Answer principles round 1: 0 🔴, 1 🟡; scope the changelog to outside directives, and keep the backtick cursor inside a closure

CHANGELOG.md

@@ -17,8 +17,9 @@
 - `losslessMarkdownToAdf` names the CommonMark spelling to write when it refuses a directive whose
   node CommonMark spells, such as `[![alt](url)](href)` for a linked `!adf:mediaSingle`.
 - Every reader and writer takes time linear in a text holding many unclosed backtick runs, or many
-  `<!--`, `<?`, `<![CDATA[` or `<!` openers without a terminator, where such a text took time
-  quadratic in its length: 160k characters of `<?` took seven seconds each way, now 50 ms.
+  `<!--`, `<?`, `<![CDATA[` or `<!` openers without a terminator, outside a directive's `[content]`,
+  where such a text took time quadratic in its length: 160k characters of `<?` took seven seconds
+  each way, now 50 ms.
 - The README compares the package with seven other ADF converters, each checked against its
   published version.
 

src/markdown/commonmark/backtick-runs.test.ts

@@ -1,24 +1,24 @@
 import assert from 'node:assert/strict'
 import test from 'node:test'
 
-import { backtickRuns, closingRun } from './backtick-runs.ts'
+import { backtickCloser } from './backtick-runs.ts'
 
 test('a code span closes on the first later run of exactly its opener length', () => {
-  const runs = backtickRuns('`a``b```c`')
-  assert.equal(closingRun(runs, 1, 1), 9)
-  assert.equal(closingRun(runs, 1, 2), 2)
-  assert.equal(closingRun(runs, 1, 3), 5)
-  assert.equal(closingRun(runs, 1, 4), undefined)
+  const closer = backtickCloser('`a``b```c`')
+  assert.equal(closer(1, 1), 9)
+  assert.equal(closer(1, 2), 2)
+  assert.equal(closer(1, 3), 5)
+  assert.equal(closer(1, 4), undefined)
 })
 
 test('a run before the opener closes nothing', () => {
-  const runs = backtickRuns('``a``b')
-  assert.equal(closingRun(runs, 2, 2), 3)
-  assert.equal(closingRun(runs, 5, 2), undefined)
+  const closer = backtickCloser('``a``b')
+  assert.equal(closer(2, 2), 3)
+  assert.equal(closer(5, 2), undefined)
 })
 
 test('an ask from earlier in the text than the last finds the earlier closer', () => {
-  const runs = backtickRuns('`a`b`c`')
-  assert.equal(closingRun(runs, 5, 1), 6)
-  assert.equal(closingRun(runs, 1, 1), 2)
+  const closer = backtickCloser('`a`b`c`')
+  assert.equal(closer(5, 1), 6)
+  assert.equal(closer(1, 1), 2)
 })

src/markdown/commonmark/backtick-runs.ts

@@ -1,16 +1,14 @@
 import { runLength } from './emphasis-matching.ts'
 
-// Each run's start by its length, read once, so asking for a closer at every opener stays linear in the text.
-export interface BacktickRuns {
-  readonly asked: Map<number, number>
-  readonly starts: ReadonlyMap<number, readonly number[]>
-}
-
 export function backtickRun(text: string, index: number): number {
   return text.charAt(index) === '`' ? runLength(text, index) : 0
 }
 
-export function backtickRuns(text: string): BacktickRuns {
+// As `closingBacktickRun`, for `from` past the end of an opener's run, with each run's start read once by its length.
+// Readers ask with `from` rising, which keeps each length's cursor moving forward, so asking at every opener stays
+// linear in the text; an ask behind the cursor restarts that length from its first run.
+export function backtickCloser(text: string): (from: number, opener: number) => number | undefined {
+  const asked = new Map<number, number>()
   const starts = new Map<number, number[]>()
   for (let start = text.indexOf('`'); start !== -1; ) {
     const length = runLength(text, start)
@@ -19,19 +17,15 @@ export function backtickRuns(text: string): BacktickRuns {
     else known.push(start)
     start = text.indexOf('`', start + length)
   }
-  return { asked: new Map(), starts }
-}
-
-// As `closingBacktickRun`, for `from` past the end of an opener's run. Readers ask with `from` rising, which keeps
-// each length's cursor moving forward; an ask behind the cursor restarts that length from its first run.
-export function closingRun(runs: BacktickRuns, from: number, opener: number): number | undefined {
-  const starts = runs.starts.get(opener)
-  if (starts === undefined) return undefined
-  let at = runs.asked.get(opener) ?? 0
-  if ((starts[at - 1] ?? -1) >= from) at = 0
-  while ((starts[at] ?? Infinity) < from) at += 1
-  runs.asked.set(opener, at)
-  return starts[at]
+  return (from, opener) => {
+    const runs = starts.get(opener)
+    if (runs === undefined) return undefined
+    let at = asked.get(opener) ?? 0
+    if ((runs[at - 1] ?? -1) >= from) at = 0
+    while ((runs[at] ?? Infinity) < from) at += 1
+    asked.set(opener, at)
+    return runs[at]
+  }
 }
 
