4.2: a link's brackets balance inside a directive's content

corpus/round-trip/combinations/directive-link-brackets.json

@@ -0,0 +1,111 @@
+{
+  "content": [
+    {
+      "content": [
+        {
+          "marks": [
+            {
+              "type": "subsup"
+            },
+            {
+              "attrs": {
+                "href": "["
+              },
+              "type": "link"
+            }
+          ],
+          "text": "a",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    },
+    {
+      "content": [
+        {
+          "marks": [
+            {
+              "type": "underline"
+            },
+            {
+              "attrs": {
+                "href": "]"
+              },
+              "type": "link"
+            }
+          ],
+          "text": "b",
+          "type": "text"
+        },
+        {
+          "marks": [
+            {
+              "type": "underline"
+            }
+          ],
+          "text": " ",
+          "type": "text"
+        },
+        {
+          "marks": [
+            {
+              "type": "underline"
+            },
+            {
+              "attrs": {
+                "href": "x",
+                "title": "["
+              },
+              "type": "link"
+            }
+          ],
+          "text": "c",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    },
+    {
+      "content": [
+        {
+          "marks": [
+            {
+              "type": "underline"
+            },
+            {
+              "attrs": {
+                "href": "e[f]"
+              },
+              "type": "link"
+            }
+          ],
+          "text": "d",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    },
+    {
+      "content": [
+        {
+          "marks": [
+            {
+              "type": "underline"
+            },
+            {
+              "attrs": {
+                "href": "http://a[b"
+              },
+              "type": "link"
+            }
+          ],
+          "text": "http://a[b",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    }
+  ],
+  "type": "doc",
+  "version": 1
+}

corpus/round-trip/combinations/directive-link-brackets.md

@@ -0,0 +1,7 @@
+:subsup[[a](\[)]
+
+:underline[[b](\]) [c](x "\[")]
+
+:underline[[d](e[f])]
+
+:underline[[http://a\[b](http://a\[b)]

spec/flavour.md

@@ -129,9 +129,11 @@ quoted where bare carries it, an escape longer than it need be, an empty `{attrs
 each a named error naming the spelling to write instead.
 
 **Escaping**: the emitter backslash-escapes whatever literal text would otherwise parse as
-directive syntax — the leading `:` of a would-be directive, `]` inside content, a `{` right
+directive syntax — the leading `:` of a would-be directive, `]` inside content, a bracket a link's
-after a directive's closing `]`, which would otherwise be read as the attributes it has none
+destination and title inside content leave unbalanced (an autolink holding one takes the
-of; outside code spans and code blocks, a backslash before `:` in input yields a literal colon.
+`[text](url)` form), a `{` right after a directive's closing `]`, which would otherwise be read as
+the attributes it has none of; outside code spans and code blocks, a backslash before `:` in input
+yields a literal colon.
 
 **Malformed directives are error results**, named: an unclosed container at end of input, a body
 fence line of the container's length or longer, a bare colon-run line outside any container or

src/markdown/emit/inline-line.ts

@@ -3,6 +3,7 @@ import type { InlineDirective } from '../../adf/inline-directives.ts'
 import { assembleInlineLine, type InlineEscaping, type InlineSegment, type LineContainer, type NodeRange } from './line-escaping.ts'
 import { carriedInline } from '../opaque-carry.ts'
 import { claimsLine, holdsNullCharacter, isAutolink } from '../commonmark-grammar.ts'
+import { escapeUnbalanced, spellDestination, spellLinkTarget } from '../link-syntax.ts'
 import { failure, faulted, success, type ConvertErrorPath, type Result } from '../../result.ts'
 import { holdsEntityReference } from '../entity-references.ts'
 import { inlineDirective } from '../../adf/inline-directives.ts'
@@ -12,7 +13,6 @@ import { markSpelling, spellMarkAttributes } from '../mark-spellings.ts'
 import { nodeAttrs, nodeContent, nodeMarks } from '../../adf/document.ts'
 import { sameMark } from '../../adf/editor-normal.ts'
 import { slotLineEndingFault, spellLeafDirective } from '../directive-syntax.ts'
-import { spellDestination, spellLinkTarget } from '../link-syntax.ts'
 import { spellInlineNodeAttributes } from './inline-directive-spelling.ts'
 import { spellTextDirective } from '../text-directive.ts'
 
