12c: one block opener speller beside its reader, the line readers split along the union, and AGENTS.md records the leaf body

AGENTS.md

@@ -133,9 +133,11 @@ reserved name is a known name, so never that code, and the two the flavour reser
 a form the grammar does not have is a claim code — `!adf:carry`, whose carry is the fence — and a
 well-formed form in the wrong place is `unsupported-node-shape`, `!adf:listBreak` parting anything
 but two adjacent lists of one type. What
-the grammar itself refuses stays a claim code, key order among it; a well-formed directive the
+the grammar itself refuses stays a claim code, key order among it, and a leaf given a body is refused
-node tables refuse — an attribute a node does not hold or spells elsewhere, a value outside its
+at its opener, as a container missing its closer is (the maintainer, 2026-09-16); a well-formed
-kind or its canonical spelling, an argument or a body its content model does not take — is
+directive the node tables refuse — an attribute a node does not hold or spells elsewhere, a value
+outside its kind or its canonical spelling, an argument, or a body of a shape its content model does
+not take — is
 `unsupported-node-shape`, the emitter's code for the same mismatch read the other way — one code
 across both directions for good, since the call site knows which direction it called and parting
 them after `0.1.0` is MAJOR. `unmappable-html` names the version rather than the element: this one

src/markdown-property.test.ts

@@ -16,6 +16,7 @@ import {
   directivePrefix,
   spellAttributes,
   spellDirectiveCloser,
+  spellDirectiveOpener,
   spellInlineDirectiveOpener,
   spellInlineLeafDirective,
   spellJsonAttribute,
@@ -160,7 +161,7 @@ const hostileArgument = fc.oneof(
   { arbitrary: fc.oneof(bareToken.map((held) => ` ${held}`), fc.constantFrom('  info', ' a b', ' "a"')), weight: 1 },
 )
 
-function directiveOpener(name: string, argument: string, attrs: string): string {
+function hostileOpener(name: string, argument: string, attrs: string): string {
   return `${directivePrefix}${name}${argument}${attrs === '' ? '' : ` ${attrs}`}`
 }
 
@@ -310,7 +311,7 @@ function leafBlocks(hostile: boolean, { destination, inlines, label, oneLine, te
       weight: 1,
     },
     {
-      arbitrary: fc.tuple(directiveName, hostileArgument, hostileAttributes).map(([name, argument, attrs]) => directiveOpener(name, argument, attrs)),
+      arbitrary: fc.tuple(directiveName, hostileArgument, hostileAttributes).map(([name, argument, attrs]) => hostileOpener(name, argument, attrs)),
       hostile: true,
       weight: 1,
     },
@@ -330,13 +331,13 @@ function blockMarkdown(hostile: boolean, { inlines, oneLine }: InlineMarkdown, {
     const tableDirectives = Object.entries(blockDirectives).map(([name, directive]) => {
       const argument =
         blockArgument(name) === undefined
-          ? fc.constant('')
+          ? fc.constant(undefined)
-          : fc.oneof({ arbitrary: fc.constantFrom(' DONE', ' TODO', ' custom', ' info', ' warning'), weight: 3 }, { arbitrary: bareToken.map((held) => ` ${held}`), weight: 1 })
+          : fc.oneof({ arbitrary: fc.constantFrom('DONE', 'TODO', 'custom', 'info', 'warning'), weight: 3 }, { arbitrary: bareToken, weight: 1 })
       const attrs = hostile ? fc.oneof({ arbitrary: tableAttributes(directive.attributes), weight: 4 }, { arbitrary: hostileAttributes, weight: 1 }) : tableAttributes(directive.attributes)
-      if (directive.contentModel === 'none') return fc.tuple(argument, attrs).map(([held, spelled]) => directiveOpener(name, held, spelled))
+      if (directive.contentModel === 'none') return fc.tuple(argument, attrs).map(([held, spelled]) => spellDirectiveOpener(name, held, spelled))
       return fc
         .tuple(argument, attrs, bodyByModel[directive.contentModel], hostile ? closerDrift : fc.constant(null))
-        .map(([held, spelled, body, closer]) => container(directiveOpener(name, held, spelled), body, closer ?? spellDirectiveCloser(name)))
+        .map(([held, spelled, body, closer]) => container(spellDirectiveOpener(name, held, spelled), body, closer ?? spellDirectiveCloser(name)))
     })
     return {
       block: choose(
@@ -365,7 +366,7 @@ function blockMarkdown(hostile: boolean, { inlines, oneLine }: InlineMarkdown, {
           {
             arbitrary: fc
               .tuple(directiveName, hostileArgument, hostileAttributes, tie('blocks'), closerDrift)
-              .map(([name, argument, attrs, body, closer]) => container(directiveOpener(name, argument, attrs), body, closer ?? spellDirectiveCloser(name))),
+              .map(([name, argument, attrs, body, closer]) => container(hostileOpener(name, argument, attrs), body, closer ?? spellDirectiveCloser(name))),
             hostile: true,
             weight: 1,
           },

