README.md

@@ -147,7 +147,7 @@ read replaces mentions, attachments and macros with text.
   `_(image not included)_`, `_(jira-issues-table not included)_`, `_(synced block not included)_`,
   `_(link card not included)_`, `_(extension not included)_`.
 - `backgroundColor`, `code`, `em`, `link`, `strike` and `strong` stay; every other mark drops,
-  keeping its text, and so does a mark CommonMark cannot spell where it stands.
+  keeping its text, and so does a mark the flavour cannot spell where it stands.
 - A newline in text is a hard break and in an expand's title a space, edge whitespace outside a
   link or code span is trimmed, carriage returns and null characters are removed, and an empty
   paragraph drops.

src/markdown/emit/adf-to-markdown.ts

@@ -162,7 +162,7 @@ function quoted(text: string): string {
     .join('\n')
 }
 
-function tryTaskList(node: AdfNode, path: ConvertErrorPath, depth: number, writing: Writing): Result<EmittedBlock> | undefined {
+function tryTaskList(node: AdfNode, path: ConvertErrorPath, depth: number, writing: Writing): Result<EmittedBlock> {
   const items: PlacedBlock[][] = []
   let headroom = largestNesting - depth - 1
   // A child other than a task nests in the task before it.
@@ -176,7 +176,8 @@ function tryTaskList(node: AdfNode, path: ConvertErrorPath, depth: number, writi
     else for (const block of walk.value.blocks) previous.push(block)
   }
   const lines = items.map((blocks) => tryListItemLines(joinBlocks(blocks, 'list-item'), '- '))
-  return lines.includes(undefined) ? undefined : success({ headroom, spelling: 'list', text: lines.join('\n') })
+  // The plain reduction leaves no task a list item cannot hold: a directive here would break the flavour.
+  return lines.includes(undefined) ? failure('unsupported-node-shape', 'a task holds blocks no list item spells', path) : success({ headroom, spelling: 'list', text: lines.join('\n') })
 }
 
 function placedBlock(node: AdfNode, path: ConvertErrorPath, depth: number, writing: Writing): Result<Walk> {

src/markdown/emit/inline-line.ts

@@ -38,7 +38,7 @@ type LineAttempt = { fallback: NodeRange | 'opening-link'; line?: undefined } |
 
 type LineFallbacks = { carried: Set<number>; flavour: Flavour; openingLinkAsDirective: boolean }
 
-export type PlainLineFallback = { kind: 'claimed-line'; line: number; text: string } | { kind: 'opening-link' } | { kind: 'unspellable-run'; run: MarkRun }
+export type PlainLineFallback = { kind: 'claimed-line'; line: number; text: string } | { kind: 'opening-link' } | { kind: 'unspellable-run'; run: MarkRun; runs: MarkRun[] }
 
 export function emitInlineLine(nodes: readonly AdfNode[], container: LineContainer, path: ConvertErrorPath, flavour: Flavour): Result<string> {
   const emitted = emitLine(nodes, container, path, flavour)
@@ -129,7 +129,8 @@ function attemptLine(segments: readonly InlineSegment[], container: LineContaine
 function lineVerdict(segments: readonly InlineSegment[], container: LineContainer, flavour: Flavour): PlainLineFallback | { kind: 'line'; text: string } {
   const assembled = assembleInlineLine(segments, container, flavour)
   if (assembled.openingLinkAsDirective) return { kind: 'opening-link' }
-  if (assembled.unspellableRun !== undefined) return { kind: 'unspellable-run', run: assembled.unspellableRun }
+  const [run] = assembled.unspellableRuns
+  if (run !== undefined) return { kind: 'unspellable-run', run, runs: assembled.unspellableRuns }
   const lines = assembled.line.split('\n')
   const claimed = container === 'paragraph' ? lines.findIndex((single, index) => claimsLine(single, index === 0 ? 'first' : 'later')) : -1
   return claimed === -1 ? { kind: 'line', text: assembled.line } : { kind: 'claimed-line', line: claimed, text: lines[claimed] ?? '' }

src/markdown/emit/line-escaping.ts

@@ -23,7 +23,7 @@ export type InlineSegment =
   | { emphasis?: undefined; escaping: 'none'; highlight?: undefined; nodes: NodeRange; text: string }
   | { emphasis?: undefined; escaping: InlineEscaping; highlight?: undefined; nodes?: undefined; text: string }
 
