warn when setting pagingEnabled when snapToInterval at the same time

Reviewed By: fkgozali

Differential Revision: D5326342

fbshipit-source-id: 2bf6b66f81e9aedaad288495f254f04af32dc63d

Libraries/Components/ScrollView/ScrollView.js

@@ -32,6 +32,7 @@ const flattenStyle = require('flattenStyle');
 const invariant = require('fbjs/lib/invariant');
 const processDecelerationRate = require('processDecelerationRate');
 const requireNativeComponent = require('requireNativeComponent');
+const warning = require('fbjs/lib/warning');
 
 import type {NativeMethodsMixinType} from 'ReactNativeTypes';
 
@@ -313,8 +314,10 @@ const ScrollView = React.createClass({
     /**
      * When set, causes the scroll view to stop at multiples of the value of
      * `snapToInterval`. This can be used for paginating through children
-     * that have lengths smaller than the scroll view. Used in combination
-     * with `snapToAlignment`.
+     * that have lengths smaller than the scroll view. Typically used in
+     * combination with `snapToAlignment` and `decelerationRate="fast"`.
+     * Overrides less configurable `pagingEnabled` prop.
+     *
      * @platform ios
      */
     snapToInterval: PropTypes.number,
@@ -605,6 +608,10 @@ const ScrollView = React.createClass({
     if (Platform.OS === 'ios') {
       ScrollViewClass = RCTScrollView;
       ScrollContentContainerViewClass = RCTScrollContentView;
+      warning(
+        !this.props.snapToInterval || !this.props.pagingEnabled,
+        'snapToInterval is currently ignored when pagingEnabled is true.'
+      );
     } else if (Platform.OS === 'android') {
       if (this.props.horizontal) {
         ScrollViewClass = AndroidHorizontalScrollView;