typescript-eslint · kirkwaiblinger · Jun 25, 2024 · Mar 20, 2024 · Mar 22, 2024 · Mar 22, 2024
diff --git a/packages/eslint-plugin/docs/rules/array-type.mdx b/packages/eslint-plugin/docs/rules/array-type.mdx
@@ -42,14 +42,16 @@ const y: readonly string[] = ['a', 'b'];
 
 ### `"generic"`
 
-Always use `Array<T>` or `ReadonlyArray<T>` for all array types.
+Always use `Array<T>`, `ReadonlyArray<T>`, or `Readonly<Array<T>>` for all array types.
+`readonly T[]` will be modified to `ReadonlyArray<T>` and `Readonly<T[]>` will be modified to `Readonly<Array<T>`.
 
 <Tabs>
 <TabItem value="❌ Incorrect">
 
 ```ts option='{ "default": "generic" }'
 const x: string[] = ['a', 'b'];
 const y: readonly string[] = ['a', 'b'];
+const z: Readonly<string[]> = ['a', 'b'];
 ```
 
 </TabItem>
@@ -58,6 +60,7 @@ const y: readonly string[] = ['a', 'b'];
 ```ts option='{ "default": "generic" }'
 const x: Array<string> = ['a', 'b'];
 const y: ReadonlyArray<string> = ['a', 'b'];
+const z: Readonly<Array<string>> = ['a', 'b'];
 ```
 
 </TabItem>

diff --git a/packages/eslint-plugin/src/rules/array-type.ts b/packages/eslint-plugin/src/rules/array-type.ts
@@ -82,7 +82,8 @@ type MessageIds =
   | 'errorStringArray'
   | 'errorStringArraySimple'
   | 'errorStringGeneric'
-  | 'errorStringGenericSimple';
+  | 'errorStringGenericSimple'
+  | 'errorStringArrayReadonly';
 
 export default createRule<Options, MessageIds>({
   name: 'array-type',
@@ -99,6 +100,8 @@ export default createRule<Options, MessageIds>({
         "Array type using '{{readonlyPrefix}}{{type}}[]' is forbidden. Use '{{className}}<{{type}}>' instead.",
       errorStringArray:
         "Array type using '{{className}}<{{type}}>' is forbidden. Use '{{readonlyPrefix}}{{type}}[]' instead.",
+      errorStringArrayReadonly:
+        "Array type using '{{className}}<{{type}}>' is forbidden. Use '{{readonlyPrefix}}{{type}}' instead.",
       errorStringArraySimple:
         "Array type using '{{className}}<{{type}}>' is forbidden for simple types. Use '{{readonlyPrefix}}{{type}}[]' instead.",
       errorStringGenericSimple:
@@ -199,13 +202,22 @@ export default createRule<Options, MessageIds>({
           node.typeName.type !== AST_NODE_TYPES.Identifier ||
           !(
             node.typeName.name === 'Array' ||
-            node.typeName.name === 'ReadonlyArray'
-          )
+            node.typeName.name === 'ReadonlyArray' ||
+            node.typeName.name === 'Readonly'
+          ) ||
+          (node.typeName.name === 'Readonly' &&
+            node.typeArguments?.params[0].type !== AST_NODE_TYPES.TSArrayType)
         ) {
           return;
         }
 
-        const isReadonlyArrayType = node.typeName.name === 'ReadonlyArray';
+        const isReadonlyWithGenericArrayType =
+          node.typeName.name === 'Readonly' &&
+          node.typeArguments?.params[0].type === AST_NODE_TYPES.TSArrayType;
+        const isReadonlyArrayType =
+          node.typeName.name === 'ReadonlyArray' ||
+          isReadonlyWithGenericArrayType;
+
         const currentOption = isReadonlyArrayType
           ? readonlyOption
           : defaultOption;
@@ -218,7 +230,9 @@ export default createRule<Options, MessageIds>({
         const typeParams = node.typeArguments?.params;
         const messageId =
           currentOption === 'array'
-            ? 'errorStringArray'
+            ? isReadonlyWithGenericArrayType
+              ? 'errorStringArrayReadonly'
+              : 'errorStringArray'
             : 'errorStringArraySimple';
 
