10b - error reads as an error alert, 10d files the literal marker, and 10b is done

src/markdown/emit/plain-inline.ts

@@ -2,6 +2,7 @@ import type { AdfAttributes, AdfMark, AdfNode } from '../../adf/document.ts'
 import type { LineContainer } from '../line-container.ts'
 import { blockNodeModel } from '../../adf/block-nodes.ts'
 import { failure, success, type ConvertErrorPath, type Result } from '../../result.ts'
+import { highlightDelimiter } from '../plain-conventions.ts'
 import { largestNesting } from '../../nesting.ts'
 import { mergeAdjacentText, sameMark } from '../../adf/editor-normal.ts'
 import { nodeAttrs, nodeContent, nodeMarks } from '../../adf/document.ts'
@@ -9,7 +10,6 @@ import { plainLineFallback, type PlainLineFallback } from './inline-line.ts'
 import { spellDestination, spellLinkTarget } from '../commonmark/link-syntax.ts'
 
 const highlight = 'backgroundColor'
-const highlightDelimiter = '=='
 const edgeStrippingMarks: readonly string[] = [highlight, 'em', 'strike', 'strong']
 const keptMarks: readonly string[] = [...edgeStrippingMarks, 'code', 'link']
 

src/markdown/emit/plain-reduction.ts

@@ -1,5 +1,6 @@
 import type { AdfDocument, AdfNode } from '../../adf/document.ts'
 import { adfDocumentFault, nodeAttrs, nodeContent } from '../../adf/document.ts'
+import { alertMarker, foldedAlertMarker, taskMarker } from '../plain-conventions.ts'
 import { blockNodeModel } from '../../adf/block-nodes.ts'
 import { commonMarkSpelling, largestListMarker, type SpellingMemo } from './adf-to-markdown.ts'
 import { failure, faulted, success, type ConvertErrorPath, type Result } from '../../result.ts'
@@ -17,15 +18,6 @@ type PlacedCell = { colspan: number; paragraph: AdfNode; rowspan: number }
 
 type Placed = { index: number; loose: AdfNode[] } | { index: number; loose?: undefined; node: AdfNode }
 
-const alertWords: Readonly<Record<string, string>> = {
-  error: 'CAUTION',
-  info: 'NOTE',
-  note: 'IMPORTANT',
-  success: 'TIP',
-  tip: 'TIP',
-  warning: 'WARNING',
-}
-
 const blockReducers: Readonly<Record<string, BlockReducer>> = {
   blockCard: paragraphOfNode,
   blockquote: (node, reduction) => quoted(success([]), node, reduction),
@@ -41,7 +33,7 @@ const blockReducers: Readonly<Record<string, BlockReducer>> = {
   mediaSingle: (node, reduction) => concatenated(nodeContent(node).map((child, index) => reduceStanding(child, childReduction(reduction, index)))),
   nestedExpand: reduceExpand,
   orderedList: reduceList,
-  panel: (node, reduction) => quoted(success([paragraph([text(`[!${alertWord(nodeAttrs(node)['panelType'])}]`)])]), node, reduction),
+  panel: (node, reduction) => quoted(success([paragraph([text(alertMarker(nodeAttrs(node)['panelType']))])]), node, reduction),
   paragraph: (node, reduction) => paragraphOf(nodeContent(node), reduction),
   rule: () => success([{ type: 'rule' }]),
   syncBlock: paragraphOfNode,
@@ -190,14 +182,9 @@ function quoted(head: Result<AdfNode[]>, node: AdfNode, reduction: Reduction): R
   return content.ok ? success([{ content: content.value, type: 'blockquote' }]) : content
 }
 
-function alertWord(panelType: unknown): string {
-  const word = typeof panelType === 'string' && Object.hasOwn(alertWords, panelType) ? alertWords[panelType] : undefined
-  return word ?? 'NOTE'
-}
-
 function reduceExpand(node: AdfNode, reduction: Reduction): Result<AdfNode[]> {
   const title = nodeAttrs(node)['title']
-  const marker = typeof title === 'string' ? `[!NOTE]- ${title.replace(/^[ \t\n\r]+/, '')}` : '[!NOTE]-'
+  const marker = typeof title === 'string' ? `${foldedAlertMarker} ${title.replace(/^[ \t\n\r]+/, '')}` : foldedAlertMarker
   return quoted(paragraphOf([text(marker)], { ...reduction, depth: reduction.depth + 1 }), node, reduction)
 }
 
