ext.duration: Fix merge_domaindata() (#12251)

Co-authored-by: Adam Turner <[email protected]>

Author: mgeier

CHANGES.rst

@@ -27,6 +27,8 @@ Bugs fixed
   Patch by Donald Hunter.
 * #12320: Fix removal of anchors from search summaries (regression in 7.3.0).
   Patch by Will Lachance.
+* #12251: Fix ``merge_domaindata()`` in ``sphinx.ext.duration``.
+  Patch by Matthias Geier.
 
 Testing
 -------

sphinx/ext/duration.py

@@ -13,10 +13,15 @@
 from sphinx.util import logging
 
 if TYPE_CHECKING:
+    from typing import TypedDict
+
     from docutils import nodes
 
     from sphinx.application import Sphinx
 
+    class _DurationDomainData(TypedDict):
+        reading_durations: dict[str, float]
+
 logger = logging.getLogger(__name__)
 
 
@@ -38,9 +43,11 @@ def clear(self) -> None:
     def clear_doc(self, docname: str) -> None:
         self.reading_durations.pop(docname, None)
 
-    def merge_domaindata(self, docnames: list[str], otherdata: dict[str, float]) -> None:
-        for docname, duration in otherdata.items():
-            if docname in docnames:
+    def merge_domaindata(self, docnames: list[str], otherdata: _DurationDomainData) -> None:  # type: ignore[override]
+        other_reading_durations = otherdata.get('reading_durations', {})
+        docnames_set = frozenset(docnames)
+        for docname, duration in other_reading_durations.items():
+            if docname in docnames_set:
                 self.reading_durations[docname] = duration