docutils_renderer.py

import inspect
import json
import os
import re
from collections import OrderedDict
from contextlib import contextmanager
from copy import deepcopy
from datetime import date, datetime
from types import ModuleType
from typing import (
    Any,
    Dict,
    Iterator,
    List,
    MutableMapping,
    Optional,
    Sequence,
    Union,
    cast,
)

import jinja2
import yaml
from docutils import nodes
from docutils.frontend import OptionParser
from docutils.languages import get_language
from docutils.parsers.rst import Directive, DirectiveError
from docutils.parsers.rst import Parser as RSTParser
from docutils.parsers.rst import directives, roles
from docutils.parsers.rst.directives.misc import Include
from docutils.parsers.rst.languages import get_language as get_language_rst
from docutils.statemachine import StringList
from docutils.transforms.components import Filter
from docutils.utils import Reporter, new_document
from markdown_it import MarkdownIt
from markdown_it.common.utils import escapeHtml
from markdown_it.renderer import RendererProtocol
from markdown_it.token import Token
from markdown_it.tree import SyntaxTreeNode

from myst_parser.mocking import (
    MockIncludeDirective,
    MockingError,
    MockInliner,
    MockRSTParser,
    MockState,
    MockStateMachine,
)
from .html_to_nodes import html_to_nodes
from .parse_directives import DirectiveParsingError, parse_directive_text
from .utils import is_external_url


def make_document(source_path="notset") -> nodes.document:
    """Create a new docutils document."""
    settings = OptionParser(components=(RSTParser,)).get_default_values()
    return new_document(source_path, settings=settings)


REGEX_DIRECTIVE_START = re.compile(r"^[\s]{0,3}([`]{3,10}|[~]{3,10}|[:]{3,10})\{")


def token_line(token: SyntaxTreeNode, default: Optional[int] = None) -> int:
    """Retrieve the initial line of a token."""
    if not getattr(token, "map", None):
        if default is not None:
            return default
        raise ValueError(f"token map not set: {token}")
    return token.map[0]  # type: ignore[index]


class DocutilsRenderer(RendererProtocol):
    """A markdown-it-py renderer to populate (in-place) a `docutils.document` AST.

    Note, this render is not dependent on Sphinx.
    """

    __output__ = "docutils"

    def __init__(self, parser: MarkdownIt) -> None:
        """Load the renderer (called by ``MarkdownIt``)"""
        self.md = parser
        self.rules = {
            k: v
            for k, v in inspect.getmembers(self, predicate=inspect.ismethod)
            if k.startswith("render_") and k != "render_children"
        }

    def setup_render(
        self, options: Dict[str, Any], env: MutableMapping[str, Any]
    ) -> None:
        """Setup the renderer with per render variables."""
        self.md_env = env
        self.config: Dict[str, Any] = options
        self.document: nodes.document = self.config.get("document", make_document())
        self.current_node: nodes.Element = self.config.get(
            "current_node", self.document
        )
        self.reporter: Reporter = self.document.reporter
        # note there are actually two possible language modules:
        # one from docutils.languages, and one from docutils.parsers.rst.languages
        self.language_module_rst: ModuleType = get_language_rst(
            self.document.settings.language_code
        )
        self._level_to_elem: Dict[int, nodes.Element] = {0: self.document}

    @property
    def sphinx_env(self) -> Optional[Any]:
        """Return the sphinx env, if using Sphinx."""
        try:
            return self.document.settings.env
        except AttributeError:
            return None

    def create_warning(
        self,
        message: str,
        *,
        line: Optional[int] = None,
        append_to: Optional[nodes.Element] = None,
        wtype: str = "myst",
        subtype: str = "other",
    ) -> Optional[nodes.system_message]:
        """Generate a warning, logging if it is necessary.

        Note this is overridden in the ``SphinxRenderer``,
        to handle suppressed warning types.
        """
        kwargs = {"line": line} if line is not None else {}
        msg_node = self.reporter.warning(message, **kwargs)
        if append_to is not None:
            append_to.append(msg_node)
        return msg_node

    def _render_tokens(self, tokens: List[Token]) -> None:
        """Render the tokens."""
        # propagate line number down to inline elements
        for token in tokens:
            if not token.map:
                continue
            # For docutils we want 1 based line numbers (not 0)
            token.map = [token.map[0] + 1, token.map[1] + 1]
            for token_child in token.children or []:
                token_child.map = token.map

        # nest tokens
        node_tree = SyntaxTreeNode(tokens)

        # move footnote definitions to env
        self.md_env.setdefault("foot_refs", {})
        for node in node_tree.walk(include_self=True):
            new_children = []
            for child in node.children:
                if child.type == "footnote_reference":
                    label = child.meta["label"]
                    self.md_env["foot_refs"].setdefault(label, []).append(child)
                else:
                    new_children.append(child)

            node.children = new_children

        # render
        for child in node_tree.children:
            # skip hidden?
            if f"render_{child.type}" in self.rules:
                self.rules[f"render_{child.type}"](child)
            else:
                self.create_warning(
                    f"No render method for: {child.type}",
                    line=token_line(child, default=0),
                    subtype="render",
                    append_to=self.current_node,
                )

    def render(
        self, tokens: Sequence[Token], options, md_env: MutableMapping[str, Any]
    ) -> nodes.document:
        """Run the render on a token stream.

