Alternate block header syntax

docs/src/markdown/extensions/blocks/index.md

@@ -131,6 +131,46 @@ Indented content should always be separated from the block header by one empty l
 option block.
 ///
 
+### Alternative syntax for options
+
+Some formatters tends to remove the leading four spaces before the additional option. In that case, an alternative syntax is possible by replacing the spaces by a single `@` :
+
+/// tab | Alternative syntax
+```text title="Admonition"
+/// admonition | Some title
+@type: warning
+
+Some content
+///
+```
+
+//// html | div.result
+///// admonition | Some title
+@type: warning
+
+Some content
+/////
+////
+///
+
+/// tab | Normal syntax
+```text title="Admonition"
+/// admonition | Some title
+    type: warning
+
+Some content
+///
+```
+
+//// html | div.result
+///// admonition | Some title
+    type: warning
+
+Some content
+/////
+////
+///
+
 ## Nesting
 
 Generic blocks can be nested as long as the block fence differs in number of leading tokens. This is similar to how

pymdownx/blocks/__init__.py

@@ -41,7 +41,7 @@
 )
 
 RE_INDENT_YAML_LINE = re.compile(r'(?m)^(?:[ ]{4,}(?!\s).*?(?:\n|$))+')
-
+RE_ALTERNATE_YAML_LINE = re.compile(r'(?m)^(?:@ *)(.*?)(?:\n|$)+')
 
 class BlockEntry:
     """Track Block entries."""
@@ -197,6 +197,7 @@ def __init__(self, parser: BlockParser, md: Markdown) -> None:
         self.start = RE_START
         self.end = RE_END
         self.yaml_line = RE_INDENT_YAML_LINE
+        self.yaml_line_alternate = RE_ALTERNATE_YAML_LINE
 
     def detab_by_length(self, text: str, length: int) -> tuple[str, str]:
         """Remove a tab from the front of each line of the given text."""
@@ -322,6 +323,12 @@ def split_header(self, block: str, length: int) -> tuple[dict[str, Any] | None,
             blocks.insert(0, end)
             block = block[:m.start(0)]
 
+        # Convert alternative yaml-ish header
+        m = self.yaml_line_alternate.match(block)
+        if m is not None:
+            block = ' ' * 4 + m.group(1)
+
+        # Extract header
         m = self.yaml_line.match(block)
         if m is not None:
             config = textwrap.dedent(m.group(0))

tests/test_extensions/test_blocks/test_general_blocks_alternate.py

@@ -0,0 +1,174 @@
+"""Using the "tab" Blocks extension, test general cases for Blocks for the alternate attribute syntax."""
+from ... import util
+import unittest
+from pymdownx.blocks import block
+import markdown
+
+class TestBlockUndefinedOptionAlternate(util.MdCase):
+    """Test Blocks with undefined options."""
+
+    extension = ['pymdownx.blocks.html', 'pymdownx.blocks.definition']
+
+    def test_undefined_option(self):
+        """An undefined option will cause the block parsing to fail."""
+
+        self.check_markdown(
+            R'''
+            /// html | div
+            @option: whatever
+
+            content
+            ///
+            ''',
+            '''
+            <p>/// html | div
+            @option: whatever</p>
+            <p>content
+            ///</p>
+            ''',
+            True
+        )
+
+    def test_bad_option(self):
+        """An undefined option will cause the block parsing to fail."""
+
+        self.check_markdown(
+            R'''
+            /// html | div
+            @attrs: whatever
+
+            content
+            ///
+            ''',
+            '''
+            <p>/// html | div
+            @attrs: whatever</p>
+            <p>content
+            ///</p>
+            ''',
+            True
+        )
+
+    def test_no_arg(self):
+        """Test no options."""
+
+        self.check_markdown(
+            R'''
+            /// html
+            @attrs: whatever
+
+            content
+            ///
+            ''',
+            '''
+            <p>/// html
+            @attrs: whatever</p>
+            <p>content
+            ///</p>
+            ''',
+            True
+        )
+
+    def test_too_many_args(self):
+        """Test too many options."""
+
+        self.check_markdown(
+            R'''
+            /// define
+            @option: whatever
+
+            content
+            ///
+            ''',
+            '''
+            <p>/// define
+            @option: whatever</p>
+            <p>content
+            ///</p>
+            ''',
+            True
+        )
+
+    def test_commented_frontmatter(self):
+        """Test commented frontmatter."""
+
+        self.check_markdown(
+            R'''
+            /// html | div
+                # @attrs: {class: test}
+
+            content
+            ///
+            ''',
+            '''
+            <div>
+            <p>content</p>
+            </div>
+            ''',
+            True
+        )
+
+
+class TestAttributesAlternate(util.MdCase):
+    """Test Blocks tab cases."""
+
+    extension = ['pymdownx.blocks.admonition']
+
+    def test_attributes(self):
+        """Test attributes."""
+
+        self.check_markdown(
+            R'''
+            /// admonition | Title
+            @attrs: {class: some classes, id: an-id, name: some value}
+
+            content
+            ///
+            ''',
+            '''
+            <div class="admonition some classes" id="an-id" name="some value">
+            <p class="admonition-title">Title</p>
+            <p>content</p>
+            </div>
+            ''',
+            True
+        )
+
+    def test_attributes_with_spaces(self):
+        """Test attributes."""
+
+        self.check_markdown(
+            R'''
+            /// admonition | Title
+            @  attrs: {class: some classes, id: an-id, name: some value}
+
+            content
+            ///
+            ''',
+            '''
+            <div class="admonition some classes" id="an-id" name="some value">
+            <p class="admonition-title">Title</p>
+            <p>content</p>
+            </div>
+            ''',
+            True
+        )
+
+    def test_bad_attributes(self):
+        """Test no attributes."""
+
+        self.check_markdown(
+            R'''
+            /// admonition | Title
+            @attrs: {'+': 'value'}
+            content
+            ///
+            ''',
+            '''
+            <p>/// admonition | Title
+            @attrs: {'+': 'value'}
+            content
+            ///</p>
+            ''',
+            True
+        )