Refactor test utilities to improve names

1 files changed, 1275 insertions, 0 deletions

diff --git a/tests/test_utils/mdast_util_to_hast.rs b/tests/test_utils/mdast_util_to_hast.rs
new file mode 100644
index 0000000..c07d15b
--- /dev/null
+++ b/tests/test_utils/mdast_util_to_hast.rs
@@ -0,0 +1,1275 @@
+//! Turn a markdown AST into an HTML AST.
+//!
+//! Port of <https://github.com/syntax-tree/mdast-util-to-hast>, by the same
+//! author:
+//!
+//! (The MIT License)
+//!
+//! Copyright (c) 2016 Titus Wormer <tituswormer@gmail.com>
+//!
+//! Permission is hereby granted, free of charge, to any person obtaining
+//! a copy of this software and associated documentation files (the
+//! 'Software'), to deal in the Software without restriction, including
+//! without limitation the rights to use, copy, modify, merge, publish,
+//! distribute, sublicense, and/or sell copies of the Software, and to
+//! permit persons to whom the Software is furnished to do so, subject to
+//! the following conditions:
+//!
+//! The above copyright notice and this permission notice shall be
+//! included in all copies or substantial portions of the Software.
+//!
+//! THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,
+//! EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+//! MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+//! IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+//! CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+//! TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+//! SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+use crate::test_utils::hast;
+use micromark::{mdast, sanitize, unist::Position};
+
+// To do: support these compile options:
+// ```
+// pub gfm_footnote_label: Option<String>,
+// pub gfm_footnote_label_tag_name: Option<String>,
+// pub gfm_footnote_label_attributes: Option<String>,
+// pub gfm_footnote_back_label: Option<String>,
+// pub gfm_footnote_clobber_prefix: Option<String>,
+// ```
+//
+// Maybe also:
+// * option to persist `meta`?
+// * option to generate a `style` attribute instead of `align`?
+// * support `Raw` nodes for HTML?
+//
+// To do:
+// * revert references when undefined?
+//   <https://github.com/syntax-tree/mdast-util-to-hast/blob/c393d0a/lib/revert.js>
+
+#[derive(Debug)]
+struct State {
+    definitions: Vec<(String, String, Option<String>)>,
+    footnote_definitions: Vec<(String, Vec<hast::Node>)>,
+    footnote_calls: Vec<(String, usize)>,
+}
+
+#[derive(Debug)]
+enum Result {
+    Fragment(Vec<hast::Node>),
+    Node(hast::Node),
+    None,
+}
+
+#[allow(dead_code)]
+pub fn mdast_util_to_hast(mdast: &mdast::Node) -> hast::Node {
+    let mut definitions = vec![];
+
+    // Collect definitions.
+    // Calls take info from their definition.
+    // Calls can come come before definitions.
+    // Footnote calls can also come before footnote definitions, but those
+    // calls *do not* take info from their definitions, so we don’t care
+    // about footnotes here.
+    visit(mdast, |node| {
+        if let mdast::Node::Definition(definition) = node {
+            definitions.push((
+                definition.identifier.clone(),
+                definition.url.clone(),
+                definition.title.clone(),
+            ));
+        }
+    });
+
+    let mut state = State {
+        definitions,
+        footnote_definitions: vec![],
+        footnote_calls: vec![],
+    };
+
+    let result = one(&mut state, mdast, None);
+
+    if state.footnote_calls.is_empty() {
+        if let Result::Node(node) = result {
+            return node;
+        }
+    }
+
+    // We either have to generate a footer, or we don’t have a single node.
+    // So we need a root.
+    let mut root = hast::Root {
+        children: vec![],
+        position: None,
+    };
+
+    match result {
+        Result::Fragment(children) => root.children = children,
+        Result::Node(node) => {
+            if let hast::Node::Root(existing) = node {
+                root = existing;
+            } else {
+                root.children.push(node);
+            }
+        }
+        Result::None => {}
+    }
+
+    if !state.footnote_calls.is_empty() {
+        let mut items = vec![];
+
+        let mut index = 0;
+        while index < state.footnote_calls.len() {
+            let (id, count) = &state.footnote_calls[index];
+            let safe_id = sanitize(&id.to_lowercase());
+
+            // Find definition: we’ll always find it.
+            let mut definition_index = 0;
+            while definition_index < state.footnote_definitions.len() {
+                if &state.footnote_definitions[definition_index].0 == id {
+                    break;
+                }
+                definition_index += 1;
+            }
+            debug_assert_ne!(
+                definition_index,
+                state.footnote_definitions.len(),
+                "expected definition"
+            );
+
+            // We’ll find each used definition once, so we can split off to take the content.
