Add type-alias-readonlydeep rule and make ducks mostly immutable

.eslint/rules/type-alias-readonlydeep.test.js

@@ -0,0 +1,79 @@
+// Copyright 2023 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+const rule = require('./type-alias-readonlydeep');
+const RuleTester = require('eslint').RuleTester;
+
+// avoid triggering mocha's global leak detection
+require('@typescript-eslint/parser');
+
+const ruleTester = new RuleTester({
+  parser: require.resolve('@typescript-eslint/parser'),
+  parserOptions: {
+    ecmaVersion: 2018,
+    sourceType: 'module',
+  },
+});
+
+ruleTester.run('type-alias-readonlydeep', rule, {
+  valid: [
+    {
+      code: `import type { ReadonlyDeep } from "type-fest"; type Foo = ReadonlyDeep<{}>`,
+    },
+    {
+      code: `import { ReadonlyDeep } from "type-fest"; type Foo = ReadonlyDeep<{}>`,
+    },
+  ],
+  invalid: [
+    {
+      code: `type Foo = {}`,
+      errors: [
+        {
+          message:
+            'Type aliases must be wrapped with ReadonlyDeep from type-fest',
+          type: 'Identifier',
+        },
+      ],
+    },
+    {
+      code: `type Foo = Bar<{}>`,
+      errors: [
+        {
+          message:
+            'Type aliases must be wrapped with ReadonlyDeep from type-fest',
+          type: 'Identifier',
+        },
+      ],
+    },
+    {
+      code: `type Foo = ReadonlyDeep<{}>`,
+      errors: [
+        {
+          message:
+            'Type aliases must be wrapped with ReadonlyDeep from type-fest',
+          type: 'Identifier',
+        },
+      ],
+    },
+    {
+      code: `interface ReadonlyDeep<T> {}; type Foo = ReadonlyDeep<{}>`,
+      errors: [
+        {
+          message:
+            'Type aliases must be wrapped with ReadonlyDeep from type-fest',
+          type: 'Identifier',
+        },
+      ],
+    },
+    {
+      code: `import type { ReadonlyDeep } from "foo"; type Foo = ReadonlyDeep<{}>`,
+      errors: [
+        {
+          message:
+            'Type aliases must be wrapped with ReadonlyDeep from type-fest',
+          type: 'Identifier',
+        },
+      ],
+    },
+  ],
+});