From f9a93e0f121ff67e88d2fcadb302006155e63658 Mon Sep 17 00:00:00 2001
From: ramfox <kasey@qri.io>
Date: Fri, 15 Nov 2019 14:18:44 -0500
Subject: [PATCH] fix(bodyValue): account for null or undefined previous body
 values

---
 app/components/ComponentList.tsx |  1 -
 app/utils/bodyValue.ts           | 17 +++++++----------
 test/app/utils/bodyValue.test.ts |  7 +++++++
 3 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/app/components/ComponentList.tsx b/app/components/ComponentList.tsx
index 6a62da41..56ceae07 100644
--- a/app/components/ComponentList.tsx
+++ b/app/components/ComponentList.tsx
@@ -126,7 +126,6 @@ function removeHiddenComponents (status: DatasetStatus) {
   }
 
   return (component): boolean => {
-    console.log(status[component.name])
     return status[component.name] || !hideWhenMissing[component.name]
   }
 }
diff --git a/app/utils/bodyValue.ts b/app/utils/bodyValue.ts
index 927e9d90..a009abdc 100644
--- a/app/utils/bodyValue.ts
+++ b/app/utils/bodyValue.ts
@@ -1,16 +1,12 @@
 import { PageInfo } from '../../app/models/store'
 
 export default function bodyValue (prev: Object | any[] | undefined, curr: Object | any[], pageInfo: PageInfo): Object | any[] {
-  // if there is no previous body value, just return the current body value
-  if (!prev) return curr
   // work through cases where the current body value is an array
   if (Array.isArray(curr)) {
-    // if the previous body value is not an array
-    // just return the current body value
-    if (!Array.isArray(prev)) {
-      return curr
+    if (curr.length === 0) {
+      if (!prev) return curr
+      return prev
     }
-    // otherwise, it is an array and we should concat the lists
 
     if (Array.isArray(curr[0])) {
       // for tabular/2D arrays only:
@@ -23,6 +19,9 @@ export default function bodyValue (prev: Object | any[] | undefined, curr: Objec
         d.unshift(index)
       })
 
+      // if there is no previous body value, just return the current body value
+      if (!prev || !Array.isArray(prev)) return curr
+
       if (prev.length !== 0) {
         const currLastIndex = curr[curr.length - 1][0]
         const prevLastIndex = prev[prev.length - 1][0] || 0
@@ -51,14 +50,12 @@ export default function bodyValue (prev: Object | any[] | undefined, curr: Objec
 
       return [...prev, ...curr]
     }
-
-    return [...prev, ...curr]
   }
   // work through cases where the current body value is an object (but not an array)
   if (typeof curr === 'object') {
     // if the previous body value is not an object (or is an object but is also an array)
     // return the current body value
-    if (!(typeof prev === 'object') && Array.isArray(prev)) {
+    if (!prev || (!(typeof prev === 'object') && Array.isArray(prev))) {
       return curr
     }
     // otherwise return the spread!
diff --git a/test/app/utils/bodyValue.test.ts b/test/app/utils/bodyValue.test.ts
index 8cf42e64..fc893f08 100644
--- a/test/app/utils/bodyValue.test.ts
+++ b/test/app/utils/bodyValue.test.ts
@@ -30,6 +30,13 @@ describe('bodyValue', () => {
       pageInfo: pageInfo2,
       expected: []
     },
+    {
+      describe: 'prev is undefined',
+      prev: undefined,
+      curr: [['a','b','c'],['d','e','f']],
+      pageInfo: initPageInfo,
+      expected: [[0, 'a','b','c'],[1, 'd','e','f']]
+    },
     {
       describe: 'prev is empty',
       prev: [],