Use efficient filters

frontend/eslint.config.mjs

@@ -55,6 +55,25 @@ export default [
 					message: "Use replaceAll instead of replace to replace all occurrences of a substring."
 				}
 			],
+			"no-restricted-syntax": [
+				"error",
+				{
+					selector: "CallExpression[callee.property.name='splice'][arguments.length=2][arguments.1.type='Literal'][arguments.1.value=1]",
+					message: "Use `removeFromArray(array, item)` instead of manually using indexOf + splice(index, 1). Import from 'sync-client/src/utils/remove-from-array'."
+				},
+				{
+					selector: "CallExpression[callee.property.name='filter'] > ArrowFunctionExpression[body.type='BinaryExpression'][body.operator='!==']",
+					message: "Use `removeFromArray(array, item)` instead of filter(x => x !== item) for better performance. Import from 'sync-client/src/utils/remove-from-array'."
+				},
+				{
+					selector: "CallExpression[callee.property.name='filter'] > ArrowFunctionExpression > BlockStatement > ReturnStatement > BinaryExpression[operator='!==']",
+					message: "Use `removeFromArray(array, item)` instead of filter(x => { return x !== item }) for better performance. Import from 'sync-client/src/utils/remove-from-array'."
+				},
+				{
+					selector: "CallExpression[callee.property.name='filter'] > FunctionExpression[body.type='BlockStatement'] > BlockStatement > ReturnStatement > BinaryExpression[operator='!==']",
+					message: "Use `removeFromArray(array, item)` instead of filter(function(x) { return x !== item }) for better performance. Import from 'sync-client/src/utils/remove-from-array'."
+				}
+			],
 			"unused-imports/no-unused-vars": [
 				"warn",
 				{

frontend/obsidian-plugin/src/views/status-description/status-description.ts

@@ -5,13 +5,14 @@ import type {
 	NetworkConnectionStatus,
 	SyncClient
 } from "sync-client";
+import { utils } from "sync-client";
 
 export class StatusDescription {
 	private lastHistoryStats: HistoryStats | undefined;
 	private lastRemaining: number | undefined;
 	private lastConnectionState: NetworkConnectionStatus | undefined;
 
-	private statusChangeListeners: (() => unknown)[] = [];
+	private readonly statusChangeListeners: (() => unknown)[] = [];
 
 	public constructor(private readonly syncClient: SyncClient) {
 		void this.updateConnectionState();
@@ -46,9 +47,7 @@ export class StatusDescription {
 		this.statusChangeListeners.push(listener);
 	}
 	public removeStatusChangeListener(listener: () => unknown): void {
-		this.statusChangeListeners = this.statusChangeListeners.filter(
+		utils.removeFromArray(this.statusChangeListeners, listener);
-			(l) => l !== listener
-		);
 	}
 
 	public renderStatusDescription(container: HTMLElement): void {

frontend/sync-client/src/index.ts

@@ -5,6 +5,7 @@ import { slowWebSocketFactory } from "./utils/debugging/slow-web-socket-factory"
 import { getRandomColor } from "./utils/get-random-color";
 import { lineAndColumnToPosition } from "./utils/line-and-column-to-position";
 import { positionToLineAndColumn } from "./utils/position-to-line-and-column";
+import { removeFromArray } from "./utils/remove-from-array";
 
 export {
 	SyncType,
@@ -43,5 +44,6 @@ export const utils = {
 	getRandomColor,
 	positionToLineAndColumn,
 	lineAndColumnToPosition,
-	awaitAll
+	awaitAll,
+	removeFromArray
 };

frontend/sync-client/src/persistence/database.ts

@@ -2,6 +2,7 @@ import type { Logger } from "../tracing/logger";
 import { EMPTY_HASH } from "../utils/hash";
 import { CoveredValues } from "../utils/data-structures/min-covered";
 import { awaitAll } from "../utils/await-all";
+import { removeFromArray } from "../utils/remove-from-array";
 
 export type VaultUpdateId = number;
 export type DocumentId = string;
@@ -93,6 +94,7 @@ export class Database {
 	public get resolvedDocuments(): DocumentRecord[] {
 		const paths = new Map<string, DocumentRecord[]>();
 		this.documents
+			// eslint-disable-next-line no-restricted-syntax -- Type narrowing, not removing a specific item
 			.filter(({ metadata }) => metadata !== undefined)
 			.forEach((record) =>
 				paths.set(record.relativePath, [
@@ -151,12 +153,12 @@ export class Database {
 			return;
 		}
 