        :param tokens: list on block tokens to render
        :param options: params of parser instance
        :param md_env: the markdown-it environment sandbox associated with the tokens,
            containing additional metadata like reference info
        """
        self.setup_render(options, md_env)

        self._render_tokens(list(tokens))

        # log warnings for duplicate reference definitions
        # "duplicate_refs": [{"href": "ijk", "label": "B", "map": [4, 5], "title": ""}],
        for dup_ref in self.md_env.get("duplicate_refs", []):
            self.create_warning(
                f"Duplicate reference definition: {dup_ref['label']}",
                line=dup_ref["map"][0] + 1,
                subtype="ref",
                append_to=self.document,
            )

        if not self.config.get("output_footnotes", True):
            return self.document

        # we don't use the foot_references stored in the env
        # since references within directives/roles will have been added after
        # those from the initial markdown parse
        # instead we gather them from a walk of the created document
        foot_refs = OrderedDict()
        for refnode in self.document.traverse(nodes.footnote_reference):
            if refnode["refname"] not in foot_refs:
                foot_refs[refnode["refname"]] = True

        if foot_refs and self.config.get("myst_footnote_transition", False):
            self.current_node.append(nodes.transition(classes=["footnotes"]))
        for footref in foot_refs:
            foot_ref_tokens = self.md_env["foot_refs"].get(footref, [])
            if len(foot_ref_tokens) > 1:
                self.create_warning(
                    f"Multiple footnote definitions found for label: '{footref}'",
                    subtype="footnote",
                    append_to=self.current_node,
                )

            if len(foot_ref_tokens) < 1:
                self.create_warning(
                    f"No footnote definitions found for label: '{footref}'",
                    subtype="footnote",
                    append_to=self.current_node,
                )
            else:
                self.render_footnote_reference(foot_ref_tokens[0])

        self.add_document_wordcount()

        return self.document

    def add_document_wordcount(self) -> None:
        """Add the wordcount, generated by the ``mdit_py_plugins.wordcount_plugin``."""

        wordcount_metadata = self.md_env.get("wordcount", {})
        if not wordcount_metadata:
            return

        # save the wordcount to the sphinx BuildEnvironment metadata
        if self.sphinx_env is not None:
            meta = self.sphinx_env.metadata.setdefault(self.sphinx_env.docname, {})
            meta["wordcount"] = wordcount_metadata

        # now add the wordcount as substitution definitions,
        # so we can reference them in the document
        for key in ("words", "minutes"):
            value = wordcount_metadata.get(key, None)
            if value is None:
                continue
            substitution_node = nodes.substitution_definition(
                str(value), nodes.Text(str(value))
            )
            substitution_node.source = self.document["source"]
            substitution_node["names"].append(f"wordcount-{key}")
            self.document.note_substitution_def(substitution_node, f"wordcount-{key}")

    def nested_render_text(self, text: str, lineno: int) -> None:
        """Render unparsed text."""

        tokens = self.md.parse(text + "\n", self.md_env)

        # remove front matter
        if tokens and tokens[0].type == "front_matter":
            tokens.pop(0)

        self._render_tokens(tokens)

    @contextmanager
    def current_node_context(
        self, node: nodes.Element, append: bool = False
    ) -> Iterator:
        """Context manager for temporarily setting the current node."""
        if append:
            self.current_node.append(node)
        current_node = self.current_node
        self.current_node = node
        yield
        self.current_node = current_node

    def render_children(self, token: SyntaxTreeNode) -> None:
        for child in token.children or []:
            if f"render_{child.type}" in self.rules:
                self.rules[f"render_{child.type}"](child)
            else:
                self.create_warning(
                    f"No render method for: {child.type}",
                    line=token_line(child, default=0),
                    subtype="render",
                    append_to=self.current_node,
                )

    def add_line_and_source_path(self, node, token: SyntaxTreeNode) -> None:
        """Copy the line number and document source path to the docutils node."""
        try:
            node.line = token_line(token)
        except ValueError:
            pass
        node.source = self.document["source"]

    def is_section_level(self, level, section):
        return self._level_to_elem.get(level, None) == section

    def add_section(self, section, level):
        parent_level = max(
            section_level
            for section_level in self._level_to_elem
            if level > section_level
        )

        if (level > parent_level) and (parent_level + 1 != level):
            self.create_warning(
                "Non-consecutive header level increase; {} to {}".format(
                    parent_level, level
                ),
                line=section.line,
                subtype="header",
                append_to=self.current_node,
            )

        parent = self._level_to_elem[parent_level]
        parent.append(section)
        self._level_to_elem[level] = section

        # Prune level to limit
        self._level_to_elem = {
            section_level: section
            for section_level, section in self._level_to_elem.items()
            if section_level <= level
        }

    def renderInlineAsText(self, tokens: List[SyntaxTreeNode]) -> str:
        """Special kludge for image `alt` attributes to conform CommonMark spec.