-export type AssembledLine = { line: string; openingLinkAsDirective?: true; unspellableRun: MarkRun | undefined }
+export type AssembledLine = { line: string; openingLinkAsDirective?: true; unspellableRuns: MarkRun[] }
 
 type ScanLine = { position: LinePosition; start: number; text: string }
 
@@ -81,10 +81,10 @@ function escape(segments: readonly InlineSegment[], container: LineContainer, hi
     output += scan.charAt(index)
   }
   if (container === 'paragraph' && opensLinkDefinition(output)) {
-    if (segments[0]?.nodes !== undefined) return { line: output, openingLinkAsDirective: true, unspellableRun: undefined }
+    if (segments[0]?.nodes !== undefined) return { line: output, openingLinkAsDirective: true, unspellableRuns: [] }
-    return { line: `\\${output}`, unspellableRun: unspellableRun(segments, output, placements) }
+    return { line: `\\${output}`, unspellableRuns: unspellableRuns(segments, output, placements) }
   }
-  return { line: output, unspellableRun: unspellableRun(segments, output, placements) }
+  return { line: output, unspellableRuns: unspellableRuns(segments, output, placements) }
 }
 
 function escapeClaims(scan: string, escapings: readonly InlineEscaping[], container: LineContainer, highlights: boolean): ReadonlySet<number> {
@@ -148,25 +148,27 @@ function escapeClosedRuns(scan: string, escapings: readonly InlineEscaping[], cl
   return escaped
 }
 
-function unspellableRun(segments: readonly InlineSegment[], output: string, placements: readonly number[]): MarkRun | undefined {
+// One emphasis run, the innermost, or every highlight run the line cannot spell.
+function unspellableRuns(segments: readonly InlineSegment[], output: string, placements: readonly number[]): MarkRun[] {
   const { nodes, runs } = emittedRuns(segments, placements, output)
   const pair = misflanked(runs) ?? unpaired(runs)
-  return pair === undefined ? unreadHighlight(segments, output, placements) : nodes[pair]
+  const run = pair === undefined ? undefined : nodes[pair]
+  return run === undefined ? unreadHighlights(segments, output, placements) : [run]
 }
 
-// No `==` in text can open or close, and highlights never nest, so a pair reads back where each delimiter flanks and both share a line.
+// No `==` in text can open or close, and highlights never nest, so a pair reads back where each delimiter flanks.
-function unreadHighlight(segments: readonly InlineSegment[], output: string, placements: readonly number[]): MarkRun | undefined {
+function unreadHighlights(segments: readonly InlineSegment[], output: string, placements: readonly number[]): MarkRun[] {
+  const unread: MarkRun[] = []
   let cursor = 0
-  let opener = 0
   for (const segment of segments) {
     const start = placements[cursor] ?? 0
     cursor += segment.text.length
     if (segment.highlight === undefined) continue
     const flanking = highlightFlanking(output, start)
-    if (segment.highlight === 'open') opener = start
+    const flanks = segment.highlight === 'open' ? flanking.opens : flanking.closes
-    if (segment.highlight === 'open' ? !flanking.opens : !flanking.closes || output.slice(opener, start).includes('\n')) return segment.nodes
+    if (!flanks && unread.at(-1) !== segment.nodes) unread.push(segment.nodes)
   }
-  return undefined
+  return unread
 }
 
 function misflanked(runs: readonly EmittedRun[]): number | undefined {

src/markdown/emit/plain-inline.ts

@@ -1,5 +1,6 @@
 import type { AdfAttributes, AdfMark, AdfNode } from '../../adf/document.ts'
 import type { LineContainer } from '../line-container.ts'
+import type { MarkRun } from './line-escaping.ts'
 import { blockNodeModel } from '../../adf/block-nodes.ts'
 import { failure, success, type ConvertErrorPath, type Result } from '../../result.ts'
 import { largestNesting } from '../../nesting.ts'
@@ -130,7 +131,7 @@ function textLeaf(text: string, marks: readonly AdfMark[]): AdfNode {
   return marks.length === 0 ? { text, type: 'text' } : { marks: [...marks], text, type: 'text' }
 }
 
-// A highlight goes outermost so its run is one run at depth 0, and code innermost, the only place its spelling holds.
+// A highlight goes first, where `highlighted` looks for it, and code last, the only place its spelling holds.
 function plainMarks(marks: readonly AdfMark[], container: LineContainer, text: string): AdfMark[] {
   const kept: AdfMark[] = []
   for (const mark of marks) {
@@ -174,7 +175,7 @@ function highlighted(leaves: readonly AdfNode[]): AdfNode[] {
     const marks = nodeMarks(leaf)
     if (marks[0]?.type === highlight) {
       const held = marks.slice(1)
-      shared = run.length === 0 ? held.filter((mark) => mark.type !== 'code') : shared.filter((mark) => held.some((other) => sameMark(other, mark)))
+      shared = run.length === 0 ? held : shared.filter((mark) => held.some((other) => sameMark(other, mark)))
       run.push(leaf)
       continue
     }
@@ -265,7 +266,7 @@ function spellableLine(leaves: AdfNode[], container: LineContainer, path: Conver
 }
 
