buffer cleanp when bof without immutableTop

Author: dhilt

src/modules/adapter.js

@@ -172,8 +172,11 @@ class Adapter {
     if (!newItems.reverse().some(newItem => newItem === wrapper.item)) {
       wrapper.op = OPERATIONS.REMOVE;
       // try to catch "first" edge case on remove
-      if (!options.immutableTop && position === 0 && !newItems.length) {
-        wrapper.shiftTop = true; 
+      if (!options.immutableTop && !newItems.length) {
+        // this is the first item, or the previous one's part of the "shift-top" group
+        if (position === 0 || this.buffer[position - 1].shiftTop) {
+          wrapper.shiftTop = true;
+        }
       }
     }
     newItems.forEach((newItem) => {

test/AdapterTestsSpec.js

@@ -1611,22 +1611,23 @@ describe('uiScroll', function () {
   });
 
   describe('buffer cleanup', function () {
-    var scrollSettings = {
-      datasource: 'myEdgeDatasource',
-      adapter: 'adapter',
-      viewportHeight: 60,
-      itemHeight: 20,
-      padding: 0.3,
-      startIndex: 3,
-      bufferSize: 3
+    var getSettings = function () {
+      return {
+        datasource: 'myEdgeDatasource',
+        adapter: 'adapter',
+        viewportHeight: 60,
+        itemHeight: 20,
+        padding: 0.3,
+        startIndex: 3,
+        bufferSize: 3
+      };
     };
 
     injectDatasource('myEdgeDatasource');
 
-    var cleanBuffer = function (datasource, scope, applyUpdateOptions) {
+    var cleanBuffer = function (scope, applyUpdateOptions) {
       var get = datasource.get;
       var removedItems = [];
-      var first = -5;
       // sync the datasource
       datasource.get = function (index, count, success) {
         var removedIndex = removedItems.indexOf('item' + index);
@@ -1644,13 +1645,13 @@ describe('uiScroll', function () {
     };
 
     it('should be consistent on forward direction when eof with immutabeTop', function () {
-      runTest(scrollSettings,
+      runTest(getSettings(),
         function (viewport, scope) {
           expect(scope.adapter.isBOF()).toBe(false);
           expect(scope.adapter.isEOF()).toBe(true);
 
           // remove items 0..6 items form -5..6 datasource
-          cleanBuffer(datasource, scope, { immutableTop: true });
+          cleanBuffer(scope, { immutableTop: true });
 
           // result [-5..-1]
           expect(scope.adapter.isBOF()).toBe(true);
@@ -1660,9 +1661,10 @@ describe('uiScroll', function () {
           expect(scope.adapter.bufferLength).toBe(5);
         }
       );
-    });
+    }); 
 
     it('should be consistent on forward direction when not eof with immutabeTop', function () {
+      var scrollSettings = getSettings();
       scrollSettings.startIndex = -1;
       scrollSettings.viewportHeight = 40;
       runTest(scrollSettings,
@@ -1671,7 +1673,7 @@ describe('uiScroll', function () {
           expect(scope.adapter.isEOF()).toBe(false);
 
           // remove items -4..1 items form -5..6 datasource
-          cleanBuffer(datasource, scope, { immutableTop: true });
+          cleanBuffer(scope, { immutableTop: true });
 
           // result [-5, 2, 3, 4]
           expect(scope.adapter.isBOF()).toBe(true);
@@ -1683,6 +1685,27 @@ describe('uiScroll', function () {
       );
     });
 
+    it('should be consistent on backward direction when bof without immutableTop', function () {
+      var scrollSettings = getSettings();
+      scrollSettings.startIndex = -3;
+      scrollSettings.padding = 0.5;
+      runTest(scrollSettings,
+        function (viewport, scope) {
+          expect(scope.adapter.isBOF()).toBe(true);
+          expect(scope.adapter.isEOF()).toBe(false);
+
+          // remove items -5..1 items form -5..6 datasource
+          cleanBuffer(scope);
+
+          expect(scope.adapter.isBOF()).toBe(true);
+          expect(scope.adapter.isEOF()).toBe(true);
+          expect(scope.adapter.bufferFirst).toBe('item2');
+          expect(scope.adapter.bufferLast).toBe('item6');
+          expect(scope.adapter.bufferLength).toBe(5);
+        }
+      );
+    });
+
   });
 
 });