Answer architecture round 4: the writers close a mark run at a hard break again, and item 91 plans the joined spelling

CHANGELOG.md

@@ -75,8 +75,7 @@
   whose text is only hard breaks reads as its destination linked, followed by those breaks, and
   `losslessMarkdownToAdf` refuses a directive mark wrapping only hard breaks as
   `unsupported-node-shape`. `adfToLosslessMarkdown` writes a hard break holding marks as
-  `!adf:carry{json="…"}`, and spells an emphasis or link across the hard breaks inside it once,
+  `!adf:carry{json="…"}`. See `MIGRATION.md`.
-  `_a\` then `b_`, where `adfToMarkdown` closed and reopened it. See `MIGRATION.md`.
 - Fix a cyclic document, in which an object holds itself: `adfToLosslessMarkdown` and
   `adfToPortableMarkdown` refuse it as `not-an-adf-document` and `isAdfDocument` returns `false`,
   where all three hung.

spec/flavour.md

@@ -540,9 +540,8 @@ gives marks `[em, underline]`, `!adf:underline[_x_]` the reverse. `adfToLossless
 the order the array holds rather than sorting it — `docs/decisions.md` §Equality is deep restores
 the array, not a set — and opens each spelling once over the longest run of adjacent inline nodes
 carrying an identical mark, attributes included, at that depth: `attrs: {}` differs from no `attrs`,
-and a directive spells it `{attrs=empty}`. An emphasis or link spelling also spans the hard breaks
+and a directive spells it `{attrs=empty}`. A run breaks at every node the emitter carries, so no
-between two nodes of its run. A run breaks at every node the emitter carries, so no emitted carry
+emitted carry sits inside a mark spelling.
-sits inside a mark spelling.
 
 An inline node whose marks no nesting spells — a hard break holding any mark, a mark type not listed
 here, an attrs key its spelling does not list, a value that is not the spelling's type, an attribute

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

@@ -713,17 +713,17 @@ test('spells the directive marks around the longest run they cover', () => {
   assert.equal(emitted(marked('a', underline), { type: 'hardBreak' }, marked('b', underline)), '!adf:underline[a]\\\n!adf:underline[b]\n')
 })
 
-test('spells a mark run across the hard break between two nodes holding the mark', () => {
+test('closes a mark run at the hard break between two nodes holding the mark', () => {
   const em: AdfMark = { type: 'em' }
   const link: AdfMark = { attrs: { href: '/u' }, type: 'link' }
   const marked = (text: string, ...marks: AdfMark[]): AdfNode => ({ marks, text, type: 'text' })
   const hardBreak: AdfNode = { type: 'hardBreak' }
-  assert.equal(readsBack(document(paragraph(marked('a', em), hardBreak, marked('b', em)))), '_a\\\nb_\n')
+  assert.equal(readsBack(document(paragraph(marked('a', em), hardBreak, marked('b', em)))), '_a_\\\n_b_\n')
-  assert.equal(readsBack(document(paragraph(marked('a', link), hardBreak, marked('b', link)))), '[a\\\nb](/u)\n')
+  assert.equal(readsBack(document(paragraph(marked('a', link), hardBreak, marked('b', link)))), '[a](/u)\\\n[b](/u)\n')
-  assert.equal(readsBack(document(paragraph(marked('a', em, link), hardBreak, marked('b', em)))), '_[a](/u)\\\nb_\n')
+  assert.equal(readsBack(document(paragraph(marked('a', em, link), hardBreak, marked('b', em)))), '_[a](/u)_\\\n_b_\n')
-  assert.equal(readsBack(document(paragraph(marked('a', em), hardBreak, hardBreak, marked('b', em)))), '_a\\\n\\\nb_\n')
+  assert.equal(readsBack(document(paragraph(marked('a', em), hardBreak, hardBreak, marked('b', em)))), '_a_\\\n\\\n_b_\n')
   const directive: AdfMark = { attrs: { href: '/u', id: 'x' }, type: 'link' }
-  assert.equal(readsBack(document(paragraph(marked('a', directive), hardBreak, marked('b', directive)))), '!adf:link[a!adf:hardBreak{}b]{href="/u" id=x}\n')
+  assert.equal(readsBack(document(paragraph(marked('a', directive), hardBreak, marked('b', directive)))), '!adf:link[a]{href="/u" id=x}\\\n!adf:link[b]{href="/u" id=x}\n')
   readsBack(document(paragraph(marked(']: /x', link, { type: 'code' }), hardBreak, marked('b', link))))
   assert.equal(readsBack(document(paragraph({ text: 'x', type: 'text' }, marked('.', em), hardBreak, marked('b', em)))), 'x!adf:carry{json="{\\"marks\\":[{\\"type\\":\\"em\\"}],\\"text\\":\\".\\",\\"type\\":\\"text\\"}"}\\\n_b_\n')
 })

