feat($interceptor): Added support handling request cancellations

If the user unsubscribes while the request is still being handled, interceptor can now implement
`onUnsubscribe` method to perform any cleaup operations

README.md

@@ -93,6 +93,13 @@ Basically, an interceptor has the option to selectively implement one more of th
 Here is the interceptor interface that details which method is invoked in what part of the flow
 
 ```ts
+import { Request, RequestOptionsArgs } from '@angular/http';
+import { Observable } from 'rxjs/Rx';
+
+import { InterceptorRequest } from './interceptor-request';
+import { InterceptorRequestOptionsArgs } from './interceptor-request-options-args';
+import { InterceptorResponseWrapper } from './interceptor-response-wrapper';
+
 /**
  * Represents an intermediary in the interceptor chain that intercept both HTTP request & response flow
  *
@@ -101,52 +108,75 @@ Here is the interceptor interface that details which method is invoked in what p
  * 2. Modify the response along the chain
  * 3. Intercept errors; Can chose to cascade/generate responses
  * 4. Short circuit complete request flow dynamically based on the dynamic conditions without affecting the actual controller/service
- * 5. Ability to perform custom logic; such as redirecting the users to login page, if the server returns 401, transparantly without polluting all your services
+ * 5. Ability to perform custom logic; such as redirecting the users to login page,\
+ *  if the server returns 401, transparantly without polluting all your services
  *
- * NOTE: Never store any data that's request specific as properties on the Interceptor implementation, as the interceptor instance is shared across all http requests within the application. Instead use `InterceptorRequestOptionsArgs.sharedData` (or) `InterceptorRequest.sharedData` (or) `InterceptorResponseWrapper.sharedData` as request private storage
+ * NOTE: Never store any data that's request specific as properties on the Interceptor implementation,
+ * as the interceptor instance is shared across all http requests within the application.
+ * Instead use `InterceptorRequestOptionsArgs.sharedData` (or) `InterceptorRequest.sharedData` (or) `InterceptorResponseWrapper.sharedData`
+ * as request private storage
  */
 export interface Interceptor {
 
   /**
-   * Invoked once for each of the interceptors in the chain; in the order defined in the chain, unless any of the earlier interceptors asked to complete the flow/return response/throw error to subscriber
+   * Invoked once for each of the interceptors in the chain; in the order defined in the chain,\
+   *  unless any of the earlier interceptors asked to complete the flow/return response/throw error to subscriber
    *
    * Gives the ability to transform the request
    */
-  beforeRequest?(request: InterceptorRequest, interceptorStep?: number): Observable<InterceptorRequest> | InterceptorRequest | void;
+  beforeRequest?(request: InterceptorRequest, interceptorStep: number): Observable<InterceptorRequest> | InterceptorRequest | void;
 
   /**
-   * Invoked once for each of the interceptors in the chain; in the reverse order of chain, unless any of the earlier interceptors asked to complete the flow/return response/throw error to subscriber
-   *
-   * Gives the ability to transform the response in each of the following scenarios
-   * 1. For normal response flow; i.e no errors along the chain/no interceptor wanted to short the circuit
-   * 2. One of the interceptor indicated to short the circuit & one of the earlier interceptor in chain returned a InterceptorResponseWrapper when its onShortCircuit(..) method is invoked
-   * 3. One of the interceptor threw error & one of the earlier interceptor in chain returned a `InterceptorResponseWrapper` when its onErr(..) method is invoked
+   * Invoked once for each of the interceptors in the chain; in the reverse order of chain,\
+   *  unless any of the earlier interceptors asked to complete the flow/short the circuit/return response/throw error to subscriber
    *
    * Set any of the following properties of `InterceptorResponseWrapper` to be able to change the way response to sent to subscriber
    * a. `forceReturnResponse` - will send the `Response` to the subscriber directly by skipping all intermediate steps
    * b. `forceRequestCompletion` - will send completion event, so that complete(..) will be invoked on the subscriber
    *
-   * You can know if the respons is generated by short circuit handler/err handler, by looking at the `responseGeneratedByShortCircuitHandler` & `responseGeneratedByErrHandler` flags
+   * You can know if the respons is generated by short circuit handler/err handler,\
+   *  by looking at the `responseGeneratedByShortCircuitHandler` & `responseGeneratedByErrHandler` flags
    */
-  onResponse?(response: InterceptorResponseWrapper, interceptorStep?: number): Observable<InterceptorResponseWrapper> | InterceptorResponseWrapper | void;
+  onResponse?(response: InterceptorResponseWrapper,
+    interceptorStep: number): Observable<InterceptorResponseWrapper> | InterceptorResponseWrapper | void;
 
   /**
-   * Invoked once for each of the interceptors in the chain; in the reverse order of chain, if any of the `beforeRequest(..)` responded by setting `shortCircuitAtCurrentStep` property of `InterceptorRequest`
+   * Invoked once for each of the interceptors in the chain; in the reverse order of chain,\
+   *  if any of the `beforeRequest(..)` responded by setting `shortCircuitAtCurrentStep` property of `InterceptorRequest`
    * Use this method to generate a response that gets sent to the subscriber.
-   * If you return nothing, the `onShortCircuit(..) will be cascaded along the interceptor chain
-   * If you return an Observable<InterceptorResponseWrapper> | InterceptorResponseWrapper, this rest of the flow would be continued on `onResponse(..)` instead of `onErr(..)` on the next interceptor in the chain & the final result would be sent to the subscriber via next(..) callback
-   * If no `onShortCircuit(..)` handlers before this handler returns any response, an error will be thrown back to the subscriber
+   * The result returned by the first interceptor(last in the response flow) would be sent to the subscriber via next(..) callback
+   * If no `onShortCircuit(..)` handlers before this handler returns any response/force request to complete
+   * An error will be thrown back to the subscriber
    */
-  onShortCircuit?(response: InterceptorResponseWrapper, interceptorStep?: number): Observable<InterceptorResponseWrapper> | InterceptorResponseWrapper | void;
+  onShortCircuit?(response: InterceptorResponseWrapper,
+    interceptorStep: number): Observable<InterceptorResponseWrapper> | InterceptorResponseWrapper | void;
 
   /**
    * Invoked when the flow encounters any error along the interceptor chain.
-   * Use this method to generate a response that gets sent to the subscriber.
+   * Use this method to generate a response that gets sent to the subscriber. `response.err` will contain th actual error
    * If you return nothing, the `onErr(..) will be cascaded along the interceptor chain
-   * If you return an Observable<InterceptorResponseWrapper> | InterceptorResponseWrapper, this rest of the flow would be continued on `onResponse(..)` instead of `onErr(..)` on the next interceptor in the chain & the final result would be sent to the subscriber via next(..) callback
-   * If no `onErr(..)` handlers before this handler returns any response, the error will be thrown back to the subscriber
+   * If you return an Observable<InterceptorResponseWrapper> | InterceptorResponseWrapper
+   *  & the final interceptor in the result chain (first interceptor) would be sent to the subscriber via next(..) callback
+   * If no `onErr(..)` handlers before the first interceptor (last in the response cycle)
+   * handler returns any response, the error will be thrown back to the subscriber
+   */
+  onErr?(response: InterceptorResponseWrapper,
+    interceptorStep: number): Observable<InterceptorResponseWrapper> | InterceptorResponseWrapper | void;
+
+  /**
+   * Invoked when any one in the interceptor chain forces request completion/return response/error
+   * Use this method to perform operations that should be performed irrespective of what the other interceptors in the chain does
+   * such as stopping progress bar/logging
+   */
+  onForceCompleteOrForceReturn?(response: InterceptorResponseWrapper,
+    interceptorStep: number): void;
+
+  /**
+   * Invoked when the user unsubscribes while the request is still being handled
+   * Use this method to perform cleanup operations that should be performed when the request is cancelled by user
+   * such as stopping progress bar
    */
-  onErr?(err: any): Observable<InterceptorResponseWrapper> | InterceptorResponseWrapper | void;
+  onUnsubscribe?(interceptorStep: number, url: string | Request, options?: RequestOptionsArgs | InterceptorRequestOptionsArgs): void;
 
 }
 ```

