fix(render): only render br as a trailing-space break if it round-trips

packages/comark/SPEC/COMARK/inline-component-br.md

@@ -0,0 +1,91 @@
+## Input
+
+```md
+::warning
+Beware that using only `$fetch` will not provide network calls de-duplication. :br
+It is recommended to use `$fetch` for client-side interactions.
+::
+
+Published modules cannot leverage auto-imports.
+:br :br
+Auto-imports are not enabled for files within `node_modules`.
+```
+
+## AST
+
+```json
+{
+  "frontmatter": {},
+  "meta": {},
+  "nodes": [
+    [
+      "warning",
+      {},
+      "Beware that using only ",
+      [
+        "code",
+        {},
+        "$fetch"
+      ],
+      " will not provide network calls de-duplication. ",
+      [
+        "br",
+        {}
+      ],
+      "\nIt is recommended to use ",
+      [
+        "code",
+        {},
+        "$fetch"
+      ],
+      " for client-side interactions."
+    ],
+    [
+      "p",
+      {},
+      "Published modules cannot leverage auto-imports.\n",
+      [
+        "br",
+        {}
+      ],
+      " ",
+      [
+        "br",
+        {}
+      ],
+      "\nAuto-imports are not enabled for files within ",
+      [
+        "code",
+        {},
+        "node_modules"
+      ],
+      "."
+    ]
+  ]
+}
+```
+
+## HTML
+
+```html
+<warning>
+  Beware that using only <code>$fetch</code> will not provide network calls de-duplication. <br>
+  It is recommended to use <code>$fetch</code> for client-side interactions.
+</warning>
+<p>Published modules cannot leverage auto-imports.
+<br> <br>
+Auto-imports are not enabled for files within <code>node_modules</code>.</p>
+```
+
+## Markdown
+
+```md
+::warning
+Beware that using only `$fetch` will not provide network calls de-duplication. :br
+It is recommended to use `$fetch` for client-side interactions.
+::
+
+Published modules cannot leverage auto-imports.
+:br :br
+Auto-imports are not enabled for files within `node_modules`.
+```

packages/comark/SPEC/markdown-directive/directive-no-content.md

@@ -71,8 +71,7 @@ a :br with no content or attributes
 ```md
 a :hr directive with no content
 
-a   
- with no content or attributes
+a :br with no content or attributes
 
 ::video{file="movie.mp4"}
 ::

packages/comark/src/internal/parse/auto-close/index.ts

@@ -584,11 +584,11 @@ function healRegion(text: string, o: Opts): string {
       while (text.charCodeAt(i + n) === c) n++
       const prev = codePointBefore(text, i)
       const next = i + n < len ? codePointAt(text, i + n) : ''
-      const attachedLeft = prev !== '' && !isSpaceCp(prev) && i !== escEnd
+      const attachedLeft = prev !== '' && !isSpaceCode(prev.charCodeAt(0)) && i !== escEnd
       // `_` only opens at a boundary: whitespace, an escape or another marker.
       // That keeps `func(_arg` literal while `**_text` and `\___bold` still open.
       const openLeft = !attachedLeft || (c === 95 && (prev === '*' || prev === '_' || prev === '~'))
-      const openRight = next !== '' && !isSpaceCp(next)
+      const openRight = next !== '' && !isSpaceCode(next.charCodeAt(0))
       const enabled = n === 1 ? o.italic : n === 2 ? o.bold : o.boldItalic
 
       if (c === 42) {
@@ -629,10 +629,10 @@ function healRegion(text: string, o: Opts): string {
       while (text.charCodeAt(i + n) === 126) n++
       const prev = codePointBefore(text, i)
       const next = i + n < len ? codePointAt(text, i + n) : ''
-      const attachedLeft = prev !== '' && !isSpaceCp(prev)
+      const attachedLeft = prev !== '' && !isSpaceCode(prev.charCodeAt(0))
       if (top !== null && top.k === F_TILDE && attachedLeft) {
         closeRun(frames, F_TILDE, n)
-      } else if (n === 2 && o.strikethrough && next !== '' && !isSpaceCp(next)) {
+      } else if (n === 2 && o.strikethrough && next !== '' && !isSpaceCode(next.charCodeAt(0))) {
         frames.push({ k: F_TILDE, len: 2, pos: i })
       } else if (n === 1 && o.singleTilde && isAlnum(prev) && isAlnum(next) && !isSubscriptTilde(text, i)) {
         // A lone mid-word `~` would become GFM strikethrough — keep it literal.
