35b - review: escape a task marker opening any list item's first paragraph

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

@@ -317,12 +317,12 @@ function tryList(node: AdfNode, path: ConvertErrorPath, depth: number, writing:
     headroom = Math.min(headroom, walk.value.headroom)
     walked.push({ node: item, walk: walk.value })
   }
-  const inners = walked.map((item) => joinBlocks(item.walk.blocks, 'list-item'))
-  // A bullet list whose every item opens with a task marker reads as a task list (README §Plain markdown).
-  if (writing.flavour === 'plain' && !ordered && inners.every((inner) => leadingMarker(inner, readTaskMarker) !== undefined)) inners[0] = `\\${inners[0] ?? ''}`
   const lines: string[] = []
-  for (const [offset, inner] of inners.entries()) {
-    const line = tryListItemLines(inner, ordered ? `${start + offset}. ` : '- ')
+  for (const [offset, item] of walked.entries()) {
+    const inner = joinBlocks(item.walk.blocks, 'list-item')
+    // GitHub reads a task marker opening any item's first paragraph as a checkbox, whatever its siblings hold.
+    const escaped = writing.flavour === 'plain' && leadingMarker(inner, readTaskMarker) !== undefined ? `\\${inner}` : inner
+    const line = tryListItemLines(escaped, ordered ? `${start + offset}. ` : '- ')
     if (line === undefined) {
       // The directive form spends a level the walk did not count.
       if (headroom < 1) return tooDeep(path)

src/markdown/emit/plain-reduction.test.ts

@@ -123,16 +123,16 @@ test('spells a task list as a bullet list whose items lead with their state', ()
   const task = (state: string, value: string): AdfNode => node('taskItem', { localId: '01a0d99b-1f58-7b95-829b-6f9860371d54', state }, text(value))
   const nested = node('taskList', {}, task('TODO', 'Review'))
   assert.equal(plain(node('taskList', {}, task('DONE', 'Write the spec'), nested, task('TODO', 'Ship it'))), '- [x] Write the spec\n  - [ ] Review\n- [ ] Ship it\n')
-  assert.equal(plain(node('taskList', {}, nested, task('DONE', ''), said('Stray'))), '- - [ ] Review\n- [x]\n- Stray\n')
-  assert.equal(plain(node('taskList', {}, node('taskList', {}), task('DONE', 'a'), said('b'), node('taskList', {}, task('TODO', 'c')))), '- [x] a\n- b\n  - [ ] c\n')
+  assert.equal(plain(node('taskList', {}, nested, task('DONE', ''), said('Stray'))), '- - [ ] Review\n- \\[x]\n- Stray\n')
+  assert.equal(plain(node('taskList', {}, node('taskList', {}), task('DONE', 'a'), said('b'), node('taskList', {}, task('TODO', 'c')))), '- \\[x] a\n- b\n  - [ ] c\n')
   assert.equal(plain(node('taskList', {}, paragraph(), task('DONE', 'a'))), '- [x] a\n')
-  assert.equal(plain(bulletList(item(said('x'))), node('taskList', {}, task('DONE', 'a'), node('taskList', {}, task('TODO', 'c')))), '- x\n- [x] a\n  - [ ] c\n')
+  assert.equal(plain(bulletList(item(said('x'))), node('taskList', {}, task('DONE', 'a'), node('taskList', {}, task('TODO', 'c')))), '- x\n- \\[x] a\n  - [ ] c\n')
   assert.equal(plain(node('taskList', {}), task('TODO', 'Loose')), 'Loose\n')
   const blockTask = node('blockTaskItem', { state: 'DONE' }, said('First.'), said('Second.'))
   const codeTask = node('blockTaskItem', { state: 'TODO' }, { content: [text('x')], type: 'codeBlock' })
   assert.equal(plain(node('taskList', {}, blockTask, codeTask)), '- [x] First.\n\n  Second.\n- [ ]\n\n  ```\n  x\n  ```\n')
   const listTask = node('blockTaskItem', { state: 'DONE' }, bulletList(item(said('a'))))
-  assert.equal(plain(node('taskList', {}, task('TODO', ''), listTask, node('taskList', {}, task('TODO', 'b')))), '- [ ]\n- [x]\n  - a\n  - [ ] b\n')
+  assert.equal(plain(node('taskList', {}, task('TODO', ''), listTask, node('taskList', {}, task('TODO', 'b')))), '- [ ]\n- [x]\n  - a\n  - \\[ ] b\n')
   assert.equal(plain(node('taskList', {}, task('DONE', 'a'), node('taskList', {}, task('TODO', '')))), '- [x] a\n  - [ ]\n')
 })
 
@@ -154,8 +154,8 @@ test('escapes text that would read back as a flavour marker, and only there', ()
   assert.equal(plain(said('==x== a == b a==b ===')), '\\==x\\== a == b a==b \\=\\==\n')
   assert.equal(plain({ content: [said('[!NOTE] x'), said('[!TIP]')], type: 'blockquote' }), '> \\[!NOTE] x\n>\n> [!TIP]\n')
   assert.equal(plain({ content: [said('[!NOTE]x')], type: 'blockquote' }, said('[!NOTE]')), '> [!NOTE]x\n\n[!NOTE]\n')
-  assert.equal(plain(bulletList(item(said('[x] a')), item(said('[ ]')))), '- \\[x] a\n- [ ]\n')
-  assert.equal(plain(bulletList(item(said('[x] a')), item(said('b'))), node('orderedList', { order: 1 }, item(said('[x] c')))), '- [x] a\n- b\n\n1. [x] c\n')
+  assert.equal(plain(bulletList(item(said('[x] a')), item(said('[ ]')))), '- \\[x] a\n- \\[ ]\n')
+  assert.equal(plain(bulletList(item(said('[x] a')), item(said('b'))), node('orderedList', { order: 1 }, item(said('[x] c')))), '- \\[x] a\n- b\n\n1. \\[x] c\n')
   const task = (state: string, value: string): AdfNode => node('taskItem', { state }, text(value))
   assert.equal(plain(node('taskList', {}, task('DONE', '[x] a'), task('TODO', '==b=='))), '- [x] [x] a\n- [ ] \\==b\\==\n')
 })
@@ -184,7 +184,7 @@ test('keeps the CommonMark blocks in their spelling and drops their attributes a
   assert.equal(plain(node('orderedList', { order: 1e10 }, item(said('Alpha')), item(code), item())), '- 10000000000. Alpha\n- 10000000001.\n\n  ```\n  x\n  ```\n- 10000000002.\n')
   const long = node('orderedList', { order: 1e10 }, item(said('y')))
   assert.equal(plain(bulletList(item(said('x'))), long, bulletList(item(said('z')))), '- x\n- 10000000000. y\n- z\n')
-  assert.equal(plain(node('taskList', {}, node('taskItem', { state: 'DONE' }, text('t'))), long), '- [x] t\n- 10000000000. y\n')
+  assert.equal(plain(node('taskList', {}, node('taskItem', { state: 'DONE' }, text('t'))), long), '- \\[x] t\n- 10000000000. y\n')
   assert.equal(plain(bulletList(item(said('a'), bulletList(item(said('x'))), long))), '- a\n  - x\n  - 10000000000. y\n')
   const givesWay = node('orderedList', { order: 1e10 }, item(node('rule', {})), item(bulletList(item(bulletList(item())))))
   assert.equal(plain(givesWay, bulletList(item(said('z')))), '- 10000000000.\n- 10000000001.\n  - -\n- z\n')