support findAndUpdate with same predicate semantics in SortedArray too

src/matrix/room/timeline/Timeline.js

@@ -90,27 +90,23 @@ export class Timeline {
     }
 
     _applyAndEmitLocalRelationChange(pe, updater) {
-        // first, look in local entries (separately, as it has its own update mechanism)
+        const updateOrFalse = e => {
-        const foundInLocalEntries = this._localEntries.findAndUpdate(
-            e => e.id === pe.relatedTxnId,
-            e => {
             const params = updater(e);
             return params ? params : false;
-            },
+        };
+        // first, look in local entries based on txn id
+        const foundInLocalEntries = this._localEntries.findAndUpdate(
+            e => e.id === pe.relatedTxnId,
+            updateOrFalse,
         );
-        // now look in remote entries
+        // now look in remote entries based on event id
         if (!foundInLocalEntries && pe.relatedEventId) {
             // TODO: ideally iterate in reverse as target is likely to be most recent,
             // but not easy through ObservableList contract
-            for (const entry of this._remoteEntries) {
+            this._remoteEntries.findAndUpdate(
-                if (pe.relatedEventId === entry.id) {
+                e => e.id === pe.relatedEventId,
-                    const params = updater(entry);
+                updateOrFalse
-                    if (params) {
+            );
-                        this._remoteEntries.update(entry, params);
-                    }
-                    return;
-                }
-            }
         }
     }
 

src/observable/list/MappedList.js

@@ -16,6 +16,7 @@ limitations under the License.
 */
 
 import {BaseObservableList} from "./BaseObservableList.js";
+import {findAndUpdateInArray} from "./common.js";
 
 export class MappedList extends BaseObservableList {
     constructor(sourceList, mapper, updater, removeCallback) {
@@ -80,18 +81,7 @@ export class MappedList extends BaseObservableList {
     }
 
     findAndUpdate(predicate, updater) {
-        const index = this._mappedValues.findIndex(predicate);
+        return findAndUpdateInArray(predicate, this._mappedValues, this, updater);
-        if (index !== -1) {
-            const mappedValue = this._mappedValues[index];
-            // allow bailing out of sending an emit if updater determined its not needed
-            const params = updater(mappedValue);
-            if (params !== false) {
-                this.emitUpdate(index, mappedValue, params);
-            }
-            // found
-            return true;
-        }
-        return false;
     }
 
     get length() {

src/observable/list/SortedArray.js

@@ -16,6 +16,7 @@ limitations under the License.
 
 import {BaseObservableList} from "./BaseObservableList.js";
 import {sortedIndex} from "../../utils/sortedIndex.js";
+import {findAndUpdateInArray} from "./common.js";
 
 export class SortedArray extends BaseObservableList {
     constructor(comparator) {
@@ -41,20 +42,8 @@ export class SortedArray extends BaseObservableList {
         }
     }
 
-    findAndUpdate(newValue, updater) {
+    findAndUpdate(predicate, updater) {
-        const index = this.indexOf(newValue);
+        return findAndUpdateInArray(predicate, this._items, this, updater);
-        if (index !== -1) {
-            const oldValue = this._items[index];
-            // allow bailing out of sending an emit if updater determined its not needed
-            const params = updater(oldValue, newValue);
-            if (params !== false) {
-                this._items[index] = newValue;
-                this.emitUpdate(index, newValue, params);
-            }
-            // found
-            return true;
-        }
-        return false;
     }
 
     update(item, updateParams = null, previousCallback = null) {

src/observable/list/common.js

@@ -0,0 +1,32 @@
+/*
+Copyright 2020 Bruno Windels <bruno@windels.cloud>
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+/* inline update of item in collection backed by array, without replacing the preexising item */
+export function findAndUpdateInArray(predicate, array, observable, updater) {
+    const index = array.findIndex(predicate);
+    if (index !== -1) {
+        const value = array[index];
+        // allow bailing out of sending an emit if updater determined its not needed
+        const params = updater(value);
+        if (params !== false) {
+            observable.emitUpdate(index, value, params);
+        }
+        // found
+        return true;
+    }
+    return false;
+}