Repository: facebook/react
Pull request: Unwrap a reference to a Lazy value

If we are referencing a lazy value that isn't explicitly lazy ($L...) it's because we added it around an element that was blocked to be able to defer things inside.

However, once that is unblocked we can start unwrap it and just use the inner element instead for any future reference. The race condition is still there since it's a race condition whether we added the wrapper in the first place.

This just makes it consistent with unwrapping of the rest of the path.


Changed files:
filename: packages/react-client/src/ReactFlightClient.js
patch: @@ -1337,7 +1337,11 @@ function fulfillReference(
   const {response, handler, parentObject, key, map, path} = reference;
 
   for (let i = 1; i < path.length; i++) {
-    while (value.$$typeof === REACT_LAZY_TYPE) {
+    while (
+      typeof value === 'object' &&
+      value !== null &&
+      value.$$typeof === REACT_LAZY_TYPE
+    ) {
       // We never expect to see a Lazy node on this path because we encode those as
       // separate models. This must mean that we have inserted an extra lazy node
       // e.g. to replace a blocked element. We must instead look for it inside.
@@ -1408,6 +1412,39 @@ function fulfillReference(
     }
     value = value[path[i]];
   }
+
+  while (
+    typeof value === 'object' &&
+    value !== null &&
+    value.$$typeof === REACT_LAZY_TYPE
+  ) {
+    // If what we're referencing is a Lazy it must be because we inserted one as a virtual node
+    // while it was blocked by other data. If it's no longer blocked, we can unwrap it.
+    const referencedChunk: SomeChunk<any> = value._payload;
+    if (referencedChunk === handler.chunk) {
+      // This is a reference to the thing we're currently blocking. We can peak
+      // inside of it to get the value.
+      value = handler.value;
+      continue;
+    } else {
+      switch (referencedChunk.status) {
+        case RESOLVED_MODEL:
+          initializeModelChunk(referencedChunk);
+          break;
+        case RESOLVED_MODULE:
+          initializeModuleChunk(referencedChunk);
+          break;
+      }
+      switch (referencedChunk.status) {
+        case INITIALIZED: {
+          value = referencedChunk.value;
+          continue;
+        }
+      }
+    }
+    break;
+  }
+
   const mappedValue = map(response, value, parentObject, key);
   parentObject[key] = mappedValue;
 
@@ -1855,7 +1892,11 @@ function getOutlinedModel<T>(
     case INITIALIZED:
       let value = chunk.value;
       for (let i = 1; i < path.length; i++) {
-        while (value.$$typeof === REACT_LAZY_TYPE) {
+        while (
+          typeof value === 'object' &&
+          value !== null &&
+          value.$$typeof === REACT_LAZY_TYPE
+        ) {
           const referencedChunk: SomeChunk<any> = value._payload;
           switch (referencedChunk.status) {
             case RESOLVED_MODEL:
@@ -1924,6 +1965,32 @@ function getOutlinedModel<T>(
         }
         value = value[path[i]];
       }
+
+      while (
+        typeof value === 'object' &&
+        value !== null &&
+        value.$$typeof === REACT_LAZY_TYPE
+      ) {
+        // If what we're referencing is a Lazy it must be because we inserted one as a virtual node
+        // while it was blocked by other data. If it's no longer blocked, we can unwrap it.
+        const referencedChunk: SomeChunk<any> = value._payload;
+        switch (referencedChunk.status) {
+          case RESOLVED_MODEL:
+            initializeModelChunk(referencedChunk);
+            break;
+          case RESOLVED_MODULE:
+            initializeModuleChunk(referencedChunk);
+            break;
+        }
+        switch (referencedChunk.status) {
+          case INITIALIZED: {
+            value = referencedChunk.value;
+            continue;
+          }
+        }
+        break;
+      }
+
       const chunkValue = map(response, value, parentObject, key);
       if (
         parentObject[0] === REACT_ELEMENT_TYPE &&