feat: add svelte/no-svelte-internal rule (#749)

`svelte/internal` is deprecated in Svelte 5 and will be removed in
Svelte 6 according to our current plan.
The Svelte compiler only compiles `.svelte` files and `.svelte.[jt]s`
files, so the compiler can not check normal `.[jt]s` files. Therefore,
the ESLint plugin checks this.

.changeset/chilly-bats-allow.md

@@ -0,0 +1,5 @@
+---
+"eslint-plugin-svelte": minor
+---
+
+feat: add `svelte/no-svelte-internal` rule

README.md

@@ -385,6 +385,7 @@ These rules relate to better ways of doing things to help you avoid problems:
 | [svelte/no-inline-styles](https://sveltejs.github.io/eslint-plugin-svelte/rules/no-inline-styles/) | disallow attributes and directives that produce inline styles |  |
 | [svelte/no-reactive-functions](https://sveltejs.github.io/eslint-plugin-svelte/rules/no-reactive-functions/) | it's not necessary to define functions in reactive statements | :bulb: |
 | [svelte/no-reactive-literals](https://sveltejs.github.io/eslint-plugin-svelte/rules/no-reactive-literals/) | don't assign literal values in reactive statements | :bulb: |
+| [svelte/no-svelte-internal](https://sveltejs.github.io/eslint-plugin-svelte/rules/no-svelte-internal/) | svelte/internal will be removed in Svelte 6. |  |
 | [svelte/no-unused-class-name](https://sveltejs.github.io/eslint-plugin-svelte/rules/no-unused-class-name/) | disallow the use of a class in the template without a corresponding style |  |
 | [svelte/no-unused-svelte-ignore](https://sveltejs.github.io/eslint-plugin-svelte/rules/no-unused-svelte-ignore/) | disallow unused svelte-ignore comments | :star: |
 | [svelte/no-useless-mustaches](https://sveltejs.github.io/eslint-plugin-svelte/rules/no-useless-mustaches/) | disallow unnecessary mustache interpolations | :wrench: |

docs/rules.md

@@ -58,6 +58,7 @@ These rules relate to better ways of doing things to help you avoid problems:
 | [svelte/no-inline-styles](./rules/no-inline-styles.md)                                   | disallow attributes and directives that produce inline styles                                                                             |          |
 | [svelte/no-reactive-functions](./rules/no-reactive-functions.md)                         | it's not necessary to define functions in reactive statements                                                                             | :bulb:   |
 | [svelte/no-reactive-literals](./rules/no-reactive-literals.md)                           | don't assign literal values in reactive statements                                                                                        | :bulb:   |
+| [svelte/no-svelte-internal](./rules/no-svelte-internal.md)                               | svelte/internal will be removed in Svelte 6.                                                                                              |          |
 | [svelte/no-unused-class-name](./rules/no-unused-class-name.md)                           | disallow the use of a class in the template without a corresponding style                                                                 |          |
 | [svelte/no-unused-svelte-ignore](./rules/no-unused-svelte-ignore.md)                     | disallow unused svelte-ignore comments                                                                                                    | :star:   |
 | [svelte/no-useless-mustaches](./rules/no-useless-mustaches.md)                           | disallow unnecessary mustache interpolations                                                                                              | :wrench: |

docs/rules/no-svelte-internal.md

@@ -0,0 +1,55 @@
+---
+pageClass: 'rule-details'
+sidebarDepth: 0
+title: 'svelte/no-svelte-internal'
+description: 'svelte/internal will be removed in Svelte 6.'
+---
+
+# svelte/no-svelte-internal
+
+> svelte/internal will be removed in Svelte 6.
+
+- :exclamation: <badge text="This rule has not been released yet." vertical="middle" type="error"> **_This rule has not been released yet._** </badge>
+
+## :book: Rule Details
+
+This rule reports the use of the deprecated API `svelte/internal` and `svelte/internal/xxx`. `svelte/internal` is deprecated in Svelte 5. And it will be deleted in Svelte 6. These APIs can change in breaking ways at any time without notice.
+
+<ESLintCodeBlock>
+
+<!--eslint-skip-->
+
+```svelte
+<script>
+  /* eslint svelte/no-svelte-internal: "error" */
+  // ✓ GOOD
+  import { mount } from 'svelte';
+
+  // ✗ BAD
+  import { get_current_component } from 'svelte/internal';
+  import { inspect } from 'svelte/internal/client';
+  import('svelte/internal');
+  import('svelte/internal/disclose-version');
+
+  export * from 'svelte/internal';
+  export { listen } from 'svelte/internal';
+  export * from 'svelte/internal/server';
+</script>
+```
+
+</ESLintCodeBlock>
+
+## :wrench: Options
+
+Nothing.
+
+## :books: Further Reading
+
+<!--TODO: update here when relevant statements are added in Svelte 5 documentation -->
+
+Nothing.
+
+## :mag: Implementation
+
+- [Rule source](https://github.com/sveltejs/eslint-plugin-svelte/blob/main/src/rules/no-svelte-internal.ts)
+- [Test source](https://github.com/sveltejs/eslint-plugin-svelte/blob/main/tests/src/rules/no-svelte-internal.ts)