@@ -1088,12 +1088,9 @@ function isAsciiAlpha(c: number): boolean {
   return (c >= 97 && c <= 122) || (c >= 65 && c <= 90)
 }
 
-function isSpaceCp(cp: string): boolean {
-  return cp === ' ' || cp === '\t' || cp === '\n' || cp === '\r'
-}
-
+/** Space, tab, line feed, form feed or carriage return. */
 function isSpaceCode(c: number): boolean {
-  return c === 32 || c === 9 || c === 10 || c === 13
+  return c === 32 || c === 9 || c === 10 || c === 12 || c === 13
 }
 
 /** Full code point before `i` (surrogate aware), `''` at the start. */

packages/comark/src/internal/parse/utils.ts

@@ -1,6 +1,11 @@
 import type { Node, ElementNode, ElementNodeAttributes, MarkdownDocument } from 'comark'
 import { decodeHTML, isHtmlVoidElement, TREE_WALK_MAX_DEPTH } from 'comark/utils'
 
+/** Space, tab, line feed, form feed or carriage return. Defined per file so it stays inlinable on hot paths. */
+function isSpaceCode(c: number): boolean {
+  return c === 32 || c === 9 || c === 10 || c === 12 || c === 13
+}
+
 export type ParsedHtmlTag =
   | { kind: 'open'; tag: string; attrs: Record<string, unknown>; selfClosing: boolean }
   | { kind: 'close'; tag: string }
@@ -29,8 +34,7 @@ export type ParsedHtmlTag =
  */
 function isBlankText(value: string): boolean {
   for (let i = 0; i < value.length; i++) {
-    const c = value.charCodeAt(i)
-    if (c !== 32 && c !== 10 && c !== 9 && c !== 13 && c !== 12) return false
+    if (!isSpaceCode(value.charCodeAt(i))) return false
   }
   return true
 }

packages/comark/src/internal/stringify/handlers/br.ts

@@ -1,6 +1,31 @@
 import type { State } from 'comark/render'
-import type { ElementNode } from 'comark'
+import type { ElementNode, Node } from 'comark'
 
-export function br(_n: ElementNode, _state: State) {
-  return '  \n'
+/** Space, tab, line feed, form feed or carriage return. Defined per file so it stays inlinable on hot paths. */
+function isSpaceCode(c: number): boolean {
+  return c === 32 || c === 9 || c === 10 || c === 12 || c === 13
+}
+
+function isBr(node: Node | undefined) {
+  return Array.isArray(node) && node[0] === 'br'
+}
+
+export function br(node: ElementNode, state: State, parent?: ElementNode) {
+  const index = parent ? parent.indexOf(node) : -1
+  if (index < 2) return '  \n'
+
+  const prev = index > 2 ? (parent![index - 1] as Node) : undefined
+  const next = parent![index + 1] as Node | undefined
+  const prevSpace = typeof prev === 'string' && isSpaceCode(prev.charCodeAt(prev.length - 1))
+  const nextSpace = typeof next === 'string' && isSpaceCode(next.charCodeAt(0))
+
+  // A trailing-space break drops adjacent whitespace and needs content on both sides
+  const hardBreak = prev !== undefined && next !== undefined && !isBr(prev) && !isBr(next) && !prevSpace && !nextSpace
+  if (hardBreak) return '  \n'
+
+  if (state.context.format !== 'markdown/comark' || prev === undefined) return '<br>'
+
+  // Empty `{}` delimits `:br` from content that would otherwise join it
