feat: Add support undefinedable (#52)

coercion.ts

@@ -244,6 +244,7 @@ export function enableTypeCoercion<
         schema: generateReturnSchema(type, exactOptionalSchema),
       };
     }
+    case "undefinedable":
     case "optional":
     case "nullish":
     case "nullable":

tests/coercion/schema/undefinedable.test.ts

@@ -0,0 +1,27 @@
+import { number, object, string, undefinedable } from "valibot";
+import { describe, expect, test } from "vitest";
+import { parseWithValibot } from "../../../parse";
+import { createFormData } from "../../helpers/FormData";
+
+describe("undefinedable", () => {
+  test("should pass only undefinedable", () => {
+    const schema = object({ name: string(), age: undefinedable(number()) });
+    const formData1 = createFormData("name", "Jane");
+    formData1.append("age", "");
+    expect(parseWithValibot(formData1, { schema })).toMatchObject({
+      status: "success",
+      value: { name: "Jane", age: undefined },
+    });
+
+    const formData2 = createFormData("name", "Jane");
+    expect(parseWithValibot(formData2, { schema })).toMatchObject({
+      error: { age: expect.anything() },
+    });
+
+    formData2.append("age", "20");
+    expect(parseWithValibot(formData2, { schema })).toMatchObject({
+      status: "success",
+      value: { name: "Jane", age: 20 },
+    });
+  });
+});

tests/coercion/schema/undefinedableAsync.test.ts

@@ -0,0 +1,30 @@
+import { number, objectAsync, string, undefinedableAsync } from "valibot";
+import { describe, expect, test } from "vitest";
+import { parseWithValibot } from "../../../parse";
+import { createFormData } from "../../helpers/FormData";
+
+describe("undefinedableAsync", () => {
+  test("should pass only undefinedable", async () => {
+    const schema = objectAsync({
+      name: string(),
+      age: undefinedableAsync(number()),
+    });
+    const formData1 = createFormData("name", "Jane");
+    formData1.append("age", "");
+    expect(await parseWithValibot(formData1, { schema })).toMatchObject({
+      status: "success",
+      value: { name: "Jane", age: undefined },
+    });
+
+    const formData2 = createFormData("name", "Jane");
+    expect(await parseWithValibot(formData2, { schema })).toMatchObject({
+      error: { age: expect.anything() },
+    });
+
+    formData2.append("age", "20");
+    expect(await parseWithValibot(formData2, { schema })).toMatchObject({
+      status: "success",
+      value: { name: "Jane", age: 20 },
+    });
+  });
+});