Linter: Implement turbo-permanent-require-id rule

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

@@ -59,6 +59,7 @@ This page contains documentation for all Herb Linter rules.
 - [`html-tag-name-lowercase`](./html-tag-name-lowercase.md) - Enforces lowercase tag names in HTML
 - [`parser-no-errors`](./parser-no-errors.md) - Disallow parser errors in HTML+ERB documents
 - [`svg-tag-name-capitalization`](./svg-tag-name-capitalization.md) - Enforces proper camelCase capitalization for SVG elements
+- [`turbo-permanent-require-id`](./turbo-permanent-require-id.md) - Require `id` attribute on elements with `data-turbo-permanent`
 
 ## Contributing
 

javascript/packages/linter/docs/rules/turbo-permanent-require-id.md

@@ -0,0 +1,41 @@
+# Linter Rule: Require `id` attribute on elements with `data-turbo-permanent`
+
+**Rule:** `turbo-permanent-require-id`
+
+## Description
+
+Ensure that all HTML elements with the `data-turbo-permanent` attribute also have an `id` attribute. Without an `id`, Turbo can't track the element across page changes and the permanent behavior won't work as expected.
+
+## Rationale
+
+Turbo's `data-turbo-permanent` attribute marks an element to be persisted across page navigations. Turbo uses the element's `id` to match it between the current page and the new page. If no `id` is present, Turbo has no way to identify and preserve the element, so the `data-turbo-permanent` attribute has no effect.
+
+## Examples
+
+### ✅ Good
+
+```erb
+<div id="player" data-turbo-permanent>
+  <!-- This element will persist across page navigations -->
+</div>
+
+<audio id="background-music" data-turbo-permanent>
+  <source src="/music.mp3" type="audio/mpeg">
+</audio>
+```
+
+### 🚫 Bad
+
+```erb
+<div data-turbo-permanent>
+  <!-- Missing id: Turbo can't track this element -->
+</div>
+
+<audio data-turbo-permanent>
+  <source src="/music.mp3" type="audio/mpeg">
+</audio>
+```
+
+## References
+
+- [Turbo Handbook: Persisting Elements Across Page Loads](https://turbo.hotwired.dev/handbook/building#persisting-elements-across-page-loads)

javascript/packages/linter/src/rules.ts

@@ -59,6 +59,7 @@ import { HTMLNoTitleAttributeRule } from "./rules/html-no-title-attribute.js"
 import { HTMLNoUnderscoresInAttributeNamesRule } from "./rules/html-no-underscores-in-attribute-names.js"
 import { HTMLRequireClosingTagsRule } from "./rules/html-require-closing-tags.js"
 import { HTMLTagNameLowercaseRule } from "./rules/html-tag-name-lowercase.js"
+import { TurboPermanentRequireIdRule } from "./rules/turbo-permanent-require-id.js"
 
 import { SVGTagNameCapitalizationRule } from "./rules/svg-tag-name-capitalization.js"
 
@@ -124,6 +125,7 @@ export const rules: RuleClass[] = [
   HTMLNoUnderscoresInAttributeNamesRule,
   HTMLRequireClosingTagsRule,
   HTMLTagNameLowercaseRule,
+  TurboPermanentRequireIdRule,
 
   SVGTagNameCapitalizationRule,
 

javascript/packages/linter/src/rules/turbo-permanent-require-id.ts

@@ -0,0 +1,48 @@
+import { BaseRuleVisitor, getAttribute } 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"
+
+class TurboPermanentRequireIdVisitor extends BaseRuleVisitor {
+  visitHTMLOpenTagNode(node: HTMLOpenTagNode): void {
+    this.checkTurboPermanent(node)
+    super.visitHTMLOpenTagNode(node)
+  }
+
+  private checkTurboPermanent(node: HTMLOpenTagNode): void {
+    const turboPermanentAttribute = getAttribute(node, "data-turbo-permanent")
+
+    if (!turboPermanentAttribute) {
+      return
+    }
+
+    const idAttribute = getAttribute(node, "id")
+
+    if (!idAttribute) {
+      this.addOffense(
+        "Elements with `data-turbo-permanent` must have an `id` attribute. Without an `id`, Turbo can't track the element across page changes and the permanent behavior won't work as expected.",
+        turboPermanentAttribute.location,
+      )
+    }
+  }
+}
+
+export class TurboPermanentRequireIdRule extends ParserRule {
+  name = "turbo-permanent-require-id"
+
+  get defaultConfig(): FullRuleConfig {
+    return {
+      enabled: true,
+      severity: "error"
+    }
+  }
+
+  check(result: ParseResult, context?: Partial<LintContext>): UnboundLintOffense[] {
+    const visitor = new TurboPermanentRequireIdVisitor(this.name, context)
+
+    visitor.visit(result.value)
+
+    return visitor.offenses
+  }
+}

javascript/packages/linter/test/rules/turbo-permanent-require-id-rule.test.ts

@@ -0,0 +1,58 @@
+import { describe, test } from "vitest"
+import { TurboPermanentRequireIdRule } from "../../src/rules/turbo-permanent-require-id.js"
+import { createLinterTest } from "../helpers/linter-test-helper.js"
+
+const { expectNoOffenses, expectError, assertOffenses } = createLinterTest(TurboPermanentRequireIdRule)
+
+const MESSAGE = "Elements with `data-turbo-permanent` must have an `id` attribute. Without an `id`, Turbo can't track the element across page changes and the permanent behavior won't work as expected."
+
+describe("turbo-permanent-require-id", () => {
+  test("passes for element with data-turbo-permanent and id", () => {
+    expectNoOffenses('<div id="flash-messages" data-turbo-permanent>Flash</div>')
+  })
+
+  test("fails for element with data-turbo-permanent but no id", () => {
+    expectError(MESSAGE)
+
+    assertOffenses('<div data-turbo-permanent>Flash</div>')
+  })
+
+  test("passes for element without data-turbo-permanent", () => {
+    expectNoOffenses('<div class="container">Content</div>')
+  })
+
+  test("passes for element with only id", () => {
+    expectNoOffenses('<div id="my-element">Content</div>')
+  })
+
+  test("fails for self-closing element with data-turbo-permanent but no id", () => {
+    expectError(MESSAGE)
+
+    assertOffenses('<input data-turbo-permanent>')
+  })
+
+  test("passes for self-closing element with data-turbo-permanent and id", () => {
+    expectNoOffenses('<input id="my-input" data-turbo-permanent>')
+  })
+
+  test("fails for multiple elements with data-turbo-permanent but no id", () => {
+    expectError(MESSAGE)
+    expectError(MESSAGE)
+
+    assertOffenses('<div data-turbo-permanent>Flash</div>\n<span data-turbo-permanent>Notice</span>')
+  })
+
+  test("passes for element with data-turbo-permanent and ERB id", () => {
+    expectNoOffenses('<div id="<%= dom_id(record) %>" data-turbo-permanent>Content</div>')
+  })
+
+  test("passes for element with data-turbo-permanent value and id", () => {
+    expectNoOffenses('<div id="cart" data-turbo-permanent="">Cart</div>')
+  })
+
+  test("fails for element with other data attributes but no id", () => {
+    expectError(MESSAGE)
+
+    assertOffenses('<div class="flash" data-turbo-permanent data-controller="flash">Flash</div>')
+  })
+})