From b971de0717a66ae6085670fe5d3a469e236a9446 Mon Sep 17 00:00:00 2001
From: Kristóf Marussy <kristof@marussy.com>
Date: Tue, 26 Apr 2022 16:55:57 +0200
Subject: refactor: config file saving and debugging
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Reduce the number of dependencies and the amount of code running in a
security sensitive context.

Instead of a deep comparison, we just compare the serialized versions
of the config files.

Signed-off-by: Kristóf Marussy <kristof@marussy.com>
---
 packages/main/src/reactions/synchronizeConfig.ts | 40 +++++++++++++-----------
 1 file changed, 21 insertions(+), 19 deletions(-)

(limited to 'packages/main/src/reactions/synchronizeConfig.ts')

diff --git a/packages/main/src/reactions/synchronizeConfig.ts b/packages/main/src/reactions/synchronizeConfig.ts
index 7e366e2..247c2e2 100644
--- a/packages/main/src/reactions/synchronizeConfig.ts
+++ b/packages/main/src/reactions/synchronizeConfig.ts
@@ -18,7 +18,6 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-import deepEqual from 'deep-equal';
 import { debounce } from 'lodash-es';
 import { reaction } from 'mobx';
 
@@ -32,36 +31,38 @@ const DEFAULT_CONFIG_DEBOUNCE_TIME_MS = 1000;
 
 const log = getLogger('synchronizeConfig');
 
+export function serializeConfig(config: Config): string {
+  return `${JSON.stringify(config, undefined, 2)}\n`;
+}
+
 export default async function synchronizeConfig(
   sharedStore: SharedStore,
   repository: ConfigRepository,
   debounceTime: number = DEFAULT_CONFIG_DEBOUNCE_TIME_MS,
 ): Promise<Disposer> {
-  let lastConfigOnDisk: Config | undefined;
+  let lastConfigOnDisk: string | undefined;
 
-  async function writeConfig(): Promise<void> {
-    const { config } = sharedStore;
-    await repository.writeConfig(config);
-    lastConfigOnDisk = config;
+  async function writeConfig(serializedConfig: string): Promise<void> {
+    await repository.writeConfig(serializedConfig);
+    lastConfigOnDisk = serializedConfig;
   }
 
   async function readConfig(): Promise<boolean> {
     const result = await repository.readConfig();
     if (result.found) {
+      const { contents } = result;
       try {
         // This cast is unsound if the config file is invalid,
         // but we'll throw an error in the end anyways.
-        sharedStore.loadConfig(result.data as Config);
+        const data = JSON.parse(contents) as Config;
+        sharedStore.loadConfig(data);
       } catch (error) {
-        log.error('Failed to apply config snapshot', result.data, error);
+        log.error('Failed to apply config snapshot', contents, error);
         return true;
       }
-      lastConfigOnDisk = sharedStore.config;
-      // We can't use `comparer.structural` from `mobx`, because
-      // it handles missing values and `undefined` values differently,
-      // but JSON is unable to distinguish them.
-      if (!deepEqual(result.data, lastConfigOnDisk, { strict: true })) {
-        await writeConfig();
+      lastConfigOnDisk = serializeConfig(sharedStore.config);
+      if (contents !== lastConfigOnDisk) {
+        await writeConfig(lastConfigOnDisk);
       }
     }
     return result.found;
@@ -69,16 +70,17 @@ export default async function synchronizeConfig(
 
   if (!(await readConfig())) {
     log.info('Config file was not found');
-    await writeConfig();
+    const serializedConfig = serializeConfig(sharedStore.config);
+    await writeConfig(serializedConfig);
     log.info('Created config file');
   }
 
   const disposeReaction = reaction(
     () => sharedStore.config,
-    debounce((config) => {
-      // We can compare snapshots by reference, since it is only recreated on store changes.
-      if (!deepEqual(config, lastConfigOnDisk, { strict: true })) {
-        writeConfig().catch((error) => {
+    debounce(() => {
+      const serializedConfig = serializeConfig(sharedStore.config);
+      if (serializedConfig !== lastConfigOnDisk) {
+        writeConfig(serializedConfig).catch((error) => {
           log.error('Failed to write config on config change', error);
         });
       }
-- 
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