Bug 1698795 - Add an option to send exposure once per instance r=k88hudson

Differential Revision: https://phabricator.services.mozilla.com/D110944

toolkit/components/nimbus/ExperimentAPI.jsm

@@ -361,6 +361,8 @@ class ExperimentFeature {
         `No manifest entry for ${featureId}. Please add one to toolkit/components/messaging-system/experiments/ExperimentAPI.jsm`
       );
     }
+    // Prevent the instance from sending multiple exposure events
+    this._sendExposureEventOnce = true;
     this._onRemoteReady = null;
     this._waitForRemote = new Promise(
       resolve => (this._onRemoteReady = resolve)
@@ -458,9 +460,14 @@ class ExperimentFeature {
   isEnabled({ sendExposureEvent, defaultValue = null } = {}) {
     const branch = ExperimentAPI.activateBranch({
       featureId: this.featureId,
-      sendExposureEvent,
+      sendExposureEvent: sendExposureEvent && this._sendExposureEventOnce,
     });
 
+    // Prevent future exposure events if user is enrolled in an experiment
+    if (branch && sendExposureEvent) {
+      this._sendExposureEventOnce = false;
+    }
+
     // First, try to return an experiment value if it exists.
     if (isBooleanValueDefined(branch?.feature.enabled)) {
       return branch.feature.enabled;
@@ -490,8 +497,14 @@ class ExperimentFeature {
     let userPrefs = this._getUserPrefsValues();
     const branch = ExperimentAPI.activateBranch({
       featureId: this.featureId,
-      sendExposureEvent,
+      sendExposureEvent: sendExposureEvent && this._sendExposureEventOnce,
     });
+
+    // Prevent future exposure events if user is enrolled in an experiment
+    if (branch && sendExposureEvent) {
+      this._sendExposureEventOnce = false;
+    }
+
     if (branch?.feature?.value) {
       return { ...branch.feature.value, ...userPrefs };
     }
@@ -516,10 +529,17 @@ class ExperimentFeature {
   }
 
   recordExposureEvent() {
-    ExperimentAPI.activateBranch({
-      featureId: this.featureId,
-      sendExposureEvent: true,
-    });
+    if (this._sendExposureEventOnce) {
+      let experimentData = ExperimentAPI.activateBranch({
+        featureId: this.featureId,
+        sendExposureEvent: true,
+      });
+
+      // Exposure only sent if user is enrolled in an experiment
+      if (experimentData) {
+        this._sendExposureEventOnce = false;
+      }
+    }
   }
 
   onUpdate(callback) {

toolkit/components/nimbus/test/unit/test_ExperimentAPI_ExperimentFeature.js

@@ -352,3 +352,99 @@ add_task(async function test_record_exposure_event() {
 
   sandbox.restore();
 });
+
+add_task(async function test_record_exposure_event_once() {
+  const { sandbox, manager } = await setupForExperimentFeature();
+
+  const featureInstance = new ExperimentFeature("foo", FAKE_FEATURE_MANIFEST);
+  const exposureSpy = sandbox.spy(ExperimentAPI, "recordExposureEvent");
+  sandbox.stub(ExperimentAPI, "_store").get(() => manager.store);
+
+  manager.store.addExperiment(
+    ExperimentFakes.experiment("blah", {
+      featureIds: ["foo"],
+      branch: {
+        slug: "treatment",
+        feature: {
+          featureId: "foo",
+          enabled: false,
+          value: null,
+        },
+      },
+    })
+  );
+
+  featureInstance.recordExposureEvent();
+  featureInstance.recordExposureEvent();
+  featureInstance.recordExposureEvent();
+
+  Assert.ok(exposureSpy.calledOnce, "Should emit a single exposure event.");
+
+  sandbox.restore();
+});
+
+add_task(async function test_prevent_double_exposure_getValue() {
+  const { sandbox, manager } = await setupForExperimentFeature();
+
+  const featureInstance = new ExperimentFeature("foo", FAKE_FEATURE_MANIFEST);
+  const exposureSpy = sandbox.spy(ExperimentAPI, "recordExposureEvent");
+  sandbox.stub(ExperimentAPI, "_store").get(() => manager.store);
+
+  manager.store.addExperiment(
+    ExperimentFakes.experiment("blah", {
+      featureIds: ["foo"],
+      branch: {
+        slug: "treatment",
+        feature: {
+          featureId: "foo",
+          enabled: false,
+          value: null,
+        },
+      },
+    })
+  );
+
+  featureInstance.getValue({ sendExposureEvent: true });
+  featureInstance.getValue({ sendExposureEvent: true });
+  featureInstance.getValue({ sendExposureEvent: true });
+
+  Assert.ok(
+    exposureSpy.calledOnce,
+    "Should emit a single exposure event (getValue)."
+  );
+
+  sandbox.restore();
+});
+
+add_task(async function test_prevent_double_exposure_isEnabled() {
+  const { sandbox, manager } = await setupForExperimentFeature();
+
+  const featureInstance = new ExperimentFeature("foo", FAKE_FEATURE_MANIFEST);
+  const exposureSpy = sandbox.spy(ExperimentAPI, "recordExposureEvent");
+  sandbox.stub(ExperimentAPI, "_store").get(() => manager.store);
+
+  manager.store.addExperiment(
+    ExperimentFakes.experiment("blah", {
+      featureIds: ["foo"],
+      branch: {
+        slug: "treatment",
+        feature: {
+          featureId: "foo",
+          enabled: false,
+          value: null,
+        },
+      },
+    })
+  );
+
+  featureInstance.isEnabled({ sendExposureEvent: true });
+  featureInstance.isEnabled({ sendExposureEvent: true });
+  featureInstance.isEnabled({ sendExposureEvent: true });
+
+  Assert.ok(
+    exposureSpy.calledOnce,
+    "Should emit a single exposure event (getValue)."
+  );
+
+  sandbox.restore();
+});