👌 IMPROVE: Alternative proposal for allowing colon fences

mdformat_myst/_directives.py

@@ -1,9 +1,13 @@
+"""Helpers to handle directives---including their headers and fence syntax."""
+
 from __future__ import annotations
 
 from collections.abc import Mapping, MutableMapping, Sequence
 import io
 
 from markdown_it import MarkdownIt
+import mdformat
+import mdformat.plugins
 from mdformat.renderer import LOGGER, RenderContext, RenderTreeNode
 import ruamel.yaml
 
@@ -13,7 +17,12 @@
 
 def longest_consecutive_sequence(seq: str, char: str) -> int:
     """Return length of the longest consecutive sequence of `char` characters
-    in string `seq`."""
+    in string `seq`.
+
+    This measured faster than the more "Pythonic":
+
+    `max((len(list(g)) for k, g in groupby(s) if k == char), default=0)`
+    """
     assert len(char) == 1
     longest = 0
     current_streak = 0
@@ -30,27 +39,32 @@ def longest_consecutive_sequence(seq: str, char: str) -> int:
 def fence(node: "RenderTreeNode", context: "RenderContext") -> str:
     """Render fences (and directives).
 
-    Copied from upstream `mdformat` core and should be kept up-to-date
-    if upstream introduces changes. Note that only two lines are added
-    to the upstream implementation, i.e. the condition that calls
-    `format_directive_content` function.
+    Originally copied from upstream `mdformat` core. Key changes so far:
+    - call our `format_directive_content` function when a directive is detected (instead
+      of treating the contents as code in that case).
+    - allow colon fences (and use a heuristic to ensure good spacing when recombining
+      those).
     """
     info_str = node.info.strip()
     lang = info_str.split(maxsplit=1)[0] if info_str else ""
-    code_block = node.content
+    is_directive = lang.startswith("{") and lang.endswith("}")
+    unformatted_body = node.content
 
+    if node.type == "colon_fence":
+        fence_char = ":"
     # Info strings of backtick code fences can not contain backticks or tildes.
     # If that is the case, we make a tilde code fence instead.
-    if "`" in info_str or "~" in info_str:
+    elif "`" in info_str or "~" in info_str:
         fence_char = "~"
     else:
         fence_char = "`"
 
-    # Format the code block using enabled codeformatter funcs
-    if lang in context.options.get("codeformatters", {}):
+    if is_directive:
+        body = format_directive_content(unformatted_body, context=context)
+    elif lang in context.options.get("codeformatters", {}):
         fmt_func = context.options["codeformatters"][lang]
         try:
-            code_block = fmt_func(code_block, info_str)
+            body = fmt_func(unformatted_body, info_str)
         except Exception:
             # Swallow exceptions so that formatter errors (e.g. due to
             # invalid code) do not crash mdformat.
@@ -59,49 +73,68 @@ def fence(node: "RenderTreeNode", context: "RenderContext") -> str:
                 f"Failed formatting content of a {lang} code block "
                 f"(line {node.map[0] + 1} before formatting)"
             )
-    # This "elif" is the *only* thing added to the upstream `fence` implementation!
-    elif lang.startswith("{") and lang.endswith("}"):
-        code_block = format_directive_content(code_block)
+            body = unformatted_body
+    else:
+        body = unformatted_body
 
