Answer the architecture pass: the list a blank line split, and the slot the seam names

src/markdown/code-language.ts

@@ -3,10 +3,12 @@ import { carryName } from './opaque-carry.ts'
 import { holdsControlCharacter } from './commonmark-grammar.ts'
 import { holdsEntityReference } from './entity-references.ts'
 
-// spec/flavour.md, The CommonMark blocks: the info string the language rides, `undefined` where the attribute carries it.
-export function fenceInfo(language: JsonValue | undefined): string | undefined {
-  if (language === undefined) return ''
-  if (typeof language !== 'string' || language === '' || language === carryName) return undefined
-  if (/[`\\]/.test(language) || holdsControlCharacter(language) || language !== language.trim() || holdsEntityReference(language)) return undefined
-  return language
+export type LanguageSlot = { info: string; kind: 'fence' } | { kind: 'attribute' } | { kind: 'none' }
+
+// spec/flavour.md, The CommonMark blocks: the one slot a codeBlock's language rides, both directions.
+export function languageSlot(language: JsonValue | undefined): LanguageSlot {
+  if (language === undefined) return { kind: 'none' }
+  if (typeof language !== 'string' || language === '' || language === carryName) return { kind: 'attribute' }
+  if (/[`\\]/.test(language) || holdsControlCharacter(language) || language !== language.trim() || holdsEntityReference(language)) return { kind: 'attribute' }
+  return { info: language, kind: 'fence' }
 }

src/markdown/commonmark-grammar.ts

@@ -171,13 +171,13 @@ export function isUnicodeWhitespace(character: string): boolean {
 }
 
 // `start` is the list's first number, `undefined` for a bullet.
-export function listMarker(line: string): { delimiter: string; start: number | undefined; width: number } | undefined {
+export function listMarker(line: string): { start: number | undefined; width: number } | undefined {
   const ordered = orderedListOpener.exec(line)
   if (ordered !== null) {
     const digits = ordered[1] ?? ''
-    return { delimiter: ordered[2] ?? '', start: Number(digits), width: digits.length + 1 }
+    return { start: Number(digits), width: digits.length + 1 }
   }
-  return bulletListOpener.test(line) ? { delimiter: line.charAt(0), start: undefined, width: 1 } : undefined
+  return bulletListOpener.test(line) ? { start: undefined, width: 1 } : undefined
 }
 
 export function markerInterruptsParagraph(start: number | undefined, empty: boolean): boolean {

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

@@ -6,7 +6,7 @@ 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 { fenceInfo } from '../code-language.ts'
+import { languageSlot } from '../code-language.ts'
 import { holdsNullCharacter, isThematicBreak, markerInterruptsParagraph } from '../commonmark-grammar.ts'
 import { largestNesting } from '../../nesting.ts'
 import { spellDirectiveHeader } from './block-directive-spelling.ts'
@@ -147,20 +147,21 @@ function emitBlockquote(node: AdfNode, path: ConvertErrorPath, depth: number): R
 
 function emitCodeBlock(node: AdfNode, path: ConvertErrorPath): Result<EmittedBlock> | undefined {
   if (!carriesOnly(node, ['language'])) return undefined
-  const info = fenceInfo(node.attrs?.['language'])
-  if (info === undefined) return undefined
+  const slot = languageSlot(node.attrs?.['language'])
+  if (slot.kind === 'attribute') return undefined
   const text = codeBlockText(node, path)
   if (!text.ok) return text
-  return success(commonMarkText(fencedCodeBlock(info, text.value)))
+  return success(commonMarkText(fencedCodeBlock(slot.kind === 'fence' ? slot.info : '', text.value)))
 }
 
 function emitCodeDirective(node: AdfNode, directive: BlockDirective, path: ConvertErrorPath): Result<EmittedBlock> {
-  const info = fenceInfo(node.attrs?.['language'])
-  const header = spellDirectiveHeader(node, directive, info === undefined ? [] : ['language'])
+  const slot = languageSlot(node.attrs?.['language'])
+  const header = spellDirectiveHeader(node, directive, slot.kind === 'attribute' ? [] : ['language'])
   if (header === undefined) return commonMarkLine(carriedBlock(node, path))
   const text = codeBlockText(node, path)
   if (!text.ok) return text
-  return success({ fenceColons: 3, spelling: 'directive', text: `:::${header}\n${fencedCodeBlock(info ?? '', text.value)}\n:::` })
+  const info = slot.kind === 'fence' ? slot.info : ''
+  return success({ fenceColons: 3, spelling: 'directive', text: `:::${header}\n${fencedCodeBlock(info, text.value)}\n:::` })
 }
 