src/rule-types.ts

@@ -209,6 +209,11 @@ export interface RuleOptions {
    * @see https://sveltejs.github.io/eslint-plugin-svelte/rules/no-store-async/
    */
   'svelte/no-store-async'?: Linter.RuleEntry<[]>
+  /**
+   * svelte/internal will be removed in Svelte 6.
+   * @see https://sveltejs.github.io/eslint-plugin-svelte/rules/no-svelte-internal/
+   */
+  'svelte/no-svelte-internal'?: Linter.RuleEntry<[]>
   /**
    * disallow `target="_blank"` attribute without `rel="noopener noreferrer"`
    * @see https://sveltejs.github.io/eslint-plugin-svelte/rules/no-target-blank/

src/rules/no-svelte-internal.ts

@@ -0,0 +1,59 @@
+import { createRule } from '../utils';
+import type { TSESTree } from '@typescript-eslint/types';
+
+export default createRule('no-svelte-internal', {
+	meta: {
+		docs: {
+			description: 'svelte/internal will be removed in Svelte 6.',
+			category: 'Best Practices',
+			// TODO Switch to recommended in the major version.
+			// recommended: true,
+			recommended: false
+		},
+		schema: [],
+		messages: {
+			unexpected: 'Using svelte/internal is prohibited. This will be removed in Svelte 6.'
+		},
+		type: 'problem'
+	},
+	create(context) {
+		function report(node: TSESTree.Node) {
+			context.report({
+				node,
+				messageId: 'unexpected'
+			});
+		}
+
+		function isSvelteInternal(value: string) {
+			return value === 'svelte/internal' || value.startsWith('svelte/internal/');
+		}
+
+		return {
+			ImportDeclaration(node) {
+				if (node.source && isSvelteInternal(node.source.value)) {
+					report(node);
+				}
+			},
+			ImportExpression(node) {
+				if (
+					node.source &&
+					node.source.type === 'Literal' &&
+					typeof node.source.value === 'string' &&
+					isSvelteInternal(node.source.value)
+				) {
+					report(node);
+				}
+			},
+			ExportNamedDeclaration(node) {
+				if (node.source && isSvelteInternal(node.source.value)) {
+					report(node);
+				}
+			},
+			ExportAllDeclaration(node) {
+				if (node.source && isSvelteInternal(node.source.value)) {
+					report(node);
+				}
+			}
+		};
+	}
+});

src/utils/rules.ts

@@ -41,6 +41,7 @@ import noRestrictedHtmlElements from '../rules/no-restricted-html-elements';
 import noShorthandStylePropertyOverrides from '../rules/no-shorthand-style-property-overrides';
 import noSpacesAroundEqualSignsInAttribute from '../rules/no-spaces-around-equal-signs-in-attribute';
 import noStoreAsync from '../rules/no-store-async';
+import noSvelteInternal from '../rules/no-svelte-internal';
 import noTargetBlank from '../rules/no-target-blank';
 import noTrailingSpaces from '../rules/no-trailing-spaces';
 import noUnknownStyleDirectiveProperty from '../rules/no-unknown-style-directive-property';
@@ -105,6 +106,7 @@ export const rules = [
 	noShorthandStylePropertyOverrides,
 	noSpacesAroundEqualSignsInAttribute,
 	noStoreAsync,
+	noSvelteInternal,
 	noTargetBlank,
 	noTrailingSpaces,
 	noUnknownStyleDirectiveProperty,

tests/fixtures/rules/no-svelte-internal/invalid/no-svelte-internal01-errors.yaml

@@ -0,0 +1,4 @@
+- message: Using svelte/internal is prohibited. This will be removed in Svelte 6.
+  line: 3
+  column: 2
+  suggestions: null

tests/fixtures/rules/no-svelte-internal/invalid/no-svelte-internal01-input.svelte