src/markdown/directive-syntax.ts

@@ -77,17 +77,7 @@ export function malformedDirective(message: string): ConvertFault {
 
 export function readDirectiveLine(line: string): Read<DirectiveLine> | undefined {
   if (!claimsDirectivePrefix(line, 0)) return undefined
-  const closer = line.charAt(directivePrefix.length) === '/'
+  return line.charAt(directivePrefix.length) === '/' ? readCloserLine(line) : readOpenerLine(line)
-  const start = directivePrefix.length + (closer ? 1 : 0)
-  directiveName.lastIndex = start
-  const name = directiveName.exec(line)?.[0]
-  if (name === undefined) return undefined
-  const rest = line.slice(start + name.length)
-  if (closer) return lineEnd.test(rest) ? { value: { kind: 'closer', name } } : { fault: malformedDirective(closerFault) }
-  if (!rest.startsWith(' ') && !lineEnd.test(rest)) return undefined
-  const opener = readOpenerRest(rest)
-  if (opener.fault !== undefined) return { fault: opener.fault }
-  return { value: { argument: opener.value.argument, attributes: opener.value.attributes, kind: 'opener', name } }
 }
 
 export function readInlineDirective(text: string, index: number): Read<DirectiveSpan> | undefined {
@@ -119,6 +109,10 @@ export function spellDirectiveCloser(name: string): string {
   return `${directivePrefix}/${name}`
 }
 
+export function spellDirectiveOpener(name: string, argument: string | undefined, attributes: string): string {
+  return `${directivePrefix}${name}${argument === undefined ? '' : ` ${argument}`}${attributes === '' ? '' : ` ${attributes}`}`
+}
+
 export function spellJsonAttribute(value: JsonValue): string {
   return quote(serializeCanonicalJson(value, 'compact'))
 }
@@ -173,24 +167,39 @@ function inlineDirectiveName(text: string, index: number): string | undefined {
   return opened === undefined ? undefined : opened.slice(directivePrefix.length, -1)
 }
 