src/markdown/emit/inline-line.ts

@@ -27,7 +27,6 @@ type InlineContext = {
   bracketed: boolean
   carried: ReadonlySet<number>
   flavour: WrittenFlavour
-  joinsBreaks: boolean
   openingLinkAsDirective: boolean
   path: ConvertErrorPath
   spansLines: boolean
@@ -37,7 +36,7 @@ type InlineRun = { index: number; kind: 'marked'; mark: AdfMark; nodes: AdfNode[
 
 type LineAttempt = { fallback: NodeRange | 'opening-link'; line?: undefined } | { fallback?: undefined; line: string }
 
-type LineFallbacks = { carried: Set<number>; flavour: WrittenFlavour; joinsBreaks: boolean; openingLinkAsDirective: boolean }
+type LineFallbacks = { carried: Set<number>; flavour: WrittenFlavour; openingLinkAsDirective: boolean }
 
 export type PortableLineFallback = { kind: 'opening-link' } | { kind: 'unspellable-run'; runs: [MarkRun, ...MarkRun[]] }
 
@@ -54,8 +53,7 @@ export function openingLinkTakesDirective(nodes: readonly AdfNode[], path: Conve
 }
 
 export function portableLineFallback(nodes: readonly AdfNode[], container: LineContainer, path: ConvertErrorPath): Result<PortableLineFallback | undefined> {
-  // Unjoined: the spelling `emitLine` falls back to where the joined one fails.
+  const emission = lineSegments(nodes, container, path, { carried: new Set(), flavour: 'portable', openingLinkAsDirective: false })
-  const emission = lineSegments(nodes, container, path, { carried: new Set(), flavour: 'portable', joinsBreaks: false, openingLinkAsDirective: false })
   if (!emission.ok) return emission
   if (emission.value.carry !== undefined) return failure('unsupported-node-shape', 'an inline node on a portable line has no spelling but the carry', path)
   const verdict = lineVerdict(emission.value.segments, container, 'portable')
@@ -78,7 +76,7 @@ export function tryImageLine(alt: string | undefined, href: string): string | un
 }
 
 function emitLine(nodes: readonly AdfNode[], container: LineContainer, path: ConvertErrorPath, flavour: WrittenFlavour): Result<EmittedLine> {
-  const fallbacks: LineFallbacks = { carried: new Set(), flavour, joinsBreaks: nodes.some((node) => node.type === 'hardBreak'), openingLinkAsDirective: false }
+  const fallbacks: LineFallbacks = { carried: new Set(), flavour, openingLinkAsDirective: false }
   // Terminates because takeFallback refuses a pass that took no new fallback.
   for (;;) {
     const emission = lineSegments(nodes, container, path, fallbacks)
@@ -97,12 +95,7 @@ function emitLine(nodes: readonly AdfNode[], container: LineContainer, path: Con
   }
 }
 
-// A line's first fallback stops runs joining across hard breaks, so no fallback takes a break `joinedBreaks` joined.
 function takeFallback(fallbacks: LineFallbacks, fallback: NodeRange | 'opening-link', path: ConvertErrorPath): Result<null> {
-  if (fallbacks.joinsBreaks) {
-    fallbacks.joinsBreaks = false
-    return success(null)
-  }
   if (fallback === 'opening-link') {
     if (fallbacks.openingLinkAsDirective) return failure('unsupported-node-shape', 'an opening link spelled as a directive still reads as a link definition, so the line has no spelling left', path)
     fallbacks.openingLinkAsDirective = true
@@ -184,7 +177,7 @@ function emitRun(nodes: readonly AdfNode[], depth: number, firstIndex: number, c
   if (depth > largestNesting) {
     return failure('unsupported-nesting-depth', `the marks nest deeper than the ${largestNesting} levels the emitter carries`, context.path)
   }
-  const runs = inlineRuns(nodes, depth, firstIndex, context)
+  const runs = inlineRuns(nodes, depth, firstIndex, context.carried)
   const segments: InlineSegment[] = []
   for (const [offset, run] of runs.entries()) {
     if (takesTextBreak(runs[offset - 1], run, context.carried)) segments.push(syntax(textBreakSpelling))
@@ -197,47 +190,23 @@ function emitRun(nodes: readonly AdfNode[], depth: number, firstIndex: number, c
   return success({ segments })
 }
 