        Don't try to use it! Spec requires to show `alt` content with stripped markup,
        instead of simple escaping.
        """
        result = ""

        for token in tokens or []:
            if token.type == "text":
                result += token.content
            # elif token.type == "image":
            #     result += self.renderInlineAsText(token.children)
            else:
                result += self.renderInlineAsText(token.children or [])
        return result

    # ### render methods for commonmark tokens

    def render_paragraph(self, token: SyntaxTreeNode) -> None:
        para = nodes.paragraph(token.children[0].content if token.children else "")
        self.add_line_and_source_path(para, token)
        with self.current_node_context(para, append=True):
            self.render_children(token)

    def render_inline(self, token: SyntaxTreeNode) -> None:
        self.render_children(token)

    def render_text(self, token: SyntaxTreeNode) -> None:
        self.current_node.append(nodes.Text(token.content, token.content))

    def render_bullet_list(self, token: SyntaxTreeNode) -> None:
        list_node = nodes.bullet_list()
        if token.attrs.get("class"):
            # this is used e.g. by tasklist
            list_node["classes"] = str(token.attrs["class"]).split()
        self.add_line_and_source_path(list_node, token)
        with self.current_node_context(list_node, append=True):
            self.render_children(token)

    def render_ordered_list(self, token: SyntaxTreeNode) -> None:
        list_node = nodes.enumerated_list()
        list_node["enumtype"] = "arabic"
        list_node["suffix"] = "."
        self.add_line_and_source_path(list_node, token)
        with self.current_node_context(list_node, append=True):
            self.render_children(token)

    def render_list_item(self, token: SyntaxTreeNode) -> None:
        item_node = nodes.list_item()
        if token.attrs.get("class"):
            # this is used e.g. by tasklist
            item_node["classes"] = str(token.attrs["class"]).split()
        self.add_line_and_source_path(item_node, token)
        with self.current_node_context(item_node, append=True):
            self.render_children(token)

    def render_em(self, token: SyntaxTreeNode) -> None:
        node = nodes.emphasis()
        self.add_line_and_source_path(node, token)
        with self.current_node_context(node, append=True):
            self.render_children(token)

    def render_softbreak(self, token: SyntaxTreeNode) -> None:
        self.current_node.append(nodes.Text("\n"))

    def render_hardbreak(self, token: SyntaxTreeNode) -> None:
        self.current_node.append(nodes.raw("", "<br />\n", format="html"))

    def render_strong(self, token: SyntaxTreeNode) -> None:
        node = nodes.strong()
        self.add_line_and_source_path(node, token)
        with self.current_node_context(node, append=True):
            self.render_children(token)

    def render_blockquote(self, token: SyntaxTreeNode) -> None:
        quote = nodes.block_quote()
        self.add_line_and_source_path(quote, token)
        with self.current_node_context(quote, append=True):
            self.render_children(token)

    def render_hr(self, token: SyntaxTreeNode) -> None:
        node = nodes.transition()
        self.add_line_and_source_path(node, token)
        self.current_node.append(node)

    def render_code_inline(self, token: SyntaxTreeNode) -> None:
        node = nodes.literal(token.content, token.content)
        self.add_line_and_source_path(node, token)
        self.current_node.append(node)

    def render_code_block(self, token: SyntaxTreeNode) -> None:
        # this should never have a language, since it is just indented text, however,
        # creating a literal_block with no language will raise a warning in sphinx
        text = token.content
        language = token.info.split()[0] if token.info else "none"
        language = language or "none"
        node = nodes.literal_block(text, text, language=language)
        self.add_line_and_source_path(node, token)
        self.current_node.append(node)

    def render_fence(self, token: SyntaxTreeNode) -> None:
        text = token.content
        # Ensure that we'll have an empty string if info exists but is only spaces
        info = token.info.strip() if token.info else token.info
        language = info.split()[0] if info else ""

