AGENTS.md

@@ -142,7 +142,9 @@ live Atlassian APIs; property-generated ADF trees; the CommonMark spec suite aga
 - `src/adf/` holds ADF's own knowledge and imports no format. Each format directory (`markdown/`,
   `html/`) parts into `emit/` (ADF→format) and `parse/` (format→ADF), its root holding what both
   directions read. A construct's reader lives in that root beside the regex the emitter escapes
-  against, so the two cannot drift; a reader with no emit counterpart goes in `parse/`.
+  against, so the two cannot drift; a reader with no emit counterpart goes in `parse/`. A rule both
+  directions must answer alike — whether a list marker interrupts a paragraph — is one function
+  there too, never a copy per direction, however conservative the copy would be.
 - The attribute vocabulary is ADF's: `adf/` walks it and narrows each value to its kind, and a
   format spells the narrowed value. A spelling that re-checks the type is the check's second copy.
 - Explicit over implicit; descriptive names; no catch-all files (`utils`, `helpers`, `misc`); a

spec/flavour.md

@@ -19,9 +19,9 @@ normalizes to it through the round-trip.
 - Bullet lists `- `; ordered lists incrementing `1.` `2.` `3.`, the first number the node's
   `order` attribute. Continuation lines align with the first character after the marker
   (two spaces for `- `, three for `1. `); blank lines inside an item are empty lines, none
-  between a nested list and a CommonMark block above it — one where the nested list's own marker
-  cannot interrupt a paragraph (any ordered list, or a bullet list whose first item opens with an
-  empty block), which the block above would otherwise swallow. Blank lines between items normalize
+  between a nested list and a CommonMark block above it — one wherever the nested list's own
+  marker cannot interrupt a paragraph (an ordered list whose first number is not 1, or a list
+  whose first item is empty), whatever block sits above it. Blank lines between items normalize
   away; ADF does not record tightness.
 - Blockquotes prefix lines with `> `; a blank line inside a blockquote is a bare `>`.
 - ATX headings (`#` … `######`); setext input normalizes to ATX.

src/markdown/commonmark-grammar.ts

@@ -86,6 +86,12 @@ export function isUnicodeWhitespace(character: string): boolean {
   return unicodeWhitespace.test(character)
 }
 
+// The first marker of a list, `undefined` for a bullet: one answer both directions read, or the emitter
+// spells a list the parser folds into the paragraph above it.
+export function markerInterruptsParagraph(start: number | undefined, empty: boolean): boolean {
+  return !empty && (start === undefined || start === 1)
+}
+
 export function openingCodeFence(line: string): { info: string; marker: string } | undefined {
   const marker = codeFenceOpener.exec(line)?.[1]
   if (marker === undefined) return undefined

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

@@ -267,6 +267,7 @@ test('parts a nested list the tight spelling would swallow from the block above
   const outer = (...content: AdfNode[]): AdfDocument => document({ content: [item(...content)], type: 'bulletList' })
   const ordered: AdfNode = { attrs: { order: 2 }, content: [item(text('b'))], type: 'orderedList' }
   assert.equal(markdown(adfToMarkdown(outer(text('a'), ordered))), '- a\n\n  2. b\n')
+  assert.equal(markdown(adfToMarkdown(outer(text('a'), { ...ordered, attrs: { order: 1 } }))), '- a\n  1. b\n')
   assert.equal(markdown(adfToMarkdown(outer(text('a'), { content: [item()], type: 'bulletList' }))), '- a\n\n  -\n')
   assert.equal(markdown(adfToMarkdown(outer(text('a'), { content: [item(text('b'))], type: 'bulletList' }))), '- a\n  - b\n')
 })
@@ -381,6 +382,9 @@ test('refuses a document nested deeper than the emitter carries', () => {
   let node: AdfNode = paragraph({ text: 'x', type: 'text' })
   for (let depth = 0; depth < 600; depth += 1) node = { content: [node], type: 'blockquote' }
   assert.equal(code(adfToMarkdown(document(node))), 'unsupported-nesting-depth')
+  let carried: AdfNode = paragraph({ text: 'x', type: 'text' })
+  for (let depth = 0; depth < 500; depth += 1) carried = { content: [carried], type: 'blockquote' }
+  assert.ok(adfToMarkdown(document(carried)).ok)
 })
 
