✨ NEW: Add fieldlist extension (#455)

Field lists are mappings from field names to field bodies, based on the
[reStructureText syntax](https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html#field-lists).

A prominent use case of field lists is for use in API docstrings,
as used in [Sphinx's docstring renderers](https://www.sphinx-doc.org/en/master/usage/restructuredtext/domains.html#the-python-domain).
This should hopefully pave the way for use with `sphinx.ext.autodoc`

.pre-commit-config.yaml

@@ -52,8 +52,8 @@ repos:
       args: [--config-file=setup.cfg]
       additional_dependencies:
       - sphinx~=3.3
-      - markdown-it-py>=1.0.0,<2.0.0
-      - mdit-py-plugins~=0.2.8
+      - markdown-it-py>=1.0.0,<3.0.0
+      - mdit-py-plugins~=0.3.0
       files: >
         (?x)^(
             myst_parser/.*py|

docs/conf.py

@@ -75,6 +75,7 @@
     "dollarmath",
     "amsmath",
     "deflist",
+    "fieldlist",
     "html_admonition",
     "html_image",
     "colon_fence",

docs/sphinx/reference.md

@@ -47,9 +47,10 @@ List of extensions:
 
 - "amsmath": enable direct parsing of [amsmath](https://ctan.org/pkg/amsmath) LaTeX equations
 - "colon_fence": Enable code fences using `:::` delimiters, [see here](syntax/colon_fence) for details
-- "deflist"
+- "deflist": Enable definition lists, [see here](syntax/definition-lists) for details
 - "dollarmath": Enable parsing of dollar `$` and `$$` encapsulated math
 - "html_admonition": Convert `<div class="admonition">` elements to sphinx admonition nodes, see the [HTML admonition syntax](syntax/html-admonition) for details
+- "fieldlist": Enable field lists, [see here](syntax/fieldlists) for details
 - "html_image": Convert HTML `<img>` elements to sphinx image nodes, see the [image syntax](syntax/images) for details
 - "linkify": automatically identify "bare" web URLs and add hyperlinks
 - "replacements": automatically convert some common typographic texts

docs/syntax/optional.md

@@ -30,6 +30,7 @@ myst_enable_extensions = [
     "colon_fence",
     "deflist",
     "dollarmath",
+    "fieldlist",
     "html_admonition",
     "html_image",
     "linkify",
@@ -589,6 +590,96 @@ and are applied to markdown list items starting with `[ ]` or `[x]`:
 - [ ] An item that needs doing
 - [x] An item that is complete
 
+(syntax/fieldlists)=
+## Field Lists
+
+Field lists are mappings from field names to field bodies,
+based on the [reStructureText syntax](https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html#field-lists).
+
+````md
+:name only:
+:name: body
+:*Nested syntax*: Both name and body may contain **nested syntax**.
+:Paragraphs: Since the field marker may be quite long, the second
+   and subsequent lines of a paragraph do not have to line up
+   with the first line.
+:Alignment 1: If the field body starts on the first line...
+
+              Then the entire field body must be indented the same.
+:Alignment 2:
+  If the field body starts on a subsequent line...
+
+  Then the indentation is always two spaces.
+:Blocks:
+
+  As well as paragraphs, any block syntaxes may be used in a field body:
+
+  - Me
+  - Myself
+  - I
+
+  ```python
+  print("Hello, world!")
+  ```
+````
+
+:name only:
+:name: body
+:*Nested syntax*: Both name and body may contain **nested syntax**.
+:Paragraphs: Since the field marker may be quite long, the second
+   and subsequent lines of a paragraph do not have to line up
+   with the first line.
+:Alignment 1: If the field body starts on the first line...
+
+              Then the entire field body must be indented the same.
+:Alignment 2:
+  If the field body starts on a subsequent line...
+
+  Then the indentation is always two spaces.
+:Blocks:
+
+  As well as paragraphs, any block syntaxes may be used in a field body:
+
+  - Me
+  - Myself
+  - I
+
+  ```python
+  print("Hello, world!")
+  ```
+
+A prominent use case of field lists is for use in API docstrings, as used in [Sphinx's docstring renderers](sphinx:python-domain):
+
+````md
+```{py:function} send_message(sender, priority)
+
+Send a message to a recipient
+
+:param str sender: The person sending the message
+:param priority: The priority of the message, can be a number 1-5
+:type priority: int
+:return: the message id
+:rtype: int
+:raises ValueError: if the message_body exceeds 160 characters
+```
+````
+
+```{py:function} send_message(sender, priority)
+
+Send a message to a recipient
+
+:param str sender: The person sending the message
+:param priority: The priority of the message, can be a number 1-5
+:type priority: int
+:return: the message id
+:rtype: int
+:raises ValueError: if the message_body exceeds 160 characters
+```
+
+:::{note}
+Currently `sphinx.ext.autodoc` does not support MyST, see [](howto/autodoc).
+:::
+
 (syntax/images)=
 
 ## Images

myst_parser/docutils_renderer.py

@@ -942,6 +942,42 @@ def render_dl(self, token: SyntaxTreeNode) -> None:
                     )
                     self.current_node += [error_msg]
 
