fix: update date handling tests

src/decorators/is-date.spec.ts

@@ -61,7 +61,21 @@ describe('IsDate', () => {
       const dto = make(TestOptional, {});
       expect(output(dto)).toStrictEqual({});
 
-      expect(await input(Test, {})).toStrictEqual(Result.ok(make(TestOptional, {})));
+      expect(await input(TestOptional, {})).toStrictEqual(Result.ok(make(TestOptional, {})));
+    });
+
+    it('works with nullable fields', async () => {
+      class TestNullable {
+        @IsDate({ format: 'date', nullable: true })
+        date!: Date | null;
+      }
+
+      const dto = make(TestNullable, { date: null });
+      expect(output(dto)).toStrictEqual({ date: null });
+
+      expect(await input(TestNullable, { date: null })).toStrictEqual(
+        Result.ok(make(TestNullable, { date: null }))
+      );
     });
   });
 
@@ -124,5 +138,19 @@ describe('IsDate', () => {
 
       expect(await input(TestOptional, {})).toStrictEqual(Result.ok(make(TestOptional, {})));
     });
+
+    it('works with nullable fields', async () => {
+      class TestNullable {
+        @IsDate({ format: 'date-time', nullable: true })
+        date!: Date | null;
+      }
+
+      const dto = make(TestNullable, { date: null });
+      expect(output(dto)).toStrictEqual({ date: null });
+
+      expect(await input(TestNullable, { date: null })).toStrictEqual(
+        Result.ok(make(TestNullable, { date: null }))
+      );
+    });
   });
 });

src/decorators/is-date.ts

@@ -1,7 +1,8 @@
-import { Transform, TransformationType } from 'class-transformer';
+import { TransformationType, TransformFnParams } from 'class-transformer';
 import { IsDate as IsDateCV, isDateString } from 'class-validator';
 
 import { compose, PropertyOptions } from '../core';
+import { TransformHandlingOptional } from './utils/transform-handling-optional';
 
 const dateRegex = /^\d{4}-\d{2}-\d{2}$/;
 
@@ -13,17 +14,13 @@ export const IsDate = ({
   compose(
     { type: 'string', format },
     base,
-    format === 'date' ? TransformDate : TransformDateTime,
+    TransformHandlingOptional(base, format === 'date' ? transformDate : transformDateTime),
     IsDateCV({ message: ({ value }) => value?.message })
   );
 
-const TransformDate = Transform(({ key, value, type }) => {
-  if (value === undefined) {
-    return new Error(`${key} does not exist`);
-  }
-
+function transformDate({ key, value, type }: TransformFnParams) {
   if (type === TransformationType.CLASS_TO_PLAIN) {
-    return stripTime(value.toISOString());
+    return value.toISOString().split('T')[0];
   }
 
   if (!dateRegex.test(value)) {
@@ -36,13 +33,9 @@ const TransformDate = Transform(({ key, value, type }) => {
   }
 
   return date;
-});
-
-const TransformDateTime = Transform(({ key, value, type }) => {
-  if (value === undefined) {
-    return new Error(`${key} does not exist`);
-  }
+}
 
+function transformDateTime({ key, value, type }: TransformFnParams) {
   if (type === TransformationType.CLASS_TO_PLAIN) {
     return value.toISOString();
   }
@@ -52,8 +45,4 @@ const TransformDateTime = Transform(({ key, value, type }) => {
   }
 
   return new Date(value);
-});
-
-function stripTime(isoDate: string) {
-  return isoDate.split('T')[0];
 }

src/decorators/utils/transform-handling-optional.ts

@@ -0,0 +1,22 @@
+import { Transform, TransformFnParams } from 'class-transformer';
+
+export function TransformHandlingOptional(
+  config: { optional?: true; nullable?: true },
+  transform: (params: TransformFnParams) => unknown
+) {
+  return Transform((params: TransformFnParams) => {
+    if (config.optional && params.value === undefined) {
+      return params.value;
+    }
+
+    if (config.nullable && params.value === null) {
+      return params.value;
+    }
+
+    if (params.value === null || params.value === undefined) {
+      return new Error(`${params.key} does not exist`);
+    }
+
+    return transform(params);
+  });
+}