4.2: the review's generator, runner and pattern fixes

AGENTS.md

@@ -67,7 +67,8 @@ deliberate re-pin, exceptions re-derived by hand beside it. Atlassian's ADF JSON
 vendored the same way, at `spec/adf-schema/`, rather than as the `@atlaskit/adf-schema` dev
 dependency — CommonJS-only, some fifty packages with React among them, and a release most days for
 Renovate to automerge — re-pinned by hand when a payload or a report shows the need.
-`devDependencies`: few, each earning its keep; they never reach a consumer.
+`devDependencies`: few, each earning its keep; they never reach a consumer. `fast-check` earns its
+place shrinking a failing generated document to the nodes that break it.
 
 ## 6. The package contract
 
@@ -225,6 +226,10 @@ compared against `undefined` — have a half no valid document reaches.
 The corpus, all checked in: hand-built fixtures per node and combination; real sanitized ADF from
 live Atlassian APIs; the CommonMark spec suite against `markdownToAdf` and `markdownToHtml`.
 
+Beside the corpus, properties run over documents generated from the node tables, on a fixed seed in
+the gate; `PROPERTY_RUNS=<runs>` raises the runs and randomizes the seed for local digging, and a
+counterexample found becomes a round-trip fixture.
+
 `spec/flavour.md` is read as a source too, so the node tables cannot drift from the prose they
 copy: each `- ` bullet in `## Block nodes`, `## Inline nodes` and `## Marks` declares the nodes
 named before its first em dash, with the attributes following `Attributes: ` — a parenthesized

ci.sh

@@ -16,7 +16,7 @@ if printf '%s' "$test_output" | grep -q 'ℹ tests 0'; then
   exit 1
 fi
 
-in_image "$deno_image" deno test --allow-read --no-check src/
+in_image "$deno_image" deno test --allow-env=PROPERTY_RUNS --allow-read --no-check src/
 in_image "$bun_image" bun test src/
 
 in_image "$node_image" npm run build

corpus/round-trip/combinations/directive-autolink-backtick.json

@@ -0,0 +1,50 @@
+{
+  "content": [
+    {
+      "content": [
+        {
+          "marks": [
+            {
+              "type": "underline"
+            },
+            {
+              "attrs": {
+                "href": "http://a`b"
+              },
+              "type": "link"
+            }
+          ],
+          "text": "http://a`b",
+          "type": "text"
+        },
+        {
+          "text": "`c",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    },
+    {
+      "content": [
+        {
+          "marks": [
+            {
+              "type": "underline"
+            },
+            {
+              "attrs": {
+                "href": "http://d`e"
+              },
+              "type": "link"
+            }
+          ],
+          "text": "http://d`e",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    }
+  ],
+  "type": "doc",
+  "version": 1
+}

corpus/round-trip/combinations/directive-autolink-backtick.md

@@ -0,0 +1,3 @@
+:underline[[http://a\`b](http://a\`b)]`c
+
+:underline[[http://d\`e](http://d`e)]

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

@@ -0,0 +1,83 @@
+{
+  "content": [
+    {
+      "content": [
+        {
+          "marks": [
+            {
+              "attrs": {
+                "color": ""
+              },
+              "type": "textColor"
+            },
+            {
+              "attrs": {
+                "href": "`"
+              },
+              "type": "link"
+            }
+          ],
+          "text": " ",
+          "type": "text"
+        },
+        {
+          "text": "`a",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    },
+    {
+      "content": [
+        {
+          "marks": [
+            {
+              "type": "underline"
+            },
+            {
+              "attrs": {
+                "href": "c",
+                "title": "`"
+              },
+              "type": "link"
+            }
+          ],
+          "text": "b",
+          "type": "text"
+        },
+        {
+          "marks": [
+            {
+              "type": "code"
+            }
+          ],
+          "text": "c",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    },
+    {
+      "content": [
+        {
+          "marks": [
+            {
+              "type": "underline"
+            },
+            {
+              "attrs": {
+                "href": "e`f"
+              },
+              "type": "link"
+            }
+          ],
+          "text": "d",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    }
+  ],
+  "type": "doc",
+  "version": 1
+}

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

@@ -0,0 +1,5 @@
+:textColor[[ ](\`)]{color=""}`a
+
+:underline[[b](c "\`")]`c`
+
+:underline[[d](e`f)]

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)]