 function withoutFallback(leaves: readonly AdfNode[], fallback: PlainLineFallback): AdfNode[] | undefined {
-  if (fallback.kind === 'unspellable-run') return withoutMark(leaves, fallback.run.first, fallback.run.last, fallback.run.depth)
+  if (fallback.kind === 'unspellable-run') return withoutMarks(leaves, fallback.runs)
   const first = fallback.kind === 'opening-link' ? 0 : lineStart(leaves, fallback.line)
   const mark = nodeMarks(leaves[first] ?? {})[0]
   if (mark === undefined || mark.type !== (fallback.kind === 'opening-link' ? 'link' : 'code')) return undefined
@@ -274,7 +275,7 @@ function withoutFallback(leaves: readonly AdfNode[], fallback: PlainLineFallback
   // A code span is what binds the `]` a link definition reads, and dropping it keeps the link target.
   const spans = leaves.slice(first, last + 1).some((leaf) => nodeMarks(leaf).length > 1 && nodeMarks(leaf).at(-1)?.type === 'code')
   if (mark.type === 'link' && spans) return leaves.map((leaf, index) => (index < first || index > last ? leaf : withMarks(leaf, nodeMarks(leaf).filter((held) => held.type !== 'code'))))
-  return withoutMark(leaves, first, last, 0)
+  return withoutMarks(leaves, [{ depth: 0, first, last }])
 }
 
 function lineStart(leaves: readonly AdfNode[], line: number): number {
@@ -283,6 +284,12 @@ function lineStart(leaves: readonly AdfNode[], line: number): number {
   return index
 }
 
-function withoutMark(leaves: readonly AdfNode[], first: number, last: number, depth: number): AdfNode[] {
+// The runs cover disjoint leaves, so one pass drops them all.
-  return leaves.map((leaf, index) => (index < first || index > last ? leaf : withMarks(leaf, nodeMarks(leaf).filter((_, held) => held !== depth))))
+function withoutMarks(leaves: readonly AdfNode[], runs: readonly MarkRun[]): AdfNode[] {
+  const depths = new Map<number, number>()
+  for (const run of runs) for (let index = run.first; index <= run.last; index += 1) depths.set(index, run.depth)
+  return leaves.map((leaf, index) => {
+    const depth = depths.get(index)
+    return depth === undefined ? leaf : withMarks(leaf, nodeMarks(leaf).filter((_, held) => held !== depth))
+  })
 }

src/markdown/emit/plain-reduction.ts

@@ -164,18 +164,24 @@ function joinedLists(first: AdfNode, second: AdfNode): AdfNode {
   return { ...head, content: [...nodeContent(head), ...nodeContent(tail)] }
 }
 
+// A task keeps its marker as text; a list item stands as one, and anything else nests in the item before it.
 function tasksAsText(list: AdfNode): AdfNode {
   if (list.type !== 'taskList') return list
   const items: AdfNode[] = []
   for (const child of nodeContent(list)) {
-    const marker = taskMarker(nodeAttrs(child)['state'])
+    const previous = isTask(child) || child.type === 'listItem' ? undefined : items.pop()
-    const previous = child.type === 'taskItem' || child.type === 'blockTaskItem' ? undefined : items.pop()
+    items.push(itemOf(previous === undefined ? taskAsText(child) : mergedLists([...nodeContent(previous), child])))
-    if (previous !== undefined) items.push(itemOf([...nodeContent(previous), child]))
-    else items.push(itemOf(child.type === 'taskItem' ? [paragraph(nodeContent(child).length === 0 ? [text(marker)] : [text(`${marker} `), ...nodeContent(child)])] : marked(nodeContent(child), marker)))
   }
   return { content: items, type: 'bulletList' }
 }
 
+function taskAsText(child: AdfNode): readonly AdfNode[] {
+  const marker = taskMarker(nodeAttrs(child)['state'])
+  if (child.type === 'taskItem') return [paragraph(nodeContent(child).length === 0 ? [text(marker)] : [text(`${marker} `), ...nodeContent(child)])]
+  if (child.type === 'blockTaskItem') return marked(nodeContent(child), marker)
+  return child.type === 'listItem' ? nodeContent(child) : [child]
+}
+
 function paragraph(content: readonly AdfNode[]): AdfNode {
   return { content: [...content], type: 'paragraph' }
 }
@@ -209,10 +215,17 @@ function reducePanel(node: AdfNode, reduction: Reduction): Result<AdfNode[]> {
 
 function reduceExpand(node: AdfNode, reduction: Reduction): Result<AdfNode[]> {
   const held = nodeAttrs(node)['title']
-  const title = typeof held === 'string' ? oneLine(held).replace(/^[ \t]+|[ \t]+$/g, '') : ''
+  const title = typeof held === 'string' ? withoutTrailingBlanks(oneLine(held).replace(/^[ \t]+/, '')) : ''
   return contained(title === '' ? { type: node.type } : { attrs: { title }, type: node.type }, node, reduction)
 }
 
