Fix performance of debug logs view

js/views/debug_log_view.js

@@ -111,8 +111,7 @@
       //   we need to scroll, but not so many that things get slow.
       const linesToShow = Math.ceil(Math.min(window.innerHeight, 2000) / 5);
       this.textarea.value = this.logText
-        .split(/\n/g)
-        .slice(0, linesToShow)
+        .split(/\n/g, linesToShow)
         .concat(['', i18n('loading')])
         .join('\n');
 

ts/logging/shared.ts

@@ -1,7 +1,6 @@
 // Copyright 2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
-import { z } from 'zod';
 import * as pino from 'pino';
 import { redactAll } from '../util/privacy';
 import { missingCaseError } from '../util/missingCaseError';
@@ -20,15 +19,40 @@ export enum LogLevel {
 
 // These match [Pino's core fields][1].
 // [1]: https://getpino.io/#/?id=usage
-const logEntrySchema = z.object({
-  level: z.nativeEnum(LogLevel),
-  msg: z.string(),
-  time: z.string().refine(value => !Number.isNaN(new Date(value).getTime())),
-});
-export type LogEntryType = z.infer<typeof logEntrySchema>;
+export type LogEntryType = Readonly<{
+  level: LogLevel;
+  msg: string;
+  time: string;
+}>;
 
-export const isLogEntry = (data: unknown): data is LogEntryType =>
-  logEntrySchema.safeParse(data).success;
+// The code below is performance sensitive since it runs for > 100k log entries
+// whenever we want to send the debug log. We can't use `zod` because it clones
+// the data on successful parse and ruins the performance.
+export const isLogEntry = (data: unknown): data is LogEntryType => {
+  if (data === null || typeof data !== 'object') {
+    return false;
+  }
+
+  const { level, msg, time } = data as Partial<LogEntryType>;
+
+  if (typeof level !== 'number') {
+    return false;
+  }
+
+  if (!LogLevel[level]) {
+    return false;
+  }
+
+  if (typeof msg !== 'string') {
+    return false;
+  }
+
+  if (typeof time !== 'string') {
+    return false;
+  }
+
+  return !Number.isNaN(new Date(time).getTime());
+};
 
 export function getLogLevelString(value: LogLevel): pino.Level {
   switch (value) {