fix: edge case with a single group

Fixes #886
petyosi · Apr 26, 2023 · 2e73470 · 2e73470
1 parent f4dd1a5
commit 2e73470
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Showing 2 changed files with 4 additions and 2 deletions.
diff --git a/src/sizeSystem.ts b/src/sizeSystem.ts
@@ -459,7 +459,8 @@ export const sizeSystem = u.system(
 
             while (prependedGroupItemsCount < unshiftWith) {
               const theGroupIndex = sizes.groupIndices[groupIndex]
-              const groupItemCount = sizes.groupIndices[groupIndex + 1] - theGroupIndex - 1
+              const groupItemCount =
+                sizes.groupIndices.length === groupIndex + 1 ? Infinity : sizes.groupIndices[groupIndex + 1] - theGroupIndex - 1
 
               initialRanges.push({
                 startIndex: theGroupIndex,

diff --git a/src/upwardScrollFixSystem.ts b/src/upwardScrollFixSystem.ts
@@ -124,7 +124,8 @@ export const upwardScrollFixSystem = u.system(
               recognizedOffsetItems++
               amount += defaultGroupSize
 
-              let groupItemCount = groupIndices[groupIndex + 1] - groupIndices[groupIndex] - 1
+              let groupItemCount =
+                groupIndices.length === groupIndex + 1 ? Infinity : groupIndices[groupIndex + 1] - groupIndices[groupIndex] - 1
 
               // if the group is larger than the offset, we have an expanded group. remove the group size, and replace with 1 item.
               if (recognizedOffsetItems + groupItemCount > offset) {