Fixed loss of "this" identifier inside callMiddlewareInterceptor.

src/service-broker.js

@@ -394,9 +394,11 @@ class ServiceBroker {
 	 * It is necessary to keep the context of the call when using call middleware.
 	 */
 	interceptCallMiddleware(createMiddleware) {
-		return next => {
+		// We need to use ordinary function here, so "this" identifier can be bound to it later via call method.
+		return function (next) {
 			let result = null;
-			const call = createMiddleware((...args) => (result = next(...args)));
+			// Preserve "this" identifier inside intercepted middleware.
+			const call = createMiddleware.call(this, (...args) => (result = next(...args)));
 			return (...args) => {
 				const promise = call(...args);
 				if (result) promise.ctx = result.ctx;

test/integration/middlewares.spec.js

@@ -9,6 +9,18 @@ describe("Test middleware system", () => {
 			validator: false,
 			internalMiddlewares: false,
 			middlewares: [
+				{
+					call(next) {
+						return (...args) => {
+							if (this.nodeID !== broker.nodeID) {
+								throw new Error(
+									"This identifier inside call middleware is incorrect."
+								);
+							}
+							return next(...args);
+						};
+					}
+				},
 				{
 					call(next) {
 						return (actionName, params, opts) => {
@@ -56,7 +68,7 @@ describe("Test middleware system", () => {
 		beforeAll(() => broker.start());
 		afterAll(() => broker.stop());
 
-		it("The context is passed through the call middlware.", async () => {
+		it("The context is passed through the call middleware.", async () => {
 			const p = broker.call("test.testAction");
 			await expect(p).resolves.toBe("testmeta!");
 			expect(p.ctx).toBeDefined();

test/unit/service-broker.spec.js

@@ -543,6 +543,24 @@ describe("Test broker.interceptCallMiddleware", () => {
 		expect(result.ctx).toEqual({ test: "test" });
 		await expect(result).resolves.toBe("middleware-result");
 	});
+
+	it("call interceptor should preserve this identifier", async () => {
+		const testThis = "test-this";
+
+		const createTestMiddleware = function (next) {
+			return async (...args) => {
+				await next(...args);
+				// This must be equal to testThis.
+				return this;
+			};
+		};
+
+		const createInterceptedMiddleware = broker.interceptCallMiddleware(createTestMiddleware);
+
+		const result = createInterceptedMiddleware.call(testThis, () => Promise.resolve())();
+
+		await expect(result).resolves.toBe(testThis);
+	});
 });
 
 describe("Test broker.start", () => {