Better handling of one-liner Block HTML

Fixes Python-Markdown#1074

Author: facelessuser

docs/changelog.md

@@ -17,10 +17,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 * Backslash Unescape IDs set via `attr_list` on `toc` (#1493).
-* `md_in_html` should now process content inside "markdown" blocks a similar way
+* `md_in_html` will process content inside "markdown" blocks a similar way
   as they are parsed outside of "markdown" blocks giving a more consistent
   expectation to external extensions (#1503).
-* `md_in_html` should not handle tags within inline code blocks better (#1075).
+* `md_in_html` handle tags within inline code blocks better (#1075).
+* `md_in_html` fix handling of one-liner block HTML handling (#1074)
 
 ## [3.7] -- 2024-08-16
 

markdown/extensions/md_in_html.py

@@ -61,6 +61,7 @@ def reset(self):
         self.mdstack: list[str] = []  # When markdown=1, stack contains a list of tags
         self.treebuilder = etree.TreeBuilder()
         self.mdstate: list[Literal['block', 'span', 'off', None]] = []
+        self.mdstarted: list[bool] = []
         super().reset()
 
     def close(self):
@@ -126,8 +127,24 @@ def handle_starttag(self, tag, attrs):
                     self.handle_endtag('p')
                 self.mdstate.append(state)
                 self.mdstack.append(tag)
+                self.mdstarted.append(True)
                 attrs['markdown'] = state
                 self.treebuilder.start(tag, attrs)
+
+        elif not self.inraw and tag in self.block_level_tags and self.mdstarted and self.mdstarted[-1]:
+            # Nested one-liner block tags `<tag><tag>...`
+            attrs = {key: value if value is not None else key for key, value in attrs}
+            state = self.get_state(tag, attrs)
+            if 'p' in self.mdstack and tag in self.block_level_tags:
+                # Close unclosed 'p' tag
+                self.handle_endtag('p')
+            self.mdstate.append(state)
+            self.mdstack.append(tag)
+            self.mdstarted.append(True)
+            attrs['markdown'] = state
+            self.treebuilder.start(tag, attrs)
+            return
+
         else:
             # Span level tag
             if self.inraw:
@@ -151,6 +168,7 @@ def handle_endtag(self, tag):
                 while self.mdstack:
                     item = self.mdstack.pop()
                     self.mdstate.pop()
+                    self.mdstarted.pop()
                     self.treebuilder.end(item)
                     if item == tag:
                         break
@@ -247,6 +265,8 @@ def handle_data(self, data):
         if self.inraw or not self.mdstack:
             super().handle_data(data)
         else:
+            for i in range(len(self.mdstarted)):
+                self.mdstarted[i] = False
             self.treebuilder.data(data)
 
     def handle_empty_tag(self, data, is_block):

tests/test_syntax/extensions/test_md_in_html.py

@@ -1274,6 +1274,107 @@ def test_md1_code_void_tag_multiline(self):
             extensions=['md_in_html']
         )
 
+    def test_md1_oneliner_block(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                '<div class="outer" markdown="block"><div class="inner" markdown="block">*foo*</div></div>'
+            ),
+            '<div class="outer">\n'
+            '<div class="inner">\n'
+            '<p><em>foo</em></p>\n'
+            '</div>\n'
+            '</div>',
+            extensions=['md_in_html']
+        )
+
+    def test_md1_oneliner_block_mixed(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                <div class="a" markdown="block"><div class="b" markdown="block">
+
+                <div class="c" markdown="block"><div class="d" markdown="block">
+                *foo*
+                </div></div>
+
+                </div></div>
+                """
+            ),
+            '<div class="a">\n'
+            '<div class="b">\n'
+            '<div class="c">\n'
+            '<div class="d">\n'
+            '<p><em>foo</em></p>\n'
+            '</div>\n'
+            '</div>\n'
+            '</div>\n'
+            '</div>',
+            extensions=['md_in_html']
+        )
+
+    def test_md1_oneliner_block_start(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                <div class="outer" markdown="block"><div class="inner" markdown="block">
+                *foo*
+                </div></div>
+                """
+            ),
+            '<div class="outer">\n'
+            '<div class="inner">\n'
+            '<p><em>foo</em></p>\n'
+            '</div>\n'
+            '</div>',
+            extensions=['md_in_html']
+        )
+
+    def test_md1_oneliner_block_span(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                '<div class="outer" markdown="block"><div class="inner" markdown="span">*foo*</div></div>'
+            ),
+            '<div class="outer">\n'
+            '<div class="inner"><em>foo</em></div>\n'
+            '</div>',
+            extensions=['md_in_html']
+        )
+
+    def test_md1_oneliner_block_span_start(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                <div class="outer" markdown="block"><div class="inner" markdown="span">
+                *foo*
+                </div></div>
+                """
+            ),
+            '<div class="outer">\n'
+            '<div class="inner">\n'
+            '<em>foo</em>\n'
+            '</div>\n'
+            '</div>',
+            extensions=['md_in_html']
+        )
+
+    def test_md1_oneliner_span_block_start(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                <div class="outer" markdown="span"><div class="inner" markdown="block">
+                *foo*
+                </div>
+                *foo*
+                </div>
+                """
+            ),
+            '<div class="outer">\n'
+            '<div class="inner">\n'
+            '<em>foo</em>\n'
+            '</div>\n\n'
+            '<em>foo</em></div>',
+            extensions=['md_in_html']
+        )
 
     def test_md1_code_comment(self):