fix: make plugin a "no-op" in unsupported browsers

Previously the plugin would throw an error when it was running in an
unsupported browser. This was not great for plugin consumers who run
their cypress tests in both supported and unsupported browsers and are
fine with only having HAR recording in supported browsers: It forced
them to conditionally enable this plugin.

To address this, we're changing the plugin to do nothing except `warn`
that HAR recording is not supported when running in an unsupported
browser.

Author: rmacklin

src/Plugin.spec.ts

@@ -193,15 +193,17 @@ describe('Plugin', () => {
       expect(result).not.toContain(expectedArgs);
     });
 
-    it('should throw an error if an unsupported browser family is used', () => {
+    it('should log a warning if an unsupported browser family is used', () => {
       // arrange
       const args = ['--flag1', '--flag2'];
       // act
-      const act = () => plugin.ensureBrowserFlags(firefox, args);
+      plugin.ensureBrowserFlags(firefox, args);
       // assert
-      expect(act).toThrowError(
-        `An unsupported browser family was used: ${firefox.name}`
-      );
+      verify(
+        loggerMock.warn(
+          `HAR recording is not supported in this browser: ${firefox.name}`
+        )
+      ).once();
     });
 
     it('should throw an error when Electron is used and switches are missed', () => {
@@ -402,6 +404,19 @@ describe('Plugin', () => {
       verify(harExporterMock.end()).once();
       verify(fileManagerMock.removeFile(tempFilePath)).once();
     });
+
+    it('should be a no-op if an unsupported browser family is used', async () => {
+      // arrange
+      plugin.ensureBrowserFlags(firefox, []);
+      await plugin.recordHar({
+        rootDir: '/'
+      });
+
+      // act
+      await plugin.saveHar(options);
+      // assert
+      verify(fileManagerMock.createFolder(options.outDir)).never();
+    });
   });
 
   describe('recordHar', () => {
@@ -495,6 +510,26 @@ describe('Plugin', () => {
       // assert
       verify(harExporterMock.write(request)).never();
     });
+
+    it('should be a no-op if an unsupported browser family is used', async () => {
+      const request = new NetworkRequest(
+        '1',
+        'https://example.com',
+        'https://example.com',
+        '1'
+      );
+      when(harExporterFactoryMock.create(anything())).thenResolve(
+        resolvableInstance(harExporterMock)
+      );
+      when(networkObserverMock.subscribe(anyFunction())).thenCall(callback =>
+        callback(request)
+      );
+      plugin.ensureBrowserFlags(firefox, []);
+      // act
+      await plugin.recordHar(options);
+      // assert
+      verify(harExporterMock.write(request)).never();
+    });
   });
 
   describe('disposeOfHar', () => {
@@ -541,5 +576,17 @@ describe('Plugin', () => {
       // assert
       verify(networkObserverMock.unsubscribe()).never();
     });
+
+    it('should be a no-op if an unsupported browser family is used', async () => {
+      // arrange
+      plugin.ensureBrowserFlags(firefox, []);
+      await plugin.recordHar({
+        rootDir: '/'
+      });
+      // act
+      await plugin.disposeOfHar();
+      // assert
+      verify(harExporterMock.end()).never();
+    });
   });
 });

src/Plugin.ts

@@ -44,6 +44,7 @@ export class Plugin {
   private networkObservable?: Observer<NetworkRequest>;
   private addr?: Addr;
   private _connection?: Connection;
+  private supported?: boolean;
 
   constructor(
     private readonly logger: Logger,
@@ -57,9 +58,10 @@ export class Plugin {
     browser: Cypress.Browser,
     args: string[]
   ): string[] {
-    if (!this.isSupportedBrowser(browser)) {
-      throw new Error(
-        `An unsupported browser family was used: ${browser.name}`
+    this.supported = this.isSupportedBrowser(browser);
+    if (!this.supported) {
+      this.logger.warn(
+        `HAR recording is not supported in this browser: ${browser.name}`
       );
     }
 
@@ -83,6 +85,10 @@ export class Plugin {
       );
     }
 
+    if (!this.supported) {
+      return;
+    }
+
     await this.closeConnection();
 
     this.exporter = await this.exporterFactory.create(options);
@@ -99,6 +105,10 @@ export class Plugin {
   }
 
   public async saveHar(options: SaveOptions): Promise<void> {
+    if (!this.supported) {
+      return;
+    }
+
     const filePath = join(options.outDir, options.fileName);
 
     if (!this._connection) {
@@ -130,6 +140,10 @@ export class Plugin {
   }
 
   public async disposeOfHar(): Promise<void> {
+    if (!this.supported) {
+      return;
+    }
+
     await this.networkObservable?.unsubscribe();
     delete this.networkObservable;