fix(markdown): keep positions exact in github alert bodies

The vp_github_alerts rule strips the alert marker from the first inline
token's content before inline parsing, shifting every position in the
body up by the marker line and breaking column re-alignment. The rule now
records how many lines it removed (token.meta.vpLineOffset) and the
source positions plugin adds them back.

Also re-emit the source-location attribute from the remaining hand-built
renderers that dropped it (::: v-pre and ::: raw wrappers, math blocks),
and pop it off fence tokens in preWrapper so a custom highlight falling
back to markdown-it's default fence renderer cannot emit it twice.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

__tests__/unit/node/markdown/plugins/include.test.ts

@@ -628,6 +628,15 @@ describe('node/markdown/plugins/include', () => {
       ])
     })
 
+    test('alert bodies inside includes resolve exactly', async () => {
+      await write('sub/part.md', '> [!NOTE]\n> body [x](./x)\n')
+
+      const { locs } = await renderLocs('<!-- @include: ./sub/part.md -->\n')
+      expect(locs).toEqual([
+        { file: path.join(root, 'sub/part.md'), line: 2, column: 8 }
+      ])
+    })
+
     test('pages without includes get an identity line map', async () => {
       const { env } = await render('# Hi\n\n[a](./a)\n')
       expect(env.lineMap!.resolve(2)).toEqual({

__tests__/unit/node/markdown/plugins/sourceAttrs.test.ts

@@ -72,6 +72,32 @@ describe('node/markdown/plugins/sourceAttrs', () => {
     )
   })
 
+  test('hand-built wrappers re-emit the attribute', async () => {
+    const { vueSrc, file } = await renderPage(
+      {
+        'index.md': '::: v-pre\nvp\n:::\n\n::: raw\nrw\n:::\n\n$$\nx^2\n$$\n'
+      },
+      { markdown: { math: true } }
+    )
+    const at = (line: number) => `data-v-inspector="${rel(file)}:${line}:1"`
+    expect(vueSrc).toContain(`<div v-pre ${at(1)}>`)
+    expect(vueSrc).toContain(`<div class="vp-raw" ${at(5)}>`)
+    expect(vueSrc).toContain(`tabindex="0" ${at(9)}`)
+  })
+
+  test('a custom highlight fallback does not double-stamp fences', async () => {
+    const { vueSrc, file } = await renderPage(
+      { 'index.md': '```ts\ncode\n```\n' },
+      { markdown: { highlight: (code: string) => code } }
+    )
+    const occurrences = vueSrc.match(/data-v-inspector="[^"]*:1:1"/g)
+    expect(occurrences).toHaveLength(1)
+    // and it sits on the wrapper, not the inner code element
+    expect(vueSrc).toContain(
+      `<div class="language-ts" data-v-inspector="${rel(file)}:1:1">`
+    )
+  })
+
   test('builds render without source attributes', async () => {
     const { vueSrc } = await renderPage(
       { 'index.md': '# Head\n\npara\n' },

__tests__/unit/node/markdown/plugins/sourcePositions.test.ts

@@ -127,6 +127,25 @@ describe('markdown/plugins/sourcePositions', () => {
     ])
   })
 
+  test('github alert bodies report exact positions', async () => {
+    const links = await collect(
+      '> [!TIP]\n> a [one](./one)\n> b [two](./two)\n'
+    )
+    expect(links.map((l) => l.loc)).toEqual([
+      { file: '/docs/page.md', line: 2, column: 5 },
+      { file: '/docs/page.md', line: 3, column: 5 }
+    ])
+  })
+
+  test('github alert with a custom title keeps positions exact', async () => {
+    const links = await collect('> [!WARNING] Custom\n> body [x](./x)\n')
+    expect(links[0].loc).toEqual({
+      file: '/docs/page.md',
+      line: 2,
+      column: 8
+    })
+  })
+
   test('header anchors get no synthetic position', async () => {
     disposeMdItInstance()
     const md = await createMarkdownRenderer('.', {

src/node/markdown/markdown.ts

@@ -64,7 +64,7 @@ import {
   snippetPlugin,
   type Options as SnippetPluginOptions
 } from './plugins/snippet'
-import { sourceAttrsPlugin } from './plugins/sourceAttrs'
+import { renderSourceLocAttr, sourceAttrsPlugin } from './plugins/sourceAttrs'
 import { sourcePositionsPlugin } from './plugins/sourcePositions'
 import { tablePlugin } from './plugins/table'
 
