fix(conform-zod): Zod v4 required field coercion (#1084)

Author: chimame

.changeset/strong-elephants-marry.md

@@ -0,0 +1,5 @@
+---
+'@conform-to/zod': patch
+---
+
+fix(conform-zod): Zod v4 required field coercion

packages/conform-zod/v3/tests/coercion/schema/required.test.ts

@@ -0,0 +1,32 @@
+import { describe, test, expect } from 'vitest';
+import { coerceFormValue } from '../../../coercion';
+import { z } from 'zod';
+import { getResult } from '../../../../tests/helpers/zod';
+
+describe('coercion', () => {
+	describe('required', () => {
+		test('should pass required', () => {
+			const schema = z
+				.object({
+					a: z.string().optional(),
+				})
+				.required();
+
+			expect(getResult(coerceFormValue(schema).safeParse({ a: '' }))).toEqual({
+				success: false,
+				error: {
+					a: ['Required'],
+				},
+			});
+
+			expect(
+				getResult(coerceFormValue(schema).safeParse({ a: 'string' })),
+			).toEqual({
+				success: true,
+				data: {
+					a: 'string',
+				},
+			});
+		});
+	});
+});

packages/conform-zod/v4/coercion.ts

@@ -235,7 +235,7 @@ export function enableTypeCoercion<Schema extends $ZodType>(
 				),
 			}) as $ZodType<unknown, {}>,
 		);
-	} else if (def.type === 'optional') {
+	} else if (def.type === 'optional' || def.type === 'nonoptional') {
 		schema = pipe(
 			transform(options.stripEmptyValue),
 			new constr({

packages/conform-zod/v4/tests/coercion/schema/required.test.ts

@@ -0,0 +1,53 @@
+import { describe, test, expect } from 'vitest';
+import { coerceFormValue } from '../../../coercion';
+import { z } from 'zod-v4';
+import { object, string, optional, required } from 'zod-v4/mini';
+import { getResult } from '../../../../tests/helpers/zod';
+
+describe('coercion', () => {
+	describe('required', () => {
+		test('should pass required', () => {
+			const schema = z
+				.object({
+					a: z.string().optional(),
+				})
+				.required();
+			const schemaWithMini = required(
+				object({
+					a: optional(string()),
+				}),
+			);
+
+			expect(getResult(coerceFormValue(schema).safeParse({ a: '' }))).toEqual({
+				success: false,
+				error: {
+					a: ['Invalid input'],
+				},
+			});
+			expect(
+				getResult(coerceFormValue(schemaWithMini).safeParse({ a: '' })),
+			).toEqual({
+				success: false,
+				error: {
+					a: ['Invalid input'],
+				},
+			});
+			expect(
+				getResult(coerceFormValue(schema).safeParse({ a: 'string' })),
+			).toEqual({
+				success: true,
+				data: {
+					a: 'string',
+				},
+			});
+			expect(
+				getResult(coerceFormValue(schemaWithMini).safeParse({ a: 'string' })),
+			).toEqual({
+				success: true,
+				data: {
+					a: 'string',
+				},
+			});
+		});
+	});
+});