fix: invoice edit tax code diff (#4621)

Author: turip

app/config/taxcode.go

@@ -98,7 +98,7 @@ func (c TaxCodeConfiguration) Validate() error {
 func ConfigureTaxCode(v *viper.Viper) {
 	v.SetDefault("taxcode.seeds", []map[string]any{
 		{
-			"key":              "default",
+			"key":              taxcode.ProviderDefaultTaxCodeKey,
 			"name":             "Provider default",
 			"defaultInvoicing": true,
 		},

e2e/billinginvoice_discount_edit_test.go

@@ -17,7 +17,7 @@ import (
 	"github.com/openmeterio/openmeter/pkg/models"
 )
 
-func TestInvoiceEditFlatFeeDiscountCreditThenInvoice(t *testing.T) {
+func TestInvoiceEditFlatFeeDiscountCreditThenInvoiceWithDefaultedTaxCode(t *testing.T) {
 	ctx := t.Context()
 	client := initClient(t)
 	prefix := "discount_edit_" + strings.ToLower(ulid.Make().String())
@@ -111,6 +111,9 @@ func TestInvoiceEditFlatFeeDiscountCreditThenInvoice(t *testing.T) {
 			PaymentTerm: lo.ToPtr(api.PricePaymentTermInAdvance),
 		},
 		BillingCadence: lo.ToPtr("P1M"),
+		TaxConfig: &api.TaxConfig{
+			Behavior: lo.ToPtr(api.TaxBehaviorExclusive),
+		},
 	}))
 
 	planResp, err := client.CreatePlanWithResponse(ctx, api.PlanCreate{
@@ -156,6 +159,7 @@ func TestInvoiceEditFlatFeeDiscountCreditThenInvoice(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, http.StatusCreated, subscriptionResp.StatusCode(), "create subscription: %s", string(subscriptionResp.Body))
 	require.NotNil(t, subscriptionResp.JSON201)
+	t.Logf("created customer=%s subscription=%s", customerResp.JSON201.Id, subscriptionResp.JSON201.Id)
 
 	customers := api.InvoiceListParamsCustomers{customerResp.JSON201.Id}
 	invoiceExpand := api.InvoiceListParamsExpand{api.InvoiceExpandLines, api.InvoiceExpandWorkflowApps}
@@ -214,10 +218,13 @@ func TestInvoiceEditFlatFeeDiscountCreditThenInvoice(t *testing.T) {
 	require.NotNil(t, invoice.Lines)
 
 	lineIdx := slices.IndexFunc(*invoice.Lines, func(line api.InvoiceLine) bool {
-		return line.Name == lineName
+		return line.Name == lineName && line.Subscription != nil
 	})
 	require.NotEqual(t, -1, lineIdx, "invoice line %q", lineName)
 	lineID := (*invoice.Lines)[lineIdx].Id
+	require.NotNil(t, (*invoice.Lines)[lineIdx].TaxConfig, "line[%s] tax config", lineID)
+	require.NotNil(t, (*invoice.Lines)[lineIdx].TaxConfig.TaxCodeId, "line[%s] defaulted tax code", lineID)
+	t.Logf("editing invoice=%s line=%s default_tax_code=%s", invoice.Id, lineID, *(*invoice.Lines)[lineIdx].TaxConfig.TaxCodeId)
 
 	replacementLines := make([]api.InvoiceLineReplaceUpdate, 0, len(*invoice.Lines))
 	for _, line := range *invoice.Lines {
@@ -235,6 +242,10 @@ func TestInvoiceEditFlatFeeDiscountCreditThenInvoice(t *testing.T) {
 		}
 		if line.Id == lineID {
 			require.NotNil(t, lineUpdate.RateCard, "line[%s] rate card", line.Id)
+			require.NotNil(t, lineUpdate.RateCard.TaxConfig, "line[%s] rate card tax config", line.Id)
+			lineUpdate.RateCard.TaxConfig.TaxCodeId = nil
+			require.NotNil(t, lineUpdate.TaxConfig, "line[%s] tax config", line.Id)
+			lineUpdate.TaxConfig.TaxCodeId = nil
 			lineUpdate.RateCard.Discounts = &api.BillingDiscounts{
 				Percentage: &api.BillingDiscountPercentage{
 					Percentage: models.NewPercentage(50),

