From 721ee0e95f0c30419b1377a4f6cc65fce83c6bb5 Mon Sep 17 00:00:00 2001
From: Quincy Morgan <quincy.morgan@icloud.com>
Date: Sat, 18 Jan 2020 12:30:35 -0500
Subject: [PATCH] Prevent unnecessary reloading of raw tag editor (close #7248)

---
 modules/ui/raw_tag_editor.js |  5 +++--
 modules/ui/sidebar.js        |  6 +++---
 modules/util/array.js        | 10 ++++++++++
 modules/util/index.js        |  1 +
 4 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/modules/ui/raw_tag_editor.js b/modules/ui/raw_tag_editor.js
index e7680e184..c9fca6983 100644
--- a/modules/ui/raw_tag_editor.js
+++ b/modules/ui/raw_tag_editor.js
@@ -7,7 +7,8 @@ import { svgIcon } from '../svg/icon';
 import { uiCombobox } from './combobox';
 import { uiDisclosure } from './disclosure';
 import { uiTagReference } from './tag_reference';
-import { utilArrayDifference, utilGetSetValue, utilNoAuto, utilRebind, utilTagDiff } from '../util';
+import { utilArrayDifference, utilArrayIdentical } from '../util/array';
+import { utilGetSetValue, utilNoAuto, utilRebind, utilTagDiff } from '../util';
 
 
 export function uiRawTagEditor(context) {
@@ -609,7 +610,7 @@ export function uiRawTagEditor(context) {
 
     rawTagEditor.entityIDs = function(val) {
         if (!arguments.length) return _entityIDs;
-        if (_entityIDs !== val) {
+        if (!_entityIDs || !val || !utilArrayIdentical(_entityIDs, val)) {
             _entityIDs = val;
             _orderedKeys = [];
         }
diff --git a/modules/ui/sidebar.js b/modules/ui/sidebar.js
index 7ee9a8dd6..74ceeb52f 100644
--- a/modules/ui/sidebar.js
+++ b/modules/ui/sidebar.js
@@ -8,7 +8,7 @@ import {
     event as d3_event,
     selectAll as d3_selectAll
 } from 'd3-selection';
-
+import { utilArrayIdentical } from '../util/array';
 import { osmEntity, osmNote, qaError } from '../osm';
 import { services } from '../services';
 import { uiDataEditor } from './data_editor';
@@ -167,7 +167,7 @@ export function uiSidebar(context) {
                     .classed('inspector-hidden', false)
                     .classed('inspector-hover', true);
 
-                if (inspector.entityIDs() !== [datum.id] || inspector.state() !== 'hover') {
+                if (!inspector.entityIDs() || !utilArrayIdentical(inspector.entityIDs(), [datum.id]) || inspector.state() !== 'hover') {
                     inspector
                         .state('hover')
                         .entityIDs([datum.id]);
@@ -225,7 +225,7 @@ export function uiSidebar(context) {
                     .classed('inspector-hidden', false)
                     .classed('inspector-hover', false);
 
-                if (inspector.entityIDs() !== ids || inspector.state() !== 'select') {
+                if (!inspector.entityIDs() || !utilArrayIdentical(inspector.entityIDs(), ids) || inspector.state() !== 'select') {
                     inspector
                         .state('select')
                         .entityIDs(ids)
diff --git a/modules/util/array.js b/modules/util/array.js
index c06e66cde..aab92222d 100644
--- a/modules/util/array.js
+++ b/modules/util/array.js
@@ -1,4 +1,14 @@
 
+// Returns true if a and b have the same elements at the same indices.
+export function utilArrayIdentical(a, b) {
+    var i = a.length;
+    if (i !== b.length) return false;
+    while (i--) {
+        if (a[i] !== b[i]) return false;
+    }
+    return true;
+}
+
 // http://2ality.com/2015/01/es6-set-operations.html
 
 // Difference (a \ b): create a set that contains those elements of set a that are not in set b.
diff --git a/modules/util/index.js b/modules/util/index.js
index ec202812b..9c83d6bd5 100644
--- a/modules/util/index.js
+++ b/modules/util/index.js
@@ -2,6 +2,7 @@ export { utilArrayChunk } from './array';
 export { utilArrayDifference } from './array';
 export { utilArrayFlatten } from './array';
 export { utilArrayGroupBy } from './array';
+export { utilArrayIdentical } from './array';
 export { utilArrayIntersection } from './array';
 export { utilArrayUnion } from './array';
 export { utilArrayUniq } from './array';