drop translator-specific unknown_visit calls

Removes the need for various translators from raising a
`NotImplementedError` exception when missing support for a specific node
type. docutils will already raise [1][2] a `NotImplementedError`
exception for these cases. This help reduce the implementation inside
Sphinx as well as prevents the possible undesired replication of
unknown-node handling with third-party extensions [3].

In most cases, generating a warning message for an unsupported node type
can be preferred. Providing an indication that a node is not supported
can be easier for a user of Sphinx to understand a limitation of a
builder over a generic "not implemented" exception. This commit takes
the logging call which is already used by `texinfo` and applies it to
the `SphinxTranslator` base class -- which any Sphinx translator
implementation can use.

[1]: https://repo.or.cz/docutils.git/blob/d169015ee0f412cffd69b33654d8a119d99bc0f3:/docutils/nodes.py#l2048
[2]: https://repo.or.cz/docutils.git/blob/53716a13b48128af6045139d3cd2909f61e7ed8e:/docutils/nodes.py#l1897
[3]: https://github.com/sphinx-doc/sphinx/issues/9921

Signed-off-by: James Knight <james.d.knight@live.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/sphinx/util/docutils.py b/sphinx/util/docutils.py
index c3d385306..39fa02d31 100644
--- a/sphinx/util/docutils.py
+++ b/sphinx/util/docutils.py
@@ -28,7 +28,7 @@ from docutils.utils import Reporter, unescape
 from packaging import version
 
 from sphinx.errors import SphinxError
-from sphinx.locale import _
+from sphinx.locale import _, __
 from sphinx.util import logging
 from sphinx.util.typing import RoleFunction
 
@@ -496,6 +496,9 @@ class SphinxTranslator(nodes.NodeVisitor):
         else:
             super().dispatch_departure(node)
 
+    def unknown_visit(self, node: Node) -> None:
+        logger.warning(__('unknown node type: %r'), node, location=node)
+
 
 # cache a vanilla instance of nodes.document
 # Used in new_document() function