fix: infinite update loop with zero measured value (#45)

Author: adbayb

src/index.js

@@ -57,8 +57,10 @@ export function useVirtual({
     const reversedMeasurements = []
 
     for (let i = 0, j = size - 1; i < size; i++, j--) {
+      const measuredSize = measuredCache[i]
       const start = measurements[i - 1] ? measurements[i - 1].end : paddingStart
-      const size = measuredCache[i] || estimateSize(i)
+      const size =
+        typeof measuredSize === 'number' ? measuredSize : estimateSize(i)
       const end = start + size
       const bounds = { index: i, start, size, end }
       measurements[i] = {

src/tests/index.test.js

@@ -87,6 +87,47 @@ describe('useVirtual', () => {
     rendered.getByText('Row 1')
   })
 
+  it('should render given dynamic size', async () => {
+    function App() {
+      const parentRef = React.useRef()
+
+      const rowVirtualizer = useVirtual({
+        size: 20,
+        parentRef,
+        overscan: 5,
+      })
+
+      return (
+        <>
+          <Container ref={parentRef}>
+            <Inner
+              style={{
+                height: `${rowVirtualizer.totalSize}px`,
+              }}
+            >
+              {rowVirtualizer.virtualItems.map(virtualRow => (
+                <Row
+                  key={virtualRow.index}
+                  ref={virtualRow.measureRef}
+                  style={{
+                    height: `${virtualRow.size}px`,
+                    transform: `translateY(${virtualRow.start}px)`,
+                  }}
+                >
+                  Row {virtualRow.index}
+                </Row>
+              ))}
+            </Inner>
+          </Container>
+        </>
+      )
+    }
+
+    const rendered = render(<App />)
+
+    rendered.getByText('Row 1')
+  })
+
   // it('scrolling utilities should work', async () => {
   //   function App() {
   //     const parentRef = React.useRef()

yarn.lock

@@ -1062,11 +1062,6 @@
     estree-walker "^1.0.1"
     picomatch "^2.2.2"
 
-"@scarf/scarf@^1.0.0":
-  version "1.0.4"
-  resolved "https://registry.yarnpkg.com/@scarf/scarf/-/scarf-1.0.4.tgz#d7c09e7d38428123df18a8d83a4bb5d09517d952"
-  integrity sha512-lkhjzeYyYAG4VvdrjvbZCOYzXH5vCwfzYj9xJ4zHDgyYIOzObZwcsbW6W1q5Z4tywrb14oG/tfsFAMMQPCTFqw==
-
 "@sheerun/mutationobserver-shim@^0.3.2":
   version "0.3.3"
   resolved "https://registry.yarnpkg.com/@sheerun/mutationobserver-shim/-/mutationobserver-shim-0.3.3.tgz#5405ee8e444ed212db44e79351f0c70a582aae25"