         if (!typeParams || typeParams.length === 0) {
@@ -256,13 +270,13 @@ export default createRule<Options, MessageIds>({
         const start = `${parentParens ? '(' : ''}${readonlyPrefix}${
           typeParens ? '(' : ''
         }`;
-        const end = `${typeParens ? ')' : ''}[]${parentParens ? ')' : ''}`;
+        const end = `${typeParens ? ')' : ''}${isReadonlyWithGenericArrayType ? '' : `[]`}${parentParens ? ')' : ''}`;
 
         context.report({
           node,
           messageId,
           data: {
-            className: isReadonlyArrayType ? 'ReadonlyArray' : 'Array',
+            className: isReadonlyArrayType ? node.typeName.name : 'Array',
             readonlyPrefix,
             type: getMessageType(type),
           },

diff --git a/packages/eslint-plugin/tests/docs-eslint-output-snapshots/array-type.shot b/packages/eslint-plugin/tests/docs-eslint-output-snapshots/array-type.shot
diff --git a/packages/eslint-plugin/tests/rules/array-type.test.ts b/packages/eslint-plugin/tests/rules/array-type.test.ts
@@ -397,6 +397,14 @@ function bazFunction(baz: Arr<ArrayClass<String>>) {
       code: 'let a: readonly Array<number>[] = [[]];',
       options: [{ default: 'generic', readonly: 'array' }],
     },
+    {
+      code: 'let a: Readonly = [];',
+      options: [{ default: 'generic', readonly: 'array' }],
+    },
+    {
+      code: "const x: Readonly<string> = 'a';",
+      options: [{ default: 'array' }],
+    },
   ],
   invalid: [
     // Base cases from https://github.com/typescript-eslint/typescript-eslint/issues/2323#issuecomment-663977655
@@ -1918,6 +1926,21 @@ interface FooInterface {
         },
       ],
     },
+    {
+      code: "const x: Readonly<string[]> = ['a', 'b'];",
+      output: "const x: readonly string[] = ['a', 'b'];",
+      options: [{ default: 'array' }],
+      errors: [
+        {
+          messageId: 'errorStringArrayReadonly',
+          data: {
+            className: 'Readonly',
+            readonlyPrefix: 'readonly ',
+            type: 'string[]',
+          },
+        },
+      ],
+    },
   ],
 });
 

diff --git a/packages/rule-tester/src/RuleTester.ts b/packages/rule-tester/src/RuleTester.ts
@@ -187,16 +187,16 @@ export class RuleTester extends TestFramework {
   /**
    * Adds the `only` property to a test to run it in isolation.
    */
-  static only<Options extends Readonly<unknown[]>>(
+  static only<Options extends readonly unknown[]>(
     item: ValidTestCase<Options> | string,
   ): ValidTestCase<Options>;
   /**
    * Adds the `only` property to a test to run it in isolation.
    */
-  static only<MessageIds extends string, Options extends Readonly<unknown[]>>(
+  static only<MessageIds extends string, Options extends readonly unknown[]>(
     item: InvalidTestCase<MessageIds, Options>,
   ): InvalidTestCase<MessageIds, Options>;
-  static only<MessageIds extends string, Options extends Readonly<unknown[]>>(
+  static only<MessageIds extends string, Options extends readonly unknown[]>(
     item:
       | InvalidTestCase<MessageIds, Options>
       | ValidTestCase<Options>

diff --git a/packages/rule-tester/src/types/InvalidTestCase.ts b/packages/rule-tester/src/types/InvalidTestCase.ts
@@ -63,7 +63,7 @@ export interface TestCaseError<MessageIds extends string> {
 
 export interface InvalidTestCase<
   MessageIds extends string,
-  Options extends Readonly<unknown[]>,
+  Options extends readonly unknown[],
 > extends ValidTestCase<Options> {
   /**
    * Expected errors.

