Fix omitData for top level array (rjsf-team#1406)

* Fixes omitData converting root array to object

* Fixed conditional

* Little bit of cleanup

* Added test of getUsedFormData with top level array

Author: Tonexus

src/components/Form.js

@@ -139,7 +139,12 @@ export default class Form extends Component {
       return formData;
     }
 
-    return _pick(formData, fields);
+    let data = _pick(formData, fields);
+    if (Array.isArray(formData)) {
+      return Object.keys(data).map(key => data[key]);
+    }
+
+    return data;
   };
 
   getFieldNames = (pathSchema, formData) => {

test/Form_test.js

@@ -866,6 +866,25 @@ describe("Form", () => {
       expect(result).eql("foo");
     });
 
+    it("should return the root level array", () => {
+      const schema = {
+        type: "array",
+        items: {
+          type: "string",
+        },
+      };
+      const formData = [];
+      const onSubmit = sandbox.spy();
+      const { comp } = createFormComponent({
+        schema,
+        formData,
+        onSubmit,
+      });
+
+      const result = comp.getUsedFormData(formData, []);
+      expect(result).eql([]);
+    });
+
     it("should call getUsedFormData with data from fields in event", () => {
       const schema = {
         type: "object",