@@ -0,0 +1,4 @@
+<script>
+	// eslint-disable-next-line camelcase -- this is a test
+	import { get_current_component } from 'svelte/internal';
+</script>

tests/fixtures/rules/no-svelte-internal/invalid/no-svelte-internal02-errors.yaml

@@ -0,0 +1,4 @@
+- message: Using svelte/internal is prohibited. This will be removed in Svelte 6.
+  line: 2
+  column: 2
+  suggestions: null

tests/fixtures/rules/no-svelte-internal/invalid/no-svelte-internal02-input.svelte

@@ -0,0 +1,3 @@
+<script>
+	import { inspect } from 'svelte/internal/client';
+</script>

tests/fixtures/rules/no-svelte-internal/invalid/no-svelte-internal03-errors.yaml

@@ -0,0 +1,4 @@
+- message: Using svelte/internal is prohibited. This will be removed in Svelte 6.
+  line: 2
+  column: 2
+  suggestions: null

tests/fixtures/rules/no-svelte-internal/invalid/no-svelte-internal03-input.svelte

@@ -0,0 +1,3 @@
+<script>
+	import * as svelteInternal from 'svelte/internal';
+</script>

tests/fixtures/rules/no-svelte-internal/invalid/no-svelte-internal04-errors.yaml

@@ -0,0 +1,4 @@
+- message: Using svelte/internal is prohibited. This will be removed in Svelte 6.
+  line: 2
+  column: 2
+  suggestions: null

tests/fixtures/rules/no-svelte-internal/invalid/no-svelte-internal04-input.svelte

@@ -0,0 +1,3 @@
+<script>
+	export * from 'svelte/internal';
+</script>

tests/fixtures/rules/no-svelte-internal/invalid/no-svelte-internal05-errors.yaml

@@ -0,0 +1,4 @@
+- message: Using svelte/internal is prohibited. This will be removed in Svelte 6.
+  line: 2
+  column: 2
+  suggestions: null

tests/fixtures/rules/no-svelte-internal/invalid/no-svelte-internal05-input.svelte

@@ -0,0 +1,3 @@
+<script>
+	export * from 'svelte/internal/client';
+</script>

tests/fixtures/rules/no-svelte-internal/invalid/no-svelte-internal06-errors.yaml

@@ -0,0 +1,4 @@
+- message: Using svelte/internal is prohibited. This will be removed in Svelte 6.
+  line: 2
+  column: 2
+  suggestions: null

tests/fixtures/rules/no-svelte-internal/invalid/no-svelte-internal06-input.svelte

@@ -0,0 +1,3 @@
+<script>
+	export { inspect } from 'svelte/internal/client';
+</script>

tests/fixtures/rules/no-svelte-internal/invalid/no-svelte-internal07-errors.yaml

@@ -0,0 +1,4 @@
+- message: Using svelte/internal is prohibited. This will be removed in Svelte 6.
+  line: 2
+  column: 2
+  suggestions: null

tests/fixtures/rules/no-svelte-internal/invalid/no-svelte-internal07-input.svelte

@@ -0,0 +1,3 @@
+<script>
+	import('svelte/internal');
+</script>

tests/fixtures/rules/no-svelte-internal/valid/no-svelte-internal01-input.svelte

@@ -0,0 +1,3 @@
+<script>
+	import { mount } from 'svelte';
+</script>

tests/src/rules/no-svelte-internal.ts

@@ -0,0 +1,12 @@
+import { RuleTester } from '../../utils/eslint-compat';
+import rule from '../../../src/rules/no-svelte-internal';
+import { loadTestCases } from '../../utils/utils';
+
+const tester = new RuleTester({
+	languageOptions: {
+		ecmaVersion: 2020,
+		sourceType: 'module'
+	}
+});
+
+tester.run('no-svelte-internal', rule as any, loadTestCases('no-svelte-internal'));