@@ -257,7 +244,7 @@ function reduceTaskList(node: AdfNode, reduction: Reduction): Result<AdfNode[]>
 }
 
 function taskBlocks(child: AdfNode, at: Reduction): Result<AdfNode[]> {
-  const marker = nodeAttrs(child)['state'] === 'DONE' ? '[x]' : '[ ]'
+  const marker = taskMarker(nodeAttrs(child)['state'])
   if (child.type === 'taskItem') {
     const content = reduceInline(nodeContent(child), 'paragraph', at.path, at.depth)
     return content.ok ? success([paragraph(content.value.length === 0 ? [text(marker)] : [text(`${marker} `), ...content.value])]) : content

src/markdown/parse/plain-lift.test.ts

@@ -0,0 +1,195 @@
+import assert from 'node:assert/strict'
+import test from 'node:test'
+
+import type { AdfAttributes, AdfDocument, AdfMark, AdfNode } from '../../adf/document.ts'
+import { adfToMarkdown } from '../emit/adf-to-markdown.ts'
+import { largestNesting } from '../../nesting.ts'
+import { liftFromPlain } from './plain-lift.ts'
+import { markdownToAdf } from './markdown-to-adf.ts'
+import { reduceToPlain } from '../emit/plain-reduction.ts'
+import { toEditorNormal } from '../../adf/editor-normal.ts'
+
+const code: AdfMark = { type: 'code' }
+const em: AdfMark = { type: 'em' }
+const highlight: AdfMark = { attrs: { color: '#f8e6a0' }, type: 'backgroundColor' }
+const strong: AdfMark = { type: 'strong' }
+
+function lifted(markdown: string): readonly AdfNode[] | string {
+  const parsed = markdownToAdf(markdown)
+  return parsed.ok ? (toEditorNormal(liftFromPlain(parsed.value)).content ?? []) : parsed.error.code
+}
+
+function normal(...blocks: AdfNode[]): readonly AdfNode[] {
+  return toEditorNormal(document(...blocks)).content ?? []
+}
+
+function document(...content: AdfNode[]): AdfDocument {
+  return { content, type: 'doc', version: 1 }
+}
+
+// ADF the reduction wrote, spelled and read back through the lift.
+function roundTripped(...content: AdfNode[]): readonly AdfNode[] | string {
+  const reduced = reduceToPlain(document(...content))
+  const markdown = reduced.ok ? adfToMarkdown(reduced.value) : reduced
+  return markdown.ok ? lifted(markdown.value) : markdown.error.code
+}
+
+function text(value: string, ...marks: AdfMark[]): AdfNode {
+  return marks.length === 0 ? { text: value, type: 'text' } : { marks, text: value, type: 'text' }
+}
+
+function node(type: string, attrs: AdfAttributes, ...content: AdfNode[]): AdfNode {
+  return { attrs, content, type }
+}
+
+function bare(type: string, ...content: AdfNode[]): AdfNode {
+  return { content, type }
+}
+
+function paragraph(...content: AdfNode[]): AdfNode {
+  return bare('paragraph', ...content)
+}
+
+function said(value: string): AdfNode {
+  return paragraph(text(value))
+}
+
+function panel(panelType: string, ...content: AdfNode[]): AdfNode {
+  return node('panel', { panelType }, ...content)
+}
+
+function task(state: string, ...content: AdfNode[]): AdfNode {
+  return node('taskItem', { state }, ...content)
+}
+
+test('lifts an alert to a panel by its GitHub word, in any case', () => {
+  const alert = (word: string): readonly AdfNode[] | string => lifted(`> [!${word}]\n>\n> Check it.\n`)
+  assert.deepEqual(alert('NOTE'), [panel('info', said('Check it.'))])
+  assert.deepEqual(alert('IMPORTANT'), [panel('note', said('Check it.'))])
+  assert.deepEqual(alert('TIP'), [panel('tip', said('Check it.'))])
+  assert.deepEqual(alert('WARNING'), [panel('warning', said('Check it.'))])
+  assert.deepEqual(alert('CAUTION'), [panel('error', said('Check it.'))])
+  assert.deepEqual(alert('Warning'), [panel('warning', said('Check it.'))])
+  assert.deepEqual(alert('caution'), [panel('error', said('Check it.'))])
+})
+
+test('lifts an Obsidian callout to a panel by what its word means, any other word info', () => {
+  const alert = (word: string): unknown => {
+    const blocks = lifted(`> [!${word}]\n> Body.\n`)
+    return typeof blocks === 'string' ? blocks : blocks[0]?.attrs
+  }
+  assert.deepEqual(alert('hint'), { panelType: 'tip' })