src/interceptor-service.ts

@@ -1,3 +1,4 @@
+import { Subscriber } from 'rxjs/Rx';
 import { InterceptorRequestInternal } from './interceptor-request-internal';
 import {
   ConnectionBackend,
@@ -50,7 +51,7 @@ import { RealResponseObservableTransformer } from './real-response-observable-tr
  */
 export class InterceptorService extends Http {
 
-  private interceptors: Array<Interceptor>;
+  private interceptors: Interceptor[];
   private _realResponseObservableTransformer: RealResponseObservableTransformer;
 
   constructor(backend: ConnectionBackend, defaultOptions: RequestOptions) {
@@ -75,7 +76,19 @@ export class InterceptorService extends Http {
       .options(interceptorOptions)
       .sharedData(interceptorOptions.sharedData || {})
       .build();
-    return this.httpRequest(request);
+    return Observable.create(function (observer: Subscriber<Response>) {
+      const subscription = this.httpRequest(request).subscribe(
+        (response: Response) => observer.next(response),
+        (e: Error) => observer.error(e),
+        () => observer.complete()
+      );
+      observer.add(() => {
+        this.interceptors.reverse().forEach((interceptor: Interceptor, index: number) => {
+          interceptor.onUnsubscribe(index, url, options);
+        });
+      });
+      return this;
+    });
   }
 
   /**

src/interceptor.ts

@@ -1,6 +1,8 @@
+import { Request, RequestOptionsArgs } from '@angular/http';
 import { Observable } from 'rxjs/Rx';
 
 import { InterceptorRequest } from './interceptor-request';
+import { InterceptorRequestOptionsArgs } from './interceptor-request-options-args';
 import { InterceptorResponseWrapper } from './interceptor-response-wrapper';
 
 /**
@@ -68,10 +70,17 @@ export interface Interceptor {
 
   /**
    * Invoked when any one in the interceptor chain forces request completion/return response/error
-   * Use this method to perform opeations that should be performed irrespective of what the interceptors in the chain want
+   * Use this method to perform operations that should be performed irrespective of what the other interceptors in the chain does
    * such as stopping progress bar/logging
    */
   onForceCompleteOrForceReturn?(response: InterceptorResponseWrapper,
     interceptorStep: number): void;
 
+  /**
+   * Invoked when the user unsubscribes while the request is still being handled
+   * Use this method to perform cleanup operations that should be performed when the request is cancelled by user
+   * such as stopping progress bar
+   */
+  onUnsubscribe?(interceptorStep: number, url: string | Request, options?: RequestOptionsArgs | InterceptorRequestOptionsArgs): void;
+
 }