fix: regression in gathering invoice rendering

openmeter/billing/adapter/gatheringinvoice.go

@@ -422,6 +422,8 @@ func (a *adapter) mapGatheringInvoiceFromDB(ctx context.Context, invoice *db.Bil
 			NextCollectionAt: invoice.CollectionAt.In(time.UTC),
 			SchemaLevel:      invoice.SchemaLevel,
 		},
+
+		Expands: expand,
 	}
 
 	if expand.Has(billing.GatheringInvoiceExpandLines) {

openmeter/billing/gatheringinvoice.go

@@ -75,7 +75,7 @@ type GatheringInvoice struct {
 	// these lines too.
 	AvailableActions *GatheringInvoiceAvailableActions `json:"availableActions,omitempty"`
 
-	SplitLineHierarchy *SplitLineHierarchy `json:"splitLineHierarchy,omitempty"`
+	Expands GatheringInvoiceExpands `json:"expands,omitempty"`
 }
 
 func (g GatheringInvoice) WithoutDBState() (GatheringInvoice, error) {
@@ -158,6 +158,7 @@ func (g GatheringInvoice) Clone() (GatheringInvoice, error) {
 	}
 
 	clone.Lines = clonedLines
+	clone.Expands = g.Expands.Clone()
 
 	return clone, nil
 }
@@ -681,6 +682,16 @@ func (g GatheringLine) AsNewStandardLine(invoiceID string) (*StandardLine, error
 		subscription = g.Subscription.Clone()
 	}
 
+	var splitLineHierarchy *SplitLineHierarchy
+	if g.SplitLineHierarchy != nil {
+		clonedSHierarchy, err := g.SplitLineHierarchy.Clone()
+		if err != nil {
+			return nil, fmt.Errorf("cloning split line hierarchy: %w", err)
+		}
+
+		splitLineHierarchy = lo.ToPtr(clonedSHierarchy)
+	}
+
 	convertedLine := &StandardLine{
 		StandardLineBase: StandardLineBase{
 			ManagedResource: g.ManagedResource,
@@ -708,6 +719,8 @@ func (g GatheringLine) AsNewStandardLine(invoiceID string) (*StandardLine, error
 			FeatureKey: g.FeatureKey,
 		},
 
+		SplitLineHierarchy: splitLineHierarchy,
+
 		DBState: nil, // We don't want to reuse the state from the gathering line (so let's make it explicit)
 	}
 

openmeter/billing/service/invoice.go

@@ -166,13 +166,35 @@ func (s *Service) calculateGatheringInvoiceAsStandardInvoice(ctx context.Context
 		return nil, fmt.Errorf("creating standard invoice from gathering invoice: %w", err)
 	}
 
-	wasLinesAbsent := invoice.Lines.IsAbsent()
+	wasLinesPresent := invoice.Lines.IsPresent()
 
-	if wasLinesAbsent {
+	shouldReloadLines := !wasLinesPresent
+
+	if !invoice.Expands.Has(billing.GatheringInvoiceExpandSplitLineHierarchy) && wasLinesPresent {
+		// If the invoice has lines and the splitline hierarchy is not expanded, we need to check if there are any progressive billed lines
+		// and reload the invoice as price calculations depend on the presence of the split line hierarchy.
+
+		progressiveBilledLineCount := lo.CountBy(invoice.Lines.OrEmpty(), func(line billing.GatheringLine) bool {
+			if line.DeletedAt != nil {
+				return false
+			}
+
+			return line.SplitLineGroupID != nil
+		})
+
+		if progressiveBilledLineCount > 0 {
+			shouldReloadLines = true
+		}
+	}
+
+	// If the gathering invoice has no splitline hierarchy expanded we need to reload the invoice so that the price calculations can
+	// properly proceed.
+	if shouldReloadLines {
 		// Let's reload the whole invoice with lines expanded
 		invoice, err = s.adapter.GetGatheringInvoiceById(ctx, billing.GetGatheringInvoiceByIdInput{
 			Invoice: in.Invoice.GetInvoiceID(),
-			Expand:  billing.GatheringInvoiceExpandAll,
+			Expand: billing.GatheringInvoiceExpandAll.
+				With(billing.GatheringInvoiceExpandSplitLineHierarchy),
 		})
 		if err != nil {
 			return nil, fmt.Errorf("fetching gathering invoice: %w", err)
@@ -223,7 +245,7 @@ func (s *Service) calculateGatheringInvoiceAsStandardInvoice(ctx context.Context
 		return nil, fmt.Errorf("calculating invoice: %w", err)
 	}
 
-	if wasLinesAbsent {
+	if !wasLinesPresent {
 		// If the original user intent was to not to receive the lines, let's not send them
 		out.Lines = billing.StandardInvoiceLines{}
 	} else {

test/billing/invoice_test.go

@@ -283,6 +283,8 @@ func (s *InvoicingTestSuite) TestPendingLineCreation() {
 			},
 
 			Lines: billing.NewGatheringInvoiceLines([]billing.GatheringLine{expectedUSDLine}),
+
+			Expands: []billing.GatheringInvoiceExpand{billing.GatheringInvoiceExpandLines},
 		}
 
 		s.NoError(invoicecalc.GatheringInvoiceCollectionAt(&expectedInvoice))