+            let mut content = state.footnote_definitions[definition_index].1.split_off(0);
+
+            let mut reference_index = 0;
+            let mut backreferences = vec![];
+            while reference_index < *count {
+                let mut backref_children = vec![hast::Node::Text(hast::Text {
+                    value: "↩".into(),
+                    position: None,
+                })];
+
+                if reference_index != 0 {
+                    backreferences.push(hast::Node::Text(hast::Text {
+                        value: " ".into(),
+                        position: None,
+                    }));
+
+                    backref_children.push(hast::Node::Element(hast::Element {
+                        tag_name: "sup".into(),
+                        properties: vec![],
+                        children: vec![hast::Node::Text(hast::Text {
+                            value: (reference_index + 1).to_string(),
+                            position: None,
+                        })],
+                        position: None,
+                    }));
+                }
+
+                backreferences.push(hast::Node::Element(hast::Element {
+                    tag_name: "a".into(),
+                    properties: vec![
+                        (
+                            "href".into(),
+                            hast::PropertyValue::String(format!(
+                                "#fnref-{}{}",
+                                safe_id,
+                                if reference_index == 0 {
+                                    "".into()
+                                } else {
+                                    format!("-{}", &(reference_index + 1).to_string())
+                                }
+                            )),
+                        ),
+                        (
+                            "dataFootnoteBackref".into(),
+                            hast::PropertyValue::Boolean(true),
+                        ),
+                        (
+                            "ariaLabel".into(),
+                            hast::PropertyValue::String("Back to content".into()),
+                        ),
+                        (
+                            "className".into(),
+                            hast::PropertyValue::SpaceSeparated(vec![
+                                "data-footnote-backref".into()
+                            ]),
+                        ),
+                    ],
+                    children: backref_children,
+                    position: None,
+                }));
+
+                reference_index += 1;
+            }
+
+            let mut backreference_opt = Some(backreferences);
+
+            if let Some(hast::Node::Element(tail_element)) = content.last_mut() {
+                if tail_element.tag_name == "p" {
+                    if let Some(hast::Node::Text(text)) = tail_element.children.last_mut() {
+                        text.value.push(' ');
+                    } else {
+                        tail_element.children.push(hast::Node::Text(hast::Text {
+                            value: " ".into(),
+                            position: None,
+                        }));
+                    }
+
+                    tail_element
+                        .children
+                        .append(&mut backreference_opt.take().unwrap());
+                }
+            }
+
+            // No paragraph, just push them.
+            if let Some(mut backreference) = backreference_opt {
+                content.append(&mut backreference);
+            }
+
+            items.push(hast::Node::Element(hast::Element {
+                tag_name: "li".into(),
+                properties: vec![(
+                    "id".into(),
+                    hast::PropertyValue::String(format!("#fn-{}", safe_id)),
+                )],
+                children: wrap(content, true),
+                position: None,
+            }));
+            index += 1;
+        }
+
+        root.children.push(hast::Node::Text(hast::Text {
+            value: "\n".into(),
+            position: None,
+        }));
+        root.children.push(hast::Node::Element(hast::Element {
+            tag_name: "section".into(),
+            properties: vec![
+                ("dataFootnotes".into(), hast::PropertyValue::Boolean(true)),
+                (
+                    "className".into(),
+                    hast::PropertyValue::SpaceSeparated(vec!["footnotes".into()]),
+                ),
+            ],
+            children: vec![
+                hast::Node::Element(hast::Element {
+                    tag_name: "h2".into(),
+                    properties: vec![
+                        (
+                            "id".into(),
+                            hast::PropertyValue::String("footnote-label".into()),
+                        ),
+                        (
+                            "className".into(),
+                            hast::PropertyValue::SpaceSeparated(vec!["sr-only".into()]),
+                        ),
+                    ],
+                    children: vec![hast::Node::Text(hast::Text {
+                        value: "Footnotes".into(),
+                        position: None,
+                    })],
+                    position: None,
+                }),
+                hast::Node::Text(hast::Text {
+                    value: "\n".into(),
+                    position: None,
+                }),
+                hast::Node::Element(hast::Element {
+                    tag_name: "ol".into(),
+                    properties: vec![],
+                    children: wrap(items, true),
+                    position: None,
+                }),
+                hast::Node::Text(hast::Text {
