filtering cards that are already available when adding new cards as this will lead to a react error

Author: orangecoding

src/helpers/LaneHelper.js

@@ -17,14 +17,17 @@ const LaneHelper = {
   },
 
   appendCardsToLane: (state, {laneId, newCards, index}) => {
-    newCards = newCards.map(c => update(c, {laneId: {$set: laneId}}))
+    const lane = state.lanes.find(lane => lane.id === laneId)
+    newCards = newCards
+      .map(c => update(c, {laneId: {$set: laneId}}))
+      .filter(c => lane.cards.find(card => card.id === c.id) == null)
     return state.lanes.map(lane => {
       if (lane.id === laneId) {
         if (index !== undefined) {
           return update(lane, {cards: {$splice: [[index, 0, ...newCards]]}})
         } else {
-					const cardsToUpdate = [...lane.cards, ...newCards]
-					return update(lane, {cards: {$set: cardsToUpdate}})
+          const cardsToUpdate = [...lane.cards, ...newCards]
+          return update(lane, {cards: {$set: cardsToUpdate}})
         }
       } else {
         return lane