diff --git a/packages/rule-tester/src/types/ValidTestCase.ts b/packages/rule-tester/src/types/ValidTestCase.ts
@@ -6,7 +6,7 @@ import type {
 
 import type { DependencyConstraint } from './DependencyConstraint';
 
-export interface ValidTestCase<Options extends Readonly<unknown[]>> {
+export interface ValidTestCase<Options extends readonly unknown[]> {
   /**
    * Name for the test case.
    */

diff --git a/packages/rule-tester/src/types/index.ts b/packages/rule-tester/src/types/index.ts
@@ -12,7 +12,7 @@ export type TesterConfigWithDefaults = Mutable<
 
 export interface RunTests<
   MessageIds extends string,
-  Options extends Readonly<unknown[]>,
+  Options extends readonly unknown[],
 > {
   // RuleTester.run also accepts strings for valid cases
   readonly valid: readonly (ValidTestCase<Options> | string)[];
@@ -21,7 +21,7 @@ export interface RunTests<
 
 export interface NormalizedRunTests<
   MessageIds extends string,
-  Options extends Readonly<unknown[]>,
+  Options extends readonly unknown[],
 > {
   readonly valid: readonly ValidTestCase<Options>[];
   readonly invalid: readonly InvalidTestCase<MessageIds, Options>[];

diff --git a/packages/utils/src/ts-eslint/RuleTester.ts b/packages/utils/src/ts-eslint/RuleTester.ts
@@ -11,7 +11,7 @@ import type {
   SharedConfigurationSettings,
 } from './Rule';
 
-interface ValidTestCase<Options extends Readonly<unknown[]>> {
+interface ValidTestCase<Options extends readonly unknown[]> {
   /**
    * Name for the test case.
    */
@@ -75,7 +75,7 @@ interface SuggestionOutput<MessageIds extends string> {
 
 interface InvalidTestCase<
   MessageIds extends string,
-  Options extends Readonly<unknown[]>,
+  Options extends readonly unknown[],
 > extends ValidTestCase<Options> {
   /**
    * Expected errors.
@@ -135,7 +135,7 @@ type RuleTesterTestFrameworkFunction = (
 
 interface RunTests<
   MessageIds extends string,
-  Options extends Readonly<unknown[]>,
+  Options extends readonly unknown[],
 > {
   // RuleTester.run also accepts strings for valid cases
   readonly valid: readonly (ValidTestCase<Options> | string)[];
@@ -160,7 +160,7 @@ declare class RuleTesterBase {
    * @param rule The rule to test.
    * @param test The collection of tests to run.
    */
-  run<MessageIds extends string, Options extends Readonly<unknown[]>>(
+  run<MessageIds extends string, Options extends readonly unknown[]>(
     ruleName: string,
     rule: RuleModule<MessageIds, Options>,
     tests: RunTests<MessageIds, Options>,
@@ -190,7 +190,7 @@ declare class RuleTesterBase {
   /**
    * Define a rule for one particular run of tests.
    */
-  defineRule<MessageIds extends string, Options extends Readonly<unknown[]>>(
+  defineRule<MessageIds extends string, Options extends readonly unknown[]>(
     name: string,
     rule:
       | RuleCreateFunction<MessageIds, Options>

diff --git a/packages/website/plugins/generated-rule-docs/RuleDocsPage.ts b/packages/website/plugins/generated-rule-docs/RuleDocsPage.ts
@@ -26,7 +26,7 @@ export class RuleDocsPage {
   #headingIndices: RequiredHeadingIndices;
   #rule: Readonly<RuleModuleWithMetaDocs>;
 
-  get children(): Readonly<unist.Node[]> {
+  get children(): readonly unist.Node[] {
     return this.#children;
   }