feat: support custom required validation messages

packages/validation/test/validation.test.ts

@@ -1,5 +1,6 @@
 import { test, expect } from "bun:test";
-import { v, invalid, parseBody, checkField, parseEnv } from "../src/index.ts";
+import { Window } from "happy-dom";
+import { v, invalid, parseBody, checkField, parseEnv, VALIDATE_RUNTIME } from "../src/index.ts";
 
 const login = v.object({
   email: v.string().email(),
@@ -33,6 +34,51 @@ test("required (non-optional) empty fields fail", () => {
   expect(r.errors.password).toBe("Required");
 });
 
+test("required(message) customizes empty-field errors and overrides optional", () => {
+  const schema = v.object({
+    email: v.string().required("Enter your email or username"),
+    password: v.string().optional().required("Enter your password"),
+    accepted: v.boolean().required("Accept the terms to continue"),
+  });
+  const result = schema.parse({ accepted: false });
+
+  expect(result.errors).toEqual({
+    email: "Enter your email or username",
+    password: "Enter your password",
+    accepted: "Accept the terms to continue",
+  });
+  expect(schema.describe().fields.email.requiredMessage).toBe("Enter your email or username");
+});
+
+test("browser validation displays the serialized custom required message", () => {
+  const schema = v.object({
+    email: v.string().required("Enter your email or username"),
+  });
+  const win = new Window() as unknown as Window & Record<string, unknown>;
+  win.document.body.innerHTML = `
+    <form data-schema="login">
+      <input name="email">
+      <span data-error="email"></span>
+    </form>`;
+  win.__wireSchemas = { login: schema.describe() };
+  (globalThis as Record<string, unknown>).window = win;
+  (globalThis as Record<string, unknown>).document = win.document;
+
+  try {
+    (0, eval)(VALIDATE_RUNTIME);
+    const runtime = win.__wireValidate as { init(root: Document): void };
+    runtime.init(win.document as unknown as Document);
+    win.document.querySelector("input")!.dispatchEvent(new win.Event("blur", { bubbles: true }));
+
+    expect(win.document.querySelector("[data-error=email]")!.textContent).toBe(
+      "Enter your email or username",
+    );
+  } finally {
+    delete (globalThis as Record<string, unknown>).window;
+    delete (globalThis as Record<string, unknown>).document;
+  }
+});
+
 test("describe emits a JSON descriptor", () => {
   const d = login.describe();
   expect(d.type).toBe("object");
@@ -46,6 +92,9 @@ test("checkField coerces and applies rules", () => {
   );
   expect(checkField({ type: "number", rules: [{ kind: "min", n: 18 }] }, "20").value).toBe(20);
   expect(checkField({ type: "string", optional: true, rules: [] }, "").error).toBeNull();
+  expect(
+    checkField({ type: "string", requiredMessage: "Email is required", rules: [] }, "").error,
+  ).toBe("Email is required");
 });
 
 test("invalid() returns a 400 with errors", async () => {