-function inlineRuns(nodes: readonly AdfNode[], depth: number, firstIndex: number, context: InlineContext): InlineRun[] {
+function inlineRuns(nodes: readonly AdfNode[], depth: number, firstIndex: number, carried: ReadonlySet<number>): InlineRun[] {
   const runs: InlineRun[] = []
-  for (let offset = 0; offset < nodes.length; offset += 1) {
+  for (const [offset, node] of nodes.entries()) {
-    const node = nodes[offset]
-    if (node === undefined) continue
     const index = firstIndex + offset
     // `depth` indexes each node's marks, outermost first; a carried node spells its marks inside the carry.
-    const mark = carries(node, context.carried, index) ? undefined : nodeMarks(node)[depth]
+    const mark = carries(node, carried, index) ? undefined : nodeMarks(node)[depth]
-    const previous = runs[runs.length - 1]
-    const joined = mark === undefined && previous?.kind === 'marked' && context.joinsBreaks ? joinedBreaks(nodes, offset, firstIndex, previous.mark, depth, context.carried) : 0
-    if (previous?.kind === 'marked' && joined > 0) {
-      for (const held of nodes.slice(offset, offset + joined)) previous.nodes.push(held)
-      offset += joined - 1
-      continue
-    }
     if (mark === undefined) {
       runs.push({ index, kind: 'plain', node })
       continue
     }
+    const previous = runs[runs.length - 1]
     if (previous?.kind === 'marked' && identicalMark(previous.mark, mark)) previous.nodes.push(node)
     else runs.push({ index, kind: 'marked', mark, nodes: [node] })
   }
   return runs
 }
 
-// The hard breaks from `offset` an emphasis or link run spans because the node after them holds its mark; a directive would spell each `!adf:hardBreak{}`.
-function joinedBreaks(nodes: readonly AdfNode[], offset: number, firstIndex: number, mark: AdfMark, depth: number, carried: ReadonlySet<number>): number {
-  const kind = markSpelling(mark.type)?.kind
-  if (kind !== 'emphasis' && kind !== 'link') return 0
-  let ahead = offset
-  while (isUncarriedBreak(nodes[ahead], carried, firstIndex + ahead)) ahead += 1
-  const next = nodes[ahead]
-  if (next === undefined || carries(next, carried, firstIndex + ahead)) return 0
-  const nextMark = nodeMarks(next)[depth]
-  return nextMark !== undefined && identicalMark(nextMark, mark) ? ahead - offset : 0
-}
-
-function isUncarriedBreak(node: AdfNode | undefined, carried: ReadonlySet<number>, index: number): boolean {
-  return node?.type === 'hardBreak' && !carries(node, carried, index)
-}
-
 function takesTextBreak(previous: InlineRun | undefined, run: InlineRun, carried: ReadonlySet<number>): boolean {
   if (previous?.kind !== 'plain' || run.kind !== 'plain') return false
   if (carries(previous.node, carried, previous.index) || carries(run.node, carried, run.index)) return false
@@ -313,7 +282,7 @@ function emitMarkedRun(nodes: readonly AdfNode[], mark: AdfMark, depth: number,
   if (spelling.kind === 'emphasis') return emitEmphasis(nodes, spelling.spelling, depth, range, context)
   const link = spelling.kind === 'link' ? tryLink(nodes, mark, depth, range, context) : undefined
   if (link !== undefined) return link
-  const inner = emitRun(nodes, depth + 1, index, { ...context, bracketed: true, spansLines: false })
+  const inner = emitRun(nodes, depth + 1, index, { ...context, bracketed: true })
   if (!inner.ok) return inner
   if (inner.value.carry !== undefined) return inner
   return success({ segments: [syntax(spellInlineDirectiveOpener(mark.type)), ...inner.value.segments, syntax(`]${attributes}`)] })

