Reimplement rjsf-team#1755 and and rjsf-team#2460 in new Form.tsx

- Reimplement two fixes related to `onChange` in the new `Form.tsx`
  - rjsf-team#1755 fixes the calling of the proper `onChange` during props update
  - rjsf-team#2460 fixes race condition on calling `onChange` after setState.

Author: heath-freenome

CHANGELOG.md

@@ -33,6 +33,7 @@ should change the heading of the (upcoming) version to include a major version b
 - Added `ui:duplicateKeySuffixSeparator` to customize how duplicate object keys are renamed when using `additionalProperties`.
 - The `extraErrors` are now consistently appended onto the end of the schema validation-based `errors` information that is returned via the `onErrors()` callback when submit fails.
   - In addition, the extra information provided by AJV is no longer stripped from the `errors` during the merge process, fixing (https://github.com/rjsf-team/react-jsonschema-form/issues/1596).
+- Correctly call the `onChange` handler in the new set of props if it changed, fixing (https://github.com/rjsf-team/react-jsonschema-form/issues/1708).
 
 ## @rjsf/antd
 - Fix esm build to use `@rollup/plugin-replace` to replace `antd/lib` and `rc-picker/lib` with `antd/es` and `rc-picker/es` respectively, fixing (https://github.com/rjsf-team/react-jsonschema-form/issues/2962)

packages/core/src/components/Form.tsx

@@ -260,9 +260,9 @@ export default class Form<T = any, F = any> extends Component<
     if (
       !deepEquals(nextState.formData, nextProps.formData) &&
       !deepEquals(nextState.formData, this.state.formData) &&
-      this.props.onChange
+      nextProps.onChange
     ) {
-      this.props.onChange(nextState);
+      nextProps.onChange(nextState);
     }
     this.setState(nextState);
   }
@@ -562,7 +562,7 @@ export default class Form<T = any, F = any> extends Component<
     }
     this.setState(
       state as FormState<T, F>,
-      () => onChange && onChange(this.state)
+      () => onChange && onChange({ ...this.state, ...state })
     );
   };
 

packages/core/test/Form_test.js

@@ -1,7 +1,7 @@
 import { expect } from "chai";
 import sinon from "sinon";
 import React, { createRef } from "react";
-import { renderIntoDocument, Simulate } from "react-dom/test-utils";
+import { renderIntoDocument, act, Simulate } from "react-dom/test-utils";
 import { render, findDOMNode } from "react-dom";
 import { Portal } from "react-portal";
 import validator, { customizeValidator } from "@rjsf/validator-ajv6";
@@ -1012,6 +1012,52 @@ describeRepeated("Form common", (createFormComponent) => {
         uiSchema,
       });
     });
+    it("should call last provided change handler", async () => {
+      const schema = {
+        type: "object",
+        properties: {
+          foo: {
+            type: "string",
+            default: "bar",
+          },
+        },
+      };
+
+      const secondOnChange = sandbox.spy();
+
+      const { comp, onChange } = createFormComponent({
+        schema,
+        formData: { foo: "bar1" },
+      });
+
+      act(() => {
+        setProps(comp, {
+          schema,
+          formData: {},
+          onChange,
+        });
+      });
+
+      sinon.assert.callCount(onChange, 1);
+
+      act(() => {
+        setProps(comp, {
+          schema,
+          formData: { foo: "bar2" },
+        });
+      });
+
+      act(() => {
+        setProps(comp, {
+          schema,
+          formData: {},
+          onChange: secondOnChange,
+        });
+      });
+
+      sinon.assert.callCount(onChange, 1);
+      sinon.assert.callCount(secondOnChange, 1);
+    });
   });
   describe("Blur handler", () => {
     it("should call provided blur handler on form input blur event", () => {
@@ -3402,4 +3448,62 @@ describe("Form omitExtraData and liveOmit", () => {
 
     expect(node.querySelectorAll(".error-detail li")).to.have.length.of(2);
   });
+  describe("Calling onChange right after updating a Form with props formData", () => {
+    const schema = {
+      type: "array",
+      items: {
+        type: "string",
+      },
+    };
+
+    let changed = false;
+    class ArrayThatTriggersOnChangeRightAfterUpdated extends React.Component {
+      componentDidUpdate = () => {
+        if (changed) {
+          return;
+        }
+        changed = true;
+        this.props.onChange([...this.props.formData, "test"]);
+      };
+      render() {
+        const { ArrayField } = this.props.registry.fields;
+        return <ArrayField {...this.props} />;
+      }
+    }
+
+    const uiSchema = {
+      "ui:field": ArrayThatTriggersOnChangeRightAfterUpdated,
+    };
+
+    const props = {
+      schema,
+      uiSchema,
+    };
+
+    class Container extends React.Component {
+      constructor(props) {
+        super(props);
+        this.state = {};
+      }
+
+      onChange = ({ formData }) => {
+        this.setState({ formData });
+      };
+
+      render() {
+        return (
+          <Form {...this.props} {...this.state} onChange={this.onChange} />
+        );
+      }
+    }
+
+    it("doesn't cause a race condition", () => {
+      const { node } = createComponent(Container, { ...props });
+
+      Simulate.click(node.querySelector(".array-item-add button"));
+
+      expect(node.querySelector("#root_0")).to.exist;
+      expect(node.querySelector("#root_1").getAttribute("value")).to.eq("test");
+    });
+  });
 });