feat(eslint-plugin): [no-type-alias]: add allowGenerics option (typescript-eslint#3865)

scottohara · web-flow · commit 41959199735a · 2021-09-20T17:23:54.000-07:00
diff --git a/packages/eslint-plugin/docs/rules/no-type-alias.md b/packages/eslint-plugin/docs/rules/no-type-alias.md
@@ -89,6 +89,7 @@ or more of the following you may pass an object with the options set as follows:
 - `allowLiterals` set to `"always"` will allow you to use type aliases with literal objects (Defaults to `"never"`)
 - `allowMappedTypes` set to `"always"` will allow you to use type aliases as mapping tools (Defaults to `"never"`)
 - `allowTupleTypes` set to `"always"` will allow you to use type aliases with tuples (Defaults to `"never"`)
+- `allowGenerics` set to `"always"` will allow you to use type aliases with generics (Defaults to `"never"`)
 
 ### `allowAliases`
 
@@ -555,6 +556,28 @@ type Foo = [number] & [number, number];
 type Foo = [string] | [number];
 ```
 
+### `allowGenerics`
+
+This applies to generic types, including TypeScript provided global utility types (`type Foo = Record<string, number>`).
+
+The setting accepts the following options:
+
+- `"always"` or `"never"` to active or deactivate the feature.
+
+Examples of **correct** code for the `{ "allowGenerics": "always" }` options:
+
+```ts
+type Foo = Bar<string>;
+
+type Foo = Record<string, number>;
+
+type Foo = Readonly<Bar>;
+
+type Foo = Partial<Bar>;
+
+type Foo = Omit<Bar, 'a' | 'b'>;
+```
+
 ## When Not To Use It
 
 When you can't express some shape with an interface or you need to use a union, tuple type,
diff --git a/packages/eslint-plugin/src/rules/no-type-alias.ts b/packages/eslint-plugin/src/rules/no-type-alias.ts
@@ -27,6 +27,7 @@ type Options = [
     allowLiterals?: Values;
     allowMappedTypes?: Values;
     allowTupleTypes?: Values;
+    allowGenerics?: 'always' | 'never';
   },
 ];
 type MessageIds = 'noTypeAlias' | 'noCompositionAlias';
@@ -79,6 +80,9 @@ export default util.createRule<Options, MessageIds>({
           allowTupleTypes: {
             enum: enumValues,
           },
+          allowGenerics: {
+            enum: ['always', 'never'],
+          },
         },
         additionalProperties: false,
       },
@@ -93,6 +97,7 @@ export default util.createRule<Options, MessageIds>({
       allowLiterals: 'never',
       allowMappedTypes: 'never',
       allowTupleTypes: 'never',
+      allowGenerics: 'never',
     },
   ],
   create(
@@ -106,6 +111,7 @@ export default util.createRule<Options, MessageIds>({
         allowLiterals,
         allowMappedTypes,
         allowTupleTypes,
+        allowGenerics,
       },
     ],
   ) {
@@ -203,6 +209,13 @@ export default util.createRule<Options, MessageIds>({
       return false;
     };
 
+    const isValidGeneric = (type: TypeWithLabel): boolean => {
+      return (
+        type.node.type === AST_NODE_TYPES.TSTypeReference &&
+        type.node.typeParameters !== undefined
+      );
+    };
+
     const checkAndReport = (
       optionValue: Values,
       isTopLevel: boolean,
@@ -260,6 +273,10 @@ export default util.createRule<Options, MessageIds>({
       } else if (isValidTupleType(type)) {
         // tuple types
         checkAndReport(allowTupleTypes!, isTopLevel, type, 'Tuple Types');
+      } else if (isValidGeneric(type)) {
+        if (allowGenerics === 'never') {
+          reportError(type.node, type.compositionType, isTopLevel, 'Generics');
+        }
       } else if (
         // eslint-disable-next-line @typescript-eslint/internal/prefer-ast-types-enum
         type.node.type.endsWith('Keyword') ||
diff --git a/packages/eslint-plugin/tests/rules/no-type-alias.test.ts b/packages/eslint-plugin/tests/rules/no-type-alias.test.ts
@@ -481,6 +481,10 @@ type KeyNames = keyof typeof SCALARS;
       code: 'type Foo = new (bar: number) => string | null;',
       options: [{ allowConstructors: 'always' }],
     },
+    {
+      code: 'type Foo = Record<string, number>;',
+      options: [{ allowGenerics: 'always' }],
+    },
   ],
   invalid: [
     {
@@ -3329,5 +3333,18 @@ type Foo<T> = {
         },
       ],
     },
+    {
+      code: 'type Foo = Record<string, number>;',
+      errors: [
+        {
+          messageId: 'noTypeAlias',
+          data: {
+            alias: 'generics',
+          },
+          line: 1,
+          column: 12,
+        },
+      ],
+    },
   ],
 });
