Filter experiment data to match the gitlab_experiment context

The main thing we need to filter out, for now, is the `excluded` key.
Using an allowlist which aligns with the currently used
`gitlab_experiment` context schema is the best way to ensure all of our
frontend experiment events continue working.

app/assets/javascripts/experimentation/utils.js

 // This file only applies to use of experiments through https://gitlab.com/gitlab-org/gitlab-experiment
-import { get } from 'lodash';
+import { get, mapValues, pick } from 'lodash';
 import { DEFAULT_VARIANT, CANDIDATE_VARIANT, TRACKING_CONTEXT_SCHEMA } from './constants';
 
 function getExperimentsData() {
@@ -8,19 +8,18 @@ function getExperimentsData() {
   // Pull from preferred window.gl.experiments
   const experimentsFromGl = get(window, ['gl', 'experiments'], {});
 
-  return { ...experimentsFromGon, ...experimentsFromGl };
-}
-
-function convertExperimentDataToExperimentContext(experimentData) {
-  // Bandaid to allow-list only the properties which the current gitlab_experiment context schema suppports.
+  // Bandaid to allow-list only the properties which the current gitlab_experiment
+  // context schema suppports, since we most often use this data to create that
+  // Snowplow context.
   // See TRACKING_CONTEXT_SCHEMA for current version (1-0-0)
   // https://gitlab.com/gitlab-org/iglu/-/blob/master/public/schemas/com.gitlab/gitlab_experiment/jsonschema/1-0-0
-  const { experiment: experimentName, key, variant, migration_keys } = experimentData;
+  return mapValues({ ...experimentsFromGon, ...experimentsFromGl }, (xp) => {
+    return pick(xp, ['experiment', 'key', 'variant', 'migration_keys']);
+  });
+}
 
-  return {
-    schema: TRACKING_CONTEXT_SCHEMA,
-    data: { experiment: experimentName, key, variant, migration_keys },
-  };
+function createGitlabExperimentContext(experimentData) {
+  return { schema: TRACKING_CONTEXT_SCHEMA, data: experimentData };
 }
 
 export function getExperimentData(experimentName) {
@@ -28,7 +27,7 @@ export function getExperimentData(experimentName) {
 }
 
 export function getAllExperimentContexts() {
-  return Object.values(getExperimentsData()).map(convertExperimentDataToExperimentContext);
+  return Object.values(getExperimentsData()).map(createGitlabExperimentContext);
 }
 
 export function isExperimentVariant(experimentName, variantName) {

spec/frontend/experimentation/utils_spec.js

@@ -51,6 +51,29 @@ describe('experiment Utilities', () => {
         expect(experimentUtils.getExperimentData(...input)).toEqual(output);
       });
     });
+
+    it('only collects the data properties which are supported by the schema', () => {
+      origGl = window.gl;
+      window.gl.experiments = {
+        my_experiment: {
+          experiment: 'my_experiment',
+          variant: 'control',
+          key: 'randomization-unit-key',
+          migration_keys: 'migration_keys object',
+          excluded: false,
+          other: 'foobar',
+        },
+      };
+
+      expect(experimentUtils.getExperimentData('my_experiment')).toEqual({
+        experiment: 'my_experiment',
+        variant: 'control',
+        key: 'randomization-unit-key',
+        migration_keys: 'migration_keys object',
+      });
+
+      window.gl = origGl;
+    });
   });
 
   describe('getAllExperimentContexts', () => {
@@ -72,19 +95,6 @@ describe('experiment Utilities', () => {
     it('returns an empty array if there are no experiments', () => {
       expect(experimentUtils.getAllExperimentContexts()).toEqual([]);
     });
-
-    it('only collects the data properties which are supported by the schema', () => {
-      origGl = window.gl;
-      window.gl.experiments = {
-        my_experiment: { experiment: 'my_experiment', variant: 'control', excluded: false },
-      };
-
-      expect(experimentUtils.getAllExperimentContexts()).toEqual([
-        { schema, data: { experiment: 'my_experiment', variant: 'control' } },
-      ]);
-
-      window.gl = origGl;
-    });
   });
 
   describe('isExperimentVariant', () => {