add published_date field to experiment schema

components/nimbus/src/enrollment.rs

@@ -681,6 +681,7 @@ impl<'a> EnrollmentsEvolver<'a> {
 
         // Step 3. Evolve the remaining enrollments with the previous and
         // next data.
+        let next_experiments = sort_experiments_by_published_date(next_experiments);
         for next_experiment in next_experiments {
             let slug = &next_experiment.slug;
 
@@ -946,6 +947,12 @@ where
         .collect()
 }
 
+pub(crate) fn sort_experiments_by_published_date(experiments: &[Experiment]) -> Vec<&Experiment> {
+    let mut experiments: Vec<_> = experiments.iter().collect();
+    experiments.sort_by(|a, b| a.published_date.cmp(&b.published_date));
+    experiments
+}
+
 /// Take a list of enrollments and a map of experiments, and generate mapping of `feature_id` to
 /// `EnrolledFeatureConfig` structs.
 fn map_features(

components/nimbus/src/schema.rs

@@ -46,6 +46,7 @@ pub struct Experiment {
     pub reference_branch: Option<String>,
     #[serde(default)]
     pub is_rollout: bool,
+    pub published_date: Option<chrono::DateTime<chrono::Utc>>,
     // N.B. records in RemoteSettings will have `id` and `filter_expression` fields,
     // but we ignore them because they're for internal use by RemoteSettings.
 }
@@ -76,6 +77,19 @@ impl Experiment {
 
         feature_ids.into_iter().collect()
     }
+
+    #[cfg(test)]
+    pub(crate) fn patch(&self, patch: Value) -> Self {
+        let mut experiment = serde_json::to_value(self).unwrap();
+        if let (Some(e), Some(w)) = (experiment.as_object(), patch.as_object()) {
+            let mut e = e.clone();
+            for (key, value) in w {
+                e.insert(key.clone(), value.clone());
+            }
+            experiment = serde_json::to_value(e).unwrap();
+        }
+        serde_json::from_value(experiment).unwrap()
+    }
 }
 
 impl ExperimentMetadata for Experiment {

components/nimbus/src/tests/helpers.rs

@@ -552,3 +552,55 @@ pub fn get_targeted_experiment(slug: &str, targeting: &str) -> serde_json::Value
         "last_modified": 1_602_197_324_372i64,
     })
 }
+
+pub(crate) fn get_experiment_with_published_date(
+    slug: &str,
+    published_date: Option<String>,
+) -> Experiment {
+    serde_json::from_value(json!({
+        "schemaVersion": "1.0.0",
+        "slug": slug,
+        "endDate": null,
+        "branches":[
+            {
+                "slug": "control",
+                "ratio": 1,
+                "feature": {
+                    "featureId": "about_welcome",
+                    "enabled": true,
+                }
+            },
+            {
+                "slug": "treatment",
+                "ratio": 1,
+                "feature": {
+                    "featureId": "about_welcome",
+                    "enabled": false,
+                }
+            },
+        ],
+        "featureIds": ["about_welcome"],
+        "channel": "nightly",
+        "probeSets":[],
+        "startDate":null,
+        "appName":"fenix",
+        "appId":"org.mozilla.fenix",
+        "bucketConfig":{
+            // Also enroll everyone.
+            "count":10_000,
+            "start":0,
+            "total":10_000,
+            "namespace":"secure-silver",
+            "randomizationUnit":"nimbus_id"
+        },
+        "userFacingName":"2nd test experiment",
+        "referenceBranch":"control",
+        "isEnrollmentPaused":false,
+        "proposedEnrollment":7,
+        "userFacingDescription":"2nd test experiment.",
+        "id":"secure-silver",
+        "last_modified":1_602_197_324_372i64,
+        "publishedDate": published_date
+    }))
+    .unwrap()
+}

components/nimbus/src/tests/test_enrollment.rs

@@ -4,7 +4,7 @@
 
 // Testing enrollment.rs
 
-use crate::tests::helpers::get_bucketed_rollout;
+use crate::tests::helpers::{get_bucketed_rollout, get_experiment_with_published_date};
 use crate::{
     defaults::Defaults,
     enrollment::*,
@@ -3136,3 +3136,58 @@ fn test_populate_feature_maps() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn test_sort_experiments_by_published_date() -> Result<()> {
+    let slug_1 = "slug-1";
+    let slug_2 = "slug-2";
+    let slug_3 = "slug-3";
+    let slug_4 = "slug-4";
+    let experiments = vec![
+        get_experiment_with_published_date(slug_1, None),
+        get_experiment_with_published_date(slug_2, Some("2023-11-21T18:00:00Z".into())),
+        get_experiment_with_published_date(slug_3, None),
+        get_experiment_with_published_date(slug_4, Some("2023-11-21T15:00:00Z".into())),
+    ];
+    let result = sort_experiments_by_published_date(&experiments);
+
+    assert_eq!(slug_1, result[0].slug);
+    assert_eq!(slug_3, result[1].slug);
+    assert_eq!(slug_4, result[2].slug);
+    assert_eq!(slug_2, result[3].slug);
+    Ok(())
+}
+
+#[test]
+fn test_evolve_enrollments_ordering() -> Result<()> {
+    let _ = env_logger::try_init();
+    let (_, app_ctx, aru) = local_ctx();
+    let th = app_ctx.into();
+    let ids = HashSet::new();
+    let evolver = EnrollmentsEvolver::new(&aru, &th, &ids);
+
+    let exp1 = get_single_feature_experiment("slug-1", "colliding-feature", json!({"x": 1 }))
+        .patch(json!({"publishedDate": "2023-11-21T18:00:00Z"}));
+    let exp2 = get_single_feature_experiment("slug-2", "colliding-feature", json!({"x": 2 }))
+        .patch(json!({"publishedDate": "2023-11-21T15:00:00Z"}));
+
+    let all_experiments = [exp1, exp2];
+    let no_experiments: [Experiment; 0] = [];
+
+    let (enrollments, _) =
+        evolver.evolve_enrollment_recipes(true, &no_experiments, &all_experiments, &[])?;
+
+    let observed = map_features_by_feature_id(&enrollments, &all_experiments, &ids);
+    let expected = HashMap::from([(
+        "colliding-feature".to_string(),
+        EnrolledFeatureConfig::new(
+            "colliding-feature",
+            json!({"x": 2 }),
+            "slug-2",
+            Some("control"),
+        ),
+    )]);
+    assert_eq!(observed, expected);
+
+    Ok(())
+}