+  for (const word of ['success', 'check', 'Done']) assert.deepEqual(alert(word), { panelType: 'success' }, word)
+  assert.deepEqual(alert('attention'), { panelType: 'warning' })
+  for (const word of ['danger', 'error', 'failure', 'fail', 'missing', 'BUG']) assert.deepEqual(alert(word), { panelType: 'error' }, word)
+  for (const word of ['info', 'note', 'question', 'my-type']) assert.deepEqual(alert(word), { panelType: 'info' }, word)
+})
+
+test('reads text after an alert marker in its paragraph as the panel first body paragraph', () => {
+  assert.deepEqual(lifted('> [!NOTE]\n> Line **one**.\n>\n> Two.\n'), [panel('info', paragraph(text('Line '), text('one', strong), text('.')), said('Two.'))])
+  assert.deepEqual(lifted('> [!tip] Title\n'), [panel('tip', said('Title'))])
+  assert.deepEqual(lifted('> [!NOTE]\\\n> Broken.\n'), [panel('info', said('Broken.'))])
+  assert.deepEqual(lifted('> [!NOTE]\n'), normal(panel('info')))
+  assert.deepEqual(lifted('> > [!WARNING]\n> > Inner.\n'), [bare('blockquote', panel('warning', said('Inner.')))])
+})
+
+test('leaves a quote plain where its first line is no alert marker', () => {
+  for (const markdown of ['> [!NOTE]x\n', '> **[!NOTE]**\n', '> See [!NOTE]\n', '> [!NOTE]**x**\n', '> [!]\n', '> ```\n> [!NOTE]\n> ```\n']) {
+    const blocks = lifted(markdown)
+    assert.equal(typeof blocks !== 'string' && blocks[0]?.type, 'blockquote', markdown)
+  }
+})
+
+test('lifts a folded callout to an expand titled by the rest of its marker paragraph, whatever the word', () => {
+  assert.deepEqual(lifted('> [!NOTE]- Build log\n>\n> Line.\n'), [node('expand', { title: 'Build log' }, said('Line.'))])
+  assert.deepEqual(lifted('> [!bug]+ Open **by** default\n> still title\n>\n> Line.\n'), [node('expand', { title: 'Open by default still title' }, said('Line.'))])
+  assert.deepEqual(lifted('> [!NOTE]- Two\\\n> lines\n'), normal(node('expand', { title: 'Two\nlines' })))
+  assert.deepEqual(lifted('> [!NOTE]-\n>\n> Line.\n'), [bare('expand', said('Line.'))])
+})
+
+test('lifts a folded callout inside an expand to a nested expand', () => {
+  const markdown = '> [!NOTE]- Outer\n>\n> > [!NOTE]- Inner\n> >\n> > Deep.\n>\n> > [!TIP]\n> >\n> > > [!NOTE]-\n'
+  assert.deepEqual(lifted(markdown), normal(node('expand', { title: 'Outer' }, node('nestedExpand', { title: 'Inner' }, said('Deep.')), panel('tip', bare('nestedExpand')))))
+  assert.deepEqual(lifted('- > [!NOTE]-\n'), normal(bare('bulletList', bare('listItem', bare('expand')))))
+})
+
+test('lifts a bullet list whose every item leads with a task marker to a task list', () => {
+  assert.deepEqual(lifted('- [x] Write the spec\n- [ ] Ship **it**\n- [X] Tell\n'), [
+    bare('taskList', task('DONE', text('Write the spec')), task('TODO', text('Ship '), text('it', strong)), task('DONE', text('Tell'))),
+  ])
+  assert.deepEqual(lifted('- [x]\n- [ ]\\\n  after\n'), normal(bare('taskList', task('DONE'), task('TODO', text('after')))))
+})
+
+test('moves a nested task list beside its item and makes an item holding more than one block a block task item', () => {
+  assert.deepEqual(lifted('- [x] Parent\n  - [ ] Child\n- [ ] Next\n'), [bare('taskList', task('DONE', text('Parent')), bare('taskList', task('TODO', text('Child'))), task('TODO', text('Next')))])
+  assert.deepEqual(lifted('- [x] First.\n\n  Second.\n- [ ]\n\n  ```\n  x\n  ```\n'), [
+    bare('taskList', node('blockTaskItem', { state: 'DONE' }, said('First.'), said('Second.')), node('blockTaskItem', { state: 'TODO' }, bare('codeBlock', text('x')))),
+  ])
+  assert.deepEqual(lifted('- [x] A\n  - plain\n'), [bare('taskList', node('blockTaskItem', { state: 'DONE' }, said('A'), bare('bulletList', bare('listItem', said('plain')))))])
+})
+
+test('leaves mixed, ordered and unmarked lists plain', () => {
+  for (const markdown of ['- [x] a\n- b\n', '1. [x] a\n', '- [x]a\n', '- **[x]** a\n', '- [x]**a**\n', '- [-] a\n', '- > [x] a\n']) {
+    const blocks = lifted(markdown)
