5b1: name the line and the offset in the input a parse refusal sits at

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

@@ -2,7 +2,7 @@ import assert from 'node:assert/strict'
 import test from 'node:test'
 
 import type { AdfAttributes, AdfDocument, AdfMark, AdfNode } from '../../adf/document.ts'
-import type { Result } from '../../result.ts'
+import type { Result, SourcePosition } from '../../result.ts'
 import { largestNesting } from '../../nesting.ts'
 import { markdownToAdf } from './markdown-to-adf.ts'
 
@@ -23,6 +23,11 @@ function path(result: Result<AdfDocument>): readonly (number | string)[] {
   return result.ok ? ['built'] : result.error.path
 }
 
+function position(result: Result<AdfDocument>): SourcePosition | string {
+  if (result.ok) return 'built'
+  return result.error.position ?? 'no position'
+}
+
 function text(value: string): AdfNode {
   return { text: value, type: 'text' }
 }
@@ -443,6 +448,19 @@ test('swallows an HTML block ahead of the claim a line inside it would make', ()
   assert.equal(code(markdownToAdf('<div>\n| x |\n</div>\n')), 'unmappable-html')
 })
 
+test('names the line and the offset in the input a refusal sits at, the innermost block winning', () => {
+  assert.deepEqual(position(markdownToAdf('<div>\n')), { line: 1, offset: 0 })
+  assert.deepEqual(position(markdownToAdf('Part.\n\n<div>\n')), { line: 3, offset: 7 })
+  assert.deepEqual(position(markdownToAdf('> Part.\n>\n> a <span>b</span>\n')), { line: 3, offset: 10 })
+  assert.deepEqual(position(markdownToAdf('- Part.\n- a <span>b</span>\n')), { line: 2, offset: 8 })
+  assert.deepEqual(position(markdownToAdf('Part.\n\n:::panel info\nMore.\n')), { line: 3, offset: 7 })
+  assert.deepEqual(position(markdownToAdf('x\n\na <span>b</span>\n===\n')), { line: 3, offset: 3 })
+  assert.deepEqual(position(markdownToAdf('x\n\n```adf\n{\n```\n')), { line: 3, offset: 3 })
+  assert.deepEqual(position(markdownToAdf('x\n\n| a |\n')), { line: 3, offset: 3 })
+  assert.deepEqual(position(markdownToAdf('a\nb <span>c</span>\n')), { line: 1, offset: 0 })
+  assert.deepEqual(position(markdownToAdf('Part.\r\n\r\n<div>\r\n')), { line: 3, offset: 9 })
+})
+
 test('gives up the link reference definitions a paragraph opens with', () => {
   assert.deepEqual(content(markdownToAdf('[a]: /url\n')), [])
   assert.deepEqual(content(markdownToAdf('[a]: /url\n[b]: /other\nPart.\n')), [paragraph('Part.')])