feat: Fetch adapter support for context provided via adapterOptions (…

…#66)

docs/adapters/fetch.md

@@ -43,3 +43,25 @@ polly.connectTo('fetch');
 // Disconnect using the `disconnectFrom` API
 polly.disconnectFrom('fetch');
 ```
+
+## Options
+
+### context
+
+_Type_: 'Object'
+_Default_: `global|self|window`
+
+The context object which contains the fetch API.  Typically this is `window` or `self` in the browser and `global` in node.
+
+__Example__
+
+```js
+polly.configure({
+  adapters: ['fetch'],
+  adapterOptions: {
+    fetch: {
+      context: window
+    }
+  }
+});
+```

packages/@pollyjs/adapter-fetch/src/index.js

@@ -1,34 +1,46 @@
 import Adapter from '@pollyjs/adapter';
 import { Fetch as FetchUtils } from '@pollyjs/utils';
 
-const nativeFetch = global.fetch;
 const { defineProperty } = Object;
+const STUB_META = Symbol();
 
 export default class FetchAdapter extends Adapter {
   static get name() {
     return 'fetch';
   }
 
+  get defaultOptions() {
+    return {
+      context: global
+    };
+  }
+
   onConnect() {
-    this.assert('Fetch global not found.', nativeFetch);
+    const { context } = this.options;
+
+    this.assert('Fetch global not found.', !!(context && context.fetch));
     this.assert(
       'Running concurrent fetch adapters is unsupported, stop any running Polly instances.',
-      global.fetch === nativeFetch
+      !(STUB_META in context.fetch)
     );
 
-    this.native = nativeFetch;
-    global.fetch = (url, options = {}) =>
+    this.native = context.fetch;
+
+    context.fetch = (url, options = {}) =>
       this.handleRequest({
         url,
         method: options.method || 'GET',
         headers: FetchUtils.serializeHeaders(options.headers),
         body: options.body,
         requestArguments: [url, options]
       });
+
+    defineProperty(context.fetch, STUB_META, { value: true });
   }
 
   onDisconnect() {
-    global.fetch = nativeFetch;
+    this.options.context.fetch = this.native;
+    this.native = null;
   }
 
   async onRecord(pollyRequest) {

packages/@pollyjs/adapter-fetch/tests/integration/adapter-test.js

@@ -1,4 +1,4 @@
-import { setupMocha as setupPolly } from '@pollyjs/core';
+import { setupMocha as setupPolly, Polly } from '@pollyjs/core';
 import setupFetchRecord from '@pollyjs-tests/helpers/setup-fetch-record';
 import adapterTests from '@pollyjs-tests/integration/adapter-tests';
 import adapterBrowserTests from '@pollyjs-tests/integration/adapter-browser-tests';
@@ -21,3 +21,102 @@ describe('Integration | Fetch Adapter', function() {
   adapterTests();
   adapterBrowserTests();
 });
+
+describe('Integration | Fetch Adapter | Context', function() {
+  it(`should assign context's fetch as the native fetch`, async function() {
+    const polly = new Polly('context', { adapters: [] });
+    const adapterOptions = {
+      fetch: {
+        context: {
+          fetch() {}
+        }
+      }
+    };
+
+    polly.configure({
+      adapters: [FetchAdapter],
+      adapterOptions
+    });
+
+    expect(polly.adapters.get('fetch').native).to.equal(
+      adapterOptions.fetch.context.fetch
+    );
+
+    expect(function() {
+      polly.configure({
+        adapterOptions: {
+          fetch: {
+            context: undefined
+          }
+        }
+      });
+    }).to.throw(`[Polly] [adapter:fetch] Fetch global not found.`);
+
+    await polly.stop();
+  });
+
+  it('should throw when context and fetch are undefined', async function() {
+    const polly = new Polly('context', { adapters: [] });
+
+    polly.configure({
+      adapters: [FetchAdapter]
+    });
+
+    expect(function() {
+      polly.configure({
+        adapterOptions: {
+          fetch: {
+            context: undefined
+          }
+        }
+      });
+    }).to.throw(`[Polly] [adapter:fetch] Fetch global not found.`);
+
+    expect(function() {
+      polly.configure({
+        adapterOptions: {
+          fetch: {
+            context: {
+              fetch: undefined
+            }
+          }
+        }
+      });
+    }).to.throw(`[Polly] [adapter:fetch] Fetch global not found.`);
+
+    await polly.stop();
+  });
+});
+
+describe('Integration | Fetch Adapter | Concurrency', function() {
+  it('should prevent concurrent fetch adapter instances', async function() {
+    const one = new Polly('one');
+    const two = new Polly('two');
+
+    one.connectTo(FetchAdapter);
+
+    expect(function() {
+      two.connectTo(FetchAdapter);
+    }).to.throw(
+      `[Polly] [adapter:fetch] Running concurrent fetch adapters is unsupported, stop any running Polly instances.`
+    );
+
+    await one.stop();
+    await two.stop();
+  });
+
+  it('should allow you to register new instances once stopped', async function() {
+    const one = new Polly('one');
+    const two = new Polly('two');
+
+    one.connectTo(FetchAdapter);
+    one.stop();
+
+    expect(function() {
+      two.connectTo(FetchAdapter);
+    }).to.not.throw();
+
+    await one.stop();
+    await two.stop();
+  });
+});

packages/@pollyjs/core/src/polly.js

@@ -121,13 +121,11 @@ export default class Polly {
       this.mode !== MODES.STOPPED
     );
 
-    this.config = mergeOptions(DefaultConfig, this.config, config);
-
-    /* Handle Adapters */
-
-    // Disconnect from all current adapters
+    // Disconnect from all current adapters before updating the config
     this.disconnect();
 
+    this.config = mergeOptions(DefaultConfig, this.config, config);
+
     // Register and connect to all specified adapters
     this.config.adapters.forEach(adapter => this.connectTo(adapter));