+    assert.notEqual(typeof blocks !== 'string' && blocks[0]?.type, 'taskList', markdown)
+    assert.equal(JSON.stringify(blocks).includes('taskItem'), false, markdown)
+  }
+  assert.deepEqual(lifted('- plain\n  - [ ] nested\n'), [bare('bulletList', bare('listItem', said('plain'), bare('taskList', task('TODO', text('nested')))))])
+})
+
+test('lifts a == pair to the editor default highlight, Yellow200 #f8e6a0 in @atlaskit/adf-schema 57.6.8', () => {
+  assert.deepEqual(lifted('a ==hi there== b\n'), [paragraph(text('a '), text('hi there', highlight), text(' b'))])
+  assert.deepEqual(lifted('**==hi==** b\n'), [paragraph(text('hi', highlight, strong), text(' b'))])
+  assert.deepEqual(lifted('==**a**_b_ `c`==\n'), [paragraph(text('a', highlight, strong), text('b', highlight, em), text(' ', highlight), text('c', code))])
+  assert.deepEqual(lifted('==`a`==\n'), [paragraph(text('a', code))])
+  assert.deepEqual(lifted('x==y==z ==a == b==\n'), [paragraph(text('x'), text('y', highlight), text('z '), text('a == b', highlight))])
+  assert.deepEqual(lifted('# ==h==\n\n| ==c== |\n| --- |\n'), [
+    node('heading', { level: 1 }, text('h', highlight)),
+    bare('table', bare('tableRow', bare('tableHeader', paragraph(text('c', highlight))))),
+  ])
+  assert.deepEqual(lifted('> [!NOTE]\n> ==x==\n'), [panel('info', paragraph(text('x', highlight)))])
+  assert.deepEqual(lifted('==a==\\\n==b==\n'), [paragraph(text('a', highlight), { type: 'hardBreak' }, text('b', highlight))])
+})
+
+test('leaves a == no pair flanks as text', () => {
+  for (const markdown of ['a == b == c\n', '====\n', '`==x==`\n', '==a\\\nb==\n', '**==a**==\n', '==a', '== a==\n', '==a ==\n']) {
+    assert.equal(JSON.stringify(lifted(markdown)).includes('backgroundColor'), false, markdown)
+  }
+})
+
+test('lifts what the reduction wrote back to the node it reduced, less the attributes it drops', () => {
+  const localId = '01a0d99b-1f59-7e2c-a3d4-62c1f0b8e7a1'
+  for (const panelType of ['info', 'note', 'tip', 'warning', 'error']) {
+    assert.deepEqual(roundTripped(node('panel', { localId, panelType }, said('Check.'))), [panel(panelType, said('Check.'))], panelType)
+  }
+  const expand = node('expand', { localId, title: 'Log' }, said('Line.'), node('nestedExpand', { title: 'Inner' }, said('Deep.')))
+  assert.deepEqual(roundTripped(expand), [node('expand', { title: 'Log' }, said('Line.'), node('nestedExpand', { title: 'Inner' }, said('Deep.')))])
+  const tasks = bare(
+    'taskList',
+    node('taskItem', { localId, state: 'DONE' }, text('Write')),
+    bare('taskList', task('TODO', text('Review'))),
+    node('blockTaskItem', { state: 'TODO' }, said('First.'), said('Second.')),
+    node('blockTaskItem', { state: 'DONE' }, bare('codeBlock', text('x'))),
+  )
+  const plainTasks = bare(
+    'taskList',
+    task('DONE', text('Write')),
+    bare('taskList', task('TODO', text('Review'))),
+    node('blockTaskItem', { state: 'TODO' }, said('First.'), said('Second.')),
+    node('blockTaskItem', { state: 'DONE' }, bare('codeBlock', text('x'))),
+  )
+  assert.deepEqual(roundTripped(tasks), [plainTasks])
+  const colour: AdfMark = { attrs: { color: '#c6edfb' }, type: 'backgroundColor' }
+  assert.deepEqual(roundTripped(paragraph(text('a '), text('hi', colour, strong), text(' b'))), [paragraph(text('a '), text('hi', highlight, strong), text(' b'))])
+})
+
+test('keeps what markdownToAdf reads that no row lifts, and refuses only what it refuses', () => {
+  assert.deepEqual(lifted('!adf:panel warning\n- [x] a\n!adf:/panel\n'), [panel('warning', bare('taskList', task('DONE', text('a'))))])
+  const future = bare('futureBlock', text('==x=='))
+  const carried = adfToMarkdown(document(future))
+  assert.deepEqual(carried.ok ? lifted(carried.value) : carried.error.code, [future])
+  assert.equal(lifted('!adf:panel\n'), 'malformed-directive')
+  let deep = 'x\n'
+  for (let level = 0; level < largestNesting; level += 1) deep = `> ${deep}`
+  assert.equal(typeof lifted(deep), 'object')
+})

