dx(compiler-dom): warn on invalid html nesting

packages/compiler-dom/__tests__/transforms/validateHtmlNesting.spec.ts

@@ -0,0 +1,20 @@
+import { type CompilerError, compile } from '../../src'
+
+describe('validate html nesting', () => {
+  it('should warn with p > div', () => {
+    let err: CompilerError | undefined
+    compile(`<p><div></div></p>`, {
+      onWarn: e => (err = e),
+    })
+    expect(err).toBeDefined()
+    expect(err!.message).toMatch(`<div> cannot be child of <p>`)
+  })
+
+  it('should not warn with select > hr', () => {
+    let err: CompilerError | undefined
+    compile(`<select><hr></select>`, {
+      onWarn: e => (err = e),
+    })
+    expect(err).toBeUndefined()
+  })
+})

packages/compiler-dom/src/htmlNesting.ts

@@ -0,0 +1,195 @@
+/**
+ * Copied from https://github.com/MananTank/validate-html-nesting
+ * with ISC license
+ *
+ * To avoid runtime dependency on validate-html-nesting
+ * This file should not change very often in the original repo
+ * but we may need to keep it up-to-date from time to time.
+ */
+
+/**
+ * returns true if given parent-child nesting is valid HTML
+ */
+export function isValidHTMLNesting(parent: string, child: string): boolean {
+  // if we know the list of children that are the only valid children for the given parent
+  if (parent in onlyValidChildren) {
+    return onlyValidChildren[parent].has(child)
+  }
+
+  // if we know the list of parents that are the only valid parents for the given child
+  if (child in onlyValidParents) {
+    return onlyValidParents[child].has(parent)
+  }
+
+  // if we know the list of children that are NOT valid for the given parent
+  if (parent in knownInvalidChildren) {
+    // check if the child is in the list of invalid children
+    // if so, return false
+    if (knownInvalidChildren[parent].has(child)) return false
+  }
+
+  // if we know the list of parents that are NOT valid for the given child
+  if (child in knownInvalidParents) {
+    // check if the parent is in the list of invalid parents
+    // if so, return false
+    if (knownInvalidParents[child].has(parent)) return false
+  }
+
+  return true
+}
+
+const headings = new Set(['h1', 'h2', 'h3', 'h4', 'h5', 'h6'])
+const emptySet = new Set([])
+
+/**
+ * maps element to set of elements that can be it's children, no other */
+const onlyValidChildren: Record<string, Set<string>> = {
+  head: new Set([
+    'base',
+    'basefront',
+    'bgsound',
+    'link',
+    'meta',
+    'title',
+    'noscript',
+    'noframes',
+    'style',
+    'script',
+    'template',
+  ]),
+  optgroup: new Set(['option']),
+  select: new Set(['optgroup', 'option', 'hr']),
+  // table
+  table: new Set(['caption', 'colgroup', 'tbody', 'tfoot', 'thead']),
+  tr: new Set(['td', 'th']),
+  colgroup: new Set(['col']),
+  tbody: new Set(['tr']),
+  thead: new Set(['tr']),
+  tfoot: new Set(['tr']),
+  // these elements can not have any children elements
+  script: emptySet,
+  iframe: emptySet,
+  option: emptySet,
+  textarea: emptySet,
+  style: emptySet,
+  title: emptySet,
+}
+
+/** maps elements to set of elements which can be it's parent, no other */
+const onlyValidParents: Record<string, Set<string>> = {
+  // sections
+  html: emptySet,
+  body: new Set(['html']),
+  head: new Set(['html']),
+  // table
+  td: new Set(['tr']),
+  colgroup: new Set(['table']),
+  caption: new Set(['table']),
+  tbody: new Set(['table']),
+  tfoot: new Set(['table']),
+  col: new Set(['colgroup']),
+  th: new Set(['tr']),
+  thead: new Set(['table']),
+  tr: new Set(['tbody', 'thead', 'tfoot']),
+  // data list
+  dd: new Set(['dl', 'div']),
+  dt: new Set(['dl', 'div']),
+  // other
+  figcaption: new Set(['figure']),
+  // li: new Set(["ul", "ol"]),
+  summary: new Set(['details']),
+  area: new Set(['map']),
+} as const
+
+/** maps element to set of elements that can not be it's children, others can */
+const knownInvalidChildren: Record<string, Set<string>> = {
+  p: new Set([
+    'address',
+    'article',
+    'aside',
+    'blockquote',
+    'center',
+    'details',
+    'dialog',
+    'dir',
+    'div',
+    'dl',
+    'fieldset',
+    'figure',
+    'footer',
+    'form',
+    'h1',
+    'h2',
+    'h3',
+    'h4',
+    'h5',
+    'h6',
+    'header',
+    'hgroup',
+    'hr',
+    'li',
+    'main',
+    'nav',
+    'menu',
+    'ol',
+    'p',
+    'pre',
+    'section',
+    'table',
+    'ul',
+  ]),
+  svg: new Set([
+    'b',
+    'blockquote',
+    'br',
+    'code',
+    'dd',
+    'div',
+    'dl',
+    'dt',
+    'em',
+    'embed',
+    'h1',
+    'h2',
+    'h3',
+    'h4',
+    'h5',
+    'h6',
+    'hr',
+    'i',
+    'img',
+    'li',
+    'menu',
+    'meta',
+    'ol',
+    'p',
+    'pre',
+    'ruby',
+    's',
+    'small',
+    'span',
+    'strong',
+    'sub',
+    'sup',
+    'table',
+    'u',
+    'ul',
+    'var',
+  ]),
+} as const
+
+/** maps element to set of elements that can not be it's parent, others can */
+const knownInvalidParents: Record<string, Set<string>> = {
+  a: new Set(['a']),
+  button: new Set(['button']),
+  dd: new Set(['dd', 'dt']),
+  dt: new Set(['dd', 'dt']),
+  form: new Set(['form']),
+  li: new Set(['li']),
+  h1: headings,
+  h2: headings,
+  h3: headings,
+  h4: headings,
+  h5: headings,
+  h6: headings,
+}

