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Linter Rule: Don't flag meta[itemprop] for html-head-only-elements #867

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Merged
marcoroth merged 1 commit into from
Nov 13, 2025
Merged

Linter Rule: Don't flag meta[itemprop] for html-head-only-elements #867

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26 changes: 24 additions & 2 deletions javascript/packages/linter/docs/rules/html-head-only-elements.md
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Original file line number Diff line number Diff line change
Expand Up @@ -8,8 +8,9 @@ Enforce that certain elements only appear inside the `<head>` section of the doc

Elements like `<title>`, `<meta>`, `<base>`, `<link>`, and `<style>` are permitted only inside the `<head>` element. They must not appear inside `<body>` or outside of `<html>`. Placing them elsewhere produces invalid HTML and relies on browser error correction.

> [!NOTE] Exception
> `<title>` elements are allowed inside `<svg>` elements for accessibility purposes.
> [!NOTE] Exceptions
> - `<title>` elements are allowed inside `<svg>` elements for accessibility purposes.
> - `<meta>` elements with the `itemprop` attribute are allowed in the `<body>` for [microdata](https://html.spec.whatwg.org/multipage/microdata.html#the-itemprop-attribute) markup (e.g., Schema.org structured data).

## Rationale

Expand Down Expand Up @@ -56,6 +57,16 @@ Placing these elements outside `<head>` leads to invalid HTML and undefined beha
</body>
```

```erb
<body>
<div itemscope itemtype="https://schema.org/Book">
<span itemprop="name">The Hobbit</span>
<meta itemprop="author" content="J.R.R. Tolkien">
<meta itemprop="isbn" content="978-0618260300">
</div>
</body>
```

### 🚫 Bad

```erb
Expand All @@ -76,6 +87,17 @@ Placing these elements outside `<head>` leads to invalid HTML and undefined beha
</body>
```

```erb
<body>
<!-- Regular meta tags (name, charset, http-equiv) must be in <head> -->
<meta name="description" content="Page description">
<meta charset="UTF-8">
<meta http-equiv="refresh" content="30">
</body>
```

## References

* [HTML Living Standard - The `head` element](https://html.spec.whatwg.org/multipage/semantics.html#the-head-element)
* [MDN - The `<meta>` element](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/meta#technical_summary)
* [HTML Living Standard - Microdata (`itemprop`)](https://html.spec.whatwg.org/multipage/microdata.html#the-itemprop-attribute)
7 changes: 6 additions & 1 deletion javascript/packages/linter/src/rules/html-head-only-elements.ts
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
import { ParserRule } from "../types"
import { BaseRuleVisitor, getTagName, isHeadOnlyTag } from "./rule-utils"
import { BaseRuleVisitor, getTagName, isHeadOnlyTag, hasAttribute } from "./rule-utils"

import type { ParseResult, HTMLElementNode } from "@herb-tools/core"
import type { UnboundLintOffense, LintContext, FullRuleConfig } from "../types"
Expand All @@ -23,13 +23,18 @@ class HeadOnlyElementsVisitor extends BaseRuleVisitor {
if (!this.insideBody) return
if (!isHeadOnlyTag(tagName)) return
if (tagName === "title" && this.insideSVG) return
if (tagName === "meta" && this.hasItempropAttribute(node)) return

this.addOffense(
`Element \`<${tagName}>\` must be placed inside the \`<head>\` tag.`,
node.location,
)
}

private hasItempropAttribute(node: HTMLElementNode): boolean {
return hasAttribute(node.open_tag, "itemprop")
}

private get insideHead(): boolean {
return this.elementStack.includes("head")
}
Expand Down
4 changes: 3 additions & 1 deletion javascript/packages/linter/src/rules/rule-utils.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -378,7 +378,9 @@ export function findAttributeByName(attributes: Node[], attributeName: string):
/**
* Checks if a tag has a specific attribute
*/
export function hasAttribute(node: HTMLOpenTagNode, attributeName: string): boolean {
export function hasAttribute(node: HTMLOpenTagNode | null | undefined, attributeName: string): boolean {
if (!node) return false

return getAttribute(node, attributeName) !== null
}

Expand Down
83 changes: 83 additions & 0 deletions javascript/packages/linter/test/rules/html-head-only-elements.test.ts
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Expand Up @@ -94,6 +94,89 @@ describe("html-head-only-elements", () => {
`)
})

test("passes when meta with itemprop is in body (microdata)", () => {
expectNoOffenses(dedent`
<html>
<head>
<title>My Page</title>
</head>
<body>
<div itemscope itemtype="https://schema.org/Book">
<span itemprop="name">The Hobbit</span>
<meta itemprop="author" content="J.R.R. Tolkien">
<meta itemprop="isbn" content="978-0618260300">
</div>
</body>
</html>
`)
})

test("passes when meta with itemprop is deeply nested in body", () => {
expectNoOffenses(dedent`
<html>
<head>
<title>My Page</title>
</head>
<body>
<article>
<div itemscope itemtype="https://schema.org/Product">
<h1 itemprop="name">Widget</h1>
<div class="details">
<meta itemprop="sku" content="12345">
<span itemprop="price" content="29.99">$29.99</span>
</div>
</div>
</article>
</body>
</html>
`)
})

test("fails when meta with name attribute is in body", () => {
expectError("Element `<meta>` must be placed inside the `<head>` tag.")

assertOffenses(dedent`
<html>
<head>
</head>
<body>
<meta name="description" content="Page description">
<h1>Welcome</h1>
</body>
</html>
`)
})

test("fails when meta with http-equiv attribute is in body", () => {
expectError("Element `<meta>` must be placed inside the `<head>` tag.")

assertOffenses(dedent`
<html>
<head>
</head>
<body>
<meta http-equiv="refresh" content="30">
<h1>Welcome</h1>
</body>
</html>
`)
})

test("fails when meta with charset attribute is in body", () => {
expectError("Element `<meta>` must be placed inside the `<head>` tag.")

assertOffenses(dedent`
<html>
<head>
</head>
<body>
<meta charset="UTF-8">
<h1>Welcome</h1>
</body>
</html>
`)
})

test("fails when link is in body", () => {
expectError("Element `<link>` must be placed inside the `<head>` tag.")

Expand Down
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