+                    value: "\n".into(),
+                    position: None,
+                }),
+            ],
+            position: None,
+        }));
+        root.children.push(hast::Node::Text(hast::Text {
+            value: "\n".into(),
+            position: None,
+        }));
+    }
+
+    hast::Node::Root(root)
+}
+
+fn one(state: &mut State, node: &mdast::Node, parent: Option<&mdast::Node>) -> Result {
+    match node {
+        mdast::Node::BlockQuote(d) => transform_block_quote(state, node, d),
+        mdast::Node::Break(d) => transform_break(state, node, d),
+        mdast::Node::Code(d) => transform_code(state, node, d),
+        mdast::Node::Delete(d) => transform_delete(state, node, d),
+        mdast::Node::Emphasis(d) => transform_emphasis(state, node, d),
+        mdast::Node::FootnoteDefinition(d) => transform_footnote_definition(state, node, d),
+        mdast::Node::FootnoteReference(d) => transform_footnote_reference(state, node, d),
+        mdast::Node::Heading(d) => transform_heading(state, node, d),
+        mdast::Node::Image(d) => transform_image(state, node, d),
+        mdast::Node::ImageReference(d) => transform_image_reference(state, node, d),
+        mdast::Node::InlineCode(d) => transform_inline_code(state, node, d),
+        mdast::Node::InlineMath(d) => transform_inline_math(state, node, d),
+        mdast::Node::Link(d) => transform_link(state, node, d),
+        mdast::Node::LinkReference(d) => transform_link_reference(state, node, d),
+        mdast::Node::ListItem(d) => transform_list_item(state, node, parent, d),
+        mdast::Node::List(d) => transform_list(state, node, d),
+        mdast::Node::Math(d) => transform_math(state, node, d),
+        mdast::Node::MdxFlowExpression(_) | mdast::Node::MdxTextExpression(_) => {
+            transform_mdx_expression(state, node)
+        }
+        mdast::Node::MdxJsxFlowElement(_) | mdast::Node::MdxJsxTextElement(_) => {
+            transform_mdx_jsx_element(state, node)
+        }
+        mdast::Node::MdxjsEsm(d) => transform_mdxjs_esm(state, node, d),
+        mdast::Node::Paragraph(d) => transform_paragraph(state, node, d),
+        mdast::Node::Root(d) => transform_root(state, node, d),
+        mdast::Node::Strong(d) => transform_strong(state, node, d),
+        // Note: this is only called here if there is a single cell passed, not when one is found in a table.
+        mdast::Node::TableCell(d) => {
+            transform_table_cell(state, node, false, mdast::AlignKind::None, d)
+        }
+        // Note: this is only called here if there is a single row passed, not when one is found in a table.
+        mdast::Node::TableRow(d) => transform_table_row(state, node, false, None, d),
+        mdast::Node::Table(d) => transform_table(state, node, d),
+        mdast::Node::Text(d) => transform_text(state, node, d),
+        mdast::Node::ThematicBreak(d) => transform_thematic_break(state, node, d),
+        // Ignore.
+        mdast::Node::Definition(_)
+        | mdast::Node::Html(_)
+        | mdast::Node::Yaml(_)
+        | mdast::Node::Toml(_) => Result::None,
+    }
+}
+
+/// [`BlockQuote`][mdast::BlockQuote].
+fn transform_block_quote(
+    state: &mut State,
+    node: &mdast::Node,
+    block_quote: &mdast::BlockQuote,
+) -> Result {
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: "blockquote".into(),
+        properties: vec![],
+        children: wrap(all(state, node), true),
+        position: block_quote.position.clone(),
+    }))
+}
+
+/// [`Break`][mdast::Break].
+fn transform_break(_state: &mut State, _node: &mdast::Node, break_: &mdast::Break) -> Result {
+    Result::Fragment(vec![
+        hast::Node::Element(hast::Element {
+            tag_name: "br".into(),
+            properties: vec![],
+            children: vec![],
+            position: break_.position.clone(),
+        }),
+        hast::Node::Text(hast::Text {
+            value: "\n".into(),
+            position: None,
+        }),
+    ])
+}
+
+/// [`Code`][mdast::Code].
+fn transform_code(_state: &mut State, _node: &mdast::Node, code: &mdast::Code) -> Result {
+    let mut value = code.value.clone();
+    value.push('\n');
+    let mut properties = vec![];
+
+    if let Some(lang) = code.lang.as_ref() {
+        properties.push((
+            "className".into(),
+            hast::PropertyValue::SpaceSeparated(vec![format!("language-{}", lang)]),
+        ));
+    }
+
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: "pre".into(),
+        properties: vec![],
+        children: vec![hast::Node::Element(hast::Element {
+            tag_name: "code".into(),
+            properties,
+            children: vec![hast::Node::Text(hast::Text {
+                value,
+                position: None,
+            })],
+            position: code.position.clone(),
+        })],
+        position: code.position.clone(),
+    }))
+}
+
+/// [`Delete`][mdast::Delete].
+fn transform_delete(state: &mut State, node: &mdast::Node, delete: &mdast::Delete) -> Result {
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: "del".into(),
+        properties: vec![],
+        children: all(state, node),
+        position: delete.position.clone(),
+    }))
+}
+
+/// [`Emphasis`][mdast::Emphasis].
+fn transform_emphasis(state: &mut State, node: &mdast::Node, emphasis: &mdast::Emphasis) -> Result {
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: "em".into(),
+        properties: vec![],
+        children: all(state, node),
+        position: emphasis.position.clone(),
+    }))
+}
+
+/// [`FootnoteDefinition`][mdast::FootnoteDefinition].
+fn transform_footnote_definition(
+    state: &mut State,
+    node: &mdast::Node,
+    footnote_definition: &mdast::FootnoteDefinition,
+) -> Result {
+    let children = all(state, node);
+    // Set aside.
