test(type-utils): add conditional type tests to isTypeReadonly

typescript-eslint · Jan 9, 2022 · ae4a614 · ae4a614
1 parent a137c76
commit ae4a614
Showing 1 changed file with 51 additions and 0 deletions.
diff --git a/packages/type-utils/tests/isTypeReadonly.test.ts b/packages/type-utils/tests/isTypeReadonly.test.ts
@@ -215,5 +215,56 @@ describe('isTypeReadonly', () => {
         });
       });
     });
+
+    describe('Conditional Types', () => {
+      describe('is readonly', () => {
+        it('handles a conditional type that is readonly', () => {
+          const { type, checker } = getType(
+            `type Test<T> = T extends readonly number[] ? readonly string[] : readonly number[];`,
+          );
+
+          const result = isTypeReadonly(checker, type);
+          expect(result).toBe(true);
+        });
+
+        it('should ignore a mutable condition', () => {
+          const { type, checker } = getType(
+            `type Test<T> = T extends number[] ? readonly string[] : readonly number[];`,
+          );
+
+          const result = isTypeReadonly(checker, type);
+          expect(result).toBe(true);
+        });
+      });
+
+      describe('is not readonly', () => {
+        it('fails with a conditional type that is mutables', () => {
+          const { type, checker } = getType(
+            `type Test<T> = T extends number[] ? string[] : number[];`,
+          );
+
+          const result = isTypeReadonly(checker, type);
+          expect(result).toBe(false);
+        });
+
+        it('fails with a conditional type that is mutable or readonly', () => {
+          const { type, checker } = getType(
+            `type Test<T> = T extends number[] ? string[] : readonly number[];`,
+          );
+
+          const result = isTypeReadonly(checker, type);
+          expect(result).toBe(false);
+        });
+
+        it('fails with a conditional type that is readonly or mutable', () => {
+          const { type, checker } = getType(
+            `type Test<T> = T extends number[] ? readonly string[] : number[];`,
+          );
+
+          const result = isTypeReadonly(checker, type);
+          expect(result).toBe(false);
+        });
+      });
+    });
   });
 });