feat: Warn if the logger doesn't start due to duplicate logger (#56)

- add new forceEnable option to override default behaviour

README.md

@@ -120,6 +120,14 @@ import NetworkLogger from 'react-native-network-logger';
 const MyScreen = () => <NetworkLogger sort="asc" />;
 ```
 
+#### Force Enable
+
+If you are running another network logging interceptor, e.g. Reactotron, the logger will not start as only one can be run at once. You can override this behaviour and force the logger to start by using the `forceEnable` option.
+
+```ts
+startNetworkLogging({ forceEnable: true });
+```
+
 #### Integrate with existing navigation
 
 Use your existing back button (e.g. in your navigation header) to navigate within the network logger.

src/Logger.ts

@@ -2,6 +2,8 @@ import XHRInterceptor from 'react-native/Libraries/Network/XHRInterceptor';
 import NetworkRequestInfo from './NetworkRequestInfo';
 import { Headers, RequestMethod, StartNetworkLoggingOptions } from './types';
 import extractHost from './utils/extractHost';
+import { warn } from './utils/logger';
+
 let nextXHRId = 0;
 
 type XHR = {
@@ -14,6 +16,7 @@ export default class Logger {
   private xhrIdMap: { [key: number]: number } = {};
   private maxRequests: number = 500;
   private ignoredHosts: Set<string> | undefined;
+  public enabled = false;
 
   // eslint-disable-next-line @typescript-eslint/no-unused-vars
   callback = (requests: any[]) => {};
@@ -114,14 +117,22 @@ export default class Logger {
   };
 
   enableXHRInterception = (options?: StartNetworkLoggingOptions) => {
-    if (XHRInterceptor.isInterceptorEnabled()) {
+    if (
+      this.enabled ||
+      (XHRInterceptor.isInterceptorEnabled() && !options?.forceEnable)
+    ) {
+      if (!this.enabled) {
+        warn(
+          'network interceptor has not been enabled as another interceptor is already running (e.g. another debugging program). Use option `forceEnable: true` to override this behaviour.'
+        );
+      }
       return;
     }
 
     if (options?.maxRequests !== undefined) {
       if (typeof options.maxRequests !== 'number' || options.maxRequests < 1) {
-        console.warn(
-          'react-native-network-logger: maxRequests must be a number greater than 0. The logger has not been started.'
+        warn(
+          'maxRequests must be a number greater than 0. The logger has not been started.'
         );
         return;
       }
@@ -133,8 +144,8 @@ export default class Logger {
         !Array.isArray(options.ignoredHosts) ||
         typeof options.ignoredHosts[0] !== 'string'
       ) {
-        console.warn(
-          'react-native-network-logger: ignoredHosts must be an array of strings. The logger has not been started.'
+        warn(
+          'ignoredHosts must be an array of strings. The logger has not been started.'
         );
         return;
       }
@@ -148,6 +159,7 @@ export default class Logger {
     XHRInterceptor.setResponseCallback(this.responseCallback);
 
     XHRInterceptor.enableInterception();
+    this.enabled = true;
   };
 
   getRequests = () => {

src/__tests__/Logger.spec.ts

@@ -1,4 +1,5 @@
 import XHRInterceptor from 'react-native/Libraries/Network/XHRInterceptor';
+import { warn } from '../utils/logger';
 import Logger from '../Logger';
 
 jest.mock('react-native/Libraries/Blob/FileReader', () => ({}));
@@ -12,23 +13,43 @@ jest.mock('react-native/Libraries/Network/XHRInterceptor', () => ({
   enableInterception: jest.fn(),
 }));
 
+jest.mock('../utils/logger', () => ({
+  warn: jest.fn(() => {
+    throw new Error('Unexpected warning');
+  }),
+}));
+
 beforeEach(() => {
   jest.clearAllMocks();
 });
 
 describe('enableXHRInterception', () => {
   it('should do nothing if interceptor has already been enabled', () => {
+    (warn as jest.Mock).mockImplementationOnce(() => {});
     const logger = new Logger();
 
     (XHRInterceptor.isInterceptorEnabled as jest.Mock).mockReturnValueOnce(
       true
     );
 
     expect(logger.enableXHRInterception()).toBeUndefined();
+    expect(warn).toHaveBeenCalledTimes(1);
     expect(XHRInterceptor.isInterceptorEnabled).toHaveBeenCalledTimes(1);
     expect(XHRInterceptor.setOpenCallback).toHaveBeenCalledTimes(0);