+    state
+        .footnote_definitions
+        .push((footnote_definition.identifier.clone(), children));
+    Result::None
+}
+
+/// [`FootnoteReference`][mdast::FootnoteReference].
+fn transform_footnote_reference(
+    state: &mut State,
+    _node: &mdast::Node,
+    footnote_reference: &mdast::FootnoteReference,
+) -> Result {
+    let safe_id = sanitize(&footnote_reference.identifier.to_lowercase());
+    let mut call_index = 0;
+
+    // See if this has been called before.
+    while call_index < state.footnote_calls.len() {
+        if state.footnote_calls[call_index].0 == footnote_reference.identifier {
+            break;
+        }
+        call_index += 1;
+    }
+
+    // New.
+    if call_index == state.footnote_calls.len() {
+        state
+            .footnote_calls
+            .push((footnote_reference.identifier.clone(), 0));
+    }
+
+    // Increment.
+    state.footnote_calls[call_index].1 += 1;
+
+    let reuse_counter = state.footnote_calls[call_index].1;
+
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: "sup".into(),
+        properties: vec![],
+        children: vec![hast::Node::Element(hast::Element {
+            tag_name: "a".into(),
+            properties: vec![
+                (
+                    "href".into(),
+                    hast::PropertyValue::String(format!("#fn-{}", safe_id)),
+                ),
+                (
+                    "id".into(),
+                    hast::PropertyValue::String(format!(
+                        "fnref-{}{}",
+                        safe_id,
+                        if reuse_counter > 1 {
+                            format!("-{}", reuse_counter)
+                        } else {
+                            "".into()
+                        }
+                    )),
+                ),
+                ("dataFootnoteRef".into(), hast::PropertyValue::Boolean(true)),
+                (
+                    "ariaDescribedBy".into(),
+                    hast::PropertyValue::String("footnote-label".into()),
+                ),
+            ],
+            children: vec![hast::Node::Text(hast::Text {
+                value: (call_index + 1).to_string(),
+                position: None,
+            })],
+            position: None,
+        })],
+        position: footnote_reference.position.clone(),
+    }))
+}
+
+/// [`Heading`][mdast::Heading].
+fn transform_heading(state: &mut State, node: &mdast::Node, heading: &mdast::Heading) -> Result {
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: format!("h{}", heading.depth),
+        properties: vec![],
+        children: all(state, node),
+        position: heading.position.clone(),
+    }))
+}
+
+/// [`Image`][mdast::Image].
+fn transform_image(_state: &mut State, _node: &mdast::Node, image: &mdast::Image) -> Result {
+    let mut properties = vec![];
+
+    properties.push((
+        "src".into(),
+        hast::PropertyValue::String(sanitize(&image.url)),
+    ));
+
+    properties.push(("alt".into(), hast::PropertyValue::String(image.alt.clone())));
+
+    if let Some(value) = image.title.as_ref() {
+        properties.push(("title".into(), hast::PropertyValue::String(value.into())));
+    }
+
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: "img".into(),
+        properties,
+        children: vec![],
+        position: image.position.clone(),
+    }))
+}
+
+/// [`ImageReference`][mdast::ImageReference].
+fn transform_image_reference(
+    state: &mut State,
+    _node: &mdast::Node,
+    image_reference: &mdast::ImageReference,
+) -> Result {
+    let mut properties = vec![];
+
+    let definition = state
+        .definitions
+        .iter()
+        .find(|d| d.0 == image_reference.identifier);
+
+    let (_, url, title) =
+        definition.expect("expected reference to have a corresponding definition");
+
+    properties.push(("src".into(), hast::PropertyValue::String(sanitize(url))));
+
+    properties.push((
+        "alt".into(),
+        hast::PropertyValue::String(image_reference.alt.clone()),
+    ));
+
+    if let Some(value) = title {
+        properties.push(("title".into(), hast::PropertyValue::String(value.into())));
+    }
+
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: "img".into(),
+        properties,
+        children: vec![],
+        position: image_reference.position.clone(),
+    }))
+}
+
+/// [`InlineCode`][mdast::InlineCode].
+fn transform_inline_code(
+    _state: &mut State,
+    _node: &mdast::Node,
+    inline_code: &mdast::InlineCode,
+) -> Result {
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: "code".into(),
+        properties: vec![],
+        children: vec![hast::Node::Text(hast::Text {
+            value: replace_eols_with_spaces(&inline_code.value),
+            position: None,
+        })],
+        position: inline_code.position.clone(),
+    }))
+}
+
+/// [`InlineMath`][mdast::InlineMath].
