SphinxTranslator calls visitor/departure method for super node class

CHANGES

@@ -36,6 +36,8 @@ Features added
 * #6696: html: ``:scale:`` option of image/figure directive not working for SVG
   images (imagesize-1.2.0 or above is required)
 * #6994: imgconverter: Support illustrator file (.ai) to .png conversion
+* SphinxTranslator now calls visitor/departure method for super node class if
+  visitor/departure method for original node class not found
 
 Bugs fixed
 ----------

sphinx/util/docutils.py

@@ -452,7 +452,10 @@ class ReferenceRole(SphinxRole):
 class SphinxTranslator(nodes.NodeVisitor):
     """A base class for Sphinx translators.
 
-    This class provides helper methods for Sphinx translators.
+    This class adds a support for visitor/departure method for super node class
+    if visitor/departure method for node class is not found.
+
+    It also provides helper methods for Sphinx translators.
 
     .. note:: The subclasses of this class might not work with docutils.
               This class is strongly coupled with Sphinx.
@@ -464,6 +467,42 @@ class SphinxTranslator(nodes.NodeVisitor):
         self.config = builder.config
         self.settings = document.settings
 
+    def dispatch_visit(self, node):
+        """
+        Dispatch node to appropriate visitor method.
+        The priority of visitor method is:
+
+        1. ``self.visit_{node_class}()``
+        2. ``self.visit_{supre_node_class}()``
+        3. ``self.unknown_visit()``
+        """
+        for node_class in node.__class__.__mro__:
+            method = getattr(self, 'visit_%s' % (node_class.__name__), None)
+            if method:
+                logger.debug('SphinxTranslator.dispatch_visit calling %s for %s' %
+                             (method.__name__, node))
+                return method(node)
+        else:
+            super().dispatch_visit(node)
+
+    def dispatch_departure(self, node):
+        """
+        Dispatch node to appropriate departure method.
+        The priority of departure method is:
+
+        1. ``self.depart_{node_class}()``
+        2. ``self.depart_{super_node_class}()``
+        3. ``self.unknown_departure()``
+        """
+        for node_class in node.__class__.__mro__:
+            method = getattr(self, 'depart_%s' % (node_class.__name__), None)
+            if method:
+                logger.debug('SphinxTranslator.dispatch_departure calling %s for %s' %
+                             (method.__name__, node))
+                return method(node)
+        else:
+            super().dispatch_departure(node)
+
 
 # cache a vanilla instance of nodes.document
 # Used in new_document() function

tests/test_util_docutils.py

@@ -12,7 +12,9 @@ import os
 
 from docutils import nodes
 
-from sphinx.util.docutils import SphinxFileOutput, docutils_namespace, register_node
+from sphinx.util.docutils import (
+    SphinxFileOutput, SphinxTranslator, docutils_namespace, new_document, register_node
+)
 
 
 def test_register_node():
@@ -61,3 +63,34 @@ def test_SphinxFileOutput(tmpdir):
     # overrite it again (content changed)
     output.write(content + "; content change")
     assert os.stat(filename).st_mtime != 0  # updated
+
+
+def test_SphinxTranslator(app):
+    class CustomNode(nodes.inline):
+        pass
+
+    class MyTranslator(SphinxTranslator):
+        def __init__(self, *args):
+            self.called = []
+            super().__init__(*args)
+
+        def visit_document(self, node):
+            pass
+
+        def depart_document(self, node):
+            pass
+
+        def visit_inline(self, node):
+            self.called.append('visit_inline')
+
+        def depart_inline(self, node):
+            self.called.append('depart_inline')
+
+    document = new_document('')
+    document += CustomNode()
+
+    translator = MyTranslator(document, app.builder)
+    document.walkabout(translator)
+
+    # MyTranslator does not have visit_CustomNode. But it calls visit_inline instead.
+    assert translator.called == ['visit_inline', 'depart_inline']