From 41723b88901b568b76cfcc5b212be35ed2b44560 Mon Sep 17 00:00:00 2001
From: Mohamed Ibrahim <mohamedhassen.ibrahim@mail.utoronto.ca>
Date: Tue, 12 May 2026 15:43:11 -0400
Subject: [PATCH] fix(nimbus): populate config_slug on mobile

---
 components/nimbus/src/enrollment.rs                  | 12 +++++++-----
 components/nimbus/src/metrics.rs                     |  9 ++++++++-
 components/nimbus/src/tests/test_enrollment.rs       |  2 +-
 .../nimbus/src/tests/test_enrollment_bw_compat.rs    |  4 ++--
 4 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/components/nimbus/src/enrollment.rs b/components/nimbus/src/enrollment.rs
index 5e73f36906..a414ad7ff0 100644
--- a/components/nimbus/src/enrollment.rs
+++ b/components/nimbus/src/enrollment.rs
@@ -57,7 +57,7 @@ pub enum NotEnrolledReason {
     /// The experiment enrollment is paused.
     EnrollmentsPaused,
     /// The experiment used a feature that was already under experiment.
-    FeatureConflict,
+    FeatureConflict { conflict_slug: Option<String> },
     /// The evaluator bucketing did not choose us.
     NotSelected,
     /// We are not being targeted for this experiment.
@@ -73,7 +73,7 @@ impl Display for NotEnrolledReason {
                 NotEnrolledReason::DifferentAppName => "DifferentAppName",
                 NotEnrolledReason::DifferentChannel => "DifferentChannel",
                 NotEnrolledReason::EnrollmentsPaused => "EnrollmentsPaused",
-                NotEnrolledReason::FeatureConflict => "FeatureConflict",
+                NotEnrolledReason::FeatureConflict { .. } => "FeatureConflict",
                 NotEnrolledReason::NotSelected => "NotSelected",
                 NotEnrolledReason::NotTargeted => "NotTargeted",
                 NotEnrolledReason::OptOut => "OptOut",
@@ -905,7 +905,7 @@ impl<'a> EnrollmentsEvolver<'a> {
             if matches!(
                 prev_enrollment.status,
                 EnrollmentStatus::NotEnrolled {
-                    reason: NotEnrolledReason::FeatureConflict
+                    reason: NotEnrolledReason::FeatureConflict { .. },
                 }
             ) {
                 continue;
@@ -985,7 +985,9 @@ impl<'a> EnrollmentsEvolver<'a> {
                     next_enrollments.push(ExperimentEnrollment {
                         slug: slug.clone(),
                         status: EnrollmentStatus::NotEnrolled {
-                            reason: NotEnrolledReason::FeatureConflict,
+                            reason: NotEnrolledReason::FeatureConflict {
+                                conflict_slug: Some(needed_features_in_use[0].slug.clone()),
+                            },
                         },
                     });
 
@@ -1014,7 +1016,7 @@ impl<'a> EnrollmentsEvolver<'a> {
                 || matches!(
                     prev_enrollment.unwrap().status,
                     EnrollmentStatus::NotEnrolled {
-                        reason: NotEnrolledReason::FeatureConflict
+                        reason: NotEnrolledReason::FeatureConflict { .. }
                     }
                 )
             {
diff --git a/components/nimbus/src/metrics.rs b/components/nimbus/src/metrics.rs
index 89d5521ce6..48794197d1 100644
--- a/components/nimbus/src/metrics.rs
+++ b/components/nimbus/src/metrics.rs
@@ -30,6 +30,7 @@ impl From<ExperimentEnrollment> for EnrollmentStatusExtraDef {
         let mut branch_value: Option<String> = None;
         let mut reason_value: Option<String> = None;
         let mut error_value: Option<String> = None;
+        let mut conflict_slug_value: Option<String> = None;
         match &enrollment.status {
             EnrollmentStatus::Enrolled { reason, branch, .. } => {
                 branch_value = Some(branch.to_owned());
@@ -41,6 +42,12 @@ impl From<ExperimentEnrollment> for EnrollmentStatusExtraDef {
             }
             EnrollmentStatus::NotEnrolled { reason } => {
                 reason_value = Some(reason.to_string());
+                conflict_slug_value = match reason {
+                    crate::enrollment::NotEnrolledReason::FeatureConflict { conflict_slug } => {
+                        conflict_slug.to_owned()
+                    }
+                    _ => None,
+                };
             }
             EnrollmentStatus::WasEnrolled { branch, .. } => branch_value = Some(branch.to_owned()),
             EnrollmentStatus::Error { reason } => {
@@ -49,7 +56,7 @@ impl From<ExperimentEnrollment> for EnrollmentStatusExtraDef {
         }
         EnrollmentStatusExtraDef {
             branch: branch_value,
-            conflict_slug: None,
+            conflict_slug: conflict_slug_value,
             error_string: error_value,
             reason: reason_value,
             slug: Some(enrollment.slug),
diff --git a/components/nimbus/src/tests/test_enrollment.rs b/components/nimbus/src/tests/test_enrollment.rs
index 92888177bb..0b776f4943 100644
--- a/components/nimbus/src/tests/test_enrollment.rs
+++ b/components/nimbus/src/tests/test_enrollment.rs
@@ -1468,7 +1468,7 @@ fn test_evolver_experiment_not_enrolled_feature_conflict() -> Result<()> {
             matches!(
                 e.status,
                 EnrollmentStatus::NotEnrolled {
-                    reason: NotEnrolledReason::FeatureConflict
+                    reason: NotEnrolledReason::FeatureConflict { .. }
                 }
             )
         })
diff --git a/components/nimbus/src/tests/test_enrollment_bw_compat.rs b/components/nimbus/src/tests/test_enrollment_bw_compat.rs
index fd70cc818b..c8ad7e1bfd 100644
--- a/components/nimbus/src/tests/test_enrollment_bw_compat.rs
+++ b/components/nimbus/src/tests/test_enrollment_bw_compat.rs
@@ -62,12 +62,12 @@ fn test_not_enrolled_reason_schema_with_feature_conflict() {
     let non_enrollment: ExperimentEnrollment = serde_json::from_value(json!({
         "slug": "secure-gold",
         "status": {"NotEnrolled": {
-            "reason": "FeatureConflict",
+            "reason": { "FeatureConflict": { "conflict_slug": Some("conflicting-feature") } },
         }}
     }))
     .unwrap();
     assert!(
-        matches!(non_enrollment.status, EnrollmentStatus::NotEnrolled{ ref reason, ..} if reason == &NotEnrolledReason::FeatureConflict)
+        matches!(non_enrollment.status, EnrollmentStatus::NotEnrolled{ ref reason, ..} if reason == &NotEnrolledReason::FeatureConflict { conflict_slug: Some("conflicting-feature".to_string()) })
     );
 }