Linter: Implement a11y-disabled-attribute rule

javascript/packages/linter/docs/rules/README.md

@@ -6,6 +6,7 @@ This page contains documentation for all Herb Linter rules.
 
 #### Accessibility
 
+- [`a11y-disabled-attribute`](./a11y-disabled-attribute.md) - Prevent usage of the `disabled` attribute on unsupported elements
 - [`a11y-no-accesskey-attribute`](./a11y-no-accesskey-attribute.md) - Prevent usage of the `accesskey` attribute
 - [`a11y-no-aria-unsupported-elements`](./a11y-no-aria-unsupported-elements.md) - Prevent usage of ARIA on unsupported elements
 - [`a11y-no-autofocus-attribute`](./a11y-no-autofocus-attribute.md) - Prevent usage of the `autofocus` attribute

javascript/packages/linter/docs/rules/a11y-disabled-attribute.md

@@ -0,0 +1,47 @@
+# Linter Rule: Disabled Attribute
+
+**Rule:** `a11y-disabled-attribute`
+
+## Description
+
+The `disabled` attribute is only valid on certain HTML elements. Using it on other elements has no effect and may confuse users or assistive technologies.
+
+## Rationale
+
+The HTML `disabled` attribute is a boolean attribute that only applies to form-related elements: `button`, `input`, `textarea`, `option`, `select`, `fieldset`, `optgroup`, and `task-lists`. Applying it to other elements like `<a>`, `<div>`, or `<span>` has no native browser behavior and can be misleading.
+
+## Examples
+
+### ✅ Good
+
+```erb
+<button disabled>Continue</button>
+```
+
+```erb
+<input type="text" disabled>
+```
+
+```erb
+<select disabled><option>A</option></select>
+```
+
+### 🚫 Bad
+
+```erb
+<a href="https://github.com/" disabled>Go to GitHub</a>
+```
+
+```erb
+<div disabled>Content</div>
+```
+
+```erb
+<span disabled>Text</span>
+```
+
+## References
+
+- [erblint-github: `DisabledAttribute`](https://github.com/github/erblint-github/blob/main/lib/erblint-github/linters/github/accessibility/disabled_attribute.rb)
+- [erblint-github docs](https://github.com/github/erblint-github/blob/main/docs/rules/accessibility/disabled-attribute.md)
+- [MDN: HTML attribute `disabled`](https://developer.mozilla.org/en-US/docs/Web/HTML/Attributes/disabled)

javascript/packages/linter/src/rules.ts

@@ -1,5 +1,6 @@
 import type { RuleClass } from "./types.js"
 
+import { A11yDisabledAttributeRule } from "./rules/a11y-disabled-attribute.js"
 import { A11yNoAccesskeyAttributeRule } from "./rules/a11y-no-accesskey-attribute.js"
 import { A11yNoAriaUnsupportedElementsRule } from "./rules/a11y-no-aria-unsupported-elements.js"
 import { A11yNoAutofocusAttributeRule } from "./rules/a11y-no-autofocus-attribute.js"
@@ -103,6 +104,7 @@ import { SVGTagNameCapitalizationRule } from "./rules/svg-tag-name-capitalizatio
 import { TurboPermanentRequireIdRule } from "./rules/turbo-permanent-require-id.js"
 
 export const rules: RuleClass[] = [
+  A11yDisabledAttributeRule,
   A11yNoAccesskeyAttributeRule,
   A11yNoAriaUnsupportedElementsRule,
   A11yNoAutofocusAttributeRule,

javascript/packages/linter/src/rules/a11y-disabled-attribute.ts

@@ -0,0 +1,50 @@
+import { hasAttribute, getTagLocalName } from "@herb-tools/core"
+
+import { BaseRuleVisitor } from "./rule-utils.js"
+import { ParserRule } from "../types.js"
+import type { UnboundLintOffense, LintContext, FullRuleConfig } from "../types.js"
+import type { HTMLOpenTagNode, ParseResult } from "@herb-tools/core"
+
+const VALID_DISABLED_TAGS = new Set([
+  "button", "fieldset", "input", "optgroup", "option", "select", "textarea", "task-lists"
+])
+
+class DisabledAttributeVisitor extends BaseRuleVisitor {
+  visitHTMLOpenTagNode(node: HTMLOpenTagNode): void {
+    this.checkDisabledAttribute(node)
+    super.visitHTMLOpenTagNode(node)
+  }
+
+  private checkDisabledAttribute(node: HTMLOpenTagNode): void {
+    if (!hasAttribute(node, "disabled")) return
+
+    const tagName = getTagLocalName(node)
+    if (!tagName) return
+    if (VALID_DISABLED_TAGS.has(tagName)) return
+
+    this.addOffense(
+      `The \`disabled\` attribute is only valid on ${[...VALID_DISABLED_TAGS].join(", ")}.`,
+      node.tag_name!.location,
+    )
+  }
+}
+
+export class A11yDisabledAttributeRule extends ParserRule {
+  static ruleName = "a11y-disabled-attribute"
+  static introducedIn = this.version("unreleased")
+
+  get defaultConfig(): FullRuleConfig {
+    return {
+      enabled: false,
+      severity: "warning"
+    }
+  }
+
+  check(result: ParseResult, context?: Partial<LintContext>): UnboundLintOffense[] {
+    const visitor = new DisabledAttributeVisitor(this.ruleName, context)
+
+    visitor.visit(result.value)
+
+    return visitor.offenses
+  }
+}

javascript/packages/linter/src/rules/index.ts

@@ -1,3 +1,4 @@
+export * from "./a11y-disabled-attribute.js"
 export * from "./a11y-no-accesskey-attribute.js"
 export * from "./a11y-no-aria-unsupported-elements.js"
 export * from "./a11y-no-autofocus-attribute.js"