Merge pull request #1148 from suhr25/fix/empty-cohort-queries-guard

fix: raise clear error when all cohorts are filtered out in _setup_cohort_queries

Author: jonbrenas

malariagen_data/anoph/sample_metadata.py

@@ -1543,6 +1543,12 @@ def _setup_cohort_queries(
             else:
                 cohort_queries_checked[cohort_label] = cohort_query
 
+        if not cohort_queries_checked:
+            raise ValueError(
+                "No cohorts remain after applying the minimum cohort size filter. "
+                "Try reducing `min_cohort_size` or broadening your sample selection."
+            )
+
         return cohort_queries_checked
 
     @_check_types

tests/anoph/test_fst.py

@@ -297,7 +297,7 @@ def test_pairwise_average_fst_with_min_cohort_size(fixture, api: AnophelesFstAna
         cohorts=cohorts,
         sample_sets=all_sample_sets,
         site_mask=site_mask,
-        min_cohort_size=15,
+        min_cohort_size=2,
         n_jack=random.randint(10, 200),
     )