+function readCloserLine(line: string): Read<DirectiveLine> | undefined {
+  const start = directivePrefix.length + 1
+  const name = readDirectiveName(line, start)
+  if (name === undefined) return undefined
+  return lineEnd.test(line.slice(start + name.length)) ? { value: { kind: 'closer', name } } : { fault: malformedDirective(closerFault) }
+}
+
+function readOpenerLine(line: string): Read<DirectiveLine> | undefined {
+  const name = readDirectiveName(line, directivePrefix.length)
+  if (name === undefined) return undefined
+  const rest = line.slice(directivePrefix.length + name.length)
+  if (!rest.startsWith(' ') && !lineEnd.test(rest)) return undefined
+  const opener = readOpenerRest(rest)
+  if (opener.fault !== undefined) return { fault: opener.fault }
+  return { value: { argument: opener.value.argument, attributes: opener.value.attributes, kind: 'opener', name } }
+}
+
+function readDirectiveName(text: string, index: number): string | undefined {
+  directiveName.lastIndex = index
+  return directiveName.exec(text)?.[0]
+}
+
 function readOpenerRest(rest: string): Read<{ argument: string | undefined; attributes: DirectiveAttributes }> {
-  let cursor = 0
+  bareRun.lastIndex = 1
-  let argument: string | undefined
+  const argument = bareRun.exec(rest)?.[0]
-  let attributes = noAttributes
+  const attributes = readOpenerAttributes(rest, argument === undefined ? 0 : 1 + argument.length)
-  if (rest.charAt(0) === ' ' && rest.charAt(1) !== '{' && !lineEnd.test(rest)) {
+  if (attributes.fault !== undefined) return { fault: attributes.fault }
-    bareRun.lastIndex = 1
+  if (!lineEnd.test(rest.slice(attributes.value.end))) return { fault: malformedDirective(openerFault) }
-    argument = bareRun.exec(rest)?.[0]
+  return { value: { argument, attributes: attributes.value.attributes } }
-    if (argument === undefined) return { fault: malformedDirective(openerFault) }
+}
-    cursor = 1 + argument.length
+
-  }
+function readOpenerAttributes(rest: string, index: number): Read<Attributes> {
-  if (rest.charAt(cursor) === ' ' && rest.charAt(cursor + 1) === '{') {
+  return rest.charAt(index) === ' ' ? readAttributesAt(rest, index + 1, false) : { value: { attributes: noAttributes, end: index } }
-    const read = readAttributesAt(rest, cursor + 1, false)
-    if (read.fault !== undefined) return { fault: read.fault }
-    attributes = read.value.attributes
-    cursor = read.value.end
-  }
-  if (!lineEnd.test(rest.slice(cursor))) return { fault: malformedDirective(openerFault) }
-  return { value: { argument, attributes } }
 }
 
 function readNestedDirective(text: string, index: number, depth: number): Read<DirectiveSpan> | undefined {

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

@@ -113,13 +113,16 @@ function directivePair(node: AdfNode, opener: string, body: string): EmittedBloc
 
 function emitDirectiveBlock(node: AdfNode, directive: BlockDirective, path: ConvertErrorPath, depth: number): Result<EmittedBlock> {
   if (node.text !== undefined) return failure('unsupported-node-shape', `a ${node.type} carries no text: this one holds text`, path)
-  const content = nodeContent(node)
+  if (blockDirectiveForm(node.type) === 'leaf' && nodeContent(node).length > 0) return failure('unsupported-node-shape', `a ${node.type} holds no content: this one holds some`, path)
-  const leaf = blockDirectiveForm(node.type) === 'leaf'
-  if (leaf && content.length > 0) return failure('unsupported-node-shape', `a ${node.type} holds no content: this one holds some`, path)
   if (directive.contentModel === 'code') return emitCodeDirective(node, directive, path, depth)
   const opener = spellBlockDirectiveOpener(node, directive)
   if (opener === undefined) return commonMarkLine(carriedBlock(node, path, depth))
-  if (leaf) return success({ spelling: 'directive', text: opener })
+  return emitDirectiveBody(node, directive, opener, path, depth)
+}
+
+function emitDirectiveBody(node: AdfNode, directive: BlockDirective, opener: string, path: ConvertErrorPath, depth: number): Result<EmittedBlock> {
+  if (blockDirectiveForm(node.type) === 'leaf') return success({ spelling: 'directive', text: opener })
+  const content = nodeContent(node)
   const body = directive.contentModel === 'inline' ? emitInlineLine(content, 'paragraph', path) : emitBlocks(content, 'directive', path, depth + 1)
   if (!body.ok) return body
   return success(directivePair(node, opener, body.value))

