Use FORWARDREF format in inspect.signature calls

Fixes #13945

Author: ruipin

sphinx/util/inspect.py

@@ -716,14 +716,26 @@ def signature(
     if type_aliases is None:
         type_aliases = {}
 
+    # Python 3.14 added the annotationlib module to the standard library as well as the
+    # 'annotation_format' keyword parameter to inspect.signature(), which allows us to handle
+    # forward references more robustly.
+    try:
+        import annotationlib
+
+        inspect_signature_extra = {'annotation_format': annotationlib.Format.FORWARDREF}
+    except ImportError:
+        inspect_signature_extra = {}
+
     try:
         if _should_unwrap(subject):
-            signature = inspect.signature(subject)  # type: ignore[arg-type]
+            signature = inspect.signature(subject, **inspect_signature_extra)  # type: ignore[arg-type]
         else:
-            signature = inspect.signature(subject, follow_wrapped=True)  # type: ignore[arg-type]
+            signature = inspect.signature(
+                subject, follow_wrapped=True, **inspect_signature_extra
+            )  # type: ignore[arg-type]
     except ValueError:
         # follow built-in wrappers up (ex. functools.lru_cache)
-        signature = inspect.signature(subject)  # type: ignore[arg-type]
+        signature = inspect.signature(subject, **inspect_signature_extra)  # type: ignore[arg-type]
     parameters = list(signature.parameters.values())
     return_annotation = signature.return_annotation