Fix memoisation leak between MMR and MMRV in OfflineSessionExporter

The `OfflineSessionExporter` was an array of programme objects as a key
for memoizing vaccine values. Because `Programme::Variant` delegates
identity methods (`hash`, `==`) to the base `Programme` class, MMR and MMRV
variants were producing identical hash keys. This caused the exporter
to return cached MMR vaccines for MMRV patients.

This commit updates the memoisation key to use the programme variant type
if it's a programe variant, otherwise fallback for programme type. This
ensures that MMR and MMRV cells have the correct vaccines.

Author: jhenderson

app/lib/reports/offline_session_exporter.rb

@@ -334,7 +334,7 @@ def add_existing_row_cells(row, vaccination_record:)
     row[:programme] = programme.import_names.first
     row[:vaccine_given] = Cell.new(
       vaccine&.upload_name,
-      allowed_values: vaccine_values_for_programmes([programme])
+      allowed_values: vaccine_values_for_programme(programme)
     )
     row[:performing_professional_email] = Cell.new(
       vaccination_record.performed_by_user&.email,
@@ -390,7 +390,7 @@ def add_new_row_cells(row, patient:, programme:)
     )
     row[:programme] = programme_variant.import_names.first
     row[:vaccine_given] = Cell.new(
-      allowed_values: vaccine_values_for_programmes([programme_variant])
+      allowed_values: vaccine_values_for_programme(programme_variant)
     )
     row[:performing_professional_email] = Cell.new(
       allowed_formula: performing_professionals_range
@@ -415,10 +415,15 @@ def add_new_row_cells(row, patient:, programme:)
     end
   end
 
-  def vaccine_values_for_programmes(programmes)
-    @vaccines[programmes] ||= Vaccine
+  def vaccine_values_for_programme(programme)
+    # We use the variant_type or type strings as the cache key because
+    # Programme::Variant delegates identity methods (hash, ==) to the base
+    # Programme. Without this, MMR vaccines would be returned for an MMRV
+    # variant.
+    cache_key = programme.try(:variant_type) || programme.type
+    @vaccines[cache_key] ||= Vaccine
       .active
-      .for_programmes(programmes)
+      .for_programmes([programme])
       .pluck(:upload_name)
   end
 

spec/lib/reports/offline_session_exporter_spec.rb

@@ -1189,4 +1189,27 @@ def validation_formula(worksheet:, column_name:, row: 1)
 
     include_examples "generates a report"
   end
+
+  describe "#vaccine_values_for_programmes" do
+    let(:programme) { Programme.mmr }
+    let(:mmr_programme_variant) do
+      Programme::Variant.new(programme, variant_type: "mmr")
+    end
+    let(:mmrv_programme_variant) do
+      Programme::Variant.new(programme, variant_type: "mmrv")
+    end
+    let(:session) { create(:session, programmes: [programme]) }
+
+    it "returns the correct vaccines for the given programme variants" do
+      exporter = described_class.send(:new, session)
+
+      expect(
+        exporter.send(:vaccine_values_for_programme, mmr_programme_variant)
+      ).to eq(%w[Priorix VaxPro])
+
+      expect(
+        exporter.send(:vaccine_values_for_programme, mmrv_programme_variant)
+      ).to eq(%w[ProQuad Priorix-Tetra])
+    end
+  end
 end