 // Where the run of exactly `opener` backticks closing a code span begins, `undefined` where none does.

src/markdown/commonmark/grammar.ts

@@ -146,7 +146,7 @@ function htmlTagName(text: string): string {
   return text.replace(tagName, '<$1>')
 }
 
-// `terminated` says whether a terminator starts at or after `from`, which a caller asking at every opener answers from what it kept.
+// `terminated` says whether `terminator` starts at or after `from` in `text`.
 export function inlineHtmlConstruct(text: string, index: number, terminated: (terminator: string, from: number) => boolean): string | undefined {
   for (const construct of inlineHtmlConstructs) {
     construct.opener.lastIndex = index

src/markdown/emit/line-escaping.ts

@@ -47,7 +47,6 @@ type EscapeWalk = {
   readonly headingCloser: number | undefined
   readonly inline: InlineSource
   readonly linkClose: number
-  readonly scan: string
 }
 
 const escapingCodes: readonly ['backslash', 'bracketed', 'bracketed-link-target', 'none'] = ['backslash', 'bracketed', 'bracketed-link-target', 'none']
@@ -148,7 +147,6 @@ function escapeClaims(scan: string, escapings: Escapings, container: LineContain
     headingCloser: container === 'heading' ? closingHashes(scan) : undefined,
     inline: inlineSource(scan),
     linkClose: lastLinkClose(scan, escapings),
-    scan,
   }
   const escaped = new Uint8Array(scan.length)
   let line = scanLine(scan, 0)
@@ -174,7 +172,7 @@ function escapeClaims(scan: string, escapings: Escapings, container: LineContain
 
 // A text character beside one of the emitter's delimiters would lengthen that delimiter's run, so every text character in such a run escapes.
 function runEscapes(walk: EscapeWalk, start: number, end: number, line: ScanLine): RunEscapes {
-  const { escapings, scan } = walk
+  const { escapings, inline: { text: scan } } = walk
   if (runHolds(escapings, start, end, isSyntax) && runHolds(escapings, start, end, isEscapable)) return { escapable: true }
   let index = start
   // A backtick run escapes whole: a bare rest would be a shorter backtick string, which can close a span an earlier run opens.
@@ -187,7 +185,8 @@ function runHolds(escapings: Escapings, start: number, end: number, kind: (escap
   return false
 }
 
-function claimsRunRest({ claims, container, escapings, inline, scan }: EscapeWalk, index: number, end: number, line: ScanLine): boolean {
+function claimsRunRest({ claims, container, escapings, inline }: EscapeWalk, index: number, end: number, line: ScanLine): boolean {
+  const scan = inline.text
   const escaping = escapings(index)
   if (escaping === 'bracketed-link-target') return readInlineToken(inline, index, claims).kind === 'code-span'
   if (!isEscapable(escaping)) return false
@@ -196,7 +195,7 @@ function claimsRunRest({ claims, container, escapings, inline, scan }: EscapeWal
   return token.kind !== 'text'
 }
 