 test('emits an empty list item without trailing whitespace', () => {

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

@@ -7,7 +7,7 @@ import { carriesOnly, isAdfDocument } from '../../adf/document.ts'
 import { emitInlineLine } from './inline-line.ts'
 import { failure, success, type ConvertErrorPath, type Result } from '../../result.ts'
 import { fencedCodeBlock } from '../backtick-runs.ts'
-import { holdsControlCharacter, holdsEntityReference, holdsNullCharacter, isThematicBreak } from '../commonmark-grammar.ts'
+import { holdsControlCharacter, holdsEntityReference, holdsNullCharacter, isThematicBreak, markerInterruptsParagraph } from '../commonmark-grammar.ts'
 import { largestNesting } from '../../nesting.ts'
 import { spellDirectiveHeader } from './block-directive-spelling.ts'
 import { tryImage } from './image.ts'
@@ -72,8 +72,10 @@ function separationBetween(previous: PlacedBlock, next: PlacedBlock, container:
 }
 
 function interruptsParagraph(node: AdfNode): boolean {
-  if (node.type === 'orderedList') return false
-  return ((node.content ?? [])[0]?.content ?? []).length > 0
+  const items = node.content ?? []
+  const empty = (items[0]?.content ?? []).length === 0
+  if (node.type !== 'orderedList') return markerInterruptsParagraph(undefined, empty)
+  return markerInterruptsParagraph(listStart(node, items.length) ?? 0, empty)
 }
 
 function emitBlock(node: AdfNode, path: ConvertErrorPath, depth: number): Result<EmittedBlock> {

src/markdown/parse/blocks.ts

@@ -1,5 +1,14 @@
 import type { LinkDefinition } from './link-reference-definitions.ts'
-import { atxHeading, claimsDirectiveLine, claimsPipeLine, closingCodeFence, isThematicBreak, openingCodeFence, setextHeadingLevel } from '../commonmark-grammar.ts'
+import {
+  atxHeading,
+  claimsDirectiveLine,
+  claimsPipeLine,
+  closingCodeFence,
+  isThematicBreak,
+  markerInterruptsParagraph,
+  openingCodeFence,
+  setextHeadingLevel,
+} from '../commonmark-grammar.ts'
 import { openingHtmlBlock } from './html-blocks.ts'
 import { readLinkDefinitions } from './link-reference-definitions.ts'
 
@@ -85,10 +94,11 @@ function continuesContainer(walk: Walk, container: OpenContainer, line: string):
 }
 
 function openContainers(walk: Walk, line: string, paragraphOpen: boolean, depth: number): { opened: boolean; rest: string } {
+  const unmatched = walk.stack[depth]
   let opened = false
   let rest = line
   while (leadingColumns(rest) < indentedCodeColumns) {
-    const start = containerStart(rest, opened ? false : paragraphOpen, opened ? undefined : walk.stack[depth])
+    const start = containerStart(rest, opened ? false : paragraphOpen, opened ? undefined : unmatched)
     if (start === undefined) break
     if (!opened) closeContainers(walk, depth)
     opened = true
@@ -102,11 +112,15 @@ function containerStart(line: string, paragraphOpen: boolean, enclosing: OpenCon
   const opener = removeColumns(line, largestOpenerIndentation)
   if (opener.startsWith('>')) return { kind: 'blockquote', rest: removeColumns(opener.slice(1), 1) }
   if (isThematicBreak(opener) || (paragraphOpen && setextHeadingLevel(opener) !== undefined)) return undefined
+  return itemStart(line, opener, paragraphOpen, enclosing)
+}
+
+function itemStart(line: string, opener: string, paragraphOpen: boolean, enclosing: OpenContainer | undefined): ContainerStart | undefined {
   const marker = itemMarker(opener)
   if (marker === undefined) return undefined
   const after = opener.slice(marker.width)
   const blank = blankLine.test(after)
-  if (paragraphOpen && (blank || (marker.list.kind === 'orderedList' && marker.list.start !== 1))) return undefined
+  if (paragraphOpen && !markerInterruptsParagraph(marker.list.kind === 'orderedList' ? marker.list.start : undefined, blank)) return undefined
   const spaces = leadingColumns(after)
   const padding = blank || spaces > indentedCodeColumns ? 1 : spaces
   const continued = enclosing?.kind === 'item' && enclosing.list.kind === marker.list.kind && enclosing.marker === marker.marker

