAPI object for "name", perhaps using the given module.
+
+        Returns a list of (name, object entry) tuples.
+
+        :param modname: The current module context (if any!)
+                        under which we are searching.
+        :param name: The name of the x-ref to resolve;
+                     may or may not include a leading module.
+        :param type: The role name of the x-ref we're resolving, if provided.
+                     (This is absent for "any" lookups.)
+        """
+        if not name:
+            return []
+
+        names: list[str] = []
+        matches: list[tuple[str, ObjectEntry]] = []
+
+        fullname = name
+        if "." in fullname:
+            # We're searching for a fully qualified reference;
+            # ignore the contextual module.
+            pass
+        elif modname:
+            # We're searching for something from somewhere;
+            # try searching the current module first.
+            # e.g. :qapi:cmd:`query-block` or `query-block` is being searched.
+            fullname = f"{modname}.{name}"
+
+        if type is None:
+            # type isn't specified, this is a generic xref.
+            # search *all* qapi-specific object types.
+            objtypes: Optional[List[str]] = list(self.object_types)
+        else:
+            # type is specified and will be a role (e.g. obj, mod, cmd)
+            # convert this to eligible object types (e.g. command, module)
+            # using the QAPIDomain.object_types table.
+            objtypes = self.objtypes_for_role(type)
+
+        # Either we should have been given no type, or the type we were
+        # given should correspond to at least one real actual object
+        # type.
+        assert objtypes
+
+        if name in self.objects and self.objects[name].objtype in objtypes:
+            names = [name]
+        elif fullname in self.objects and self.objects[fullname].objtype in objtypes:
+            names = [fullname]
+        else:
+            # exact match wasn't found; e.g. we are searching for
+            # `query-block` from a different (or no) module.
+            searchname = "." + name
+            names = [
+                oname
+                for oname in self.objects
+                if oname.endswith(searchname)
+                and self.objects[oname].objtype in objtypes
+            ]
+
+        matches = [(oname, self.objects[oname]) for oname in names]
+        if len(matches) > 1:
+            matches = [m for m in matches if not m[1].aliased]
+        return matches
+
+    def resolve_any_xref(
+        self,
+        env: BuildEnvironment,
+        fromdocname: str,
+        builder: Builder,
+        target: str,
+        node: pending_xref,
+        contnode: Element,
+    ) -> list[tuple[str, Element]]:
+        results: list[tuple[str, Element]] = []
+        matches = self.find_obj(node.get("qapi:module"), target, None)
+        for name, obj in matches:
+            role = "qapi:" + self.role_for_objtype(obj.objtype)
+            refnode = make_refnode(
+                builder, fromdocname, obj.docname, obj.node_id, contnode, name
+            )
+            results.append((role, refnode))
+        return results
+
 
 def setup(app: Sphinx) -> Dict[str, Any]:
     app.setup_extension("sphinx.directives")
-- 
2.44.0