feat(persister): Add keepUnusedRequests config option (#108)

docs/configuration.md

@@ -216,6 +216,27 @@ polly.configure({
 });
 ```
 
+### keepUnusedRequests
+
+_Type_: `Boolean`
+_Default_: `false`
+
+When disabled, requests that have not been captured by the running Polly
+instance will be removed from any previous recording. This ensures that a
+recording will only contain the requests that were made during the lifespan
+of the Polly instance. When enabled, new requests will be appended to the
+recording file.
+
+__Example__
+
+```js
+polly.configure({
+  persisterOptions: {
+    keepUnusedRequests: true
+  }
+});
+```
+
 ## timing
 
 _Type_: `Function`

packages/@pollyjs/core/src/defaults/config.js

@@ -8,7 +8,9 @@ export default {
   adapterOptions: {},
 
   persister: null,
-  persisterOptions: {},
+  persisterOptions: {
+    keepUnusedRequests: false
+  },
 
   logging: false,
 

packages/@pollyjs/persister/src/index.js

@@ -1,7 +1,7 @@
 import HAR from './har';
 import Entry from './har/entry';
 import stringify from 'fast-json-stable-stringify';
-import { assert } from '@pollyjs/utils';
+import { ACTIONS, assert } from '@pollyjs/utils';
 
 const CREATOR_NAME = 'Polly.JS';
 
@@ -84,11 +84,15 @@ export default class Persister {
                 modify the payload (i.e. encrypting the request & response).
         */
         await request._emit('beforePersist', entry);
-
         entries.push(entry);
       }
 
       har.log.addEntries(entries);
+
+      if (!this.polly.config.persisterOptions.keepUnusedRequests) {
+        this._removeUnusedEntries(recordingId, har);
+      }
+
       promises.push(this.save(recordingId, har));
     }
 
@@ -176,6 +180,25 @@ export default class Persister {
     );
   }
 
+  /**
+   * Remove all entries from the given HAR that do not match any requests in
+   * the current Polly instance.
+   *
+   * @param {String} recordingId
+   * @param {HAR} har
+   */
+  _removeUnusedEntries(recordingId, har) {
+    const requests = this.polly._requests.filter(
+      r =>
+        r.recordingId === recordingId &&
+        (r.action === ACTIONS.RECORD || r.action === ACTIONS.REPLAY)
+    );
+
+    har.log.entries = har.log.entries.filter(entry =>
+      requests.find(r => entry._id === r.id && entry._order === r.order)
+    );
+  }
+
   findRecording() {
     this.assert('Must implement the `findRecording` hook.', false);
   }

tests/integration/persister-tests.js

@@ -1,8 +1,6 @@
 import { Polly } from '@pollyjs/core';
 import * as validate from 'har-validator/lib/async';
 
-const { keys } = Object;
-
 export default function persisterTests() {
   it('should persist valid HAR', async function() {
     const { recordingId, persister } = this.polly;
@@ -162,7 +160,43 @@ export default function persisterTests() {
 
     const har = await this.polly.persister.find(this.polly.recordingId);
 
-    expect(har).to.be.a('object');
-    expect(keys(har.log.entries)).to.have.lengthOf(1);
+    expect(har).to.be.an('object');
+    expect(har.log.entries).to.have.lengthOf(1);
+  });
+
+  it('should remove unused entries when `keepUnusedRequests` is false', async function() {
+    const { recordingName, recordingId, config } = this.polly;
+
+    const orderedRecordUrl = order => `${this.recordUrl()}?order=${order}`;
+
+    await this.fetch(orderedRecordUrl(1));
+    await this.fetch(orderedRecordUrl(2));
+    await this.polly.persister.persist();
+
+    let har = await this.polly.persister.find(recordingId);
+
+    expect(har).to.be.an('object');
+    expect(har.log.entries).to.have.lengthOf(2);
+
+    await this.polly.stop();
+
+    this.polly = new Polly(recordingName, config);
+    this.polly.replay();
+    this.polly.configure({
+      persisterOptions: {
+        keepUnusedRequests: false
+      }
+    });
+
+    await this.fetch(orderedRecordUrl(1)); // -> Replay
+    await this.fetch(orderedRecordUrl(3)); // -> New recording
+    await this.polly.persister.persist();
+
+    har = await this.polly.persister.find(recordingId);
+
+    expect(har).to.be.an('object');
+    expect(har.log.entries).to.have.lengthOf(2);
+    expect(har.log.entries[0].request.url).to.include(orderedRecordUrl(1));
+    expect(har.log.entries[1].request.url).to.include(orderedRecordUrl(3));
   });
 }