1 files changed, 33 insertions, 1 deletions
diff --git a/sphinx/transforms/post_transforms/compat.py b/sphinx/transforms/post_transforms/compat.py
index 0f0b2367d..94360f038 100644
--- a/sphinx/transforms/post_transforms/compat.py
+++ b/sphinx/transforms/post_transforms/compat.py
@@ -13,7 +13,9 @@ import warnings
 from typing import TYPE_CHECKING
 
 from docutils import nodes
+from docutils.writers.docutils_xml import XMLTranslator
 
+from sphinx.addnodes import math_block, displaymath
 from sphinx.deprecation import RemovedInSphinx30Warning
 from sphinx.transforms import SphinxTransform
 from sphinx.util import logging
@@ -41,14 +43,44 @@ class MathNodeMigrator(SphinxTransform):
     def apply(self):
         # type: () -> None
         for node in self.document.traverse(nodes.math):
+            # case: old styled ``math`` node generated by old extensions
             if len(node) == 0:
-                # convert an old styled node to new one
                 warnings.warn("math node for Sphinx was replaced by docutils'. "
                               "Please use ``docutils.nodes.math`` instead.",
                               RemovedInSphinx30Warning)
                 equation = node['latex']
                 node += nodes.Text(equation, equation)
 
+        translator = self.app.builder.get_translator_class()
+        if hasattr(translator, 'visit_displaymath') and translator != XMLTranslator:
+            # case: old translators which does not support ``math_block`` node
+            warnings.warn("Translator for %s does not support math_block node'. "
+                          "Please update your extension." % translator,
+                          RemovedInSphinx30Warning)
+            for node in self.document.traverse(math_block):
+                alt = displaymath(latex=node.astext(),
+                                  number=node.get('number'),
+                                  label=node.get('label'),
+                                  nowrap=node.get('nowrap'),
+                                  docname=node.get('docname'))
+                node.replace(alt)
+        else:
+            # case: old styled ``displaymath`` node generated by old extensions
+            for node in self.document.traverse(math_block):
+                if len(node) == 0:
+                    warnings.warn("math node for Sphinx was replaced by docutils'. "
+                                  "Please use ``docutils.nodes.math_block`` instead.",
+                                  RemovedInSphinx30Warning)
+                    latex = node['latex']
+                    node += nodes.Text(latex, latex)
+
 
 def setup(app):
+    # type: (Sphinx) -> Dict[unicode, Any]
     app.add_post_transform(MathNodeMigrator)
+
+    return {
+        'version': 'builtin',
+        'parallel_read_safe': True,
+        'parallel_write_safe': True,
+    }