        if not self.config.get("commonmark_only", False) and language == "{eval-rst}":
            # copy necessary elements (source, line no, env, reporter)
            newdoc = make_document()
            newdoc["source"] = self.document["source"]
            newdoc.settings = self.document.settings
            newdoc.reporter = self.reporter
            # pad the line numbers artificially so they offset with the fence block
            pseudosource = ("\n" * token_line(token)) + token.content
            # actually parse the rst into our document
            MockRSTParser().parse(pseudosource, newdoc)
            for node in newdoc:
                if node["names"]:
                    self.document.note_explicit_target(node, node)
            self.current_node.extend(newdoc[:])
            return
        elif (
            not self.config.get("commonmark_only", False)
            and language.startswith("{")
            and language.endswith("}")
        ):
            return self.render_directive(token)

        if not language:
            if self.sphinx_env is not None:
                language = self.sphinx_env.temp_data.get(
                    "highlight_language", self.sphinx_env.config.highlight_language
                )

        if not language:
            language = self.config.get("highlight_language", "")
        node = nodes.literal_block(text, text, language=language)
        self.add_line_and_source_path(node, token)
        self.current_node.append(node)

    def render_heading(self, token: SyntaxTreeNode) -> None:

        if self.md_env.get("match_titles", None) is False:
            self.create_warning(
                "Header nested in this element can lead to unexpected outcomes",
                line=token_line(token, default=0),
                subtype="nested_header",
                append_to=self.current_node,
            )

        # Test if we're replacing a section level first
        level = int(token.tag[1])
        if isinstance(self.current_node, nodes.section):
            if self.is_section_level(level, self.current_node):
                self.current_node = cast(nodes.Element, self.current_node.parent)

        title_node = nodes.title(token.children[0].content if token.children else "")
        self.add_line_and_source_path(title_node, token)

        new_section = nodes.section()
        if level == 1 and (
            self.sphinx_env is None
            or (
                "myst_update_mathjax" in self.sphinx_env.config
                and self.sphinx_env.config.myst_update_mathjax
            )
        ):
            new_section["classes"].extend(["tex2jax_ignore", "mathjax_ignore"])
        self.add_line_and_source_path(new_section, token)
        new_section.append(title_node)

        self.add_section(new_section, level)

        self.current_node = title_node
        self.render_children(token)

        assert isinstance(self.current_node, nodes.title)
        text = self.current_node.astext()
        # if self.translate_section_name:
        #     text = self.translate_section_name(text)
        name = nodes.fully_normalize_name(text)
        section = cast(nodes.section, self.current_node.parent)
        section["names"].append(name)
        self.document.note_implicit_target(section, section)
        self.current_node = section

    def render_link(self, token: SyntaxTreeNode) -> None:
        if token.markup == "autolink":
            return self.render_autolink(token)

        ref_node = nodes.reference()
        self.add_line_and_source_path(ref_node, token)
        destination = cast(str, token.attrGet("href") or "")

        if self.config.get(
            "relative-docs", None
        ) is not None and destination.startswith(self.config["relative-docs"][0]):
            # make the path relative to an "including" document
            source_dir, include_dir = self.config["relative-docs"][1:]
            destination = os.path.relpath(
                os.path.join(include_dir, os.path.normpath(destination)), source_dir
            )

        ref_node["refuri"] = destination

        title = token.attrGet("title")
        if title:
            ref_node["title"] = title
        next_node = ref_node

        # TODO currently any reference with a fragment # is deemed external
        # (if anchors are not enabled)
        # This comes from recommonmark, but I am not sure of the rationale for it
        if is_external_url(
            destination,
            self.config.get("myst_url_schemes", None),
            "heading_anchors" not in self.config.get("myst_extensions", []),
        ):
            self.current_node.append(next_node)
            with self.current_node_context(ref_node):
                self.render_children(token)
        else:
            self.handle_cross_reference(token, destination)

    def handle_cross_reference(self, token: SyntaxTreeNode, destination: str) -> None:
        if not self.config.get("ignore_missing_refs", False):
            self.create_warning(
                f"Reference not found: {destination}",
                line=token_line(token),
                subtype="ref",
                append_to=self.current_node,
            )

    def render_autolink(self, token: SyntaxTreeNode) -> None:
        refuri = target = escapeHtml(token.attrGet("href") or "")  # type: ignore[arg-type]
        ref_node = nodes.reference(target, target, refuri=refuri)
        self.add_line_and_source_path(ref_node, token)
        self.current_node.append(ref_node)

    def render_html_inline(self, token: SyntaxTreeNode) -> None:
        self.render_html_block(token)

    def render_html_block(self, token: SyntaxTreeNode) -> None:
        node_list = html_to_nodes(token.content, token_line(token), self)
        self.current_node.extend(node_list)

    def render_image(self, token: SyntaxTreeNode) -> None:
        img_node = nodes.image()
        self.add_line_and_source_path(img_node, token)
        destination = cast(str, token.attrGet("src") or "")

        if self.config.get("relative-images", None) is not None and not is_external_url(
            destination, None, True
        ):
            # make the path relative to an "including" document
            destination = os.path.normpath(
                os.path.join(
                    self.config.get("relative-images", ""),
                    os.path.normpath(destination),
                )
            )

        img_node["uri"] = destination

        img_node["alt"] = self.renderInlineAsText(token.children or [])
        title = token.attrGet("title")
        if title:
            img_node["title"] = token.attrGet("title")
        self.current_node.append(img_node)