+fn transform_inline_math(
+    _state: &mut State,
+    _node: &mdast::Node,
+    inline_math: &mdast::InlineMath,
+) -> Result {
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: "code".into(),
+        properties: vec![(
+            "className".into(),
+            hast::PropertyValue::SpaceSeparated(vec!["language-math".into(), "math-inline".into()]),
+        )],
+        children: vec![hast::Node::Text(hast::Text {
+            value: replace_eols_with_spaces(&inline_math.value),
+            position: None,
+        })],
+        position: inline_math.position.clone(),
+    }))
+}
+
+/// [`Link`][mdast::Link].
+fn transform_link(state: &mut State, node: &mdast::Node, link: &mdast::Link) -> Result {
+    let mut properties = vec![];
+
+    properties.push((
+        "href".into(),
+        hast::PropertyValue::String(sanitize(&link.url)),
+    ));
+
+    if let Some(value) = link.title.as_ref() {
+        properties.push(("title".into(), hast::PropertyValue::String(value.into())));
+    }
+
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: "a".into(),
+        properties,
+        children: all(state, node),
+        position: link.position.clone(),
+    }))
+}
+
+/// [`LinkReference`][mdast::LinkReference].
+fn transform_link_reference(
+    state: &mut State,
+    node: &mdast::Node,
+    link_reference: &mdast::LinkReference,
+) -> Result {
+    let mut properties = vec![];
+
+    let definition = state
+        .definitions
+        .iter()
+        .find(|d| d.0 == link_reference.identifier);
+
+    let (_, url, title) =
+        definition.expect("expected reference to have a corresponding definition");
+
+    properties.push(("href".into(), hast::PropertyValue::String(sanitize(url))));
+
+    if let Some(value) = title {
+        properties.push(("title".into(), hast::PropertyValue::String(value.into())));
+    }
+
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: "a".into(),
+        properties,
+        children: all(state, node),
+        position: link_reference.position.clone(),
+    }))
+}
+
+/// [`ListItem`][mdast::ListItem].
+fn transform_list_item(
+    state: &mut State,
+    node: &mdast::Node,
+    parent: Option<&mdast::Node>,
+    list_item: &mdast::ListItem,
+) -> Result {
+    let mut children = all(state, node);
+    let mut loose = list_item_loose(node);
+
+    if let Some(parent) = parent {
+        if matches!(parent, mdast::Node::List(_)) {
+            loose = list_loose(parent);
+        }
+    };
+
+    let mut properties = vec![];
+
+    // Inject a checkbox.
+    if let Some(checked) = list_item.checked {
+        // According to github-markdown-css, this class hides bullet.
+        // See: <https://github.com/sindresorhus/github-markdown-css>.
+        properties.push((
+            "className".into(),
+            hast::PropertyValue::SpaceSeparated(vec!["task-list-item".into()]),
+        ));
+
+        let mut input = Some(hast::Node::Element(hast::Element {
+            tag_name: "input".into(),
+            properties: vec![
+                (
+                    "type".into(),
+                    hast::PropertyValue::String("checkbox".into()),
+                ),
+                ("checked".into(), hast::PropertyValue::Boolean(checked)),
+                ("disabled".into(), hast::PropertyValue::Boolean(true)),
+            ],
+            children: vec![],
+            position: None,
+        }));
+
+        if let Some(hast::Node::Element(x)) = children.first_mut() {
+            if x.tag_name == "p" {
+                if !x.children.is_empty() {
+                    x.children.insert(
+                        0,
+                        hast::Node::Text(hast::Text {
+                            value: " ".into(),
+                            position: None,
+                        }),
+                    );
+                }
+
+                x.children.insert(0, input.take().unwrap());
+            }
+        }
+
+        // If the input wasn‘t injected yet, inject a paragraph.
+        if let Some(input) = input {
+            children.insert(
+                0,
+                hast::Node::Element(hast::Element {
+                    tag_name: "p".into(),
+                    properties: vec![],
+                    children: vec![input],
+                    position: None,
+                }),
+            );
+        }
+    }
+
+    children.reverse();
+    let mut result = vec![];
+    let mut head = true;
+    let empty = children.is_empty();
+    let mut tail_p = false;
+
+    while let Some(child) = children.pop() {
+        let mut is_p = false;
+        if let hast::Node::Element(el) = &child {
+            if el.tag_name == "p" {
+                is_p = true;
+            }
+        }
+
+        // Add eols before nodes, except if this is a tight, first paragraph.
+        if loose || !head || !is_p {
+            result.push(hast::Node::Text(hast::Text {
+                value: "\n".into(),
+                position: None,
+            }));
+        }
+
+        if is_p && !loose {
+            // Unwrap the paragraph.
+            if let hast::Node::Element(mut el) = child {
+                result.append(&mut el.children);
+            }
+        } else {
+            result.push(child);
+        }
+
+        head = false;
+        tail_p = is_p;
+    }
+
+    // Add eol after last node, except if it is tight or a paragraph.