-    # The code block must not include as long or longer sequence of `fence_char`s
-    # as the fence string itself
-    fence_len = max(3, longest_consecutive_sequence(code_block, fence_char) + 1)
+    # The fenced contents must not include as long or longer sequence of `fence_char`s
+    # as the fence string itself.
+    fence_len = max(3, longest_consecutive_sequence(body, fence_char) + 1)
     fence_str = fence_char * fence_len
-
-    return f"{fence_str}{info_str}\n{code_block}{fence_str}"
-
-
-def format_directive_content(raw_content: str) -> str:
-    parse_result = parse_opts_and_content(raw_content)
-    if not parse_result:
-        return raw_content
-    unformatted_yaml, content = parse_result
-    dump_stream = io.StringIO()
-    try:
-        parsed = yaml.load(unformatted_yaml)
-        yaml.dump(parsed, stream=dump_stream)
-    except ruamel.yaml.YAMLError:
-        LOGGER.warning("Invalid YAML in MyST directive options.")
-        return raw_content
-    formatted_yaml = dump_stream.getvalue()
-
-    # Remove the YAML closing tag if added by `ruamel.yaml`
-    if formatted_yaml.endswith("\n...\n"):
-        formatted_yaml = formatted_yaml[:-4]
-
-    # Convert empty YAML to most concise form
-    if formatted_yaml == "null\n":
-        formatted_yaml = ""
-
-    formatted = "---\n" + formatted_yaml + "---\n"
+    formatted_fence = f"{fence_str}{info_str}\n"
+    # Heuristic to ensure child colon fences recombine with a leading blank line for
+    # consistency.
+    if body.startswith(":::"):
+        formatted_fence += "\n"
+    formatted_fence += f"{body}{fence_str}"
+    return formatted_fence
+
+
+def format_directive_content(raw_content: str, context) -> str:
+    unformatted_yaml, content = parse_opts_and_content(raw_content)
+    formatted = ""
+    if unformatted_yaml is not None:
+        dump_stream = io.StringIO()
+        try:
+            parsed = yaml.load(unformatted_yaml)
+            yaml.dump(parsed, stream=dump_stream)
+        except ruamel.yaml.YAMLError:
+            LOGGER.warning("Invalid YAML in MyST directive options.")
+            return raw_content
+        formatted_yaml = dump_stream.getvalue()
+
+        # Remove the YAML closing tag if added by `ruamel.yaml`
+        if formatted_yaml.endswith("\n...\n"):
+            formatted_yaml = formatted_yaml[:-4]
+
+        # Convert empty YAML to most concise form
+        if formatted_yaml == "null\n":
+            formatted_yaml = ""
+
+        formatted += "---\n" + formatted_yaml + "---\n"
     if content:
-        formatted += content + "\n"
+        # Get currently active plugin modules
+        active_plugins = context.options.get("parser_extension", [])
+
+        # Resolve modules back to their string names
+        # mdformat.text() requires names (str), not objects
+        extension_names = [
+            name
+            for name, plugin in mdformat.plugins.PARSER_EXTENSIONS.items()
+            if plugin in active_plugins
+        ]
+        formatted += mdformat.text(
+            content, options=context.options, extensions=extension_names
+        )
+        formatted = formatted.rstrip("\n") + "\n"
+        if formatted.endswith(":::\n"):
+            formatted += "\n"
     return formatted
 
 
-def parse_opts_and_content(raw_content: str) -> tuple[str, str] | None:
+def parse_opts_and_content(raw_content: str) -> tuple[str | None, str]:
     if not raw_content:
-        return None
+        return None, raw_content
     lines = raw_content.splitlines()
     line = lines.pop(0)
     yaml_lines = []
@@ -111,15 +144,17 @@ def parse_opts_and_content(raw_content: str) -> tuple[str, str] | None:
             if all(c == "-" for c in line) and len(line) >= 3:
                 break
             yaml_lines.append(line)
-    elif line.lstrip().startswith(":"):
+    elif line.lstrip().startswith(":") and not line.lstrip().startswith(":::"):
         yaml_lines.append(line.lstrip()[1:])
         while lines:
-            if not lines[0].lstrip().startswith(":"):
+            if not lines[0].lstrip().startswith(":") or lines[0].lstrip().startswith(
+                ":::"
+            ):
                 break
             line = lines.pop(0).lstrip()[1:]
             yaml_lines.append(line)
     else:
-        return None
+        return None, raw_content
 
     first_line_is_empty_but_second_line_isnt = (
         len(lines) >= 2 and not lines[0].strip() and lines[1].strip()

