Charge a carried node against the levels its position leaves, and part the causes one guard hid

src/markdown/text-directive.ts

@@ -1,6 +1,5 @@
-import type { ConvertFault } from '../result.ts'
 import type { DirectiveSpan, Read } from './directive-syntax.ts'
-import { spellAttributes, spellLeafDirective, spellStringAttribute } from './directive-syntax.ts'
+import { readSoleStringAttribute, spellAttributes, spellLeafDirective, spellStringAttribute, unsupportedNodeShape } from './directive-syntax.ts'
 
 const name = 'text'
 const whitespaceRun = /^(?:[ \t]+|\n+)$/
@@ -13,15 +12,8 @@ export function spellTextDirective(text: string): string {
 
 export function readTextDirective(span: DirectiveSpan): Read<string> | undefined {
   if (span.name !== name) return undefined
-  if (span.content !== undefined) return { fault: unsupported(`${name} takes no content`) }
-  const spelled = span.attributes.get(name)
-  if (spelled === undefined || span.attributes.size !== 1) return { fault: unsupported(`${name} holds one ${name} attribute alone`) }
-  const spelling = spellStringAttribute(spelled.decoded)
-  if (spelling !== spelled.spelling) return { fault: unsupported(`${name} spells its ${name} attribute as ${name}=${spelling}`) }
-  if (!whitespaceRun.test(spelled.decoded)) return { fault: unsupported(`${name} spells one run of spaces and tabs, or one run of newlines`) }
-  return { value: spelled.decoded }
-}
-
-function unsupported(message: string): ConvertFault {
-  return { code: 'unsupported-node-shape', message }
+  const spelled = readSoleStringAttribute(span, name)
+  if (spelled.fault !== undefined) return spelled
+  if (!whitespaceRun.test(spelled.value)) return { fault: unsupportedNodeShape(`${name} spells one run of spaces and tabs, or one run of newlines`) }
+  return spelled
 }