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

@@ -0,0 +1,107 @@
+{
+  "content": [
+    {
+      "content": [
+        {
+          "marks": [
+            {
+              "type": "underline"
+            },
+            {
+              "attrs": {
+                "href": ":a{"
+              },
+              "type": "link"
+            }
+          ],
+          "text": "x",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    },
+    {
+      "content": [
+        {
+          "marks": [
+            {
+              "type": "underline"
+            },
+            {
+              "attrs": {
+                "href": "y",
+                "title": ":a{"
+              },
+              "type": "link"
+            }
+          ],
+          "text": "x",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    },
+    {
+      "content": [
+        {
+          "marks": [
+            {
+              "type": "underline"
+            },
+            {
+              "attrs": {
+                "href": ":a[]{"
+              },
+              "type": "link"
+            }
+          ],
+          "text": "x",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    },
+    {
+      "content": [
+        {
+          "marks": [
+            {
+              "type": "underline"
+            },
+            {
+              "attrs": {
+                "href": "https://example.com/?q=:emoji{"
+              },
+              "type": "link"
+            }
+          ],
+          "text": "x",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    },
+    {
+      "content": [
+        {
+          "marks": [
+            {
+              "type": "underline"
+            },
+            {
+              "attrs": {
+                "href": "ab:c{"
+              },
+              "type": "link"
+            }
+          ],
+          "text": "ab:c{",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    }
+  ],
+  "type": "doc",
+  "version": 1
+}

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

@@ -0,0 +1,9 @@
+:underline[[x](\:a{)]
+
+:underline[[x](y "\:a{")]
+
+:underline[[x](\:a[]{)]
+
+:underline[[x](https://example.com/?q=\:emoji{)]
+
+:underline[[ab\:c{](ab\:c{)]

corpus/round-trip/combinations/list-item-whitespace-line.json

@@ -0,0 +1,57 @@
+{
+  "content": [
+    {
+      "content": [
+        {
+          "content": [
+            {
+              "content": [
+                {
+                  "text": " \na",
+                  "type": "text"
+                }
+              ],
+              "type": "codeBlock"
+            }
+          ],
+          "type": "listItem"
+        }
+      ],
+      "type": "bulletList"
+    },
+    {
+      "attrs": {
+        "order": 1
+      },
+      "content": [
+        {
+          "content": [
+            {
+              "content": [
+                {
+                  "content": [
+                    {
+                      "content": [
+                        {
+                          "text": "\t",
+                          "type": "text"
+                        }
+                      ],
+                      "type": "codeBlock"
+                    }
+                  ],
+                  "type": "listItem"
+                }
+              ],
+              "type": "bulletList"
+            }
+          ],
+          "type": "listItem"
+        }
+      ],
+      "type": "orderedList"
+    }
+  ],
+  "type": "doc",
+  "version": 1
+}

corpus/round-trip/combinations/list-item-whitespace-line.md

@@ -0,0 +1,20 @@
+::::bulletList
+:::listItem
+```
+ 
+a
+```
+:::
+::::
+
+::::::orderedList {order=1}
+:::::listItem
+::::bulletList
+:::listItem
+```
+	
+```
+:::
+::::
+:::::
+::::::

corpus/round-trip/commonmark-subset/link-empty-destination.json

@@ -0,0 +1,24 @@
+{
+  "content": [
+    {
+      "content": [
+        {
+          "marks": [
+            {
+              "attrs": {
+                "href": "",
+                "title": ""
+              },
+              "type": "link"
+            }
+          ],
+          "text": "a",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    }
+  ],
+  "type": "doc",
+  "version": 1
+}

corpus/round-trip/commonmark-subset/link-empty-destination.md

@@ -0,0 +1 @@
+[a](<> "")

docker-runner.sh

@@ -7,7 +7,7 @@ node_image=node:24.19.0-alpine3.24
 in_image() {
   local image=$1 entrypoint=$2
   shift 2
-  docker run --rm -u "$(id -u):$(id -g)" -e HOME=/tmp ${in_image_network:+--network "$in_image_network"} -v "$PWD:/app" -w /app --entrypoint "$entrypoint" "$image" "$@"
+  docker run --rm -u "$(id -u):$(id -g)" -e HOME=/tmp ${PROPERTY_RUNS:+-e PROPERTY_RUNS} ${in_image_network:+--network "$in_image_network"} -v "$PWD:/app" -w /app --entrypoint "$entrypoint" "$image" "$@"
 }
 