src/markdown/parse/plain-lift.ts

@@ -0,0 +1,165 @@
+import type { AdfDocument, AdfMark, AdfNode } from '../../adf/document.ts'
+import { blockNodeModel } from '../../adf/block-nodes.ts'
+import { highlightDelimiter, readAlertMarker, readTaskMarker } from '../plain-conventions.ts'
+import { mergeAdjacentText, sameMark } from '../../adf/editor-normal.ts'
+import { nodeContent, nodeMarks } from '../../adf/document.ts'
+
+type Delimiter = { closes: boolean; line: number; marks: readonly AdfMark[]; node: number; offset: number; opens: boolean; position: number }
+
+type MarkerLed<T> = { marker: T; rest: AdfNode[] }
+
+const editorHighlight: AdfMark = { attrs: { color: '#f8e6a0' }, type: 'backgroundColor' }
+
+export function liftFromPlain(document: AdfDocument): AdfDocument {
+  return { ...document, content: liftBlocks(nodeContent(document), false) }
+}
+
+function liftBlocks(blocks: readonly AdfNode[], inExpand: boolean): AdfNode[] {
+  return blocks.map((block) => liftBlock(block, inExpand))
+}
+
+function liftBlock(block: AdfNode, inExpand: boolean): AdfNode {
+  const model = blockNodeModel(block.type)?.contentModel
+  if (model === 'inline') return { ...block, content: highlighted(nodeContent(block)) }
+  if (model !== 'block') return block
+  if (block.type === 'blockquote') return liftQuote(block, inExpand)
+  const tasks = block.type === 'bulletList' ? taskItems(nodeContent(block), inExpand) : undefined
+  if (tasks !== undefined) return { content: tasks, type: 'taskList' }
+  return { ...block, content: liftBlocks(nodeContent(block), inExpand || block.type === 'expand' || block.type === 'nestedExpand') }
+}
+
+function paragraphOf(content: readonly AdfNode[]): AdfNode[] {
+  return content.length === 0 ? [] : [{ content: [...content], type: 'paragraph' }]
+}
+
+// The marker opens the block's unmarked text and whitespace or the line's end follows it.
+function markerLed<T extends { length: number }>(block: AdfNode | undefined, read: (text: string) => T | undefined): MarkerLed<T> | undefined {
+  if (block?.type !== 'paragraph') return undefined
+  const [first, ...others] = nodeContent(block)
+  if (first?.type !== 'text' || first.text === undefined || nodeMarks(first).length > 0) return undefined
+  const marker = read(first.text)
+  if (marker === undefined) return undefined
+  const tail = first.text.slice(marker.length)
+  const lineEnds = tail === '' && (others[0] === undefined || others[0].type === 'hardBreak')
+  if (!lineEnds && !/^[ \t]/.test(tail)) return undefined
+  const trimmed = tail.replace(/^[ \t]+/, '')
+  const rest = trimmed === '' ? others : [{ text: trimmed, type: 'text' }, ...others]
+  let from = 0
+  while (rest[from]?.type === 'hardBreak') from += 1
+  return { marker, rest: rest.slice(from) }
+}
+
+function liftQuote(quote: AdfNode, inExpand: boolean): AdfNode {
+  const [first, ...body] = nodeContent(quote)
+  const led = markerLed(first, readAlertMarker)
+  if (led === undefined) return { ...quote, content: liftBlocks(nodeContent(quote), inExpand) }
+  if (!led.marker.folded) return { attrs: { panelType: led.marker.panelType }, content: liftBlocks([...paragraphOf(led.rest), ...body], inExpand), type: 'panel' }
+  const title = led.rest.map((node) => node.text ?? (node.type === 'hardBreak' ? '\n' : '')).join('')
+  const content = liftBlocks(body, true)
+  const type = inExpand ? 'nestedExpand' : 'expand'
+  return title === '' ? { content, type } : { attrs: { title }, content, type }
+}
+
+// A task list trailing an item's blocks stands beside it, as ADF nests one.
+function taskItems(items: readonly AdfNode[], inExpand: boolean): AdfNode[] | undefined {
+  if (items.length === 0) return undefined
+  const tasks: AdfNode[] = []
+  for (const item of items) {
+    const led = item.type === 'listItem' ? markerLed(nodeContent(item)[0], readTaskMarker) : undefined
+    if (led === undefined) return undefined
+    const blocks = liftBlocks([...paragraphOf(led.rest), ...nodeContent(item).slice(1)], inExpand)
+    let beside = blocks.length
