fix(core): Always derive instanceId from the encryption key (no-changlog) (#7501)

This was the expected behavior, until I changed it in
https://github.com/n8n-io/n8n/pull/7471

packages/core/test/InstanceSettings.test.ts

@@ -0,0 +1,61 @@
+import fs from 'fs';
+import { InstanceSettings } from '@/InstanceSettings';
+
+describe('InstanceSettings', () => {
+	process.env.N8N_USER_FOLDER = '/test';
+
+	describe('If the settings file exists', () => {
+		beforeEach(() => {
+			jest.spyOn(fs, 'existsSync').mockReturnValue(true);
+		});
+
+		it('should load settings from the file', () => {
+			jest.spyOn(fs, 'readFileSync').mockReturnValue(JSON.stringify({ encryptionKey: 'test_key' }));
+			const settings = new InstanceSettings();
+			expect(settings.encryptionKey).toEqual('test_key');
+			expect(settings.instanceId).toEqual(
+				'6ce26c63596f0cc4323563c529acfca0cccb0e57f6533d79a60a42c9ff862ae7',
+			);
+		});
+
+		it('should throw error if settings file is not valid JSON', () => {
+			jest.spyOn(fs, 'readFileSync').mockReturnValue('{"encryptionKey":"test_key"');
+			expect(() => new InstanceSettings()).toThrowError();
+		});
+	});
+
+	describe('If the settings file does not exist', () => {
+		it('should create a new settings file', () => {
+			jest.spyOn(fs, 'existsSync').mockReturnValue(false);
+			const mkdirSpy = jest.spyOn(fs, 'mkdirSync').mockReturnValue('');
+			const writeFileSpy = jest.spyOn(fs, 'writeFileSync').mockReturnValue();
+			const settings = new InstanceSettings();
+			expect(settings.encryptionKey).not.toEqual('test_key');
+			expect(mkdirSpy).toHaveBeenCalledWith('/test/.n8n');
+			expect(writeFileSpy).toHaveBeenCalledWith(
+				'/test/.n8n/config',
+				expect.stringContaining('"encryptionKey":'),
+				'utf-8',
+			);
+		});
+
+		it('should pick up the encryption key from env var N8N_ENCRYPTION_KEY', () => {
+			process.env.N8N_ENCRYPTION_KEY = 'env_key';
+			jest.spyOn(fs, 'existsSync').mockReturnValue(false);
+			const mkdirSpy = jest.spyOn(fs, 'mkdirSync').mockReturnValue('');
+			const writeFileSpy = jest.spyOn(fs, 'writeFileSync').mockReturnValue();
+			const settings = new InstanceSettings();
+			expect(settings.encryptionKey).toEqual('env_key');
+			expect(settings.instanceId).toEqual(
+				'2c70e12b7a0646f92279f427c7b38e7334d8e5389cff167a1dc30e73f826b683',
+			);
+			expect(settings.encryptionKey).not.toEqual('test_key');
+			expect(mkdirSpy).toHaveBeenCalledWith('/test/.n8n');
+			expect(writeFileSpy).toHaveBeenCalledWith(
+				'/test/.n8n/config',
+				expect.stringContaining('"encryptionKey":'),
+				'utf-8',
+			);
+		});
+	});
+});