+    if !empty && (loose || !tail_p) {
+        result.push(hast::Node::Text(hast::Text {
+            value: "\n".into(),
+            position: None,
+        }));
+    }
+
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: "li".into(),
+        properties,
+        children: result,
+        position: list_item.position.clone(),
+    }))
+}
+
+/// [`List`][mdast::List].
+fn transform_list(state: &mut State, node: &mdast::Node, list: &mdast::List) -> Result {
+    let mut contains_task_list = false;
+    let mut index = 0;
+
+    while index < list.children.len() {
+        if let mdast::Node::ListItem(item) = &list.children[index] {
+            if item.checked.is_some() {
+                contains_task_list = true;
+            }
+        }
+
+        index += 1;
+    }
+
+    let mut properties = vec![];
+
+    // Add start.
+    if let Some(start) = list.start {
+        if list.ordered && start != 1 {
+            properties.push((
+                "start".into(),
+                hast::PropertyValue::String(start.to_string()),
+            ));
+        }
+    }
+
+    // Like GitHub, add a class for custom styling.
+    if contains_task_list {
+        properties.push((
+            "className".into(),
+            hast::PropertyValue::SpaceSeparated(vec!["contains-task-list".into()]),
+        ));
+    }
+
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: if list.ordered {
+            "ol".into()
+        } else {
+            "ul".into()
+        },
+        properties,
+        children: wrap(all(state, node), true),
+        position: list.position.clone(),
+    }))
+}
+
+/// [`Math`][mdast::Math].
+fn transform_math(_state: &mut State, _node: &mdast::Node, math: &mdast::Math) -> Result {
+    let mut value = math.value.clone();
+    value.push('\n');
+
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: "pre".into(),
+        properties: vec![],
+        children: vec![hast::Node::Element(hast::Element {
+            tag_name: "code".into(),
+            properties: vec![(
+                "className".into(),
+                hast::PropertyValue::SpaceSeparated(vec![
+                    "language-math".into(),
+                    "math-display".into(),
+                ]),
+            )],
+            children: vec![hast::Node::Text(hast::Text {
+                value,
+                position: None,
+            })],
+            position: math.position.clone(),
+        })],
+        position: math.position.clone(),
+    }))
+}
+
+/// [`MdxFlowExpression`][mdast::MdxFlowExpression],[`MdxTextExpression`][mdast::MdxTextExpression].
+fn transform_mdx_expression(_state: &mut State, node: &mdast::Node) -> Result {
+    match node {
+        mdast::Node::MdxFlowExpression(node) => {
+            Result::Node(hast::Node::MdxExpression(hast::MdxExpression {
+                value: node.value.clone(),
+                position: node.position.clone(),
+                stops: node.stops.clone(),
+            }))
+        }
+        mdast::Node::MdxTextExpression(node) => {
+            Result::Node(hast::Node::MdxExpression(hast::MdxExpression {
+                value: node.value.clone(),
+                position: node.position.clone(),
+                stops: node.stops.clone(),
+            }))
+        }
+        _ => unreachable!("expected expression"),
+    }
+}
+
+/// [`MdxJsxFlowElement`][mdast::MdxJsxFlowElement],[`MdxJsxTextElement`][mdast::MdxJsxTextElement].
+fn transform_mdx_jsx_element(state: &mut State, node: &mdast::Node) -> Result {
+    let (name, attributes) = match node {
+        mdast::Node::MdxJsxFlowElement(n) => (&n.name, &n.attributes),
+        mdast::Node::MdxJsxTextElement(n) => (&n.name, &n.attributes),
+        _ => unreachable!("expected mdx jsx element"),
+    };
+
+    Result::Node(hast::Node::MdxJsxElement(hast::MdxJsxElement {
+        name: name.clone(),
+        attributes: attributes.clone(),
+        children: all(state, node),
+        position: node.position().cloned(),
+    }))
+}
+
+/// [`MdxjsEsm`][mdast::MdxjsEsm].
+fn transform_mdxjs_esm(
+    _state: &mut State,
+    _node: &mdast::Node,
+    mdxjs_esm: &mdast::MdxjsEsm,
+) -> Result {
+    Result::Node(hast::Node::MdxjsEsm(hast::MdxjsEsm {
+        value: mdxjs_esm.value.clone(),
+        position: mdxjs_esm.position.clone(),
+        stops: mdxjs_esm.stops.clone(),
+    }))
+}
+
+/// [`Paragraph`][mdast::Paragraph].
+fn transform_paragraph(
+    state: &mut State,
+    node: &mdast::Node,
+    paragraph: &mdast::Paragraph,
+) -> Result {
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: "p".into(),
+        properties: vec![],
+        children: all(state, node),
+        position: paragraph.position.clone(),
+    }))
+}
+
+/// [`Root`][mdast::Root].
+fn transform_root(state: &mut State, node: &mdast::Node, root: &mdast::Root) -> Result {
+    Result::Node(hast::Node::Root(hast::Root {
+        children: wrap(all(state, node), false),
+        position: root.position.clone(),
+    }))
+}
+
+/// [`Strong`][mdast::Strong].
