🔀 MERGE: Internal improvements to the code base (#498)

Internal improvements, that should mainly not be noticed by users

docs/sphinx/use.md

@@ -185,7 +185,7 @@ All myst-parser warnings are prepended by their type, e.g. to suppress:
 ```
 
 ```
-WARNING: Non-consecutive header level increase; 1 to 3 [myst.header]
+WARNING: Non-consecutive header level increase; H1 to H3 [myst.header]
 ```
 
 Add to your `conf.py`:

myst_parser/directives.py

@@ -1,11 +1,14 @@
 """MyST specific directives"""
-from typing import List, Tuple
+from copy import copy
+from typing import List, Tuple, cast
 
 from docutils import nodes
 from docutils.parsers.rst import directives
 from sphinx.directives import SphinxDirective
 from sphinx.util.docutils import SphinxRole
 
+from myst_parser.mocking import MockState
+
 
 def align(argument):
     return directives.choice(argument, ("left", "center", "right"))
@@ -61,16 +64,20 @@ def run(self) -> List[nodes.Node]:
         figclasses = self.options.pop("class", None)
         align = self.options.pop("align", None)
 
-        node = nodes.Element()
-        # TODO test that we are using myst parser
+        if not isinstance(self.state, MockState):
+            return [self.figure_error("Directive is only supported in myst parser")]
+        state = cast(MockState, self.state)
+
         # ensure html image enabled
-        myst_extensions = self.state._renderer.config.get("myst_extensions", set())
+        myst_extensions = copy(state._renderer.md_config.enable_extensions)
+        node = nodes.Element()
         try:
-            self.state._renderer.config.setdefault("myst_extensions", set())
-            self.state._renderer.config["myst_extensions"].add("html_image")
-            self.state.nested_parse(self.content, self.content_offset, node)
+            state._renderer.md_config.enable_extensions = list(
+                state._renderer.md_config.enable_extensions
+            ) + ["html_image"]
+            state.nested_parse(self.content, self.content_offset, node)
         finally:
-            self.state._renderer.config["myst_extensions"] = myst_extensions
+            state._renderer.md_config.enable_extensions = myst_extensions
 
         if not len(node.children) == 2:
             return [