✨ NEW: Add attrs_block_plugin (#66)

docs/index.md

@@ -89,12 +89,16 @@ html_string = md.render("some *Markdown*")
 .. autofunction:: mdit_py_plugins.admon.admon_plugin
 ```
 
-## Inline Attributes
+## Attributes
 
 ```{eval-rst}
 .. autofunction:: mdit_py_plugins.attrs.attrs_plugin
 ```
 
+```{eval-rst}
+.. autofunction:: mdit_py_plugins.attrs.attrs_block_plugin
+```
+
 ## Math
 
 ```{eval-rst}

mdit_py_plugins/attrs/__init__.py

@@ -1 +1 @@
-from .index import attrs_plugin  # noqa: F401
+from .index import attrs_block_plugin, attrs_plugin  # noqa: F401

mdit_py_plugins/attrs/index.py

@@ -1,6 +1,9 @@
 from typing import List, Optional
 
 from markdown_it import MarkdownIt
+from markdown_it.common.utils import isSpace
+from markdown_it.rules_block import StateBlock
+from markdown_it.rules_core import StateCore
 from markdown_it.rules_inline import StateInline
 from markdown_it.token import Token
 
@@ -46,7 +49,7 @@ def attrs_plugin(
     :param span_after: The name of an inline rule after which spans may be specified.
     """
 
-    def _attr_rule(state: StateInline, silent: bool):
+    def _attr_inline_rule(state: StateInline, silent: bool):
         if state.pending or not state.tokens:
             return False
         token = state.tokens[-1]
@@ -69,7 +72,29 @@ def _attr_rule(state: StateInline, silent: bool):
 
     if spans:
         md.inline.ruler.after(span_after, "span", _span_rule)
-    md.inline.ruler.push("attr", _attr_rule)
+    if after:
+        md.inline.ruler.push("attr", _attr_inline_rule)
+
+
+def attrs_block_plugin(md: MarkdownIt):
+    """Parse block attributes.
+
+    Block attributes are attributes on a single line, with no other content.
+    They attach the specified attributes to the block below them::
+
+        {.a #b c=1}
+        A paragraph, that will be assigned the class ``a`` and the identifier ``b``.
+
+    Attributes can be stacked, with classes accumulating and lower attributes overriding higher::
+
+        {#a .a c=1}
+        {#b .b c=2}
+        A paragraph, that will be assigned the class ``a b c``, and the identifier ``b``.
+
+    This syntax is inspired by Djot block attributes.
+    """
+    md.block.ruler.before("fence", "attr", _attr_block_rule)
+    md.core.ruler.after("block", "attr", _attr_resolve_block_rule)
 