 function codeBlockText(node: AdfNode, path: ConvertErrorPath): Result<string> {

src/markdown/parse/blocks.ts

@@ -176,9 +176,19 @@ function openContainer(walk: Walk, start: ContainerStart): void {
     walk.stack.push(blockquote)
     return
   }
-  if (start.fresh) currentBlocks(walk).push(start.list)
-  start.list.items.push(blocks)
-  walk.stack.push({ blocks, indentation: start.indentation, kind: 'item', list: start.list })
+  const list = openedList(walk, start)
+  list.items.push(blocks)
+  walk.stack.push({ blocks, indentation: start.indentation, kind: 'item', list })
+}
+
+// Two lists of a kind never sit adjacent: one `- ` spelling reads them back as one (spec/flavour.md).
+function openedList(walk: Walk, start: Extract<ContainerStart, { kind: 'item' }>): ListBlock {
+  if (!start.fresh) return start.list
+  const blocks = currentBlocks(walk)
+  const previous = blocks.at(-1)
+  if ((previous?.kind === 'bulletList' || previous?.kind === 'orderedList') && previous.kind === start.list.kind) return previous
+  blocks.push(start.list)
+  return start.list
 }
 
 function closeContainers(walk: Walk, depth: number): void {

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

@@ -390,6 +390,8 @@ test('reads a bullet list, the marker width setting the continuation', () => {
   assert.deepEqual(content(markdownToAdf('-     Code.\n')), [bulletList(item({ content: [text('Code.')], type: 'codeBlock' }))])
   assert.deepEqual(content(markdownToAdf('- a\n* b\n')), [bulletList(item(paragraph('a')), item(paragraph('b')))])
   assert.deepEqual(content(markdownToAdf('- a\n\n+ b\n')), [bulletList(item(paragraph('a')), item(paragraph('b')))])
+  assert.deepEqual(content(markdownToAdf('- a\n-\n\n- c\n')), [bulletList(item(paragraph('a')), item(), item(paragraph('c')))])
+  assert.deepEqual(content(markdownToAdf('- a\n1. b\n')), [bulletList(item(paragraph('a'))), orderedList(1, item(paragraph('b')))])
   assert.deepEqual(content(markdownToAdf('-\n\n  Part.\n')), [bulletList(item()), paragraph('Part.')])
 })
 

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

@@ -5,7 +5,7 @@ import type { LinkDefinitions } from './inline-content.ts'
 import { carryName } from '../opaque-carry.ts'
 import { commonMarkSpelling } from '../emit/adf-to-markdown.ts'
 import { failure, faulted, success, type ConvertErrorPath, type Result } from '../../result.ts'
-import { fenceInfo } from '../code-language.ts'
+import { languageSlot } from '../code-language.ts'
 import { largestNesting } from '../../nesting.ts'
 import { parseBlocks } from './blocks.ts'
 import { parseInlineContent } from './inline-content.ts'
@@ -85,8 +85,8 @@ function codeDirectiveNode(node: AdfNode, blocks: readonly Block[], path: Conver
   if (only?.kind !== 'code') return failure('unsupported-node-shape', `${node.type} takes one fenced code block as its body`, path)
   const attribute = node.attrs?.['language']
   const fromFence = only.language !== ''
-  const info = fenceInfo(fromFence ? only.language : attribute)
-  if ((info !== undefined && info !== '') !== fromFence || (fromFence && attribute !== undefined)) {
+  const slot = languageSlot(fromFence ? only.language : attribute)
+  if ((slot.kind === 'fence') !== fromFence || (fromFence && attribute !== undefined)) {
     return failure('unsupported-node-shape', `${node.type} spells its language in the fence info string, or in the attribute where no info string carries it back`, path)
   }
   const spelled = fromFence ? { ...node, attrs: { ...node.attrs, language: only.language } } : node