-		entry.updates = entry.updates.filter((update) => update !== promise);
+		removeFromArray(entry.updates, promise);
 		// No need to save as Promises don't get serialized
 	}
 
 	public removeDocument(find: DocumentRecord): void {
-		this.documents = this.documents.filter((document) => document !== find);
+		removeFromArray(this.documents, find);
 		this.saveInTheBackground();
 	}
 

frontend/sync-client/src/persistence/settings.ts

@@ -1,6 +1,7 @@
 import type { Logger } from "../tracing/logger";
 import { awaitAll } from "../utils/await-all";
 import { Lock } from "../utils/data-structures/locks";
+import { removeFromArray } from "../utils/remove-from-array";
 
 export interface SyncSettings {
 	remoteUri: string;
@@ -69,10 +70,7 @@ export class Settings {
 	public removeOnSettingsChangeListener(
 		listener: (settings: SyncSettings, oldSettings: SyncSettings) => unknown
 	): void {
-		const index = this.onSettingsChangeHandlers.indexOf(listener);
+		removeFromArray(this.onSettingsChangeHandlers, listener);
-		if (index !== -1) {
-			this.onSettingsChangeHandlers.splice(index, 1);
-		}
 	}
 
 	public async setSetting<T extends keyof SyncSettings>(

frontend/sync-client/src/services/websocket-manager.ts

@@ -8,6 +8,7 @@ import { createPromise } from "../utils/create-promise";
 import type { WebSocketVaultUpdate } from "./types/WebSocketVaultUpdate";
 import { awaitAll } from "../utils/await-all";
 import { WEBSOCKET_DISCONNECT_TIMEOUT_IN_S } from "../consts";
+import { removeFromArray } from "../utils/remove-from-array";
 
 export class WebSocketManager {
 	private readonly webSocketStatusChangeListeners: ((
@@ -227,12 +228,10 @@ export class WebSocketManager {
 						);
 					})
 					.finally(() => {
-						const index = this.outstandingPromises.indexOf(
+						removeFromArray(
+							this.outstandingPromises,
 							messageHandlingPromise
 						);
-						if (index !== -1) {
-							void this.outstandingPromises.splice(index, 1); // ignore the returned promise
-						}
 					});
 
 				void this.outstandingPromises.push(messageHandlingPromise); // ignore the returned promise

frontend/sync-client/src/sync-operations/file-change-notifier.ts

@@ -1,4 +1,5 @@
 import type { RelativePath } from "../persistence/database";
+import { removeFromArray } from "../utils/remove-from-array";
 
 export class FileChangeNotifier {
 	private readonly listeners: ((filePath: RelativePath) => unknown)[] = [];
@@ -12,10 +13,7 @@ export class FileChangeNotifier {
 	public removeFileChangeListener(
 		listener: (filePath: RelativePath) => unknown
 	): void {
-		const index = this.listeners.indexOf(listener);
+		removeFromArray(this.listeners, listener);
-		if (index !== -1) {
-			this.listeners.splice(index, 1);
-		}
 	}
 
 	public notifyOfFileChange(filePath: RelativePath): void {

frontend/sync-client/src/sync-operations/syncer.ts

@@ -444,11 +444,13 @@ export class Syncer {
 				);
 				if (originalFile !== undefined) {
 					// `originalFile` hasn't been deleted but it got moved instead
+					/* eslint-disable no-restricted-syntax -- Comparing by property, not direct equality */
 					locallyPossiblyDeletedFiles =
 						locallyPossiblyDeletedFiles.filter(
 							(item) =>
 								item.relativePath !== originalFile.relativePath
 						);
+					/* eslint-enable no-restricted-syntax */
 
 					this.logger.debug(
 						`Document '${originalFile.relativePath}' was not found under its current path in the database but was found under a different path (${relativePath}), scheduling sync to move it`

frontend/sync-client/src/tracing/logger.ts

@@ -1,4 +1,5 @@
 import { MAX_LOG_MESSAGE_COUNT } from "../consts";
+import { removeFromArray } from "../utils/remove-from-array";
 
 export enum LogLevel {
 	DEBUG = "DEBUG",
@@ -63,10 +64,7 @@ export class Logger {
 	public removeOnMessageListener(
 		listener: (message: LogLine) => unknown
 	): void {
-		const index = this.onMessageListeners.indexOf(listener);
+		removeFromArray(this.onMessageListeners, listener);
-		if (index !== -1) {
-			this.onMessageListeners.splice(index, 1);
-		}
 	}
 