 with_firefox() {

package-lock.json

@@ -10,6 +10,7 @@
       "license": "MIT",
       "devDependencies": {
         "@types/node": "24.13.3",
+        "fast-check": "4.10.0",
         "typescript": "7.0.2"
       },
       "engines": {
@@ -366,6 +367,46 @@
         "node": ">=16.20.0"
       }
     },
+    "node_modules/fast-check": {
+      "version": "4.10.0",
+      "resolved": "https://registry.npmjs.org/fast-check/-/fast-check-4.10.0.tgz",
+      "integrity": "sha512-hhqQL+IJllZi3aM4TKvmCj3bywLEcycNTTLZeLhA9ttMxBrCqM07q7Di4kl+j9EWSTXvJH1+EpIgsDbF/+8H5Q==",
+      "dev": true,
+      "funding": [
+        {
+          "type": "individual",
+          "url": "https://github.com/sponsors/dubzzz"
+        },
+        {
+          "type": "opencollective",
+          "url": "https://opencollective.com/fast-check"
+        }
+      ],
+      "license": "MIT",
+      "dependencies": {
+        "pure-rand": "^8.0.0"
+      },
+      "engines": {
+        "node": ">=12.17.0"
+      }
+    },
+    "node_modules/pure-rand": {
+      "version": "8.4.2",
+      "resolved": "https://registry.npmjs.org/pure-rand/-/pure-rand-8.4.2.tgz",
+      "integrity": "sha512-vvuOGgcuPJAirlHvuQw1TrOiw7ptaIXXmIbNuiNOY6lNGJJH49PQ1Kj4nd783nPdQhQdicgOjVI2yI/9BD6/Ng==",
+      "dev": true,
+      "funding": [
+        {
+          "type": "individual",
+          "url": "https://github.com/sponsors/dubzzz"
+        },
+        {
+          "type": "opencollective",
+          "url": "https://opencollective.com/fast-check"
+        }
+      ],
+      "license": "MIT"
+    },
     "node_modules/typescript": {
       "version": "7.0.2",
       "resolved": "https://registry.npmjs.org/typescript/-/typescript-7.0.2.tgz",

package.json

@@ -28,6 +28,7 @@
   },
   "devDependencies": {
     "@types/node": "24.13.3",
+    "fast-check": "4.10.0",
     "typescript": "7.0.2"
   }
 }

spec/flavour.md

@@ -28,7 +28,8 @@ normalizes to it through the round-trip.
   adjacent lists of a kind back as one. The leaf `::listBreak` parts them, taking the separation
   any directive block takes where it sits. It builds no node, and it reads only between two
   adjacent lists of one type: elsewhere, or carrying an argument, `{attrs}` or a body, it is a
-  named error.
+  named error. A list whose item holds a line of spaces or tabs alone, which a list item reads
+  back empty, takes the directive form.
 - Blockquotes prefix lines with `> `; a blank line inside a blockquote is a bare `>`.
 - ATX headings (`#` … `######`); setext input normalizes to ATX.
 - Code fences ``` with the node's language as info string, the fence lengthened past any backtick
@@ -43,10 +44,12 @@ normalizes to it through the round-trip.
   CommonMark admits no spelling — the end of a block, inside an ATX heading — or where the node
   carries an attribute, it is the inline directive.
 - An empty paragraph — real payloads carry them — is `::paragraph`.
-- Links `[text](url)`; `<…>` around a destination containing spaces; title in double quotes. A
+- Links `[text](url)`; `<…>` around a destination containing spaces, `<>` an empty one beside a
-  backslash escapes a parenthesis the destination leaves unbalanced, and a quote inside the title;
+  title; title in double quotes. A backslash escapes a parenthesis the destination leaves
-  a balanced pair stays bare. `<url>` autolink form only when the text equals the destination and
+  unbalanced, and a quote inside the title; a balanced pair stays bare. `<url>` autolink form only
-  the destination is a valid CommonMark autolink (absolute URI).
+  when the text equals the destination and the destination is a valid CommonMark autolink
+  (absolute URI) — inside an inline directive's `[content]`, one holding no backtick, no
+  unbalanced bracket and no inline directive opener.
 - Paragraphs on one line — no soft wrapping; a soft line break in input becomes a single space.
 - Entity references in input decode to their characters; output backslash-escapes only where text
   would otherwise parse as syntax, scanning the assembled line rather than each text node: escape
@@ -128,9 +131,11 @@ 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, a backtick there that would open a code span
-of; outside code spans and code blocks, a backslash before `:` in input yields a literal colon.
+and a `:` there that would open an inline directive, 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/adf-property.test.ts