packages/compiler-dom/src/index.ts

@@ -19,13 +19,14 @@ import { transformShow } from './transforms/vShow'
 import { transformTransition } from './transforms/Transition'
 import { stringifyStatic } from './transforms/stringifyStatic'
 import { ignoreSideEffectTags } from './transforms/ignoreSideEffectTags'
+import { validateHtmlNesting } from './transforms/validateHtmlNesting'
 import { extend } from '@vue/shared'
 
 export { parserOptions }
 
 export const DOMNodeTransforms: NodeTransform[] = [
   transformStyle,
-  ...(__DEV__ ? [transformTransition] : []),
+  ...(__DEV__ ? [transformTransition, validateHtmlNesting] : []),
 ]
 
 export const DOMDirectiveTransforms: Record<string, DirectiveTransform> = {

packages/compiler-dom/src/transforms/validateHtmlNesting.ts

@@ -0,0 +1,27 @@
+import {
+  type CompilerError,
+  ElementTypes,
+  type NodeTransform,
+  NodeTypes,
+} from '@vue/compiler-core'
+import { isValidHTMLNesting } from '../htmlNesting'
+
+export const validateHtmlNesting: NodeTransform = (node, context) => {
+  if (
+    node.type === NodeTypes.ELEMENT &&
+    node.tagType === ElementTypes.ELEMENT &&
+    context.parent &&
+    context.parent.type === NodeTypes.ELEMENT &&
+    context.parent.tagType === ElementTypes.ELEMENT &&
+    !isValidHTMLNesting(context.parent.tag, node.tag)
+  ) {
+    const error = new SyntaxError(
+      `<${node.tag}> cannot be child of <${context.parent.tag}>, ` +
+        'according to HTML specifications. ' +
+        'This can cause hydration errors or ' +
+        'potentially disrupt future functionality.',
+    ) as CompilerError
+    error.loc = node.loc
+    context.onWarn(error)
+  }
+}