How to make an angular module to ignore http interceptor added in a core module

Per this suggestion on GitHub, we've implemented a simple header to identify requests that shouldn't be intercepted. In the interceptor:

export const InterceptorSkipHeader = 'X-Skip-Interceptor';

@Injectable()
export class SkippableInterceptor implements HttpInterceptor {

  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    if (req.headers.has(InterceptorSkipHeader)) {
      const headers = req.headers.delete(InterceptorSkipHeader);
      return next.handle(req.clone({ headers }));
    }

    ...  // intercept
  }

}

Then whenever you want to skip the interception for a particular request:

const headers = new HttpHeaders().set(InterceptorSkipHeader, '');

this.httpClient
    .get<ResponseType>(someUrl, { headers })
    ...

Note that with this method the service, not the interceptor, is choosing when the interceptor's logic gets applied; this means that the services must "know" something about the interceptors in your application. Depending on your use case, it might be better to make the interceptors decide when to apply the logic.

As of Angular 12, this can be accomplished with the HttpContext property for an HttpRequest!

This approach is nice because it doesn't require any logic for stripping headers, and can be done on a per-request basis.

export const DISABLE_GLOBAL_EXCEPTION_HANDLING = new HttpContextToken<boolean>(() => false);

@Injectable()
export class ErrorInterceptor implements HttpInterceptor {

    intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        if (this.ignoreErrorHandling(request)) {
            return next.handle(request);
        }

        return next.handle(request).pipe(
            catchError((error) => {
                // normal intercepting logic
                return throwError(() => error);
            }),
        );

    private ignoreErrorHandling(request: HttpRequest<any>) {
        return request.context.get(DISABLE_GLOBAL_EXCEPTION_HANDLING);
    }
}

An individual request can be disabled by adding the token:

this.httpClient.get<ResponseType>(`/api`, {
    context: new HttpContext().set(DISABLE_GLOBAL_EXCEPTION_HANDLING, true),
});

In order to bypass all interceptors we can use HttpBackend as @deg suggested.

In other cases we can create HttpClient factory that will allows us to exclude interceptors from the interceptors chain:

import { createHttpClient } from './http-client.factory';
// ...

@Injectable({
  providedIn: 'root'
})
export class TodosApiService {
  http = createHttpClient(this.injector, [Interceptor2]);
//                                        ^^^^^^^^^^^^
//                                    Interceptors to exclude

  constructor(private injector: Injector) { }

  getTodo() {
    // Interceptor2 will be bypassed
    return this.http.get('https://jsonplaceholder.typicode.com/todos')
  }
}

Ng-run Example

Note that you can reuse this logic by creating base class:

@Injectable()
export class BasicHttpClient {
  protected http = createHttpClient(this.injector, [Interceptor2]);

  constructor(private injector: Injector) { }
}

@Injectable({ providedIn: 'root' })
export class TodosApiService extends BaseHttpClient {

  getTodo() {
    // Interceptor2 will be bypassed
    return this.http.get('https://jsonplaceholder.typicode.com/todos')
  }
}

http-client.factory.ts

import {
  HTTP_INTERCEPTORS,
  HttpBackend,
  HttpClient,
  HttpEvent,
  HttpHandler,
  HttpInterceptor,
  HttpRequest,
} from '@angular/common/http';
import { Observable } from 'rxjs';
import { Injector, Type } from '@angular/core';

class HttpInterceptorHandler implements HttpHandler {
  constructor(private next: HttpHandler, private interceptor: HttpInterceptor) {}

  handle(req: HttpRequest<any>): Observable<HttpEvent<any>> {
    return this.interceptor.intercept(req, this.next);
  } 
}

class HttpInterceptingHandler implements HttpHandler {
  private chain: HttpHandler | null = null;

  constructor(
    private backend: HttpBackend,
    private injector: Injector,
    private interceptorsToExclude: Type<HttpInterceptor>[],
    private intercept?: (req: HttpRequest<any>) => HttpRequest<any>
  ) {}

  handle(req: HttpRequest<any>): Observable<HttpEvent<any>> {
    if (this.intercept) {
      req = this.intercept(req);
    }

    if (this.chain === null) {
      const interceptors = this.injector
        .get(HTTP_INTERCEPTORS, [])
        .filter(
          interceptor => !this.interceptorsToExclude.some(interceptorType => interceptor instanceof interceptorType)
        );

      this.chain = interceptors.reduceRight(
        (next, interceptor) => new HttpInterceptorHandler(next, interceptor),
        this.backend
      );
    }
    return this.chain.handle(req);
  }
}

export function createHttpClient(
  injector: Injector,
  excludedInterceptors: Type<HttpInterceptor>[],
  intercept?: (req: HttpRequest<any>) => HttpRequest<any>
) {
  return new HttpClient(
    new HttpInterceptingHandler(injector.get(HttpBackend), injector, excludedInterceptors, intercept)
  );
}

If the HttpClient is being used within a dependency outside of your control (such as a 3rd party lib) you can still use the HttpContextTokens that were added in Angular v12 by using a HttpClient factory provider. You can scope this to individual modules or components using the providers array:

disable-interceptor.handler.ts

import { HttpContextToken, HttpHandler, HttpRequest } from '@angular/common/http';
import { Injectable } from '@angular/core';

export const DISABLE_INTERCEPTORS = new HttpContextToken<boolean>(() => false);

@Injectable()
export class DisableInterceptorHandler extends HttpHandler {
  constructor(private httpHandler: HttpHandler) {
    super();
  }

  handle(req: HttpRequest<unknown>) {
    return this.httpHandler.handle(
      req.clone({
        context: req.context.set(DISABLE_INTERCEPTORS, true),
      }),
    );
  }
}

Provide the handler in either your component/module/service/whatever providers array

providers: [
  DisableInterceptorHandler,
  {
    provide: HttpClient,
    useFactory: (handler: DisableInterceptorHandler) => new HttpClient(handler),
    deps: [DisableInterceptorHandler],
  },
],

Respect the HttpContextToken in your interceptor!

import { HttpErrorResponse, HttpEvent, HttpHandler, HttpInterceptor, HttpRequest } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { Observable, throwError } from 'rxjs';
import { catchError } from 'rxjs/operators';
import { DISABLE_INTERCEPTORS } from './disable-interceptor.handler';

@Injectable()
export class AuthenticationInterceptor implements HttpInterceptor {
  intercept(request: HttpRequest<unknown>, next: HttpHandler): Observable<HttpEvent<unknown>> {
    if (request.context.get(DISABLE_INTERCEPTORS) === true) {
      return next.handle(request);
    }

    return next.handle(request).pipe(
      // add your typical interceptor logic
    );
  }
}