src/markdown/portable/adf-to-portable-markdown.test.ts

@@ -309,7 +309,7 @@ test('breaks a line at a newline and trims whitespace at every edge CommonMark s
   assert.equal(portable(paragraph(text(' \n a \n b\n'))), 'a\\\nb\n')
   assert.equal(portable(paragraph({ type: 'hardBreak' }, text('a'), { attrs: { text: '\n' }, type: 'hardBreak' }, text('b'), { type: 'hardBreak' })), 'a\\\nb\n')
   assert.equal(portable(paragraph(text('a'), text(' b ', strong), text('c'))), 'a **b** c\n')
-  assert.equal(portable(paragraph(text(' '), text('b', strong), text(' \n'), text('c', strong), text(' '))), '**b\\\nc**\n')
+  assert.equal(portable(paragraph(text(' '), text('b', strong), text(' \n'), text('c', strong), text(' '))), '**b**\\\n**c**\n')
   assert.equal(portable(paragraph(text('x'), text('.', em), { type: 'hardBreak' }, text('b', em))), 'x.\\\n_b_\n')
   assert.equal(portable(paragraph(text('a'), text(' b ', em, strong), text(' ', em), text('c', em))), 'a _**b**  c_\n')
   assert.equal(portable(paragraph(text(' x ', code))), '`  x  `\n')

todo.md

@@ -6,7 +6,7 @@
 
 `Bar = 9`
 
-`Next ID = 91`
+`Next ID = 92`
 
 | Goal | W |
 |---|---|
@@ -52,6 +52,7 @@
 | 52 | 0.3.0 |  | **Spell `colwidth` as a comma list, `colwidth="340,420"`.** | 3 | 3 | 5 | 6 | 6 | 11.5 |
 | 51 | 0.3.0 |  | **Match a reference label to its definition under Unicode case folding.** | 2 | 2 | 2 | 7 | 4, 5 | 10.9 |
 | 53 | 0.3.0 |  | **Put a block's `marks` spelling to the writer panel and adopt its pick.** | 4 | 5 | 5 | 6 | 6 | 10.0 |
+| 91 | 0.3.0 |  | **Spell an emphasis or link once across the hard breaks between two nodes it marks, in both writers.** | 5 | 5 | 5 | 6 | 6 | 9.0 |
 | 73 | 0.4.0 |  | **Announce the package where someone needing an ADF converter already reads: JRACLOUD-77436, the Atlassian developer community and Stack Overflow's ADF-to-markdown questions.** | 1 | 2 | 6 | 8 | 3 | 23.0 |
 | 9 | 0.4.0 |  | **Ship an online sandbox: a web page with two textboxes converting between ADF and markdown on the library's browser build.** | 2 | 6 | 6 | 8 | 3 | 21.0 |
 | 38 | 0.4.0 |  | **Spell a lone surrogate in a text node so it survives a UTF-8 encode.** | 2 | 2 | 4 | 7 | 1 | 19.5 |
@@ -145,8 +146,8 @@ types a node takes, and the emitter carries a node holding another.
 `adfToLosslessMarkdown` spends 23 s on one paragraph of 2000 × `un` plus `**-r**`: each run its
 flanking cannot spell re-emits the whole line before riding the carry, quadratic in the runs, and
 the portable reduction's `spellableLine` drops one mark per re-emit the same way. An inline node
-whose attributes no spelling writes re-emits the line the same way before riding the carry, and so
+whose attributes no spelling writes re-emits the line the same way before riding the carry. Make all
-does an emphasis or link run that parts at the hard breaks it spans. Make all four linear.
+three linear.
 
 ### 7. Ship HTML: `adfToHtml`, `htmlToAdf`, and markdown to and from HTML composed through ADF, each call named by its flavour.
 
@@ -280,6 +281,15 @@ Today `marks="[{\"attrs\":{\"mode\":\"wide\"},\"type\":\"breakout\"}]"`, the mar
 escaped JSON. Breaking where the panel picks another spelling: `MIGRATION.md`'s Spellings table
 gains its row.
 
+### 91. Spell an emphasis or link once across the hard breaks between two nodes it marks, in both writers.
+
+Lands after item 61. No reader marks a hard break, so `*One\` then `Two*` writes back as `_One_\` then
+`_Two_`, and a link typed across a line as two links. Joining the run across the break in
+`inline-line.ts` ruled worse with two comprehension panels (PR #22): a joined run that cannot be
+spelled needs its own fallback, first as a set of parted breaks, then as a flag the first fallback
+clears. Once the emitter asks the reader how a line reads back, the joined spelling can be tried and
+kept only where it reads back.
+
 ### 73. Announce the package where someone needing an ADF converter already reads: JRACLOUD-77436, the Atlassian developer community and Stack Overflow's ADF-to-markdown questions.
 
 Lands after `0.3.0` is published with item 71, so each post links the GitHub repository, the