@@ -547,9 +547,15 @@ export async function createMarkdownRenderer(
       }
       const origMathBlock = md.renderer.rules.math_block!
       md.renderer.rules.math_block = function (...args) {
+        // mathjax's renderer ignores token attrs - re-emit the source
+        // location alongside the v-pre/tabindex injection
+        const sourceLocAttr = renderSourceLocAttr(md!, args[0][args[1]])
         return origMathBlock
           .apply(this, args)
-          .replace(/^<mjx-container /, '<mjx-container v-pre tabindex="0" ')
+          .replace(
+            /^<mjx-container /,
+            `<mjx-container v-pre tabindex="0"${sourceLocAttr} `
+          )
       }
     } catch (error) {
       throw new Error(

src/node/markdown/plugins/containers.ts

@@ -8,8 +8,9 @@ import type {
   MarkdownEnv,
   MarkdownLocaleOptions
 } from '../../shared'
+import { countLineBreaks } from '../lineMap'
 import { extractTitle } from './preWrapper'
-import { SOURCE_LOC_ATTR } from './sourceAttrs'
+import { renderSourceLocAttr } from './sourceAttrs'
 
 export type { ContainerOptions } from '../../shared'
 
@@ -42,12 +43,14 @@ export const containerPlugin = (
     // explicitly escape Vue syntax
     .use(container, {
       name: 'v-pre',
-      openRender: () => `<div v-pre>\n`,
+      openRender: (tokens, idx) =>
+        `<div v-pre${renderSourceLocAttr(md, tokens[idx])}>\n`,
       closeRender: () => `</div>\n`
     })
     .use(container, {
       name: 'raw',
-      openRender: () => `<div class="vp-raw">\n`,
+      openRender: (tokens, idx) =>
+        `<div class="vp-raw"${renderSourceLocAttr(md, tokens[idx])}>\n`,
       closeRender: () => `</div>\n`
     })
     .use(container, {
@@ -185,12 +188,7 @@ function createCodeGroupOpenRender(md: MarkdownItAsync): RenderRule {
       }
     }
 
-    const sourceLoc = tokens[idx].attrGet(SOURCE_LOC_ATTR)
-    const sourceLocAttr = sourceLoc
-      ? ` ${SOURCE_LOC_ATTR}="${md.utils.escapeHtml(sourceLoc)}"`
-      : ''
-
-    return `<div class="vp-code-group"${sourceLocAttr}><div class="tabs">${tabs}</div><div class="blocks">\n`
+    return `<div class="vp-code-group"${renderSourceLocAttr(md, tokens[idx])}><div class="tabs">${tabs}</div><div class="blocks">\n`
   }
 }
 
@@ -228,9 +226,20 @@ export const gitHubAlertsPlugin = (
         const title =
           match[2].trim() ||
           titlesFor(titles, (state.env as MarkdownEnv)?.localeIndex)[type]
+        const contentBefore = firstContent.content
         firstContent.content = firstContent.content
           .slice(match[0].length)
           .trimStart()
+        // the removed marker line(s) shift the inline content relative to
+        // firstContent.map - record the offset so source positions stay exact
+        const removedLines =
+          countLineBreaks(contentBefore) - countLineBreaks(firstContent.content)
+        if (removedLines) {
+          firstContent.meta = {
+            ...firstContent.meta,
+            vpLineOffset: removedLines
+          }
+        }
         open.type = 'github_alert_open'
         open.tag = 'div'
         open.meta = { title, type }
@@ -241,10 +250,6 @@ export const gitHubAlertsPlugin = (
   })
   md.renderer.rules.github_alert_open = function (tokens, idx) {
     const { title, type } = tokens[idx].meta
-    const sourceLoc = tokens[idx].attrGet(SOURCE_LOC_ATTR)
-    const sourceLocAttr = sourceLoc
-      ? ` ${SOURCE_LOC_ATTR}="${md.utils.escapeHtml(sourceLoc)}"`
-      : ''
-    return `<div class="${type} custom-block github-alert"${sourceLocAttr}><p class="custom-block-title">${title}</p>\n`
+    return `<div class="${type} custom-block github-alert"${renderSourceLocAttr(md, tokens[idx])}><p class="custom-block-title">${title}</p>\n`
   }
 }