    # ### render methods for plugin tokens

    def render_front_matter(self, token: SyntaxTreeNode) -> None:
        """Pass document front matter data."""
        position = token_line(token, default=0)

        if not isinstance(token.content, dict):
            try:
                data = yaml.safe_load(token.content)
                assert isinstance(data, dict), "not dict"
            except (
                AssertionError,
                yaml.parser.ParserError,
                yaml.scanner.ScannerError,
            ) as error:
                msg_node = self.reporter.error(
                    "Front matter block:\n" + str(error), line=position
                )
                msg_node += nodes.literal_block(token.content, token.content)
                self.current_node.append(msg_node)
                return
        else:
            data = deepcopy(token.content)

        substitutions = data.pop("substitutions", {})
        html_meta = data.pop("html_meta", {})

        if data:
            field_list = self.dict_to_fm_field_list(
                data, language_code=self.document.settings.language_code
            )
            self.current_node.append(field_list)

        if isinstance(substitutions, dict):
            self.document.fm_substitutions = substitutions
        else:
            msg_node = self.reporter.error(
                "Front-matter 'substitutions' is not a dict", line=position
            )
            msg_node += nodes.literal_block(token.content, token.content)
            self.current_node.append(msg_node)

        if not isinstance(html_meta, dict):
            msg_node = self.reporter.error(
                "Front-matter 'html_meta' is not a dict", line=position
            )
            msg_node += nodes.literal_block(token.content, token.content)
            self.current_node.append(msg_node)

        self.current_node.extend(
            html_meta_to_nodes(
                {
                    **self.config.get("myst_html_meta", {}),
                    **html_meta,
                },
                document=self.document,
                line=position,
                reporter=self.reporter,
            )
        )

    def dict_to_fm_field_list(
        self, data: Dict[str, Any], language_code: str, line: int = 0
    ) -> nodes.field_list:
        """Render each key/val pair as a docutils ``field_node``.

        Bibliographic keys below will be parsed as Markdown,
        all others will be left as literal text.

        The field list should be at the start of the document,
        and will then be converted to a `docinfo` node during the
        `docutils.docutils.transforms.frontmatter.DocInfo` transform (priority 340),
        and bibliographic keys (or their translation) will be converted to nodes::

            {'author': docutils.nodes.author,
            'authors': docutils.nodes.authors,
            'organization': docutils.nodes.organization,
            'address': docutils.nodes.address,
            'contact': docutils.nodes.contact,
            'version': docutils.nodes.version,
            'revision': docutils.nodes.revision,
            'status': docutils.nodes.status,
            'date': docutils.nodes.date,
            'copyright': docutils.nodes.copyright,
            'dedication': docutils.nodes.topic,
            'abstract': docutils.nodes.topic}

        Also, the 'dedication' and 'abstract' will be placed outside the `docinfo`,
        and so will always be shown in the document.

        If using sphinx, this `docinfo` node will later be extracted from the AST,
        by the `DoctreeReadEvent` transform (priority 880),
        calling `MetadataCollector.process_doc`.
        In this case keys and values will be converted to strings and stored in
        `app.env.metadata[app.env.docname]`

        See
        https://www.sphinx-doc.org/en/master/usage/restructuredtext/field-lists.html
        for docinfo fields used by sphinx.

        """
        field_list = nodes.field_list()

        bibliofields = get_language(language_code).bibliographic_fields
        state_machine = MockStateMachine(self, line)
        state = MockState(self, state_machine, line)

        for key, value in data.items():
            if not isinstance(value, (str, int, float, date, datetime)):
                value = json.dumps(value)
            value = str(value)
            if key in bibliofields:
                para_nodes, _ = state.inline_text(value, line)
                body_children = [nodes.paragraph("", "", *para_nodes)]
            else:
                body_children = [nodes.Text(value, value)]

            field_node = nodes.field()
            field_node.source = value
            field_node += nodes.field_name(key, "", nodes.Text(key, key))
            field_node += nodes.field_body(value, *body_children)
            field_list += field_node

        return field_list

    def render_table(self, token: SyntaxTreeNode) -> None:

        assert token.children and len(token.children) > 1

        # markdown-it table always contains two elements:
        header = token.children[0]
        body = token.children[1]
        # with one header row
        assert header.children
        header_row = header.children[0]
        assert header_row.children

        # top-level element
        table = nodes.table()
        table["classes"] += ["colwidths-auto"]
        self.add_line_and_source_path(table, token)
        self.current_node.append(table)

