Fix figure numbering is overriden when use the extension

** Why is this change required? **

When numfig is set to true, figure directives are automatically
numbered. However, before this fix, the caption of figures is
overriden and the automatically numbering is gone. This commit
fixed the issue (also listed on github
#14).

** How does this change solve the issue? **

Instead of using nodes.caption directly (also with override when
add_node, which causes bug), we create a subclass pseudocodeCaption
and use it instead.

** Does this commit cause any expected behavior to change?  If so, what? **

** Issue: **

** Design Docs: **

sphinxcontrib/pseudocode.py

@@ -46,6 +46,9 @@ class pseudocodeContentNode(nodes.General, nodes.Element):
     """Content of pseudocode."""
     pass
 
+class pseudocodeCaption(nodes.caption):
+    """Caption of pseudocode."""
+    pass
 
 class Pseudocode(Directive):
     """An environment for pseudocode."""
@@ -173,12 +176,12 @@ def pseudocode_wrapper(directive, node, caption=None):
     """Parse caption, and append it to the node."""
     parsed = nodes.Element()
     if caption is None:
-        caption_node = nodes.caption()
+        caption_node = pseudocodeCaption()
     else:
         directive.state.nested_parse(
             ViewList([caption], source=""), directive.content_offset, parsed
         )
-        caption_node = nodes.caption(parsed[0].rawsource, "", *parsed[0].children)
+        caption_node = pseudocodeCaption(parsed[0].rawsource, "", *parsed[0].children)
         caption_node.source = parsed[0].source
         caption_node.line = parsed[0].line
     node += caption_node
@@ -255,8 +258,7 @@ def setup(app):
         html=(html_visit_stuff_node, html_depart_stuff_node),
     )
     app.add_node(
-        nodes.caption,
-        override=True,
+        pseudocodeCaption,
         html=(html_visit_caption_node, html_depart_caption_node),
     )
     app.add_node(

tests/roots/test-basic/conf.py

@@ -1,2 +1,4 @@
 extensions = ['sphinxcontrib.pseudocode']
-exclude_patterns = ['_build']
+exclude_patterns = ['_build']
+numfig = True
+html_static_path = ['_static']

tests/roots/test-basic/index.rst

@@ -6,4 +6,8 @@ Hi, basic test
 
     \begin{algorithmic}
     \PRINT \texttt{'hello world'}
-    \end{algorithmic}
+    \end{algorithmic}
+
+.. figure:: /_static/quicksort-demo.png
+
+   This figure should have a numbering in this caption.

tests/test_html.py

@@ -16,3 +16,4 @@ def index(app, build_all):
 def test_html_raw(index):
     assert '<script src="https://cdn.jsdelivr.net/npm/pseudocode@latest/build/pseudocode.js"></script>' in index
     assert '<script src="https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.11.1/katex.min.js"></script>' in index
+    assert '<span class="caption-number">Fig. 1 </span>' in index