@@ -0,0 +1,185 @@
+import fc from 'fast-check'
+import assert from 'node:assert/strict'
+import { env } from 'node:process'
+import test from 'node:test'
+
+import type { AdfAttributes, AdfDocument, AdfMark, AdfNode } from './adf/document.ts'
+import type { Arbitrary } from 'fast-check'
+import type { AttributeKind, AttributeVocabulary } from './adf/attribute-vocabulary.ts'
+import type { JsonValue } from './json-value.ts'
+import { adfToMarkdown } from './markdown/emit/adf-to-markdown.ts'
+import { blockArgument } from './markdown/block-directive-arguments.ts'
+import { blockDirectives } from './adf/block-directives.ts'
+import { inlineDirectives } from './adf/inline-directives.ts'
+import { markAttributes } from './adf/mark-attributes.ts'
+import { markdownToAdf } from './markdown/parse/markdown-to-adf.ts'
+import { toEditorNormal } from './adf/editor-normal.ts'
+
+type Positions = { block: AdfNode; inline: AdfNode }
+
+const deepRunsVariable = 'PROPERTY_RUNS'
+const gateRuns = 1600
+const gateSeed = 20260914
+// Bun's test runner stops a test after five seconds unless the test sets its own timeout.
+const propertyTimeout = 600000
+
+const depthIdentifier = fc.createDepthIdentifier()
+const emptyCell: AdfNode = { content: [{ type: 'paragraph' }], type: 'tableCell' }
+const flatCommonMarkShapeWeight = 4
+const markdownPieces = fc.constantFrom(...'aZ09 \t\n!"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}~é\xa0🎉', ':a[', ':a{', 'ab:', 'http://')
+const nestingCommonMarkShapeWeight = 21
+const spelledTypes = new Set(['text', ...Object.keys(blockDirectives), ...Object.keys(inlineDirectives), ...Object.keys(markAttributes)])
+
+function textOf(minLength: number): Arbitrary<string> {
+  return fc.oneof(
+    { arbitrary: fc.string({ maxLength: 12, minLength, unit: markdownPieces }), weight: 4 },
+    { arbitrary: fc.string({ maxLength: 6, minLength, unit: 'grapheme' }), weight: 1 },
+  )
+}
+
+const text = textOf(1)
+const unknownType = fc.oneof(fc.stringMatching(/^[a-z][A-Za-z0-9]{0,7}$/), text).filter((type) => !spelledTypes.has(type))
+const numberValue = fc.oneof({ arbitrary: fc.integer({ max: 10, min: -1 }), weight: 3 }, { arbitrary: fc.double({ noDefaultInfinity: true, noNaN: true }), weight: 1 })
+
+// V8's JSON.parse returns a wrong key after parsing a key holding an escaped backslash (https://issues.chromium.org/issues/521080746); Bun is unaffected.
+const keyPiece = fc
+  .oneof({ arbitrary: markdownPieces, weight: 4 }, { arbitrary: fc.string({ maxLength: 1, minLength: 1, unit: 'grapheme' }), weight: 1 })
+  .filter((piece) => !/[\\"\x00-\x1f]/.test(piece))
+const jsonKey = fc.string({ maxLength: 8, unit: keyPiece })
+
+const { jsonValue } = fc.letrec<{ jsonValue: JsonValue }>((tie) => ({
+  jsonValue: fc.oneof(
+    { depthSize: 'small', maxDepth: 2 },
+    fc.oneof(fc.constant(null), fc.boolean(), numberValue, textOf(0)),
+    fc.array(tie('jsonValue'), { maxLength: 3 }),
+    fc.dictionary(jsonKey, tie('jsonValue'), { maxKeys: 3, noNullPrototype: true }),
+  ),
+}))
+
+const valueByKind: Readonly<Record<AttributeKind, Arbitrary<JsonValue>>> = {
+  boolean: fc.boolean(),
+  json: jsonValue,
+  number: numberValue,
+  string: textOf(0),
+}
+
+function attributes(vocabulary: AttributeVocabulary): Arbitrary<AdfAttributes> {
+  const model = Object.fromEntries(
+    Object.entries(vocabulary).map(([key, kind]) => [key, fc.oneof({ arbitrary: fc.constant(undefined), weight: 2 }, { arbitrary: valueByKind[kind], weight: 1 })]),
+  )
+  return fc.record(model).map(heldAttributes)
+}
+
+function heldAttributes(held: Readonly<Record<string, JsonValue | undefined>>): AdfAttributes {
+  const attrs: AdfAttributes = {}
+  for (const [key, value] of Object.entries(held)) if (value !== undefined) attrs[key] = value
+  return attrs
+}
+
+function pipeTable({ body, header }: { body: AdfNode[][]; header: AdfNode[] }): AdfNode {
+  const rows = [header, ...body.map((cells) => header.map((_, index) => cells[index] ?? emptyCell))]
+  return { content: rows.map((content): AdfNode => ({ content, type: 'tableRow' })), type: 'table' }
+}
+
+const mark: Arbitrary<AdfMark> = fc.oneof(
+  { arbitrary: fc.oneof(...Object.entries(markAttributes).map(([type, vocabulary]) => attributes(vocabulary).map((attrs) => ({ attrs, type })))), weight: 9 },
+  { arbitrary: fc.record({ attrs: fc.dictionary(jsonKey, jsonValue, { maxKeys: 2, noNullPrototype: true }), type: unknownType }), weight: 1 },
+)
+const marks = fc.uniqueArray(mark, { maxLength: 3, selector: (held) => held.type })
+
+const textNode = fc.record({ marks, text }).map((held): AdfNode => ({ ...held, type: 'text' }))
+
+const autolinkTextNode = fc
+  .record({ href: fc.tuple(fc.constantFrom('ab:', 'http://'), textOf(0)).map(([scheme, rest]) => `${scheme}${rest}`), marks })
+  .map(({ href, marks: held }): AdfNode => ({ marks: [...held.filter((outer) => outer.type !== 'link'), { attrs: { href }, type: 'link' }], text: href, type: 'text' }))
+
+const inlineNodes = Object.entries(inlineDirectives).map(([type, directive]) =>
+  fc.record({ attrs: attributes(directive.attributes), marks }).map((held): AdfNode => ({ ...held, type })),
+)
+
