From 34fc16ef133884049b25eda5274f936698ea3d6d Mon Sep 17 00:00:00 2001
From: Colin Diesh <colin.diesh@gmail.com>
Date: Wed, 14 Sep 2022 11:52:03 -0600
Subject: [PATCH] Fix "dead state tree node" error by creating snapshots of
 parent region for block calculations (#3182)

Ensure parentRegion gets a snapshot
---
 packages/core/util/calculateDynamicBlocks.ts | 4 +++-
 packages/core/util/calculateStaticBlocks.ts  | 7 +++++--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/packages/core/util/calculateDynamicBlocks.ts b/packages/core/util/calculateDynamicBlocks.ts
index d2939318a3..b2c8e1cca7 100644
--- a/packages/core/util/calculateDynamicBlocks.ts
+++ b/packages/core/util/calculateDynamicBlocks.ts
@@ -1,3 +1,4 @@
+import { isStateTreeNode, getSnapshot } from 'mobx-state-tree'
 import { intersection2 } from './range'
 import { assembleLocString } from '.'
 import {
@@ -60,6 +61,7 @@ export default function calculateDynamicBlocks(
       displayedRegionLeftPx + (regionEnd - regionStart) / bpPerPx
 
     const regionWidthPx = (regionEnd - regionStart) / bpPerPx
+    const parentRegion = isStateTreeNode(region) ? getSnapshot(region) : region
 
     if (
       displayedRegionLeftPx < windowRightPx &&
@@ -104,7 +106,7 @@ export default function calculateDynamicBlocks(
         end,
         reversed,
         offsetPx: blockOffsetPx,
-        parentRegion: region,
+        parentRegion,
         regionNumber,
         widthPx,
         isLeftEndOfDisplayedRegion,
diff --git a/packages/core/util/calculateStaticBlocks.ts b/packages/core/util/calculateStaticBlocks.ts
index 2776f31dfb..a14f4a41c8 100644
--- a/packages/core/util/calculateStaticBlocks.ts
+++ b/packages/core/util/calculateStaticBlocks.ts
@@ -1,3 +1,4 @@
+import { isStateTreeNode, getSnapshot, Instance } from 'mobx-state-tree'
 import { assembleLocString } from '.'
 import {
   BlockSet,
@@ -6,11 +7,12 @@ import {
   InterRegionPaddingBlock,
 } from './blockTypes'
 import { Region } from './types'
+import { Region as RegionModel } from './types/mst'
 
 export interface Base1DViewModel {
   offsetPx: number
   width: number
-  displayedRegions: Region[]
+  displayedRegions: (Region | Instance<typeof RegionModel>)[]
   bpPerPx: number
   minimumBlockWidth: number
   interRegionPaddingWidth: number
@@ -54,6 +56,7 @@ export default function calculateStaticBlocks(
       reversed,
     } = region
     const regionBlockCount = Math.ceil((regionEnd - regionStart) / blockSizeBp)
+    const parentRegion = isStateTreeNode(region) ? getSnapshot(region) : region
 
     let windowRightBlockNum =
       Math.floor((windowRightBp - regionBpOffset) / blockSizeBp) + extra
@@ -97,7 +100,7 @@ export default function calculateStaticBlocks(
         end,
         reversed,
         offsetPx: (regionBpOffset + blockNum * blockSizeBp) / bpPerPx,
-        parentRegion: region,
+        parentRegion,
         regionNumber,
         widthPx,
         isLeftEndOfDisplayedRegion,