+    while (blocks[beside - 1]?.type === 'taskList') beside -= 1
+    const kept = blocks.slice(0, beside)
+    const [only] = kept
+    const attrs = { state: led.marker.state }
+    const inline = kept.length <= 1 && (only === undefined || only.type === 'paragraph')
+    tasks.push(inline ? { attrs, content: [...nodeContent(only ?? {})], type: 'taskItem' } : { attrs, content: kept, type: 'blockTaskItem' })
+    for (const nested of blocks.slice(beside)) tasks.push(nested)
+  }
+  return tasks
+}
+
+function highlighted(inline: readonly AdfNode[]): AdfNode[] {
+  const pairs = pairedDelimiters(inline)
+  return pairs.length === 0 ? [...inline] : mergeAdjacentText(split(inline, pairs))
+}
+
+function textOf(node: AdfNode | undefined): string | undefined {
+  return node?.type === 'text' ? node.text : undefined
+}
+
+function delimiters(inline: readonly AdfNode[]): Delimiter[] {
+  const found: Delimiter[] = []
+  let line = 0
+  let position = 0
+  for (const [index, node] of inline.entries()) {
+    const text = textOf(node)
+    if (text === undefined) line += 1
+    if (text === undefined || nodeMarks(node).some((mark) => mark.type === 'code')) {
+      position += text?.length ?? 0
+      continue
+    }
+    for (let offset = text.indexOf(highlightDelimiter); offset !== -1; offset = text.indexOf(highlightDelimiter, offset + highlightDelimiter.length)) {
+      const before = offset > 0 ? text[offset - 1] : textOf(inline[index - 1])?.at(-1)
+      const after = text[offset + highlightDelimiter.length] ?? textOf(inline[index + 1])?.[0]
+      found.push({ closes: flanks(before), line, marks: nodeMarks(node), node: index, offset, opens: flanks(after), position: position + offset })
+    }
+    position += text.length
+  }
+  return found
+}
+
+function flanks(character: string | undefined): boolean {
+  return character !== undefined && !/\s/.test(character)
+}
+
+// Each opener takes the next closer holding at least one character after it, both in one line and under the same marks.
+function pairedDelimiters(inline: readonly AdfNode[]): Delimiter[] {
+  const found = delimiters(inline)
+  const paired: Delimiter[] = []
+  let closer = 0
+  let resume = 0
+  for (const opener of found) {
+    if (!opener.opens || opener.position < resume) continue
+    const earliest = opener.position + highlightDelimiter.length + 1
+    let candidate = found[closer]
+    while (candidate !== undefined && (!candidate.closes || candidate.position < earliest)) candidate = found[(closer += 1)]
+    if (candidate === undefined) break
+    if (candidate.line !== opener.line || !sameMarks(opener.marks, candidate.marks)) continue
+    paired.push(opener, candidate)
+    resume = candidate.position + highlightDelimiter.length
+  }
+  return paired
+}
+
+function sameMarks(first: readonly AdfMark[], second: readonly AdfMark[]): boolean {
+  return first.length === second.length && first.every((mark, index) => second[index] !== undefined && sameMark(mark, second[index]))
+}
+
+function split(inline: readonly AdfNode[], paired: readonly Delimiter[]): AdfNode[] {
+  const lifted: AdfNode[] = []
+  let next = 0
+  for (const [index, node] of inline.entries()) {
+    const text = textOf(node)
+    if (text === undefined) {
+      lifted.push(node)
+      continue
+    }
+    let from = 0
+    for (let delimiter = paired[next]; delimiter?.node === index; delimiter = paired[next]) {
+      pushPiece(lifted, node, text.slice(from, delimiter.offset), next % 2 === 1)
+      from = delimiter.offset + highlightDelimiter.length
+      next += 1
+    }
+    pushPiece(lifted, node, text.slice(from), next % 2 === 1)
+  }
+  return lifted
+}
+
+function pushPiece(lifted: AdfNode[], node: AdfNode, text: string, inPair: boolean): void {
+  // Atlassian's schema refuses a highlight on code.
+  const highlights = inPair && !nodeMarks(node).some((mark) => mark.type === 'code')
+  const marks = highlights ? [editorHighlight, ...nodeMarks(node)] : [...nodeMarks(node)]
+  if (text !== '') lifted.push(marks.length === 0 ? { text, type: 'text' } : { marks, text, type: 'text' })
+}