+  const open = prevSpace ? ':br' : ' :br'
+  return nextSpace ? open : `${open} `
 }

packages/comark/src/plugins/footnotes.ts

@@ -2,6 +2,11 @@ import type { Node, ElementNode, ElementNodeAttributes, ConditionalNodeHandler }
 import { defineComarkPlugin } from 'comark'
 import { visit } from 'comark/utils'
 
+/** Space, tab, line feed, form feed or carriage return. Defined per file so it stays inlinable on hot paths. */
+function isSpaceCode(c: number): boolean {
+  return c === 32 || c === 9 || c === 10 || c === 12 || c === 13
+}
+
 export interface FootnotesConfig {
   /**
    * The label for the footnotes section
@@ -64,8 +69,7 @@ function isFootnoteRef(node: Node): string | null {
 
   // Check for whitespace using charCode scanning (avoid regex)
   for (let i = 1; i < child.length; i++) {
-    const c = child.charCodeAt(i)
-    if (c === 0x20 || c === 0x09 || c === 0x0a || c === 0x0d) return null
+    if (isSpaceCode(child.charCodeAt(i))) return null
   }
 
   return child.slice(1)

packages/comark/src/plugins/punctuation.ts

@@ -38,8 +38,13 @@ const DEFAULT_QUOTES = '\u201C\u201D\u2018\u2019' // ""''
 /** Tags whose text content should not be transformed */
 const SKIP_TAGS = new Set(['code', 'pre', 'math', 'script', 'style', 'kbd'])
 
+/** Space, tab, line feed, form feed or carriage return. Defined per file so it stays inlinable on hot paths. */
+function isSpaceCode(c: number): boolean {
+  return c === 32 || c === 9 || c === 10 || c === 12 || c === 13
+}
+
 function isWhitespaceOrOpener(ch: string): boolean {
-  return ch === ' ' || ch === '\t' || ch === '\n' || ch === '\r' || ch === '(' || ch === '[' || ch === '{'
+  return isSpaceCode(ch.charCodeAt(0)) || ch === '(' || ch === '[' || ch === '{'
 }
 
 function isLetter(ch: string): boolean {

packages/comark/test/roundtrip-safety.test.ts

@@ -94,6 +94,19 @@ describe('comarkAttributes quoting', () => {
   })
 })
 
+describe('line breaks', () => {
+  it.each([
+    ['before a word', ['p', {}, 'a ', ['br', {}], ' b']],
+    ['after a component', ['p', {}, 'A ', ['badge', {}, 'x'], ' ', ['br', {}], ' word']],
+    ['after inline code', ['p', {}, ['code', {}, 'x'], ' ', ['br', {}], '\ny']],
+    ['between breaks', ['p', {}, 'a ', ['br', {}], ' ', ['br', {}], ' b']],
+  ])('round-trips a break %s', async (_, node) => {
+    const doc = { frontmatter: {}, meta: {}, nodes: [node] } as unknown as MarkdownDocument
+    const t2 = await parseMarkdown(await renderMarkdown(doc))
+    expect(t2.nodes).toEqual(doc.nodes)
+  })
+})
+
 describe('component after a list', () => {
   it.each([
     ['in the default slot', '::card\n- one\n- two\n\n:::note\nhi\n:::\n::'],

test/bundle.test.ts

@@ -67,7 +67,7 @@ describe('package bundle size', { timeout: 60_000 }, () => {
         "@comark/react": "39.6k (76 files)",
         "@comark/svelte": "46.8k (84 files)",
         "@comark/vue": "56.4k (80 files)",
-        "comark": "401k (158 files)",
+        "comark": "402k (158 files)",
       }
     `)
   })