   });
 
+  it('should continue if interceptor has already been enabled but forceEnable is true', () => {
+    const logger = new Logger();
+
+    (XHRInterceptor.isInterceptorEnabled as jest.Mock).mockReturnValueOnce(
+      true
+    );
+
+    expect(logger.enableXHRInterception({ forceEnable: true })).toBeUndefined();
+    expect(XHRInterceptor.isInterceptorEnabled).toHaveBeenCalledTimes(1);
+    expect(XHRInterceptor.setOpenCallback).toHaveBeenCalledTimes(1);
+  });
+
   it('should update the maxRequests if provided', () => {
     const logger = new Logger();
 

src/components/NetworkLogger.tsx

@@ -6,6 +6,7 @@ import { ThemeContext, ThemeName } from '../theme';
 import RequestList from './RequestList';
 import RequestDetails from './RequestDetails';
 import { setBackHandler } from '../backHandler';
+import Unmounted from './Unmounted';
 
 interface Props {
   theme?: ThemeName;
@@ -25,6 +26,7 @@ const NetworkLogger: React.FC<Props> = ({ theme = 'light', sort = 'desc' }) => {
   );
   const [request, setRequest] = useState<NetworkRequestInfo>();
   const [showDetails, _setShowDetails] = useState(false);
+  const [mounted, setMounted] = useState(false);
 
   const setShowDetails = useCallback((shouldShow: boolean) => {
     _setShowDetails(shouldShow);
@@ -42,6 +44,7 @@ const NetworkLogger: React.FC<Props> = ({ theme = 'light', sort = 'desc' }) => {
     });
 
     logger.enableXHRInterception();
+    setMounted(true);
 
     return () => {
       // no-op if component is unmounted
@@ -91,15 +94,19 @@ const NetworkLogger: React.FC<Props> = ({ theme = 'light', sort = 'desc' }) => {
           </View>
         )}
         <View style={showDetails && !!request ? styles.hidden : styles.visible}>
-          <RequestList
-            requests={requests}
-            onShowMore={showMore}
-            showDetails={showDetails && !!request}
-            onPressItem={(item) => {
-              setRequest(item);
-              setShowDetails(true);
-            }}
-          />
+          {mounted && !logger.enabled && !requests.length ? (
+            <Unmounted />
+          ) : (
+            <RequestList
+              requests={requests}
+              onShowMore={showMore}
+              showDetails={showDetails && !!request}
+              onPressItem={(item) => {
+                setRequest(item);
+                setShowDetails(true);
+              }}
+            />
+          )}
         </View>
       </View>
     </ThemeContext.Provider>

src/components/Unmounted.tsx

@@ -0,0 +1,43 @@
+import React from 'react';
+import { View, StyleSheet, Text } from 'react-native';
+import { Theme, useThemedStyles } from '../theme';
+
+const Unmounted = () => {
+  const styles = useThemedStyles(themedStyles);
+  return (
+    <View style={styles.container}>
+      <Text style={styles.heading}>Unmounted Error</Text>
+      <Text style={styles.body}>
+        It looks like the network logger hasn’t been enabled yet.
+      </Text>
+      <Text style={styles.body}>
+        This is likely due to you running another debugging tool that is also
+        intercepting network requests. Either disable that or start the network
+        logger with the option:{' '}
+        <Text style={styles.code}>"forceEnable: true"</Text>.
+      </Text>
+    </View>
+  );
+};
+
+const themedStyles = (theme: Theme) =>
+  StyleSheet.create({
+    container: {
+      padding: 15,
+    },
+    heading: {
+      color: theme.colors.text,
+      fontWeight: '600',
+      fontSize: 25,
+      marginBottom: 10,
+    },
+    body: {
+      color: theme.colors.text,
+      marginTop: 5,
+    },
+    code: {
+      color: theme.colors.muted,
+    },
+  });
+
+export default Unmounted;

src/types.ts

@@ -8,4 +8,9 @@ export type StartNetworkLoggingOptions = {
   maxRequests?: number;
   /** List of hosts to ignore, e.g. services.test.com */
   ignoredHosts?: string[];
+  /**
+   * Force the network logger to start even if another program is using the network interceptor
+   * e.g. a dev/debuging program
+   */
+  forceEnable?: boolean;
 };

src/utils/logger.ts

@@ -0,0 +1,2 @@
+export const warn = (message: string) =>
+  console.warn(`react-native-network-logger: ${message}`);