+function weighted(arbitraries: readonly Arbitrary<AdfNode>[], weight: number): { arbitrary: Arbitrary<AdfNode>; weight: number }[] {
+  return arbitraries.map((arbitrary) => ({ arbitrary, weight }))
+}
+
+const positions = fc.letrec<Positions>((tie) => {
+  const blockContent = fc.array(tie('block'), { depthIdentifier, maxLength: 3 })
+  const inlineContent = fc.array(tie('inline'), { depthIdentifier, maxLength: 4 })
+  const contentByModel = {
+    block: blockContent,
+    code: fc.array(text.map((held): AdfNode => ({ text: held, type: 'text' })), { maxLength: 2 }),
+    inline: inlineContent,
+    none: fc.constant<AdfNode[]>([]),
+  }
+  const blockMarks = fc.oneof({ arbitrary: fc.constant<AdfMark[]>([]), weight: 4 }, { arbitrary: marks, weight: 1 })
+  const blockNodes = Object.entries(blockDirectives).map(([type, directive]) => {
+    const argument = blockArgument(type)
+    const vocabulary: AttributeVocabulary = argument === undefined ? directive.attributes : { ...directive.attributes, [argument]: 'string' }
+    const node = fc.record({ attrs: attributes(vocabulary), content: contentByModel[directive.contentModel], marks: blockMarks }).map((held): AdfNode => ({ ...held, type }))
+    return { leaf: directive.contentModel === 'code' || directive.contentModel === 'none', node }
+  })
+  const unknownNode = fc
+    .record({ attrs: fc.dictionary(jsonKey, jsonValue, { maxKeys: 2, noNullPrototype: true }), content: fc.array(tie('inline'), { depthIdentifier, maxLength: 2 }), marks, type: unknownType })
+    .map((held): AdfNode => held)
+  const leafBlocks = blockNodes.filter((entry) => entry.leaf).map((entry) => entry.node)
+  const containerBlocks = blockNodes.filter((entry) => !entry.leaf).map((entry) => entry.node)
+  const misplacedWeight = 7
+  const paragraph = inlineContent.map((content): AdfNode => ({ content, type: 'paragraph' }))
+  const cell = (type: string) => paragraph.map((held): AdfNode => ({ content: [held], type }))
+  const listItems = fc.array(
+    blockContent.map((content): AdfNode => ({ content, type: 'listItem' })),
+    { depthIdentifier, maxLength: 3, minLength: 1 },
+  )
+  const flatCommonMarkShapes = [
+    fc.record({ content: inlineContent, level: fc.integer({ max: 6, min: 1 }) }).map(({ content, level }): AdfNode => ({ attrs: { level }, content, type: 'heading' })),
+    paragraph,
+    fc.record({ body: fc.array(fc.array(cell('tableCell'), { maxLength: 3 }), { maxLength: 2 }), header: fc.array(cell('tableHeader'), { maxLength: 3, minLength: 1 }) }).map(pipeTable),
+  ]
+  const nestingCommonMarkShapes = [
+    blockContent.map((content): AdfNode => ({ content, type: 'blockquote' })),
+    listItems.map((content): AdfNode => ({ content, type: 'bulletList' })),
+    fc
+      .record({ content: listItems, order: fc.oneof({ arbitrary: fc.integer({ max: 3, min: 0 }), weight: 4 }, { arbitrary: fc.integer({ max: 999999999, min: 0 }), weight: 1 }) })
+      .map(({ content, order }): AdfNode => ({ attrs: { order }, content, type: 'orderedList' })),
+  ]
+  return {
+    block: fc.oneof(
+      { depthIdentifier, depthSize: 'small', maxDepth: 4 },
+      {
+        arbitrary: fc.oneof(...weighted(leafBlocks, 2), ...weighted(flatCommonMarkShapes, flatCommonMarkShapeWeight)),
+        weight: leafBlocks.length * 2 + flatCommonMarkShapes.length * flatCommonMarkShapeWeight,
+      },
+      { arbitrary: fc.oneof(...containerBlocks), weight: containerBlocks.length * 2 },
+      { arbitrary: fc.oneof(textNode, ...inlineNodes, unknownNode), weight: misplacedWeight },
+      { arbitrary: fc.oneof(...nestingCommonMarkShapes), weight: nestingCommonMarkShapes.length * nestingCommonMarkShapeWeight },
+    ),
+    inline: fc.oneof(
+      { depthIdentifier, depthSize: 'small', maxDepth: 4 },
+      { arbitrary: textNode, weight: 12 },
+      { arbitrary: autolinkTextNode, weight: 2 },
+      { arbitrary: fc.oneof(...inlineNodes), weight: 7 },
+      { arbitrary: fc.oneof(...blockNodes.map((entry) => entry.node), unknownNode), weight: 2 },
+    ),
+  }
+})
+
+const adfDocument = fc.array(positions.block, { depthIdentifier, maxLength: 4, minLength: 1 }).map((content): AdfDocument => toEditorNormal({ content, type: 'doc', version: 1 }))
+
+function runParameters(): { numRuns: number; seed?: number } {
+  const deepRuns = env[deepRunsVariable]
+  if (deepRuns === undefined) return { numRuns: gateRuns, seed: gateSeed }
+  assert.ok(/^[1-9]\d*$/.test(deepRuns), `${deepRunsVariable} is a run count in digits, such as ${deepRunsVariable}=10000: found ${JSON.stringify(deepRuns)}`)
+  return { numRuns: Number(deepRuns) }
+}
+
+test('a generated document refuses to emit, or its markdown reads back to it', { timeout: propertyTimeout }, () => {
+  fc.assert(
+    fc.property(adfDocument, (document) => {
+      const emitted = adfToMarkdown(document)
+      if (!emitted.ok) return
+      const read = markdownToAdf(emitted.value)
+      assert.ok(read.ok, read.ok ? '' : `${read.error.code}: ${read.error.message} — reading ${JSON.stringify(emitted.value)}`)
+      assert.deepEqual(toEditorNormal(read.value), document, `reading ${JSON.stringify(emitted.value)}`)
+    }),
+    runParameters(),
+  )
+})