+fn transform_strong(state: &mut State, node: &mdast::Node, strong: &mdast::Strong) -> Result {
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: "strong".into(),
+        properties: vec![],
+        children: all(state, node),
+        position: strong.position.clone(),
+    }))
+}
+
+/// [`TableCell`][mdast::TableCell].
+fn transform_table_cell(
+    state: &mut State,
+    node: &mdast::Node,
+    head: bool,
+    align: mdast::AlignKind,
+    table_cell: &mdast::TableCell,
+) -> Result {
+    let align_value = match align {
+        mdast::AlignKind::None => None,
+        mdast::AlignKind::Left => Some("left"),
+        mdast::AlignKind::Right => Some("right"),
+        mdast::AlignKind::Center => Some("center"),
+    };
+
+    let mut properties = vec![];
+
+    if let Some(value) = align_value {
+        properties.push(("align".into(), hast::PropertyValue::String(value.into())));
+    }
+
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: if head { "th".into() } else { "td".into() },
+        properties,
+        children: all(state, node),
+        position: table_cell.position.clone(),
+    }))
+}
+
+/// [`TableRow`][mdast::TableRow].
+fn transform_table_row(
+    state: &mut State,
+    _node: &mdast::Node,
+    head: bool,
+    align: Option<&[mdast::AlignKind]>,
+    table_row: &mdast::TableRow,
+) -> Result {
+    let mut children = vec![];
+    let mut index = 0;
+    #[allow(clippy::redundant_closure_for_method_calls)]
+    let len = align.map_or(table_row.children.len(), |d| d.len());
+    let empty_cell = mdast::Node::TableCell(mdast::TableCell {
+        children: vec![],
+        position: None,
+    });
+
+    while index < len {
+        let align_value = align
+            .and_then(|d| d.get(index))
+            .unwrap_or(&mdast::AlignKind::None);
+
+        let child = table_row.children.get(index).unwrap_or(&empty_cell);
+
+        let result = if let mdast::Node::TableCell(table_cell) = child {
+            transform_table_cell(state, child, head, *align_value, table_cell)
+        } else {
+            unreachable!("expected tale cell in table row")
+        };
+
+        append_result(&mut children, result);
+        index += 1;
+    }
+
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: "tr".into(),
+        properties: vec![],
+        children: wrap(children, true),
+        position: table_row.position.clone(),
+    }))
+}
+
+/// [`Table`][mdast::Table].
+fn transform_table(state: &mut State, _node: &mdast::Node, table: &mdast::Table) -> Result {
+    let mut rows = vec![];
+    let mut index = 0;
+
+    while index < table.children.len() {
+        let child = &table.children[index];
+        let result = if let mdast::Node::TableRow(table_row) = child {
+            transform_table_row(
+                state,
+                &table.children[index],
+                index == 0,
+                Some(&table.align),
+                table_row,
+            )
+        } else {
+            unreachable!("expected table row as child of table")
+        };
+
+        append_result(&mut rows, result);
+        index += 1;
+    }
+
+    let body_rows = rows.split_off(1);
+    let head_row = rows.pop();
+    let mut children = vec![];
+
+    if let Some(row) = head_row {
+        let position = row.position().cloned();
+        children.push(hast::Node::Element(hast::Element {
+            tag_name: "thead".into(),
+            properties: vec![],
+            children: wrap(vec![row], true),
+            position,
+        }));
+    }
+
+    if !body_rows.is_empty() {
+        let mut position = None;
+
+        if let Some(position_start) = body_rows.first().and_then(hast::Node::position) {
+            if let Some(position_end) = body_rows.last().and_then(hast::Node::position) {
+                position = Some(Position {
+                    start: position_start.start.clone(),
+                    end: position_end.end.clone(),
+                });
+            }
+        }
+
+        children.push(hast::Node::Element(hast::Element {
+            tag_name: "tbody".into(),
+            properties: vec![],
+            children: wrap(body_rows, true),
+            position,
+        }));
+    }
+
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: "table".into(),
+        properties: vec![],
+        children: wrap(children, true),
+        position: table.position.clone(),
+    }))
+}
+
+/// [`Text`][mdast::Text].
+fn transform_text(_state: &mut State, _node: &mdast::Node, text: &mdast::Text) -> Result {
+    Result::Node(hast::Node::Text(hast::Text {
+        value: text.value.clone(),
+        position: text.position.clone(),
+    }))
+}
+
+/// [`ThematicBreak`][mdast::ThematicBreak].
+fn transform_thematic_break(
+    _state: &mut State,
+    _node: &mdast::Node,
+    thematic_break: &mdast::ThematicBreak,
+) -> Result {
+    Result::Node(hast::Node::Element(hast::Element {
+        tag_name: "hr".into(),
+        properties: vec![],
+        children: vec![],
+        position: thematic_break.position.clone(),
+    }))
+}
+
+// Transform children of `parent`.
