fix: call fsync before rename (#1134)

* fix: fsync on the file descriptor used for writing

According to the POSIX spec, one needs to call fsync on the file
descriptor used for writing, see:

https://pubs.opengroup.org/onlinepubs/9699919799/functions/fsync.html

Moreover, fail if database.db.tmp exists, since this is an indication
something related to database.db writing failed in the past and we did
not notice.

* fix: Put comment back above fsync

* fix: When database.db.tmp already exists, save it

* Add a unit test

* Prettier does not like CRLF (and I agree)

* Make the test work, now that my setup works

* Make prettier happy

* Update controller.test.ts

---------

Co-authored-by: Koen Kanters <koenkanters94@gmail.com>

src/controller/database.ts

@@ -101,9 +101,20 @@ class Database {
 
         const tmpPath = this.path + '.tmp';
 
-        fs.writeFileSync(tmpPath, lines.slice(0, -1)); // remove last newline, no effect if empty string
+        try {
+            // If there already exsits a database.db.tmp, rename it to database.db.tmp.<now>
+            const dateTmpPath = tmpPath + '.' + new Date().toISOString().replaceAll(':', '-');
+            fs.renameSync(tmpPath, dateTmpPath);
+
+            // If we got this far, we succeeded! Warn the user about this
+            logger.warning(`Found '${tmpPath}' when writing database, indicating past write failure; renamed it to '${dateTmpPath}'`, NS);
+        } catch {
+            // Nothing to catch; if the renameSync fails, we ignore that exception
+        }
+
+        const fd = fs.openSync(tmpPath, 'w');
+        fs.writeFileSync(fd, lines.slice(0, -1)); // remove last newline, no effect if empty string
         // Ensure file is on disk /~https://github.com/Koenkk/zigbee2mqtt/issues/11759
-        const fd = fs.openSync(tmpPath, 'r+');
         fs.fsyncSync(fd);
         fs.closeSync(fd);
         fs.renameSync(tmpPath, this.path);

test/controller.test.ts

@@ -2185,6 +2185,25 @@ describe('Controller', () => {
         expect(databaseContents().includes('groupID')).toBeFalsy();
     });
 
+    it('Existing database.tmp should not be overwritten', async () => {
+        const databaseTmpPath = options.databasePath + '.tmp';
+        fs.writeFileSync(databaseTmpPath, 'Hello, World!');
+
+        await controller.start();
+        await mockAdapterEvents['deviceJoined']({networkAddress: 129, ieeeAddr: '0x129'});
+        controller.createGroup(1);
+
+        // The old database.db.tmp should be gone
+        expect(fs.existsSync(databaseTmpPath)).toBeFalsy();
+
+        // There should still be a database.db.tmp.<something>
+        const dbtmp = fs.readdirSync(TEMP_PATH).filter((value) => value.startsWith('database.tmp'));
+        expect(dbtmp.length).toBe(1);
+
+        // The database.db.tmp.<something> should still have our "Hello, World!"
+        expect(fs.readFileSync(getTempFile(dbtmp[0])).toString().startsWith('Hello, World!')).toBeTruthy();
+    });
+
     it('Should create backup of databse before clearing when datbaseBackupPath is provided', async () => {
         const databaseBackupPath = getTempFile('database.backup');
         if (fs.existsSync(databaseBackupPath)) fs.unlinkSync(databaseBackupPath);