mdformat_myst/plugin.py

@@ -6,6 +6,7 @@
 from markdown_it import MarkdownIt
 import mdformat.plugins
 from mdformat.renderer import RenderContext, RenderTreeNode
+from mdit_py_plugins.colon_fence import colon_fence_plugin
 from mdit_py_plugins.dollarmath import dollarmath_plugin
 from mdit_py_plugins.myst_blocks import myst_block_plugin
 from mdit_py_plugins.myst_role import myst_role_plugin
@@ -17,23 +18,16 @@
 
 
 def update_mdit(mdit: MarkdownIt) -> None:
-    # Enable mdformat-tables plugin
-    tables_plugin = mdformat.plugins.PARSER_EXTENSIONS["tables"]
-    if tables_plugin not in mdit.options["parser_extension"]:
-        mdit.options["parser_extension"].append(tables_plugin)
-        tables_plugin.update_mdit(mdit)
-
-    # Enable mdformat-front-matters plugin
-    front_matters_plugin = mdformat.plugins.PARSER_EXTENSIONS["front_matters"]
-    if front_matters_plugin not in mdit.options["parser_extension"]:
-        mdit.options["parser_extension"].append(front_matters_plugin)
-        front_matters_plugin.update_mdit(mdit)
-
-    # Enable mdformat-footnote plugin
-    footnote_plugin = mdformat.plugins.PARSER_EXTENSIONS["footnote"]
-    if footnote_plugin not in mdit.options["parser_extension"]:
-        mdit.options["parser_extension"].append(footnote_plugin)
-        footnote_plugin.update_mdit(mdit)
+    plugins_to_enable = [
+        "tables",
+        "front_matters",
+        "footnote",
+    ]
+    for plugin_name in plugins_to_enable:
+        plugin = mdformat.plugins.PARSER_EXTENSIONS[plugin_name]
+        if plugin not in mdit.options["parser_extension"]:
+            mdit.options["parser_extension"].append(plugin)
+            plugin.update_mdit(mdit)
 
     # Enable MyST role markdown-it extension
     mdit.use(myst_role_plugin)
@@ -45,6 +39,9 @@ def update_mdit(mdit: MarkdownIt) -> None:
     # Enable dollarmath markdown-it extension
     mdit.use(dollarmath_plugin)
 
+    # Enable support for the colon fence syntax
+    mdit.use(colon_fence_plugin)
+
     # Trick `mdformat`s AST validation by removing HTML rendering of code
     # blocks and fences. Directives are parsed as code fences and we
     # modify them in ways that don't break MyST AST but do break
@@ -117,7 +114,6 @@ def _escape_paragraph(text: str, node: RenderTreeNode, context: RenderContext) -
     lines = text.split("\n")
 
     for i in range(len(lines)):
-
         # Three or more "+" chars are interpreted as a block break. Escape them.
         space_removed = lines[i].replace(" ", "")
         if space_removed.startswith("+++"):
@@ -144,15 +140,17 @@ def _escape_text(text: str, node: RenderTreeNode, context: RenderContext) -> str
     return text
 
 
+CHANGES_AST = True
 RENDERERS = {
     "blockquote": _math_block_safe_blockquote_renderer,
+    "colon_fence": fence,
+    "fence": fence,
     "myst_role": _role_renderer,
     "myst_line_comment": _comment_renderer,
     "myst_block_break": _blockbreak_renderer,
     "myst_target": _target_renderer,
     "math_inline": _math_inline_renderer,
     "math_block_label": _math_block_label_renderer,
     "math_block": _math_block_renderer,
-    "fence": fence,
 }
 POSTPROCESSORS = {"paragraph": _escape_paragraph, "text": _escape_text}

pyproject.toml

@@ -20,6 +20,7 @@ keywords = "mdformat,markdown,formatter,gfm"
 
 requires-python = ">=3.10"
 requires = [
+    "markdown-it-py >= 2.0.0",
     "mdformat >=0.7.0",
     "mdit-py-plugins >=0.3.0",
     "mdformat-front-matters >= 1.0.0",