From 731f3808ed1bf2d839b408a4ac43c66ad859885a Mon Sep 17 00:00:00 2001
From: Kristóf Marussy <kristof@marussy.com>
Date: Sun, 26 Dec 2021 13:08:28 +0100
Subject: refactor: Improved config reloading

If we watch the containing directory, we can use inotify instead of stat
polling.
---
 packages/main/src/index.ts | 45 ++++++++++++++++++++++++++++++++++-----------
 1 file changed, 34 insertions(+), 11 deletions(-)

(limited to 'packages/main/src')

diff --git a/packages/main/src/index.ts b/packages/main/src/index.ts
index a79a6e2..605c17c 100644
--- a/packages/main/src/index.ts
+++ b/packages/main/src/index.ts
@@ -25,8 +25,13 @@ import {
   ipcMain,
   nativeTheme,
 } from 'electron';
-import { readFileSync, watchFile } from 'fs';
-import { readFile, stat, writeFile } from 'fs/promises';
+import { readFileSync } from 'fs';
+import {
+  readFile,
+  stat,
+  watch,
+  writeFile,
+} from 'fs/promises';
 import { autorun } from 'mobx';
 import {
   applySnapshot,
@@ -121,7 +126,9 @@ nativeTheme.on('updated', () => {
   store.setShouldUseDarkColors(nativeTheme.shouldUseDarkColors);
 });
 
-const configPath = join(app.getPath('userData'), 'config.json');
+const userDataDir = app.getPath('userData');
+const configFileName = 'config.json';
+const configPath = join(userDataDir, configFileName);
 let loadingConfig = false;
 let savingConfig = false;
 let configMtime: Date | null = null;
@@ -175,21 +182,37 @@ onSnapshot(store.config, (snapshot) => {
   }
 });
 
-async function initializeConfig(): Promise<void> {
-  await loadConfig();
-  watchFile(configPath, ({ mtime }) => {
+async function watchConfig(): Promise<void> {
+  const configWatcher = watch(userDataDir, {
+    persistent: false,
+  });
+  for await (const { eventType, filename } of configWatcher) {
+    if (eventType !== 'change'
+      && (filename !== configFileName || filename !== null)) {
+      continue;
+    }
+    let mtime: Date;
+    try {
+      const stats = await stat(configPath);
+      mtime = stats.mtime;
+    } catch (err) {
+      if ((err as NodeJS.ErrnoException).code === 'ENOENT') {
+        continue;
+      }
+      throw err;
+    }
     if (!savingConfig && (configMtime === null || mtime > configMtime)) {
-      loadConfig().catch((err) => {
-        console.error('Failed to reload config', configPath, err);
-      });
+      await loadConfig();
       configMtime = mtime;
       console.log('Reloaded config', configPath);
     }
-  });
+  }
 }
 
-initializeConfig().catch((err) => {
+loadConfig().catch((err) => {
   console.error('Failed to load config', configPath, err);
+}).then(watchConfig).catch((err) => {
+  console.error('Error when watching for config changes', configPath, err);
 });
 
 const rendererBaseUrl = getResourceUrl('../renderer/');
-- 
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