Fix #1050: useField returns Form initialValues on first render

PROBLEM:
In v7.0.0, useField returns undefined on first render even when Form
initialValues are set. This breaks apps trying to upgrade from v6.

ROOT CAUSE:
useField's useState initializer calls getFieldState() before the field
is registered. Since the field doesn't exist yet, it falls back to
creating initial state, but only checks field-level initialValue config,
NOT the Form's initialValues.

SOLUTION:
Check form.getState().initialValues[name] when creating fallback initial
state. Form-level initialValues take precedence over field-level.

TESTS:
- ✅ useField returns Form initialValues on first render
- ✅ Form initialValues override field initialValue
- ✅ Field initialValue used when Form initialValues missing that field

Fixes #1050

Author: Dinesh Agent

src/useField.test.js

@@ -508,4 +508,76 @@ describe("useField", () => {
     expect(calls).toContain("test"); // At least one call with 'test'
     expect(calls[calls.length - 1]).toBe(null); // Last call is null
   });
+
+  it("should return Form initialValues on first render (fix #1050)", () => {
+    const renderSpy = jest.fn();
+    
+    const MyField = () => {
+      const { input } = useField("username");
+      renderSpy(input.value);
+      return <input {...input} data-testid="username" />;
+    };
+    
+    const { getByTestId } = render(
+      <Form onSubmit={onSubmitMock} initialValues={{ username: "erikras" }}>
+        {() => (
+          <form>
+            <MyField />
+          </form>
+        )}
+      </Form>,
+    );
+    
+    // Critical: on the FIRST render, value should be "erikras" not undefined
+    expect(renderSpy.mock.calls[0][0]).toBe("erikras");
+    expect(getByTestId("username").value).toBe("erikras");
+  });
+
+  it("should prefer Form initialValues over field initialValue", () => {
+    const renderSpy = jest.fn();
+    
+    const MyField = () => {
+      const { input } = useField("username", { initialValue: "fallback" });
+      renderSpy(input.value);
+      return <input {...input} data-testid="username" />;
+    };
+    
+    const { getByTestId } = render(
+      <Form onSubmit={onSubmitMock} initialValues={{ username: "formLevel" }}>
+        {() => (
+          <form>
+            <MyField />
+          </form>
+        )}
+      </Form>,
+    );
+    
+    // Form-level initialValues should take precedence
+    expect(renderSpy.mock.calls[0][0]).toBe("formLevel");
+    expect(getByTestId("username").value).toBe("formLevel");
+  });
+
+  it("should use field initialValue when Form initialValues doesnt have that field", () => {
+    const renderSpy = jest.fn();
+    
+    const MyField = () => {
+      const { input } = useField("username", { initialValue: "fieldLevel" });
+      renderSpy(input.value);
+      return <input {...input} data-testid="username" />;
+    };
+    
+    const { getByTestId } = render(
+      <Form onSubmit={onSubmitMock} initialValues={{ other: "value" }}>
+        {() => (
+          <form>
+            <MyField />
+          </form>
+        )}
+      </Form>,
+    );
+    
+    // Field-level initialValue should be used as fallback
+    expect(renderSpy.mock.calls[0][0]).toBe("fieldLevel");
+    expect(getByTestId("username").value).toBe("fieldLevel");
+  });
 });

src/useField.ts

@@ -114,8 +114,16 @@ function useField<
     }
 
     // If no existing state, create a proper initial state
+    // FIX #1050: Check Form's initialValues[name] first, before field-level initialValue
+    const formState = form.getState();
     let initialStateValue = initialValue;
-    if (component === "select" && multiple && initialValue === undefined) {
+    
+    // Check Form-level initialValues (set via <Form initialValues={...}>)
+    if (formState.initialValues && name in formState.initialValues) {
+      initialStateValue = (formState.initialValues as any)[name];
+    }
+    
+    if (component === "select" && multiple && initialStateValue === undefined) {
       initialStateValue = [];
     }