        # column settings element
        maxcols = len(header_row.children)
        colwidths = [round(100 / maxcols, 2)] * maxcols
        tgroup = nodes.tgroup(cols=len(colwidths))
        table += tgroup
        for colwidth in colwidths:
            colspec = nodes.colspec(colwidth=colwidth)
            tgroup += colspec

        # header
        thead = nodes.thead()
        tgroup += thead
        with self.current_node_context(thead):
            self.render_table_row(header_row)

        # body
        tbody = nodes.tbody()
        tgroup += tbody
        with self.current_node_context(tbody):
            for body_row in body.children or []:
                self.render_table_row(body_row)

    def render_table_row(self, token: SyntaxTreeNode) -> None:
        row = nodes.row()
        with self.current_node_context(row, append=True):
            for child in token.children or []:
                entry = nodes.entry()
                para = nodes.paragraph(
                    child.children[0].content if child.children else ""
                )
                style = child.attrGet("style")  # i.e. the alignment when using e.g. :--
                if style:
                    entry["classes"].append(style)
                with self.current_node_context(entry, append=True):
                    with self.current_node_context(para, append=True):
                        self.render_children(child)

    def render_math_inline(self, token: SyntaxTreeNode) -> None:
        content = token.content
        if token.markup == "$$":
            # available when dmath_double_inline is True
            node = nodes.math_block(content, content, nowrap=False, number=None)
        else:
            node = nodes.math(content, content)
        self.add_line_and_source_path(node, token)
        self.current_node.append(node)

    def render_math_single(self, token: SyntaxTreeNode) -> None:
        content = token.content
        node = nodes.math(content, content)
        self.add_line_and_source_path(node, token)
        self.current_node.append(node)

    def render_math_block(self, token: SyntaxTreeNode) -> None:
        content = token.content
        node = nodes.math_block(content, content, nowrap=False, number=None)
        self.add_line_and_source_path(node, token)
        self.current_node.append(node)

    def render_footnote_ref(self, token: SyntaxTreeNode) -> None:
        """Footnote references are added as auto-numbered,
        .i.e. `[^a]` is read as rST `[#a]_`
        """
        target = token.meta["label"]

        refnode = nodes.footnote_reference("[^{}]".format(target))
        self.add_line_and_source_path(refnode, token)
        if not target.isdigit():
            refnode["auto"] = 1
            self.document.note_autofootnote_ref(refnode)
        else:
            refnode += nodes.Text(target)

        refnode["refname"] = target
        self.document.note_footnote_ref(refnode)

        self.current_node.append(refnode)

    def render_footnote_reference(self, token: SyntaxTreeNode) -> None:
        target = token.meta["label"]

        footnote = nodes.footnote()
        self.add_line_and_source_path(footnote, token)
        footnote["names"].append(target)
        if not target.isdigit():
            footnote["auto"] = 1
            self.document.note_autofootnote(footnote)
        else:
            footnote += nodes.label("", target)
            self.document.note_footnote(footnote)
        self.document.note_explicit_target(footnote, footnote)
        with self.current_node_context(footnote, append=True):
            self.render_children(token)

    def render_myst_block_break(self, token: SyntaxTreeNode) -> None:
        block_break = nodes.comment(token.content, token.content)
        block_break["classes"] += ["block_break"]
        self.add_line_and_source_path(block_break, token)
        self.current_node.append(block_break)

    def render_myst_target(self, token: SyntaxTreeNode) -> None:
        text = token.content
        name = nodes.fully_normalize_name(text)
        target = nodes.target(text)
        target["names"].append(name)
        self.add_line_and_source_path(target, token)
        self.document.note_explicit_target(target, self.current_node)
        self.current_node.append(target)

    def render_myst_line_comment(self, token: SyntaxTreeNode) -> None:
        self.current_node.append(nodes.comment(token.content, token.content.strip()))

    def render_myst_role(self, token: SyntaxTreeNode) -> None:
        name = token.meta["name"]
        text = token.content
        rawsource = f":{name}:`{token.content}`"
        lineno = token_line(token) if token.map else 0
        role_func, messages = roles.role(
            name, self.language_module_rst, lineno, self.reporter
        )
        inliner = MockInliner(self, lineno)
        if role_func:
            nodes, messages2 = role_func(name, rawsource, text, lineno, inliner)
            # return nodes, messages + messages2
            self.current_node += nodes
        else:
            message = self.reporter.error(
                'Unknown interpreted text role "{}".'.format(name), line=lineno
            )
            problematic = inliner.problematic(text, rawsource, message)
            self.current_node += problematic

    def render_colon_fence(self, token: SyntaxTreeNode) -> None:
        """Render a code fence with ``:`` colon delimiters."""

