fix: should not out of range (#101)

Author: zombieJ

src/List.tsx

@@ -207,10 +207,11 @@ export function RawList<T>(props: ListProps<T>, ref: React.Ref<ListRef>) {
   maxScrollHeightRef.current = maxScrollHeight;
 
   function keepInRange(newScrollTop: number) {
-    let newTop = Math.max(newScrollTop, 0);
+    let newTop = newScrollTop;
     if (!Number.isNaN(maxScrollHeightRef.current)) {
       newTop = Math.min(newTop, maxScrollHeightRef.current);
     }
+    newTop = Math.max(newScrollTop, 0);
     return newTop;
   }
 
@@ -225,8 +226,7 @@ export function RawList<T>(props: ListProps<T>, ref: React.Ref<ListRef>) {
     syncScrollTop(newTop);
   }
 
-  // This code may only trigger in test case.
-  // But we still need a sync if some special escape
+  // When data size reduce. It may trigger native scroll event back to fit scroll position
   function onFallbackScroll(e: React.UIEvent<HTMLDivElement>) {
     const { scrollTop: newScrollTop } = e.currentTarget;
     if (newScrollTop !== scrollTop) {

tests/scroll.test.js

@@ -222,4 +222,33 @@ describe('List.Scroll', () => {
         .instance(),
     );
   });
+
+  it('scroll should in range', () => {
+    const wrapper = genList({ itemHeight: 20, height: 100, data: genData(100) });
+    const ulElement = wrapper.find('ul').instance();
+
+    act(() => {
+      const wheelEvent = new Event('wheel');
+      wheelEvent.deltaY = 9999999;
+      ulElement.dispatchEvent(wheelEvent);
+
+      jest.runAllTimers();
+    });
+
+    wrapper.setProps({ data: genData(1) });
+    act(() => {
+      wrapper
+        .find('.rc-virtual-list-holder')
+        .props()
+        .onScroll({
+          currentTarget: {
+            scrollTop: 0,
+          },
+        });
+    });
+
+    wrapper.setProps({ data: genData(100) });
+
+    expect(wrapper.find('ScrollBar').props().scrollTop).toEqual(0);
+  });
 });