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

@@ -197,6 +197,7 @@ test('opens a list beside a paragraph only where the marker interrupts it', () =
   assert.deepEqual(content(markdownToAdf('Part.\n- - -\n')), [paragraph('Part.'), { type: 'rule' }])
   assert.deepEqual(content(markdownToAdf('Part.\n-\n')), [{ attrs: { level: 2 }, content: [text('Part.')], type: 'heading' }])
   assert.deepEqual(content(markdownToAdf('- a\n  2. b\n')), [bulletList(item(paragraph('a 2. b')))])
+  assert.deepEqual(content(markdownToAdf('- a\n  1. b\n')), [bulletList(item(paragraph('a'), orderedList(1, item(paragraph('b')))))])
 })
 
 test('folds a lazy continuation into the paragraph the container holds', () => {

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

@@ -22,16 +22,28 @@ function blockNodes(blocks: readonly Block[], path: ConvertErrorPath, depth: num
   return success(content)
 }
 
+// Switched, not chained: `noImplicitReturns` then refuses the kind a later milestone adds and forgets.
 function blockNode(block: Block, path: ConvertErrorPath, depth: number): Result<AdfNode> {
-  if (block.kind === 'blockquote') return containerNode({ type: 'blockquote' }, block.blocks, path, depth)
-  if (block.kind === 'bulletList') return listNode({ type: 'bulletList' }, block.items, path, depth)
-  if (block.kind === 'claim') return claimFailure(block.construct, path)
-  if (block.kind === 'code') return success(codeBlockNode(block.language, block.text))
-  if (block.kind === 'heading') return success(withContent({ attrs: { level: block.level }, type: 'heading' }, block.text))
-  if (block.kind === 'html') return failure('unmappable-html', `no ADF node carries ${block.construct}`, path)
-  if (block.kind === 'orderedList') return listNode({ attrs: { order: block.start }, type: 'orderedList' }, block.items, path, depth)
-  if (block.kind === 'paragraph') return success(withContent({ type: 'paragraph' }, block.text))
+  switch (block.kind) {
+    case 'blockquote':
+      return containerNode({ type: 'blockquote' }, block.blocks, path, depth)
+    case 'bulletList':
+      return listNode({ type: 'bulletList' }, block.items, path, depth)
+    case 'claim':
+      return claimFailure(block.construct, path)
+    case 'code':
+      return success(codeBlockNode(block.language, block.text))
+    case 'heading':
+      return success(withContent({ attrs: { level: block.level }, type: 'heading' }, block.text))
+    case 'html':
+      return failure('unmappable-html', `no ADF node carries ${block.construct}`, path)
+    case 'orderedList':
+      return listNode({ attrs: { order: block.start }, type: 'orderedList' }, block.items, path, depth)
+    case 'paragraph':
+      return success(withContent({ type: 'paragraph' }, block.text))
+    case 'rule':
       return success({ type: 'rule' })
+  }
 }
 
 function containerNode(node: AdfNode, blocks: readonly Block[], path: ConvertErrorPath, depth: number): Result<AdfNode> {
@@ -51,8 +63,12 @@ function listNode(node: AdfNode, items: readonly Block[][], path: ConvertErrorPa
 }
 
 function claimFailure(construct: ClaimedConstruct, path: ConvertErrorPath): Result<AdfNode> {
-  if (construct === 'directive') return failure('malformed-directive', 'the line claims a directive and parses as none', path)
+  switch (construct) {
+    case 'directive':
+      return failure('malformed-directive', 'the line claims a directive and parses as none', path)
+    case 'pipe-table':
       return failure('malformed-pipe-table', 'the line claims a pipe table and parses as none', path)
+  }
 }
 
 function codeBlockNode(language: string, text: string): AdfNode {

src/nesting.ts

@@ -1 +1,2 @@
+// One level per block-list recursion in either direction — a list and its items count once — or the two guards disagree.
 export const largestNesting = 500