src/corpus.test.ts

@@ -107,18 +107,6 @@ function roundTripFixtures(): { name: string; path: string }[] {
   )
 }
 
-test('no two round-trip documents share one markdown spelling', () => {
-  const spellings = new Map<string, string>()
-  for (const fixture of roundTripFixtures()) {
-    const parsed: unknown = JSON.parse(readFileSync(fixture.path, 'utf8'))
-    assert.ok(isAdfDocument(parsed), `${fixture.name} is not an ADF document`)
-    const result = adfToMarkdown(parsed)
-    assert.ok(result.ok, result.ok ? '' : `${result.error.code}: ${result.error.message}`)
-    assert.equal(spellings.get(result.value), undefined, `${fixture.name} and ${spellings.get(result.value)} share one markdown spelling`)
-    spellings.set(result.value, fixture.name)
-  }
-})
-
 test('no round-trip fixture repeats the document another holds', () => {
   const documents = new Map<string, string>()
   for (const fixture of roundTripFixtures()) {

src/markdown/commonmark-grammar.ts

@@ -51,6 +51,7 @@ const htmlBlockConditions: HtmlBlockCondition[] = [
 ]
 const asciiPunctuation = /[!"#$%&'()*+,\-./:;<=>?@[\\\]^_`{|}~]/
 const atxHeadingOpener = /^(#{1,6})(?:[ \t]|$)/
+const blankLine = /^[ \t]*$/
 const codeFenceOpener = /^(`{3,}|~{3,})/
 const directiveClaim = /^:{2,}(?:[A-Za-z0-9]|[ \t]*$)/
 const pipeClaim = /^\|/
@@ -167,6 +168,10 @@ export function isAutolink(text: string): boolean {
   return autolink.test(text)
 }
 
+export function isBlankLine(line: string): boolean {
+  return blankLine.test(line)
+}
+
 export function isThematicBreak(line: string): boolean {
   return thematicBreak.test(line)
 }

src/markdown/directive-syntax.ts

@@ -56,6 +56,11 @@ export function attributeValue(text: string, kind: AttributeKind): AttributeRead
   return overNested(parsed) ? { refusal: 'nesting' } : { value: { kind, value: parsed } }
 }
 
+export function holdsInlineDirectiveOpener(text: string): boolean {
+  for (let index = text.indexOf(':'); index !== -1; index = text.indexOf(':', index + 1)) if (opensInlineDirective(text, index)) return true
+  return false
+}
+
 export function isBareToken(text: string): boolean {
   return bareToken.test(text)
 }