        if token.content.startswith(":::"):
            # the content starts with a nested fence block,
            # but must distinguish between ``:options:``, so we add a new line
            assert token.token is not None, '"colon_fence" must have a `token`'
            linear_token = token.token.copy()
            linear_token.content = "\n" + linear_token.content
            token.token = linear_token

        return self.render_fence(token)

    def render_dl(self, token: SyntaxTreeNode) -> None:
        """Render a definition list."""
        node = nodes.definition_list(classes=["simple", "myst"])
        self.add_line_and_source_path(node, token)
        with self.current_node_context(node, append=True):
            item = None
            for child in token.children or []:
                if child.type == "dt":
                    item = nodes.definition_list_item()
                    self.add_line_and_source_path(item, child)
                    with self.current_node_context(item, append=True):
                        term = nodes.term(
                            child.children[0].content if child.children else ""
                        )
                        self.add_line_and_source_path(term, child)
                        with self.current_node_context(term, append=True):
                            self.render_children(child)
                elif child.type == "dd":
                    if item is None:
                        error = self.reporter.error(
                            (
                                "Found a definition in a definition list, "
                                "with no preceding term"
                            ),
                            # nodes.literal_block(content, content),
                            line=token_line(child),
                        )
                        self.current_node += [error]
                    with self.current_node_context(item):
                        definition = nodes.definition()
                        self.add_line_and_source_path(definition, child)
                        with self.current_node_context(definition, append=True):
                            self.render_children(child)
                else:
                    error_msg = self.reporter.error(
                        (
                            "Expected a term/definition as a child of a definition list"
                            f", but found a: {child.type}"
                        ),
                        # nodes.literal_block(content, content),
                        line=token_line(child),
                    )
                    self.current_node += [error_msg]

    def render_directive(self, token: SyntaxTreeNode) -> None:
        """Render special fenced code blocks as directives."""
        first_line = token.info.split(maxsplit=1)
        name = first_line[0][1:-1]
        arguments = "" if len(first_line) == 1 else first_line[1]
        content = token.content
        position = token_line(token)
        nodes_list = self.run_directive(name, arguments, content, position)
        self.current_node += nodes_list

    def run_directive(
        self, name: str, first_line: str, content: str, position: int
    ) -> List[nodes.Element]:
        """Run a directive and return the generated nodes.

        :param name: the name of the directive
        :param first_line: The text on the same line as the directive name.
            May be an argument or body text, dependent on the directive
        :param content: All text after the first line. Can include options.
        :param position: The line number of the first line

        """
        # TODO directive name white/black lists

        self.document.current_line = position

        # get directive class
        directive_class, messages = directives.directive(
            name, self.language_module_rst, self.document
        )  # type: (Directive, list)
        if not directive_class:
            error = self.reporter.error(
                'Unknown directive type "{}".\n'.format(name),
                # nodes.literal_block(content, content),
                line=position,
            )
            return [error] + messages

        if issubclass(directive_class, Include):
            # this is a Markdown only option,
            # to allow for altering relative image reference links
            directive_class.option_spec["relative-images"] = directives.flag
            directive_class.option_spec["relative-docs"] = directives.path

        try:
            arguments, options, body_lines = parse_directive_text(
                directive_class, first_line, content
            )
        except DirectiveParsingError as error:
            error = self.reporter.error(
                "Directive '{}': {}".format(name, error),
                nodes.literal_block(content, content),
                line=position,
            )
            return [error]

        # initialise directive
        if issubclass(directive_class, Include):
            directive_instance = MockIncludeDirective(
                self,
                name=name,
                klass=directive_class,
                arguments=arguments,
                options=options,
                body=body_lines,
                lineno=position,
            )
        else:
            state_machine = MockStateMachine(self, position)
            state = MockState(self, state_machine, position)
            directive_instance = directive_class(
                name=name,
                # the list of positional arguments
                arguments=arguments,
                # a dictionary mapping option names to values
                options=options,
                # the directive content line by line
                content=StringList(body_lines, self.document["source"]),
                # the absolute line number of the first line of the directive
                lineno=position,
                # the line offset of the first line of the content
                content_offset=0,  # TODO get content offset from `parse_directive_text`
                # a string containing the entire directive
                block_text="\n".join(body_lines),
                state=state,
                state_machine=state_machine,
            )

