fix: compare full EvaluationDetails to prevent stale data (#1287)

## This PR

- updated the `isEqual` function to compare any input
- updated the compare to evaluate the whole EvaluationDetails object
instead of just the value

### Related Issues

Fixes #1286

### Notes

This may trigger slightly more re-renders but I feel that that's better
than return stale EvaluationDetails data which has proven to be
confusing to folks attempting to debug unexpected evaluations.

---------

Signed-off-by: Michael Beemer <[email protected]>

Author: beeme1mr

packages/react/src/evaluation/use-feature-flag.ts

@@ -307,9 +307,9 @@ function attachHandlersAndResolve<T extends FlagValue>(
       isFirstRender.current = false;
       return;
     }
-    
+
     const newDetails = resolver(client).call(client, flagKey, defaultValue, options);
-    if (!isEqual(newDetails.value, evaluationDetails.value)) {
+    if (!isEqual(newDetails, evaluationDetails)) {
       setEvaluationDetails(newDetails);
     }
   }, [client, flagKey, defaultValue, options, resolver, evaluationDetails]);
@@ -324,11 +324,9 @@ function attachHandlersAndResolve<T extends FlagValue>(
     const updatedEvaluationDetails = resolver(client).call(client, flagKey, defaultValue, options);
 
     /**
-     * Avoid re-rendering if the value hasn't changed. We could expose a means
-     * to define a custom comparison function if users require a more
-     * sophisticated comparison in the future.
+     * Avoid re-rendering if the evaluation details haven't changed.
      */
-    if (!isEqual(updatedEvaluationDetails.value, evaluationDetailsRef.current.value)) {
+    if (!isEqual(updatedEvaluationDetails, evaluationDetailsRef.current)) {
       setEvaluationDetails(updatedEvaluationDetails);
     }
   }, [client, flagKey, defaultValue, options, resolver]);

packages/react/src/internal/is-equal.ts

@@ -1,13 +1,14 @@
-import { type FlagValue } from '@openfeature/web-sdk';
-
 /**
  * Deeply compare two values to determine if they are equal.
  * Supports primitives and serializable objects.
- * @param {FlagValue} value First value to compare
- * @param {FlagValue} other Second value to compare
+ * 
+ * Note: Does not handle Date, RegExp, Map, Set, or circular references.
+ * Suitable for comparing EvaluationDetails and other JSON-serializable data.
+ * @param {unknown} value First value to compare
+ * @param {unknown} other Second value to compare
  * @returns {boolean} True if the values are equal
  */
-export function isEqual(value: FlagValue, other: FlagValue): boolean {
+export function isEqual(value: unknown, other: unknown): boolean {
   if (value === other) {
     return true;
   }
@@ -16,7 +17,7 @@ export function isEqual(value: FlagValue, other: FlagValue): boolean {
     return false;
   }
 
-  if (typeof value === 'object' && value !== null && other !== null) {
+  if (typeof value === 'object' && value !== null && typeof other === 'object' && other !== null) {
     const valueKeys = Object.keys(value);
     const otherKeys = Object.keys(other);
 

packages/react/test/evaluation.spec.tsx

@@ -585,6 +585,79 @@ describe('evaluation', () => {
       return new TestingProvider(CONFIG, DELAY); // delay init by 100ms
     };
 
+    describe('provider ready event updates', () => {
+      it('should update EvaluationDetails when provider becomes ready (including reason)', async () => {
+        const PROVIDER_READY_DOMAIN = 'provider-ready-test';
+        const TEST_FLAG_KEY = 'test-flag';
+        const FLAG_VALUE = true;
+
+        // Create a provider that will delay initialization
+        const provider = new TestingProvider(
+          {
+            [TEST_FLAG_KEY]: {
+              disabled: false,
+              variants: {
+                on: FLAG_VALUE,
+                off: false,
+              },
+              defaultVariant: 'on',
+            },
+          },
+          DELAY,
+        );
+
+        OpenFeature.setProvider(PROVIDER_READY_DOMAIN, provider);
+
+        let capturedDetails: EvaluationDetails<boolean> | undefined;
+        let renderCount = 0;
+
+        function TestComponent() {
+          renderCount++;
+          const details = useBooleanFlagDetails(TEST_FLAG_KEY, FLAG_VALUE);
+          capturedDetails = details;
+
+          return (
+            <div>
+              <div data-testid="value">{String(details.value)}</div>
+              <div data-testid="reason">{details.reason}</div>
+              <div data-testid="render-count">{renderCount}</div>
+            </div>
+          );
+        }
+
+        render(
+          <OpenFeatureProvider domain={PROVIDER_READY_DOMAIN}>
+            <TestComponent />
+          </OpenFeatureProvider>,
+        );
+
+        // Initial render - provider is NOT_READY, should use default value with ERROR reason
+        expect(capturedDetails?.value).toBe(FLAG_VALUE);
+        expect(capturedDetails?.reason).toBe(StandardResolutionReasons.ERROR);
+        expect(capturedDetails?.errorCode).toBe(ErrorCode.PROVIDER_NOT_READY);
+        expect(screen.getByTestId('reason')).toHaveTextContent(StandardResolutionReasons.ERROR);
+
+        const initialRenderCount = renderCount;
+
+        // Wait for provider to become ready and component to re-render
+        await waitFor(
+          () => {
+            expect(capturedDetails?.reason).toBe(StandardResolutionReasons.STATIC);
+          },
+          { timeout: DELAY * 2 },
+        );
+
+        // After provider is ready, same value but different reason and no error
+        expect(capturedDetails?.value).toBe(FLAG_VALUE);
+        expect(capturedDetails?.errorCode).toBeUndefined();
+        expect(screen.getByTestId('value')).toHaveTextContent(String(FLAG_VALUE));
+        expect(screen.getByTestId('reason')).toHaveTextContent(StandardResolutionReasons.STATIC);
+
+        // Verify that a re-render occurred
+        expect(renderCount).toBeGreaterThan(initialRenderCount);
+      });
+    });
+
     describe('when using the noop provider', () => {
       function TestComponent() {
         const { value } = useSuspenseFlag(SUSPENSE_FLAG_KEY, DEFAULT);