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

@@ -6,7 +6,7 @@ import { carriedBlock } from '../opaque-carry.ts'
 import { emitInlineLine } from './inline-line.ts'
 import { failure, faulted, success, type ConvertErrorPath, type Result } from '../../result.ts'
 import { fencedCodeBlock } from '../backtick-runs.ts'
-import { holdsNullCharacter, isThematicBreak, markerInterruptsParagraph } from '../commonmark-grammar.ts'
+import { holdsNullCharacter, isBlankLine, isThematicBreak, markerInterruptsParagraph } from '../commonmark-grammar.ts'
 import { languageSlot } from '../code-language.ts'
 import { largestNesting } from '../../nesting.ts'
 import { listBreakSpelling } from '../list-break.ts'
@@ -225,8 +225,10 @@ function emitListItem(item: AdfNode, marker: string, path: ConvertErrorPath, dep
   const inner = emitBlocks(nodeContent(item), 'list-item', path, depth + 1)
   if (!inner.ok) return inner
   if (inner.value.text === '') return success({ fenceColons: 0, text: marker.trimEnd() })
+  const body = inner.value.text.split('\n')
+  if (body.some((line) => line !== '' && isBlankLine(line))) return undefined
   const indent = ' '.repeat(marker.length)
-  const lines = inner.value.text.split('\n').map((line, index) => (index === 0 ? `${marker}${line}` : line === '' ? '' : `${indent}${line}`))
+  const lines = body.map((line, index) => (index === 0 ? `${marker}${line}` : line === '' ? '' : `${indent}${line}`))
   if (isThematicBreak(lines[0] ?? '')) return undefined
   return success({ fenceColons: inner.value.fenceColons, text: lines.join('\n') })
 }

src/markdown/emit/inline-line.ts

@@ -1,18 +1,18 @@
 import type { AdfMark, AdfNode } from '../../adf/document.ts'
 import type { InlineDirective } from '../../adf/inline-directives.ts'
-import { assembleInlineLine, type InlineEscaping, type InlineSegment, type LineContainer, type NodeRange } from './line-escaping.ts'
+import { assembleInlineLine, isSyntax, 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 { holdsInlineDirectiveOpener, slotLineEndingFault, spellLeafDirective } from '../directive-syntax.ts'
 import { inlineDirective } from '../../adf/inline-directives.ts'
 import { largestNesting } from '../../nesting.ts'
 import { longestBacktickRun } from '../backtick-runs.ts'
 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, spellTitle } from '../link-syntax.ts'
 import { spellInlineNodeAttributes } from './inline-directive-spelling.ts'
 import { spellTextDirective } from '../text-directive.ts'
 
@@ -41,7 +41,7 @@ export function emitInlineLine(nodes: readonly AdfNode[], container: LineContain
 export function tryPipeCell(nodes: readonly AdfNode[], path: ConvertErrorPath): string | undefined {
   const emitted = emitLine(nodes, 'table-cell', path)
   if (!emitted.ok) return undefined
-  if (emitted.value.segments.some((segment) => segment.escaping === 'none' && segment.text.includes('|'))) return undefined
+  if (emitted.value.segments.some((segment) => isSyntax(segment.escaping) && segment.text.includes('|'))) return undefined
   return emitted.value.line
 }
 
@@ -284,14 +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(`<${href}>`)] })
+  const autolinkHolds = !context.bracketed || (!href.includes('`') && !holdsInlineDirectiveOpener(href) && escapeUnbalanced(href, '[', ']') === href)
-  const destination = spellDestination(href, path)
+  if (bare && autolinkHolds && title === undefined && isAutolink(href) && !holdsEntityReference(href)) return success({ segments: [syntax(`<${href}>`)] })
-  if (!destination.ok) return destination
+  const target = spellLinkTarget(href, typeof title === 'string' ? title : undefined, path)
-  const spelledTitle = typeof title === 'string' ? spellTitle(title, path) : success('')
+  if (!target.ok) return target
-  if (!spelledTitle.ok) return spelledTitle
   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(`](${destination.value}${spelledTitle.value})`)] })
+  const spelledTarget: InlineSegment = context.bracketed ? { escaping: 'bracketed-link-target', text: escapeUnbalanced(target.value, '[', ']') } : syntax(target.value)
+  return success({ segments: [syntax('['), ...inner.value.segments, syntax(']('), spelledTarget, syntax(')')] })
 }
 

src/markdown/emit/line-escaping.ts

@@ -7,7 +7,7 @@ import { readEntityReference } from '../entity-references.ts'
 
 export type EmphasisRole = 'close' | 'open'
 
-export type InlineEscaping = 'backslash' | 'bracketed' | 'none'
+export type InlineEscaping = 'backslash' | 'bracketed' | 'bracketed-link-target' | 'none'
 
 export type NodeRange = { first: number; last: number }
 
@@ -77,10 +77,12 @@ function escape(segments: readonly InlineSegment[], container: LineContainer): A
     const escaping = escapings[index]
     const escapable = escaping === 'backslash' || escaping === 'bracketed'
     if (
-      escapable &&
+      (escapable &&
         (claimsLineStart(line, index, container) ||
           mergesWithSyntax(scan, escapings, index) ||
-        opensConstruct(scan, linkClose, index, escaping === 'bracketed', container, escaped))
+          opensConstruct(scan, linkClose, index, escaping === 'bracketed', container, escaped))) ||
+      (escaping === 'bracketed-link-target' &&
+        ((scan.charAt(index) === '`' && opensCodeSpan(scan, index, escaped)) || (scan.charAt(index) === ':' && opensInlineDirective(scan, index))))
     ) {
       output += '\\'
       escaped.add(index)
@@ -181,8 +183,8 @@ function touchesSyntax(scan: string, escapings: readonly (InlineEscaping | undef
   return scan.charAt(cursor) === character && isSyntax(escapings[cursor])
 }
 