+fn all(state: &mut State, parent: &mdast::Node) -> Vec<hast::Node> {
+    let mut nodes = vec![];
+    if let Some(children) = parent.children() {
+        let mut index = 0;
+        while index < children.len() {
+            let child = &children[index];
+            let result = one(state, child, Some(parent));
+            append_result(&mut nodes, result);
+            index += 1;
+        }
+    }
+
+    nodes
+}
+
+/// Wrap `nodes` with line feeds between each entry.
+/// Optionally adds line feeds at the start and end.
+fn wrap(mut nodes: Vec<hast::Node>, loose: bool) -> Vec<hast::Node> {
+    let mut result = vec![];
+    let was_empty = nodes.is_empty();
+    let mut head = true;
+
+    nodes.reverse();
+
+    if loose {
+        result.push(hast::Node::Text(hast::Text {
+            value: "\n".into(),
+            position: None,
+        }));
+    }
+
+    while let Some(item) = nodes.pop() {
+        // Inject when there’s more:
+        if !head {
+            result.push(hast::Node::Text(hast::Text {
+                value: "\n".into(),
+                position: None,
+            }));
+        }
+        head = false;
+        result.push(item);
+    }
+
+    if loose && !was_empty {
+        result.push(hast::Node::Text(hast::Text {
+            value: "\n".into(),
+            position: None,
+        }));
+    }
+
+    result
+}
+
+/// Visit.
+fn visit<Visitor>(node: &mdast::Node, visitor: Visitor)
+where
+    Visitor: FnMut(&mdast::Node),
+{
+    visit_impl(node, visitor);
+}
+
+/// Visit, mutably.
+// Probably useful later:
+#[allow(dead_code)]
+fn visit_mut<Visitor>(node: &mut mdast::Node, visitor: Visitor)
+where
+    Visitor: FnMut(&mut mdast::Node),
+{
+    visit_mut_impl(node, visitor);
+}
+
+/// Internal implementation to visit.
+fn visit_impl<Visitor>(node: &mdast::Node, mut visitor: Visitor) -> Visitor
+where
+    Visitor: FnMut(&mdast::Node),
+{
+    visitor(node);
+
+    if let Some(children) = node.children() {
+        let mut index = 0;
+        while index < children.len() {
+            let child = &children[index];
+            visitor = visit_impl(child, visitor);
+            index += 1;
+        }
+    }
+
+    visitor
+}
+
+/// Internal implementation to visit, mutably.
+fn visit_mut_impl<Visitor>(node: &mut mdast::Node, mut visitor: Visitor) -> Visitor
+where
+    Visitor: FnMut(&mut mdast::Node),
+{
+    visitor(node);
+
+    if let Some(children) = node.children_mut() {
+        let mut index = 0;
+        while let Some(child) = children.get_mut(index) {
+            visitor = visit_mut_impl(child, visitor);
+            index += 1;
+        }
+    }
+
+    visitor
+}
+
+// To do: trim arounds breaks: <https://github.com/syntax-tree/mdast-util-to-hast/blob/c393d0a/lib/traverse.js>.
+/// Append an (optional, variadic) result.
+fn append_result(list: &mut Vec<hast::Node>, result: Result) {
+    match result {
+        Result::Fragment(mut fragment) => list.append(&mut fragment),
+        Result::Node(node) => list.push(node),
+        Result::None => {}
+    };
+}
+
+/// Replace line endings (CR, LF, CRLF) with spaces.
+///
+/// Used for inline code and inline math.
+fn replace_eols_with_spaces(value: &str) -> String {
+    // It’ll grow a bit small for each CR+LF.
+    let mut result = String::with_capacity(value.len());
+    let bytes = value.as_bytes();
+    let mut index = 0;
+    let mut start = 0;
+
+    while index < bytes.len() {
+        let byte = bytes[index];
+
+        if byte == b'\r' || byte == b'\n' {
+            result.push_str(&value[start..index]);
+            result.push(' ');
+
+            if index + 1 < bytes.len() && byte == b'\r' && bytes[index + 1] == b'\n' {
+                index += 1;
+            }
+
+            start = index + 1;
+        }
+
+        index += 1;
+    }
+
+    result.push_str(&value[start..]);
+
+    result
+}
+
+/// Check if a list is loose.
+fn list_loose(node: &mdast::Node) -> bool {
+    if let mdast::Node::List(list) = node {
+        if list.spread {
+            return true;
+        }
+
+        if let Some(children) = node.children() {
+            let mut index = 0;
+            while index < children.len() {
+                if list_item_loose(&children[index]) {
+                    return true;
+                }
+                index += 1;
+            }
+        }
+    }
+
+    false
+}
+
+/// Check if a list item is loose.
+fn list_item_loose(node: &mdast::Node) -> bool {
+    if let mdast::Node::ListItem(item) = node {
+        item.spread
+    } else {
+        false
+    }
+}