src/markdown/plain-conventions.ts

@@ -0,0 +1,54 @@
+type AlertMarker = { folded: boolean; length: number; panelType: string }
+
+export const foldedAlertMarker = '[!NOTE]-'
+export const highlightDelimiter = '=='
+
+const alertWords: Readonly<Record<string, string>> = {
+  error: 'CAUTION',
+  info: 'NOTE',
+  note: 'IMPORTANT',
+  success: 'TIP',
+  tip: 'TIP',
+  warning: 'WARNING',
+}
+
+const panelTypesByWord: Readonly<Record<string, string>> = {
+  attention: 'warning',
+  bug: 'error',
+  caution: 'error',
+  check: 'success',
+  danger: 'error',
+  done: 'success',
+  error: 'error',
+  fail: 'error',
+  failure: 'error',
+  hint: 'tip',
+  important: 'note',
+  missing: 'error',
+  success: 'success',
+  tip: 'tip',
+  warning: 'warning',
+}
+
+export function alertMarker(panelType: unknown): string {
+  const word = typeof panelType === 'string' && Object.hasOwn(alertWords, panelType) ? alertWords[panelType] : undefined
+  return `[!${word ?? 'NOTE'}]`
+}
+
+export function readAlertMarker(text: string): AlertMarker | undefined {
+  const marker = /^\[!([\w-]+)\]([+-]?)/.exec(text)
+  if (marker === null) return undefined
+  const word = (marker[1] ?? '').toLowerCase()
+  const panelType = Object.hasOwn(panelTypesByWord, word) ? panelTypesByWord[word] : undefined
+  return { folded: marker[2] !== '', length: marker[0].length, panelType: panelType ?? 'info' }
+}
+
+export function taskMarker(state: unknown): string {
+  return state === 'DONE' ? '[x]' : '[ ]'
+}
+
+export function readTaskMarker(text: string): { length: number; state: 'DONE' | 'TODO' } | undefined {
+  const marker = /^\[([ xX])\]/.exec(text)
+  if (marker === null) return undefined
+  return { length: marker[0].length, state: marker[1] === ' ' ? 'TODO' : 'DONE' }
+}