-function claimsCharacter({ container, escapings, headingCloser, linkClose, scan }: EscapeWalk, index: number, token: InlineToken, line: ScanLine): boolean {
+function claimsCharacter({ container, escapings, headingCloser, inline: { text: scan }, linkClose }: EscapeWalk, index: number, token: InlineToken, line: ScanLine): boolean {
   const escaping = escapings(index)
   if (escaping === 'bracketed-link-target') return token.kind === 'directive'
   if (!isEscapable(escaping)) return false

src/markdown/inline-tokens.test.ts

@@ -0,0 +1,23 @@
+import type { AdfDocument } from '../adf/document.ts'
+import assert from 'node:assert/strict'
+import test from 'node:test'
+
+import { adfToLosslessMarkdown } from './emit/adf-to-markdown.ts'
+import { flavourClaims } from './portable/conventions.ts'
+import { inlineSource, readInlineToken } from './inline-tokens.ts'
+import { losslessMarkdownToAdf } from './parse/markdown-to-adf.ts'
+
+const constructs = ['<!A>', '<??>', '<![CDATA[]]>']
+
+test('an HTML construct whose terminator starts right after its opener reads as HTML', () => {
+  for (const construct of constructs) assert.equal(readInlineToken(inlineSource(`a ${construct}`), 2, flavourClaims.commonmark).kind, 'html', construct)
+})
+
+test('text spelling such a construct round-trips', () => {
+  for (const construct of constructs) {
+    const document: AdfDocument = { content: [{ content: [{ text: `a ${construct}`, type: 'text' }], type: 'paragraph' }], type: 'doc', version: 1 }
+    const written = adfToLosslessMarkdown(document)
+    assert.ok(written.ok)
+    assert.deepEqual(losslessMarkdownToAdf(written.value), { ok: true, value: document }, construct)
+  }
+})

src/markdown/inline-tokens.ts

@@ -1,8 +1,7 @@
-import type { BacktickRuns } from './commonmark/backtick-runs.ts'
 import type { ClaimedPrefix } from './directive-syntax.ts'
 import type { Claims } from './portable/conventions.ts'
 import { backslashEscape, inlineHtmlConstruct, readBracketedAutolink, readEmailAutolink } from './commonmark/grammar.ts'
-import { backtickRun, backtickRuns, closingRun } from './commonmark/backtick-runs.ts'
+import { backtickCloser, backtickRun } from './commonmark/backtick-runs.ts'
 import { claimDirectivePrefix } from './directive-syntax.ts'
 import { delimiterFlags, runLength } from './commonmark/emphasis-matching.ts'
 import { highlightDelimiter, highlightFlanking } from './portable/conventions.ts'
@@ -21,14 +20,14 @@ export type InlineToken =
 
 // A text and what its openers look ahead for, read once, so a walk reading a token at every index stays linear in it.
 export type InlineSource = {
-  readonly backticks: BacktickRuns
+  readonly closingBacktickRun: (from: number, opener: number) => number | undefined
   // Each HTML construct terminator's last start in the text, -1 for none, read the first time an opener asks.
   readonly terminators: Map<string, number>
   readonly text: string
 }
 
 export function inlineSource(text: string): InlineSource {
-  return { backticks: backtickRuns(text), terminators: new Map(), text }
+  return { closingBacktickRun: backtickCloser(text), terminators: new Map(), text }
 }
 
 export function readInlineToken(inline: InlineSource, index: number, claims: Claims): InlineToken {
@@ -87,7 +86,7 @@ function angleToken(inline: InlineSource, index: number): InlineToken {
 
 function backtickToken(inline: InlineSource, index: number): InlineToken {
   const opener = backtickRun(inline.text, index)
-  const closer = closingRun(inline.backticks, index + opener, opener)
+  const closer = inline.closingBacktickRun(index + opener, opener)
   return closer === undefined ? text(opener) : { kind: 'code-span', opener, width: closer + opener - index }
 }
 

todo.md

@@ -173,9 +173,10 @@ maintainer posts them once `0.3.0` is published. Found while planning discoverab
 the rest of the text at every opener, so backtick runs of lengths 1 to k with no closers inside an
 inline directive's `[content]` cost about k·n. Measured on 2026-10-18: 24 ms at 40k characters,
 126 ms at 160k and 1004 ms at 640k, where the same runs outside a directive take 6, 18 and 63 ms.
-The inline reader reads such runs through `backtickRuns` and `closingRun`
+The inline reader reads such runs through `backtickCloser`
 (`src/markdown/commonmark/backtick-runs.ts`), kept once per text; the directive reader would need
-them kept for the source it reads from.
+them kept for the source it reads from. Delete `closingBacktickRun` once nothing calls it, so one
+reader finds a closer.
 
 ### 81. Fail the gate unless the README's error tables list exactly the codes `ConvertErrorCode` holds.