        # run directive
        try:
            result = directive_instance.run()
        except DirectiveError as error:
            msg_node = self.reporter.system_message(
                error.level, error.msg, line=position
            )
            msg_node += nodes.literal_block(content, content)
            result = [msg_node]
        except MockingError as exc:
            error_msg = self.reporter.error(
                "Directive '{}' cannot be mocked: {}: {}".format(
                    name, exc.__class__.__name__, exc
                ),
                nodes.literal_block(content, content),
                line=position,
            )
            return [error_msg]

        assert isinstance(
            result, list
        ), 'Directive "{}" must return a list of nodes.'.format(name)
        for i in range(len(result)):
            assert isinstance(
                result[i], nodes.Node
            ), 'Directive "{}" returned non-Node object (index {}): {}'.format(
                name, i, result[i]
            )
        return result

    def render_substitution_inline(self, token: SyntaxTreeNode) -> None:
        """Render inline substitution {{key}}."""
        self.render_substitution(token, inline=True)

    def render_substitution_block(self, token: SyntaxTreeNode) -> None:
        """Render block substitution {{key}}."""
        self.render_substitution(token, inline=False)

    def render_substitution(self, token: SyntaxTreeNode, inline: bool) -> None:
        """Substitutions are rendered by:

        1. Combining global substitutions with front-matter substitutions
           to create a variable context (front-matter takes priority)
        2. Add the sphinx `env` to the variable context (if available)
        3. Create the string content with Jinja2 (passing it the variable context)
        4. If the substitution is inline and not a directive,
           parse to nodes ignoring block syntaxes (like lists or block-quotes),
           otherwise parse to nodes with all syntax rules.

        """
        position = token_line(token)

        # front-matter substitutions take priority over config ones
        variable_context = {
            **self.config.get("myst_substitutions", {}),
            **getattr(self.document, "fm_substitutions", {}),
        }
        if self.sphinx_env is not None:
            variable_context["env"] = self.sphinx_env

        # fail on undefined variables
        env = jinja2.Environment(undefined=jinja2.StrictUndefined)

        # try rendering
        try:
            rendered = env.from_string(f"{{{{{token.content}}}}}").render(
                variable_context
            )
        except Exception as error:
            error_msg = self.reporter.error(
                f"Substitution error:{error.__class__.__name__}: {error}",
                line=position,
            )
            self.current_node += [error_msg]
            return

        # handle circular references
        ast = env.parse(f"{{{{{token.content}}}}}")
        references = {
            n.name for n in ast.find_all(jinja2.nodes.Name) if n.name != "env"
        }
        self.document.sub_references = getattr(self.document, "sub_references", set())
        cyclic = references.intersection(self.document.sub_references)
        if cyclic:
            error_msg = self.reporter.error(
                f"circular substitution reference: {cyclic}",
                line=position,
            )
            self.current_node += [error_msg]
            return

        # parse rendered text
        state_machine = MockStateMachine(self, position)
        state = MockState(self, state_machine, position)

        # TODO improve error reporting;
        # at present, for a multi-line substitution,
        # an error may point to a line lower than the substitution
        # should it point to the source of the substitution?
        # or the error message should at least indicate that its a substitution

        # we record used references before nested parsing, then remove them after
        self.document.sub_references.update(references)

        try:
            if inline and not REGEX_DIRECTIVE_START.match(rendered):
                sub_nodes, _ = state.inline_text(rendered, position)
            else:
                base_node = nodes.Element()
                state.nested_parse(
                    StringList(rendered.splitlines(), self.document["source"]),
                    0,
                    base_node,
                )
                sub_nodes = base_node.children
        finally:
            self.document.sub_references.difference_update(references)

        self.current_node.extend(sub_nodes)


def html_meta_to_nodes(
    data: Dict[str, Any], document: nodes.document, line: int, reporter: Reporter
) -> List[Union[nodes.pending, nodes.system_message]]:
    """Replicate the `meta` directive,
    by converting a dictionary to a list of pending meta nodes

    See:
    https://www.sphinx-doc.org/en/master/usage/restructuredtext/basics.html#html-metadata
    """
    if not data:
        return []

    try:
        from sphinx.addnodes import meta as meta_cls
    except ImportError:
        from docutils.parsers.rst.directives.html import MetaBody

        meta_cls = MetaBody.meta  # type: ignore

    output = []

    for key, value in data.items():
        content = str(value or "")
        meta_node = meta_cls(content)
        meta_node.source = document["source"]
        meta_node.line = line
        meta_node["content"] = content
        try:
            if not content:
                raise ValueError("No content")
            for i, key_part in enumerate(key.split()):
                if "=" not in key_part and i == 0:
                    meta_node["name"] = key_part
                    continue
                if "=" not in key_part:
                    raise ValueError(f"no '=' in {key_part}")
                attr_name, attr_val = key_part.split("=", 1)
                if not (attr_name and attr_val):
                    raise ValueError(f"malformed {key_part}")
                meta_node[attr_name.lower()] = attr_val
        except ValueError as error:
            msg = reporter.error(f'Error parsing meta tag attribute "{key}": {error}.')
            output.append(msg)
            continue

        pending = nodes.pending(
            Filter,
            {"component": "writer", "format": "html", "nodes": [meta_node]},
        )
        document.note_pending(pending)
        output.append(pending)

    return output