CORS issue while shaping working web app into a native Ionic app for Android

Question

I've been trying to set up this Ionic CLI proxy server following this guide, but it's from 2015 and I have no idea how to implement it in Angular 10.

So when I run my app with a command:

ionic capacitor run android --project=myApp -c=production

I have this error in Android Studio:

E/Capacitor/Console: File: http://localhost/login - Line 0 - Msg: Access to XMLHttpRequest at 'https://remoteServer.com/api/v1/oauth/v2/token' from origin 'http://localhost' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' head

This is my capacitor.config.json file:

{
  "appId": "io.ionic.starter",
  "appName": "myApp",
  "bundledWebRuntime": false,
  "npmClient": "npm",
  "webDir": "www",
  "plugins": {
    "SplashScreen": {
      "launchShowDuration": 0
    }
  },
  "cordova": {},
  "linuxAndroidStudioPath": "/opt/android-studio/bin/studio.sh"
}

And this is my ionic.config.json file:

{
  "name": "myApp",
  "integrations": {
    "capacitor": {}
  },
  "type": "angular",
  "proxies": [
    {
      "path": "/api",
      "proxyUrl": "https://remoteServer.com/api"
    }
  ]
}

ionic info

Ionic:

   Ionic CLI                     : 6.10.1 (/home/user/.nvm/versions/node/v12.18.3/lib/node_modules/@ionic/cli)
   Ionic Framework               : @ionic/angular 5.3.1
   @angular-devkit/build-angular : 0.1000.5
   @angular-devkit/schematics    : 10.0.5
   @angular/cli                  : 10.0.5
   @ionic/angular-toolkit        : 2.3.3

Capacitor:

   Capacitor CLI   : 2.4.0
   @capacitor/core : 2.4.0

Utility:

   cordova-res : not installed
   native-run  : not installed

System:

   NodeJS : v12.18.3 (/home/user/.nvm/versions/node/v12.18.3/bin/node)
   npm    : 6.14.6
   OS     : Linux 5.4

Any ideas how to resolve this? I've been searching for ages...

---

edit:

So I followed Angular's instructions on how to make an interceptor and this article that explains how to implement both HttpClient and Ionic's native HTTP, but I run into new issues.

Using the code from article, TS is complaining about this line:

headers: nativeHttpResponse.headers

(property) headers?: HttpHeaders
Type '{ [key: string]: string; }' is missing the following properties from type 'HttpHeaders': headers, normalizedNames, lazyInit, lazyUpdate, and 12 more.ts(2740)
http.d.ts(3406, 9): The expected type comes from property 'headers' which is declared here on type '{ body?: any; headers?: HttpHeaders; status?: number; statusText?: string; url?: string; }'

Here's the whole native-http.interceptor.ts:

import { Injectable } from "@angular/core";
import {
  HttpInterceptor,
  HttpRequest,
  HttpHandler,
  HttpEvent,
  HttpResponse,
} from "@angular/common/http";
import { Observable, from } from "rxjs";
import { Platform } from "@ionic/angular";
import { HTTP } from "@ionic-native/http/ngx";

type HttpMethod =
  | "get"
  | "post"
  | "put"
  | "patch"
  | "head"
  | "delete"
  | "upload"
  | "download";

@Injectable()
export class NativeHttpInterceptor implements HttpInterceptor {
  constructor(private nativeHttp: HTTP, private platform: Platform) {}

  public intercept(
    request: HttpRequest<any>,
    next: HttpHandler
  ): Observable<HttpEvent<any>> {
    if (!this.platform.is("cordova")) {
      return next.handle(request);
    }

    return from(this.handleNativeRequest(request));
  }

  private async handleNativeRequest(
    request: HttpRequest<any>
  ): Promise<HttpResponse<any>> {
    const headerKeys = request.headers.keys();
    const headers = {};

    headerKeys.forEach((key) => {
      headers[key] = request.headers.get(key);
    });

    try {
      await this.platform.ready();

      const method = <HttpMethod>request.method.toLowerCase();

      // console.log(‘— Request url’);
      // console.log(request.url)
      // console.log(‘— Request body’);
      // console.log(request.body);

      const nativeHttpResponse = await this.nativeHttp.sendRequest(
        request.url,
        {
          method: method,
          data: request.body,
          headers: headers,
          serializer: "json",
        }
      );

      let body;

      try {
        body = JSON.parse(nativeHttpResponse.data);
      } catch (error) {
        body = { response: nativeHttpResponse.data };
      }

      const response = new HttpResponse({
        body: body,
        status: nativeHttpResponse.status,
        headers: nativeHttpResponse.headers,  <--------
        url: nativeHttpResponse.url,
      });

      // console.log(‘— Response success’)
      // console.log(response);

      return Promise.resolve(response);
    } catch (error) {
      if (!error.status) {
        return Promise.reject(error);
      }

      const response = new HttpResponse({
        body: JSON.parse(error.error),
        status: error.status,
        headers: error.headers,
        url: error.url,
      });

      return Promise.reject(response);
    }
  }
}

Here's how my app.module.ts looks like:

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { RouterModule } from '@angular/router';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
import { IonicModule } from '@ionic/angular';
import { HTTP } from '@ionic-native/http/ngx';

import { CoreModule } from './core/core.module';
import { SharedModule } from './shared/shared.module';
import { AppComponent } from './app.component';
import { PageNotFoundComponent } from './shared/page-not-found/page-not-found.component';
import { appRoutes } from './app.routes';


@NgModule({
  imports: [
    BrowserModule,
    BrowserAnimationsModule,
    FormsModule,
    ReactiveFormsModule,
    SharedModule,
    CoreModule,
    RouterModule.forRoot(
      appRoutes
    ),
    IonicModule.forRoot()
  ],
  providers: [HTTP],
  declarations: [
    AppComponent,
    PageNotFoundComponent
  ],
  bootstrap: [AppComponent]
})
export class AppModule { }

Andd here is how my core.module.ts (where I want to use interceptor) looks like:

import { NgModule } from "@angular/core";
import { CommonModule } from "@angular/common";
import { HTTP_INTERCEPTORS, HttpClientModule } from "@angular/common/http";

import { NativeHttpInterceptor } from "./service/native-http.interceptor";
import { AuthService } from "./service/auth.service";
import { ApiService } from "./service/api.service";
import { AuthGuardService } from "./service/auth-guard.service";
import { AuthInterceptor } from "./service/auth-interceptor";
import { WindowRef } from "./service/window-ref-service";

@NgModule({
  imports: [CommonModule, HttpClientModule],
  providers: [
    {
      provide: HTTP_INTERCEPTORS,
      useClass: NativeHttpInterceptor,
      multi: true,
    },
    AuthService,
    ApiService,
    AuthGuardService,
    WindowRef,
    {
      provide: HTTP_INTERCEPTORS,
      useClass: AuthInterceptor,
      multi: true,
    },
  ],
})
export class CoreModule {}

Answer 1

The proxy configs will only work for the ionic serve or the livereload of the native builds.

If you can't change any option in the BE, then the easiest way is to use a native plugin for the HTTP requests cordova-plugin-advanced-http which will send the requests without the origin header (As it is not sent from the browser).

You can use the Ionic Native wrapper for this from here.