-function isSyntax(escaping: InlineEscaping | undefined): boolean {
+export function isSyntax(escaping: InlineEscaping | undefined): boolean {
-  return escaping === 'none'
+  return escaping === 'none' || escaping === 'bracketed-link-target'
 }
 
 function opensConstruct(

src/markdown/link-syntax.ts

@@ -103,27 +103,35 @@ 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 spellTitle(title: string, path: ConvertErrorPath): Result<string> {
+export function spellLinkTarget(href: string, title: string | undefined, path: ConvertErrorPath): Result<string> {
+  const destination = spellDestination(href, path)
+  if (!destination.ok || title === undefined) return destination
+  const spelledTitle = spellTitle(title, path)
+  if (!spelledTitle.ok) return spelledTitle
+  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)
   }
   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
-}

src/markdown/parse/blocks.ts

@@ -7,6 +7,7 @@ import {
   claimsPipeLine,
   closingCodeFence,
   decodeTextEscapes,
+  isBlankLine,
   isThematicBreak,
   listMarker,
   markerInterruptsParagraph,
@@ -61,7 +62,6 @@ type Line = { column: number; text: string }
 
 type Walk = ParsedBlocks & { leaf: OpenLeaf | undefined; position: SourcePosition; stack: OpenContainer[] }
 
-const blankLine = /^[ \t]*$/
 const indentedCodeColumns = 4
 const largestOpenerIndentation = 3
 const leafColons = 2
@@ -117,7 +117,7 @@ function continuesContainer(walk: Walk, container: OpenContainer, line: Line): L
   // A directive container has no continuation marker: only its own fence closes it.
   if (container.kind === 'directive') return line
   // A list item begins with at most one blank line: an empty one gives the second up.
-  if (blankLine.test(line.text)) {
+  if (isBlankLine(line.text)) {
     return container.blocks.length === 0 && walk.leaf === undefined ? undefined : { column: line.column, text: '' }
   }
   return leadingColumns(line) < container.indentation ? undefined : removeColumns(line, container.indentation)
@@ -155,7 +155,7 @@ function itemStart(line: Line, opener: Line, paragraphOpen: boolean, enclosing:
   const marker = listMarker(opener.text)
   if (marker === undefined) return undefined
   const after: Line = { column: opener.column + marker.width, text: opener.text.slice(marker.width) }
-  const blank = blankLine.test(after.text)
+  const blank = isBlankLine(after.text)
   if (paragraphOpen && !markerInterruptsParagraph(marker.start, blank)) return undefined
   const spaces = leadingColumns(after)
   const padding = blank || spaces > indentedCodeColumns ? 1 : spaces
@@ -268,7 +268,7 @@ function pushFault(walk: Walk, fault: ConvertFault): void {
 
 // A claimed line ends the lazy continuation CommonMark would fold it into (spec/flavour.md).
 function continuesLazily(walk: Walk, line: Line): boolean {
-  if (walk.leaf?.kind !== 'paragraph' || blankLine.test(line.text)) return false
+  if (walk.leaf?.kind !== 'paragraph' || isBlankLine(line.text)) return false
   if (leadingColumns(line) >= indentedCodeColumns) return true
   const opener = removeColumns(line, largestOpenerIndentation).text
   if (claimsDirectiveLine(opener) || claimsPipeLine(opener) || isThematicBreak(opener)) return false
@@ -283,7 +283,7 @@ function readBlockLine(walk: Walk, line: Line): void {
     return
   }
   if (leaf?.kind === 'html') {
-    if (leaf.closer === undefined ? blankLine.test(line.text) : leaf.closer.test(line.text)) closeLeaf(walk)
+    if (leaf.closer === undefined ? isBlankLine(line.text) : leaf.closer.test(line.text)) closeLeaf(walk)
     return
   }
   if (leaf?.kind === 'pipe-table') {
@@ -298,7 +298,7 @@ function readBlockLine(walk: Walk, line: Line): void {
     if (readIndentedCodeLine(leaf, line)) return
     closeLeaf(walk)
   }
-  if (blankLine.test(line.text)) {
+  if (isBlankLine(line.text)) {
     closeLeaf(walk)
     return
   }
@@ -310,7 +310,7 @@ function readBlockLine(walk: Walk, line: Line): void {
 }
 
 function readIndentedCodeLine(leaf: Extract<OpenLeaf, { kind: 'indented-code' }>, line: Line): boolean {
-  if (blankLine.test(line.text)) {
+  if (isBlankLine(line.text)) {
     leaf.held.push(removeColumns(line, indentedCodeColumns).text)
     return true
   }