feat: implement DataSource.stop()

Implement `stop` as an alias for `disconnect`. This way LB4 applications
don't have to include custom `stop` implementation in every datasource
file.

Signed-off-by: Miroslav Bajtoš <mbajtoss@gmail.com>

lib/datasource.js

@@ -2220,6 +2220,14 @@ DataSource.prototype.disconnect = function disconnect(cb) {
   return cb.promise;
 };
 
+/**
+ * An alias for `disconnect` to make the datasource a LB4 life-cycle observer.
+ * Please note that we are intentionally not providing a `start` method,
+ * because the logic for establishing connection(s) is more complex
+ * and usually started immediately from the datasoure constructor.
+ */
+DataSource.prototype.stop = DataSource.prototype.disconnect;
+
 /**
  * Copy the model from Master.
  * @param {Function} Master The model constructor

test/datasource.test.js

@@ -330,6 +330,31 @@ describe('DataSource', function() {
     });
   });
 
+  it('provides stop() API calling disconnect', function(done) {
+    const mockConnector = {
+      name: 'loopback-connector-mock',
+      initialize: function(ds, cb) {
+        ds.connector = mockConnector;
+        process.nextTick(function() {
+          cb(null);
+        });
+      },
+    };
+
+    const dataSource = new DataSource(mockConnector);
+    dataSource.on('connected', function() {
+      // DataSource is now connected
+      // connected: true, connecting: false
+      dataSource.connected.should.be.true();
+      dataSource.connecting.should.be.false();
+
+      dataSource.stop(() => {
+        dataSource.connected.should.be.false();
+        done();
+      });
+    });
+  });
+
   describe('deleteModelByName()', () => {
     it('removes the model from ModelBuilder registry', () => {
       const ds = new DataSource('ds', {connector: 'memory'});

types/datasource.d.ts

@@ -287,6 +287,9 @@ export declare class DataSource extends EventEmitter {
   // legacy callback style
   disconnect(callback: Callback): void;
 
+  // Only promise variant, callback is intentionally not described.
+  stop(): Promise<void>;
+
   ping(): Promise<void>;
   // legacy callback style
   ping(callback: Callback): void;