@@ -284,12 +284,14 @@ function emitLink(nodes: readonly AdfNode[], mark: AdfMark, depth: number, range
   if (typeof href !== 'string') return success({ carry: range })
   const node = nodes[0]
   const bare = nodes.length === 1 && node !== undefined && node.type === 'text' && node.text === href && nodeMarks(node).length === depth + 1
-  if (bare && title === undefined && isAutolink(href) && !holdsEntityReference(href)) return success({ segments: [syntax(`<${href}>`)] })
+  const balanced = !context.bracketed || escapeUnbalanced(href, '[', ']') === href
+  if (bare && balanced && title === undefined && isAutolink(href) && !holdsEntityReference(href)) return success({ segments: [syntax(`<${href}>`)] })
   const target = spellLinkTarget(href, typeof title === 'string' ? title : undefined, path)
   if (!target.ok) return target
   const inner = emitRun(nodes, depth + 1, range.first, { ...context, bracketed: true })
   if (!inner.ok) return inner
   if (inner.value.carry !== undefined) return inner
-  return success({ segments: [syntax('['), ...inner.value.segments, syntax(`](${target.value})`)] })
+  const spelledTarget = context.bracketed ? escapeUnbalanced(target.value, '[', ']') : target.value
+  return success({ segments: [syntax('['), ...inner.value.segments, syntax(`](${spelledTarget})`)] })
 }
 

src/markdown/link-syntax.ts

@@ -103,7 +103,7 @@ export function spellDestination(href: string, path: ConvertErrorPath): Result<s
     return success(`<${href}>`)
   }
   if (href.startsWith('<')) return failure('unspellable-link', 'a bare link destination cannot begin with an angle bracket', path)
-  return success(escapeUnbalanced(href))
+  return success(escapeUnbalanced(href, '(', ')'))
 }
 
 export function spellLinkTarget(href: string, title: string | undefined, path: ConvertErrorPath): Result<string> {
@@ -114,6 +114,20 @@ export function spellLinkTarget(href: string, title: string | undefined, path: C
   return success(`${destination.value === '' ? '<>' : destination.value}${spelledTitle.value}`)
 }
 
+export function escapeUnbalanced(spelling: string, opener: string, closer: string): string {
+  const open: number[] = []
+  const unbalanced = new Set<number>()
+  for (let index = 0; index < spelling.length; index += backslashEscape(spelling, index) === undefined ? 1 : 2) {
+    const character = spelling.charAt(index)
+    if (character === opener) open.push(index)
+    if (character === closer && open.pop() === undefined) unbalanced.add(index)
+  }
+  for (const index of open) unbalanced.add(index)
+  let spelled = ''
+  for (let index = 0; index < spelling.length; index += 1) spelled += (unbalanced.has(index) ? '\\' : '') + spelling.charAt(index)
+  return spelled
+}
+
 function spellTitle(title: string, path: ConvertErrorPath): Result<string> {
   if (/[\n\r\\]/.test(title)) {
     return failure('unspellable-link', 'no canonical escape spells a backslash or newline in a link title', path)
@@ -121,17 +135,3 @@ function spellTitle(title: string, path: ConvertErrorPath): Result<string> {
   if (holdsEntityReference(title)) return failure('unspellable-link', 'a link title holds an entity reference that decodes on the way back', path)
   return success(` "${title.replaceAll('"', '\\"')}"`)
 }
-
-function escapeUnbalanced(href: string): string {
-  const open: number[] = []
-  const unbalanced = new Set<number>()
-  for (let index = 0; index < href.length; index += 1) {
-    const character = href.charAt(index)
-    if (character === '(') open.push(index)
-    if (character === ')' && open.pop() === undefined) unbalanced.add(index)
-  }
-  for (const index of open) unbalanced.add(index)
-  let spelled = ''
-  for (let index = 0; index < href.length; index += 1) spelled += (unbalanced.has(index) ? '\\' : '') + href.charAt(index)
-  return spelled
-}