src/node/markdown/plugins/preWrapper.ts

@@ -1,7 +1,7 @@
 import type { MarkdownItAsync } from 'markdown-it-async'
 
 import type { MarkdownEnv, MarkdownLocaleOptions } from '../../shared'
-import { SOURCE_LOC_ATTR } from './sourceAttrs'
+import { popSourceLocAttr } from './sourceAttrs'
 
 export interface Options {
   codeCopyButton: { tooltipText: string; copiedText: string }
@@ -43,11 +43,10 @@ export function preWrapperPlugin(md: MarkdownItAsync, options: Options) {
       localeButton?.copiedText || options.codeCopyButton.copiedText
 
     // the fence renderer builds its markup by hand, so the source-location
-    // attribute is re-emitted on the wrapper
-    const sourceLoc = token.attrGet(SOURCE_LOC_ATTR)
-    const sourceLocAttr = sourceLoc
-      ? ` ${SOURCE_LOC_ATTR}="${md.utils.escapeHtml(sourceLoc)}"`
-      : ''
+    // attribute moves onto the wrapper - popped off the token because a
+    // custom `highlight` may fall back to markdown-it's default fence
+    // renderer, which does render token attrs
+    const sourceLocAttr = popSourceLocAttr(md, token)
 
     return (
       `<div class="language-${lang}${active}"${sourceLocAttr}>` +

src/node/markdown/plugins/sourceAttrs.ts

@@ -1,6 +1,8 @@
 import path from 'node:path'
 
+import type MarkdownIt from 'markdown-it'
 import type { MarkdownItAsync } from 'markdown-it-async'
+import type Token from 'markdown-it/lib/token.mjs'
 
 import { slash, type MarkdownEnv } from '../../shared'
 
@@ -24,6 +26,34 @@ export const SOURCE_LOC_ATTR = 'data-v-inspector'
  * alerts) re-emit the attribute themselves; `html_block` is skipped since
  * raw HTML and Vue components render their content verbatim.
  */
+/**
+ * For renderers that build their markup by hand and would otherwise drop
+ * `token.attrs`: the source-location attribute rendered as ` name="value"`,
+ * or an empty string.
+ */
+export function renderSourceLocAttr(
+  md: Pick<MarkdownIt, 'utils'>,
+  token: Token
+): string {
+  const loc = token.attrGet(SOURCE_LOC_ATTR)
+  return loc ? ` ${SOURCE_LOC_ATTR}="${md.utils.escapeHtml(loc)}"` : ''
+}
+
+/**
+ * Like `renderSourceLocAttr`, but also removes the attribute from the token —
+ * for wrappers whose inner renderer may fall back to a default rule that
+ * renders token attrs, which would emit the location twice.
+ */
+export function popSourceLocAttr(
+  md: Pick<MarkdownIt, 'utils'>,
+  token: Token
+): string {
+  const rendered = renderSourceLocAttr(md, token)
+  const index = token.attrIndex(SOURCE_LOC_ATTR)
+  if (index >= 0) token.attrs!.splice(index, 1)
+  return rendered
+}
+
 export function sourceAttrsPlugin(md: MarkdownItAsync): void {
   md.core.ruler.push('vp_source_attrs', (state) => {
     const env = state.env as MarkdownEnv

src/node/markdown/plugins/sourcePositions.ts

@@ -206,7 +206,9 @@ function sourceLocs(state: StateCore): void {
       const pos = child[POS]
       if (!pos) continue
 
-      const line = token.map[0] + pos.dLine
+      // vpLineOffset: lines a pre-inline core rule removed from the token's
+      // content (the github-alerts marker) while its map kept spanning them
+      const line = token.map[0] + (token.meta?.vpLineOffset ?? 0) + pos.dLine
       const resolved = env.lineMap?.resolve(line)
       const loc: MarkdownSourceLoc = resolved
         ? { file: resolved.file, line: resolved.line + 1 }