+// A backward scan: an unanchored-end regex retries from every blank in a long run.
+function withoutTrailingBlanks(text: string): string {
+  let end = text.length
+  while (end > 0 && (text.charAt(end - 1) === ' ' || text.charAt(end - 1) === '\t')) end -= 1
+  return text.slice(0, end)
+}
+
 function reduceHeading(node: AdfNode, reduction: Reduction): Result<AdfNode[]> {
   const level = nodeAttrs(node)['level']
   if (typeof level !== 'number' || !Number.isInteger(level) || level < 1 || level > 6) return paragraphOf(nodeContent(node), reduction)
@@ -261,16 +274,21 @@ function blankedLines(code: readonly AdfNode[]): AdfNode[] {
   return blanked === '' ? [] : [text(blanked)]
 }
 
-// A task list opening with a task and holding tasks and task lists alone keeps its spelling; a list nests in the task before it.
+// A task list opening with a task and holding tasks and task lists alone keeps its spelling, a list nesting in the task before it; any other keeps its markers as text.
 function reduceTaskList(node: AdfNode, reduction: Reduction): Result<AdfNode[]> {
   const children = nodeContent(node)
-  if (!isTask(children[0]) || children.some((child) => !isTask(child) && child.type !== 'taskList')) return reduceTasksAsText(node, reduction)
+  const regular = isTask(children[0]) && children.every((child) => isTask(child) || child.type === 'taskList')
   const tasks: AdfNode[] = []
   let nested: AdfNode[] = []
   for (const [index, child] of children.entries()) {
     const at = childReduction(reduction, index)
     const reduced = isTask(child) ? reduceTask(child, at) : reduceStanding(child, at)
     if (!reduced.ok) return reduced
+    if (!regular) {
+      const standsAlone = !isTask(child) && child.type !== 'taskList'
+      for (const block of standsAlone ? [{ content: reduced.value, type: 'listItem' }] : reduced.value) tasks.push(block)
+      continue
+    }
     if (isTask(child)) {
       nestIn(tasks, nested)
       nested = []
@@ -278,7 +296,8 @@ function reduceTaskList(node: AdfNode, reduction: Reduction): Result<AdfNode[]>
     for (const block of reduced.value) (isTask(child) ? tasks : nested).push(block)
   }
   nestIn(tasks, nested)
-  return success([{ content: tasks, type: 'taskList' }])
+  if (regular) return success([{ content: tasks, type: 'taskList' }])
+  return success(listOf(nodeContent(tasksAsText({ content: tasks, type: 'taskList' })), 'bulletList'))
 }
 
 // The writer nests a list in the task before it, so one closing a block task item's blocks merges with it.
@@ -302,28 +321,6 @@ function reduceTask(task: AdfNode, at: Reduction): Result<AdfNode[]> {
   return blocks.ok ? success([{ attrs, content: blankedCode(blocks.value), type: 'blockTaskItem' }]) : blocks
 }
 
-function reduceTasksAsText(node: AdfNode, reduction: Reduction): Result<AdfNode[]> {
-  const items: AdfNode[] = []
-  for (const [index, child] of nodeContent(node).entries()) {
-    const blocks = taskBlocks(child, childReduction(reduction, index))
-    if (!blocks.ok) return blocks
-    const previous = child.type === 'taskList' ? items.pop() : undefined
-    items.push(itemOf(previous === undefined ? blocks.value : mergedLists([...nodeContent(previous), ...blocks.value])))
-  }
-  return success(listOf(items, 'bulletList'))
-}
-
-function taskBlocks(child: AdfNode, at: Reduction): Result<AdfNode[]> {
-  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
-  }
-  if (child.type !== 'blockTaskItem') return reduceStanding(child, at)
-  const blocks = reduceBlocks(nodeContent(child), at)
-  return blocks.ok ? success(marked(blocks.value, marker)) : blocks
-}
-
 // The marker leads the first paragraph, or stands as one where the blocks open with another.
 function marked(blocks: readonly AdfNode[], marker: string): AdfNode[] {
   const [first, ...rest] = blocks