src/markdown/emit/block-directive-spelling.ts

@@ -1,28 +1,27 @@
 import type { AdfNode } from '../../adf/document.ts'
 import type { BlockDirective } from '../../adf/block-directives.ts'
 import { blockArgument } from '../block-directive-arguments.ts'
-import { directivePrefix, isBareToken, spellAttributes, spellJsonAttribute, spellVocabulary } from '../directive-syntax.ts'
+import { isBareToken, spellAttributes, spellDirectiveOpener, spellJsonAttribute, spellVocabulary } from '../directive-syntax.ts'
 import { markValues, marksAttribute } from '../block-directive-marks.ts'
 import { nodeAttrs, nodeMarks } from '../../adf/document.ts'
 import { vocabularyPairs } from '../../adf/attribute-vocabulary.ts'
 
 export function spellBlockDirectiveOpener(node: AdfNode, directive: BlockDirective, spelledByBody: readonly string[] = []): string | undefined {
   const argumentAttribute = blockArgument(node.type)
-  const argument = spellArgument(node, argumentAttribute)
+  const slot = bareArgument(node, argumentAttribute)
-  if (argument === undefined) return undefined
+  if (slot === undefined) return undefined
   const spelled = argumentAttribute === undefined ? spelledByBody : [argumentAttribute, ...spelledByBody]
   const pairs = vocabularyPairs(nodeAttrs(node), directive.attributes, spelled)
   if (pairs === undefined) return undefined
   const spelledPairs = spellVocabulary(pairs)
   const marks = nodeMarks(node)
   if (marks.length > 0) spelledPairs.push([marksAttribute, spellJsonAttribute(markValues(marks))])
-  const attributes = spellAttributes(spelledPairs)
+  return spellDirectiveOpener(node.type, slot.argument, spellAttributes(spelledPairs))
-  return `${directivePrefix}${node.type}${argument}${attributes === '' ? '' : ` ${attributes}`}`
 }
 
-function spellArgument(node: AdfNode, argumentAttribute: string | undefined): string | undefined {
+// `undefined` where the argument slot holds a value no bare token spells.
+function bareArgument(node: AdfNode, argumentAttribute: string | undefined): { argument: string | undefined } | undefined {
   const value = argumentAttribute === undefined ? undefined : nodeAttrs(node)[argumentAttribute]
-  if (value === undefined) return ''
+  if (value === undefined) return { argument: undefined }
-  if (typeof value !== 'string' || !isBareToken(value)) return undefined
+  return typeof value === 'string' && isBareToken(value) ? { argument: value } : undefined
-  return ` ${value}`
 }

src/markdown/list-break.ts

@@ -1,5 +1,5 @@
-import { directivePrefix } from './directive-syntax.ts'
+import { spellDirectiveOpener } from './directive-syntax.ts'
 
 export const listBreakName = 'listBreak'
 
-export const listBreakSpelling = `${directivePrefix}${listBreakName}`
+export const listBreakSpelling = spellDirectiveOpener(listBreakName, undefined, '')

todo.md

@@ -75,7 +75,8 @@ proves 12, 13 spells 11's gaps in 12's grammar, and 12 rewrites code 4b and 4c c
       re-scans the region below it and nested inline directives cost O(depth × content) — 3f's
       cost, which 3i's slot parse doubles rather than changes in class, bounded by the 500-level
       guard. §11's scanning rule is the whole argument; the pipeline persona feeds documents
-      nobody typed.
+      nobody typed. `readDirectiveContent`'s scan splits into named steps with that fix rather
+      than keeping its complexity (the maintainer, 2026-09-16).
 - [ ] **4d — What the gate says while it runs (`0.2.1`).** `ci.sh` runs nine legs and announces
       none of them, so five minutes of a Gitea run read as silence and a hang cannot be told from
       a slow pull — the maintainer hit exactly this on the `0.1.0` release. Three causes, each its