 
 def _find_opening(tokens: List[Token], index: int) -> Optional[int]:
@@ -121,3 +146,83 @@ def _span_rule(state: StateInline, silent: bool):
     state.pos = pos
     state.posMax = maximum
     return True
+
+
+def _attr_block_rule(
+    state: StateBlock, startLine: int, endLine: int, silent: bool
+) -> bool:
+    """Find a block of attributes.
+
+    The block must be a single line that begins with a `{`, after three or less spaces,
+    and end with a `}` followed by any number if spaces.
+    """
+    # if it's indented more than 3 spaces, it should be a code block
+    if state.sCount[startLine] - state.blkIndent >= 4:
+        return False
+
+    pos = state.bMarks[startLine] + state.tShift[startLine]
+    maximum = state.eMarks[startLine]
+
+    # if it doesn't start with a {, it's not an attribute block
+    if state.srcCharCode[pos] != 0x7B:  # /* { */
+        return False
+
+    # find first non-space character from the right
+    while maximum > pos and isSpace(state.srcCharCode[maximum - 1]):
+        maximum -= 1
+    # if it doesn't end with a }, it's not an attribute block
+    if maximum <= pos:
+        return False
+    if state.srcCharCode[maximum - 1] != 0x7D:  # /* } */
+        return False
+
+    try:
+        new_pos, attrs = parse(state.src[pos:maximum])
+    except ParseError:
+        return False
+
+    # if the block was resolved earlier than expected, it's not an attribute block
+    # TODO this was not working in some instances, so I disabled it
+    # if (maximum - 1) != new_pos:
+    #     return False
+
+    if silent:
+        return True
+
+    token = state.push("attrs_block", "", 0)
+    token.attrs = attrs  # type: ignore
+    token.map = [startLine, startLine + 1]
+
+    state.line = startLine + 1
+    return True
+
+
+def _attr_resolve_block_rule(state: StateCore):
+    """Find attribute block then move its attributes to the next block."""
+    i = 0
+    len_tokens = len(state.tokens)
+    while i < len_tokens:
+        if state.tokens[i].type != "attrs_block":
+            i += 1
+            continue
+
+        if i + 1 < len_tokens:
+            next_token = state.tokens[i + 1]
+
+            # classes are appended
+            if "class" in state.tokens[i].attrs and "class" in next_token.attrs:
+                state.tokens[i].attrs[
+                    "class"
+                ] = f"{state.tokens[i].attrs['class']} {next_token.attrs['class']}"
+
+            if next_token.type == "attrs_block":
+                # subsequent attribute blocks take precedence, when merging
+                for key, value in state.tokens[i].attrs.items():
+                    if key == "class" or key not in next_token.attrs:
+                        next_token.attrs[key] = value
+            else:
+                # attribute block takes precedence over attributes in other blocks
+                next_token.attrs.update(state.tokens[i].attrs)
+
+        state.tokens.pop(i)
+        len_tokens -= 1

tests/fixtures/attrs.md

@@ -1,3 +1,84 @@
+block indented * 4 is not a block
+.
+    {#a .a b=c}
+.
+<pre><code>{#a .a b=c}
+</code></pre>
+.
+
+block with preceding text is not a block
+.
+{#a .a b=c} a
+.
+<p>{#a .a b=c} a</p>
+.
+
+block no preceding
+.
+{#a .a c=1}
+.
+
+.
+
+block basic
+.
+{#a .a c=1}
+a
+.
+<p id="a" c="1" class="a">a</p>
+.
+
+multiple blocks
+.
+{#a .a c=1} 
+
+ {#b .b c=2}
+a
+.
+<p id="b" c="2" class="a b">a</p>
+.
+
+block list
+.
+{#a .a c=1}
+- a
+.
+<ul id="a" c="1" class="a">
+<li>a</li>
+</ul>
+.
+
+block quote
+.
+{#a .a c=1}
+> a
+.
+<blockquote id="a" c="1" class="a">
+<p>a</p>
+</blockquote>
+.
+
+block fence
+.
+{#a .b c=1}
+```python
+a = 1
+```
+.
+<pre><code id="a" c="1" class="b language-python">a = 1
+</code></pre>
+.
+
+block after paragraph
+.
+a
+{#a .a c=1}
+.
+<p>a
+{#a .a c=1}</p>
+.
+
+
 simple reference link
 .
 [text *emphasis*](a){#id .a}

tests/test_attrs.py

@@ -4,7 +4,7 @@
 from markdown_it.utils import read_fixture_file
 import pytest
 
-from mdit_py_plugins.attrs import attrs_plugin
+from mdit_py_plugins.attrs import attrs_block_plugin, attrs_plugin
 
 FIXTURE_PATH = Path(__file__).parent.joinpath("fixtures")
 
@@ -13,7 +13,7 @@
     "line,title,input,expected", read_fixture_file(FIXTURE_PATH / "attrs.md")
 )
 def test_attrs(line, title, input, expected):
-    md = MarkdownIt("commonmark").use(attrs_plugin, spans=True)
+    md = MarkdownIt("commonmark").use(attrs_plugin, spans=True).use(attrs_block_plugin)
     md.options["xhtmlOut"] = False
     text = md.render(input)
     print(text)