Fix: Infinite act loop caused by wrong shouldYield

acdlite · acdlite · commit fb31042edb60 · 2023-03-05T18:44:35.000-05:00
Fixes the bug demonstrated by the regression test in the previous
commit. Refer to previous message for details.
diff --git a/packages/react-reconciler/src/ReactFiberWorkLoop.js b/packages/react-reconciler/src/ReactFiberWorkLoop.js
@@ -2268,7 +2268,17 @@ function renderRootConcurrent(root: FiberRoot, lanes: Lanes) {
           }
         }
       }
-      workLoopConcurrent();
+
+      if (__DEV__ && ReactCurrentActQueue.current !== null) {
+        // `act` special case: If we're inside an `act` scope, don't consult
+        // `shouldYield`. Always keep working until the render is complete.
+        // This is not just an optimization: in a unit test environment, we
+        // can't trust the result of `shouldYield`, because the host I/O is
+        // likely mocked.
+        workLoopSync();
+      } else {
+        workLoopConcurrent();
+      }
       break;
     } catch (thrownValue) {
       handleThrow(root, thrownValue);

Original file line number	Diff line number	Diff line change
`@@ -2268,7 +2268,17 @@ function renderRootConcurrent(root: FiberRoot, lanes: Lanes) {`
`2268`	`2268`	`}`
`2269`	`2269`	`}`
`2270`	`2270`	`}`
`2271`		`- workLoopConcurrent();`
	`2271`	`+`
	`2272`	`+ if (__DEV__ && ReactCurrentActQueue.current !== null) {`
	`2273`	+ // `act` special case: If we're inside an `act` scope, don't consult
	`2274`	+ // `shouldYield`. Always keep working until the render is complete.
	`2275`	`+ // This is not just an optimization: in a unit test environment, we`
	`2276`	+ // can't trust the result of `shouldYield`, because the host I/O is
	`2277`	`+ // likely mocked.`
	`2278`	`+ workLoopSync();`
	`2279`	`+ } else {`
	`2280`	`+ workLoopConcurrent();`
	`2281`	`+ }`
`2272`	`2282`	`break;`
`2273`	`2283`	`} catch (thrownValue) {`
`2274`	`2284`	`handleThrow(root, thrownValue);`