todo-history.md

@@ -1074,6 +1074,8 @@ The done `todo.md` items in full, as they were written. `todo.md` keeps a one-li
 - [ ] **10 — Lossy conversion (`0.2.0`).**
   - [x] **10a — The reduction.** `adfToPlainMarkdown`'s ADF→ADF reduction, tests first, a test per
         row above.
+  - [x] **10b — The lift.** `plainMarkdownToAdf`'s ADF→ADF lift, tests first, a test per row it reads,
+        other tools' spellings included; the editor's default highlight colour looked up and cited.
 
 ## 5 — Ship `0.1.0`
 

todo.md

@@ -202,8 +202,8 @@ chunk clearing a §11 seam.
         success `TIP`, warning `WARNING`, error `CAUTION`, custom `NOTE`. The lift reads those words
         back (`NOTE` info, `IMPORTANT` note, `TIP` tip, `WARNING` warning, `CAUTION` error) and
         Obsidian's by meaning (hint tip; success, check and done success; attention warning; danger,
-        failure, fail, missing and bug error; any other word info). Text after a marker in its
+        failure, fail, missing, bug and error error — `error` by a panel, 3 of 3, 2026-09-25; any
-        paragraph is the panel's first body paragraph.
+        other word info). Text after a marker in its paragraph is the panel's first body paragraph.
       - An `expand` or `nestedExpand` is Obsidian's folded callout, `> [!NOTE]- Title`, a blank `>`,
         then the body. The lift reads a fold sign (`-` or `+`) as an expand whatever the word, the
         rest of the marker's paragraph as its title, and an expand inside an expand as a
@@ -252,12 +252,17 @@ chunk clearing a §11 seam.
         lists, wikilinks, embeds, tags, comments, TOC tokens, spoilers, task states past `[x]`/`[ ]`,
         and lifting bare URLs, `@name`, `:shortcode:` or ISO dates into nodes.
   - [x] **10a — The reduction.**
-  - [ ] **10b — The lift.** `plainMarkdownToAdf`'s ADF→ADF lift, tests first, a test per row it reads,
+  - [x] **10b — The lift.**
-        other tools' spellings included; the editor's default highlight colour looked up and cited.
   - [ ] **10c — The exports.** `adfToPlainMarkdown` and `plainMarkdownToAdf` exported with their README
         sections, and two properties over 4.2's generators: writing refuses only the guard's codes
         and writes no `!adf:`, and markdown `adfToPlainMarkdown` wrote reads back through `plainMarkdownToAdf` and writes
         again byte for byte. AGENTS.md §1 records the pair as composed around the lossless one.
+  - [ ] **10d — A literal marker survives the lossy round trip.** Text reading `==x==`, a quote
+        opening `[!NOTE]` or a list whose items all open `[x] ` comes back as a highlight, panel or
+        task list after `plainMarkdownToAdf(adfToPlainMarkdown(doc))`, and a human's `\==x==` too:
+        the lift reads ADF, where `markdownToAdf` has already spent the backslash. Give plain
+        markdown an escape that keeps such text literal through both directions — which seam carries
+        it is a gap to ask.
 - [x] **11 — Atlassian's ADF schema as the tables' truth.**
   - [x] **11a — The vendored schema.**
   - [x] **11b — The gate.**