Change default value of intersphinx_disabled_reftypes

See discussion in sphinx-doc/sphinx#9459

CHANGES

@@ -7,6 +7,13 @@ Dependencies
 Incompatible changes
 --------------------
 
+* #2068: :confval:`intersphinx_disabled_reftypes` has changed default value
+  from an empty list to ``['std:doc']`` as avoid too surprising silent
+  intersphinx resolutions.
+  To migrate: either add an explicit inventory name to the references
+  intersphinx should resolve, or explicitly set the value of this configuration
+  variable to an empty list.
+
 Deprecated
 ----------
 

doc/usage/extensions/intersphinx.rst

@@ -152,6 +152,10 @@ linking:
 
    .. versionadded:: 4.3
 
+   .. versionchanged:: 5.0
+
+      Changed default value from an empty list to ``['std:doc']``.
+
    A list of strings being either:
 
    - the name of a specific reference type in a domain,
@@ -160,7 +164,7 @@ linking:
      ``std:*``, ``py:*``, or ``cpp:*``, or
    - simply a wildcard ``*``.
 
-   The default value is an empty list.
+   The default value is ``['std:doc']``.
 
    When a cross-reference without an explicit inventory specification is being
    resolved by intersphinx, skip resolution if it matches one of the

sphinx/ext/intersphinx.py

@@ -494,7 +494,7 @@ def setup(app: Sphinx) -> Dict[str, Any]:
     app.add_config_value('intersphinx_mapping', {}, True)
     app.add_config_value('intersphinx_cache_limit', 5, False)
     app.add_config_value('intersphinx_timeout', None, False)
-    app.add_config_value('intersphinx_disabled_reftypes', [], True)
+    app.add_config_value('intersphinx_disabled_reftypes', ['std:doc'], True)
     app.connect('config-inited', normalize_intersphinx_mapping, priority=800)
     app.connect('builder-inited', load_mappings)
     app.connect('missing-reference', missing_reference)