 	public reset(): void {

frontend/sync-client/src/tracing/sync-history.ts

@@ -4,6 +4,7 @@ import {
 } from "../consts";
 import type { RelativePath } from "../persistence/database";
 import type { Logger } from "./logger";
+import { removeFromArray } from "../utils/remove-from-array";
 
 export interface SyncCreateDetails {
 	type: SyncType.CREATE;
@@ -68,7 +69,7 @@ export interface HistoryStats {
 }
 
 export class SyncHistory {
-	private _entries: HistoryEntry[] = [];
+	private readonly _entries: HistoryEntry[] = [];
 
 	private readonly syncHistoryUpdateListeners: ((
 		status: HistoryStats
@@ -99,7 +100,7 @@ export class SyncHistory {
 
 		const candidate = this.findSimilarRecentUpdateEntry(historyEntry);
 		if (candidate !== undefined) {
-			this._entries = this._entries.filter((e) => e !== candidate);
+			removeFromArray(this._entries, candidate);
 		}
 
 		// Insert the entry at the beginning
@@ -122,10 +123,7 @@ export class SyncHistory {
 	public removeSyncHistoryUpdateListener(
 		listener: (stats: HistoryStats) => unknown
 	): void {
-		const index = this.syncHistoryUpdateListeners.indexOf(listener);
+		removeFromArray(this.syncHistoryUpdateListeners, listener);
-		if (index !== -1) {
-			this.syncHistoryUpdateListeners.splice(index, 1);
-		}
 	}
 
 	public reset(): void {

frontend/sync-client/src/utils/globs-to-regexes.ts

@@ -2,17 +2,20 @@ import { makeRe } from "minimatch";
 import type { Logger } from "../tracing/logger";
 
 export function globsToRegexes(globs: string[], logger: Logger): RegExp[] {
-	return globs
+	return (
-		.map((pattern) => {
+		globs
-			const result = makeRe(pattern, {
+			.map((pattern) => {
-				dot: true
+				const result = makeRe(pattern, {
-			});
+					dot: true
-			if (result === false) {
+				});
-				logger.warn(
+				if (result === false) {
-					`Failed to parse ${pattern}' as a glob pattern, skipping it`
+					logger.warn(
-				);
+						`Failed to parse ${pattern}' as a glob pattern, skipping it`
-			}
+					);
-			return result;
+				}
-		})
+				return result;
-		.filter((pattern) => pattern !== false);
+			})
+			// eslint-disable-next-line no-restricted-syntax -- Filtering out false values, not removing a specific item
+			.filter((pattern) => pattern !== false)
+	);
 }

frontend/sync-client/src/utils/remove-from-array.ts

@@ -0,0 +1,17 @@
+/**
+ * Efficiently removes a specific item from an array by modifying it in place.
+ * This is more efficient than using `.filter(item => item !== toRemove)` as it avoids creating a new array
+ *
+ * @param array The array to modify
+ * @param item The item to remove
+ * @returns true if the item was found and removed, false otherwise
+ */
+export function removeFromArray<T>(array: T[], item: T): boolean {
+    const index = array.indexOf(item);
+    if (index !== -1) {
+        // eslint-disable-next-line no-restricted-syntax -- This is the implementation of the helper itself
+        array.splice(index, 1);
+        return true;
+    }
+    return false;
+}

frontend/test-client/src/agent/mock-agent.ts

@@ -15,7 +15,7 @@ export class MockAgent extends MockClient {
 	private readonly pendingActions: Promise<unknown>[] = [];
 
 	// The renamed file finding algorithm isn't too smart so we can't both update and rename the same file
-	private doNotTouchWhileOffline: string[] = [];
+	private readonly doNotTouchWhileOffline: string[] = [];
 
 	public constructor(
 		initialSettings: Partial<SyncSettings>,
@@ -54,10 +54,10 @@ export class MockAgent extends MockClient {
 			);
 
 			if (historyEntry) {
-				this.doNotTouchWhileOffline =
+				utils.removeFromArray(
-					this.doNotTouchWhileOffline.filter(
+					this.doNotTouchWhileOffline,
-						(file) => file !== historyEntry[1]
+					historyEntry[1]
-					);
+				);
 			}
 			switch (logLine.level) {
 				case LogLevel.ERROR: