fix: webpack v4 compatibility

Author: alexander-akait

lib/Server.js

@@ -1130,10 +1130,15 @@ class Server {
           needForceShutdown = true;
 
           this.stopCallback(() => {
-            this.compiler.close(() => {
+            if (this.compiler.close) {
+              this.compiler.close(() => {
+                // eslint-disable-next-line no-process-exit
+                process.exit();
+              });
+            } else {
               // eslint-disable-next-line no-process-exit
               process.exit();
-            });
+            }
           });
         });
       });

test/server/setupExitSignals-option.test.js

@@ -37,7 +37,10 @@ describe("setupExitSignals option", () => {
       .spyOn(process.stdin, "resume")
       .mockImplementation(() => {});
     stopCallbackSpy = jest.spyOn(server, "stopCallback");
-    closeCallbackSpy = jest.spyOn(server.compiler, "close");
+
+    if (server.compiler.close) {
+      closeCallbackSpy = jest.spyOn(server.compiler, "close");
+    }
   });
 
   afterEach(async () => {
@@ -58,7 +61,10 @@ describe("setupExitSignals option", () => {
       const interval = setInterval(() => {
         if (doExit) {
           expect(stopCallbackSpy.mock.calls.length).toEqual(1);
-          expect(closeCallbackSpy.mock.calls.length).toEqual(1);
+
+          if (server.compiler.close) {
+            expect(closeCallbackSpy.mock.calls.length).toEqual(1);
+          }
 
           clearInterval(interval);