+    def render_field_list(self, token: SyntaxTreeNode) -> None:
+        """Render a field list."""
+        field_list = nodes.field_list(classes=["myst"])
+        self.add_line_and_source_path(field_list, token)
+        with self.current_node_context(field_list, append=True):
+            # raise ValueError(token.pretty(show_text=True))
+            children = (token.children or [])[:]
+            while children:
+                child = children.pop(0)
+                if not child.type == "fieldlist_name":
+                    error_msg = self.reporter.error(
+                        (
+                            "Expected a fieldlist_name as a child of a field_list"
+                            f", but found a: {child.type}"
+                        ),
+                        # nodes.literal_block(content, content),
+                        line=token_line(child),
+                    )
+                    self.current_node += [error_msg]
+                    break
+                field = nodes.field()
+                self.add_line_and_source_path(field, child)
+                field_list += field
+                field_name = nodes.field_name()
+                self.add_line_and_source_path(field_name, child)
+                field += field_name
+                with self.current_node_context(field_name):
+                    self.render_children(child)
+                field_body = nodes.field_body()
+                self.add_line_and_source_path(field_name, child)
+                field += field_body
+                if children and children[0].type == "fieldlist_body":
+                    child = children.pop(0)
+                    with self.current_node_context(field_body):
+                        self.render_children(child)
+
     def render_directive(self, token: SyntaxTreeNode) -> None:
         """Render special fenced code blocks as directives."""
         first_line = token.info.split(maxsplit=1)

myst_parser/main.py

@@ -16,6 +16,7 @@
 from mdit_py_plugins.colon_fence import colon_fence_plugin
 from mdit_py_plugins.deflist import deflist_plugin
 from mdit_py_plugins.dollarmath import dollarmath_plugin
+from mdit_py_plugins.field_list import fieldlist_plugin
 from mdit_py_plugins.footnote import footnote_plugin
 from mdit_py_plugins.front_matter import front_matter_plugin
 from mdit_py_plugins.myst_blocks import myst_block_plugin
@@ -61,6 +62,7 @@ def check_extensions(self, attribute, value):
                 "dollarmath",
                 "amsmath",
                 "deflist",
+                "fieldlist",
                 "html_admonition",
                 "html_image",
                 "colon_fence",
@@ -193,6 +195,8 @@ def default_parser(config: MdParserConfig) -> MarkdownIt:
         md.use(amsmath_plugin)
     if "deflist" in config.enable_extensions:
         md.use(deflist_plugin)
+    if "fieldlist" in config.enable_extensions:
+        md.use(fieldlist_plugin)
     if "tasklist" in config.enable_extensions:
         md.use(tasklists_plugin)
     if "substitution" in config.enable_extensions:

myst_parser/mocking.py

@@ -87,6 +87,7 @@ def __init__(
         self.document = renderer.document
         self.reporter = renderer.document.reporter
         self.state_machine = state_machine
+        self.inliner = MockInliner(renderer, lineno)
 
         class Struct:
             document = self.document
@@ -95,7 +96,7 @@ class Struct:
             title_styles: List[str] = []
             section_level = max(renderer._level_to_elem)
             section_bubble_up_kludge = False
-            inliner = MockInliner(renderer, lineno)
+            inliner = self.inliner
 
         self.memo = Struct
 

tests/test_sphinx/sourcedirs/fieldlist/conf.py

@@ -0,0 +1,4 @@
+extensions = ["myst_parser"]
+exclude_patterns = ["_build"]
+
+myst_enable_extensions = ["fieldlist"]

tests/test_sphinx/sourcedirs/fieldlist/index.md

@@ -0,0 +1,19 @@
+:orphan:
+
+# Test
+
+:field:
+
+:*field*: content
+
+```{py:function} send_message(sender, priority)
+
+Send a message to a recipient
+
+:param str sender: The person sending the message
+:param priority: The priority of the message, can be a number 1-5
+:type priority: int
+:return: the message id
+:rtype: int
+:raises ValueError: if the message_body exceeds 160 characters
+```

tests/test_sphinx/test_sphinx_builds.py

@@ -399,3 +399,38 @@ def test_mathjax_warning(
         "overridden by myst-parser: 'other' -> 'tex2jax_process|mathjax_process|math|output_area'"
         in warnings
     )
+
+
+@pytest.mark.sphinx(
+    buildername="html",
+    srcdir=os.path.join(SOURCE_DIR, "fieldlist"),
+    freshenv=True,
+)
+def test_fieldlist_extension(
+    app,
+    status,
+    warning,
+    get_sphinx_app_doctree,
+    get_sphinx_app_output,
+    remove_sphinx_builds,
+):
+    """test setting addition configuration values."""
+    app.build()
+    assert "build succeeded" in status.getvalue()  # Build succeeded
+    warnings = warning.getvalue().strip()
+    assert warnings == ""
+
+    try:
+        get_sphinx_app_doctree(
+            app,
+            docname="index",
+            regress=True,
+            regress_ext=f".sphinx{sphinx.version_info[0]}.xml",
+        )
+    finally:
+        get_sphinx_app_output(
+            app,
+            filename="index.html",
+            regress_html=True,
+            regress_ext=f".sphinx{sphinx.version_info[0]}.html",
+        )