fix: ScrollTo should not out of range (#57)

* fix: Not scroll out of range

* add test case

Author: zombieJ

examples/basic.tsx

@@ -138,6 +138,29 @@ const Demo = () => {
           visible
         </button>
 
+        <button
+          type="button"
+          onClick={() => {
+            listRef.current.scrollTo({
+              index: data.length - 2,
+              align: 'top',
+            });
+          }}
+        >
+          Scroll To Last (top)
+        </button>
+        <button
+          type="button"
+          onClick={() => {
+            listRef.current.scrollTo({
+              index: 0,
+              align: 'bottom',
+            });
+          }}
+        >
+          Scroll To First (bottom)
+        </button>
+
         <button
           type="button"
           onClick={() => {

src/List.tsx

@@ -103,8 +103,10 @@ export function RawList<T>(props: ListProps<T>, ref: React.Ref<ListRef>) {
         value = newTop;
       }
 
-      componentRef.current.scrollTop = value;
-      return value;
+      const alignedTop = keepInRange(value);
+
+      componentRef.current.scrollTop = alignedTop;
+      return alignedTop;
     });
   }
 
@@ -205,10 +207,8 @@ export function RawList<T>(props: ListProps<T>, ref: React.Ref<ListRef>) {
 
   // ================================ Scroll ================================
   function onScrollBar(newScrollTop: number) {
-    const newTop = keepInRange(newScrollTop);
-    if (newTop !== scrollTop) {
-      syncScrollTop(newTop);
-    }
+    const newTop = newScrollTop;
+    syncScrollTop(newTop);
   }
 
   // This code may only trigger in test case.
@@ -230,8 +230,7 @@ export function RawList<T>(props: ListProps<T>, ref: React.Ref<ListRef>) {
     isScrollAtBottom,
     offsetY => {
       syncScrollTop(top => {
-        const newTop = keepInRange(top + offsetY);
-
+        const newTop = top + offsetY;
         return newTop;
       });
     },

tests/scroll.test.js

@@ -70,6 +70,12 @@ describe('List.Scroll', () => {
       expect(wrapper.find('ul').instance().scrollTop).toEqual(600);
     });
 
+    it('scroll top should not out of range', () => {
+      listRef.current.scrollTo({ index: 0, align: 'bottom' });
+      jest.runAllTimers();
+      expect(wrapper.find('ul').instance().scrollTop).toEqual(0);
+    });
+
     it('key scroll', () => {
       listRef.current.scrollTo({ key: '30', align: 'bottom' });
       jest.runAllTimers();