openmeter/billing/httpdriver/invoiceline.go

@@ -787,13 +787,7 @@ func mergeStandardLineFromInvoiceLineReplaceUpdate(existing *billing.StandardLin
 	existing.Period.To = line.Period.To.Truncate(streaming.MinimumWindowSizeDuration)
 	existing.InvoiceAt = line.InvoiceAt.Truncate(streaming.MinimumWindowSizeDuration)
 
-	taxConfig := billing.FromProductCatalog(rateCardParsed.TaxConfig)
-	if existing.TaxConfig != nil && existing.TaxConfig.ToProductCatalog().Equal(rateCardParsed.TaxConfig) {
-		clonedTaxConfig := existing.TaxConfig.Clone()
-		taxConfig = &clonedTaxConfig
-	}
-
-	existing.TaxConfig = taxConfig
+	existing.TaxConfig = billing.FromProductCatalog(rateCardParsed.TaxConfig)
 	existing.UsageBased.Price = rateCardParsed.Price
 	existing.UsageBased.FeatureKey = rateCardParsed.FeatureKey
 	existing.RateCardDiscounts = rateCardParsed.Discounts

openmeter/billing/httpdriver/invoiceline_test.go

@@ -16,7 +16,7 @@ import (
 	"github.com/openmeterio/openmeter/pkg/timeutil"
 )
 
-func TestMergeStandardLineFromInvoiceLineReplaceUpdatePreservesResolvedTaxCode(t *testing.T) {
+func TestMergeStandardLineFromInvoiceLineReplaceUpdateOverwritesTaxConfig(t *testing.T) {
 	price := api.RateCardUsageBasedPrice{}
 	require.NoError(t, price.FromUnitPriceWithCommitments(api.UnitPriceWithCommitments{
 		Amount: "1",
@@ -84,8 +84,74 @@ func TestMergeStandardLineFromInvoiceLineReplaceUpdatePreservesResolvedTaxCode(t
 	})
 	require.NoError(t, err)
 	require.NotNil(t, mergedLine.TaxConfig)
-	require.NotNil(t, mergedLine.TaxConfig.TaxCode)
-	require.Equal(t, taxCodeID, mergedLine.TaxConfig.TaxCode.ID)
+	require.Equal(t, taxCodeID, *mergedLine.TaxConfig.TaxCodeID)
+	require.Nil(t, mergedLine.TaxConfig.TaxCode)
+}
+
+func TestMergeStandardLineFromInvoiceLineReplaceUpdateLeavesProviderDefaultOmissionForInvoiceNormalization(t *testing.T) {
+	period := invoiceLineTestPeriod()
+	line := standardInvoiceLineForMergeTest(t, period)
+
+	defaultTaxCodeID := "default-tax-code-id"
+	productCatalogTaxBehavior := productcatalog.ExclusiveTaxBehavior
+	line.TaxConfig = &billing.TaxConfig{
+		TaxConfig: productcatalog.TaxConfig{
+			Behavior:  &productCatalogTaxBehavior,
+			TaxCodeID: &defaultTaxCodeID,
+		},
+		TaxCode: &taxcode.TaxCode{
+			NamespacedID: models.NamespacedID{
+				Namespace: "ns",
+				ID:        defaultTaxCodeID,
+			},
+			Name: "Default Tax Code",
+		},
+	}
+
+	taxBehavior := api.TaxBehaviorExclusive
+	mergedLine, err := mergeStandardLineFromInvoiceLineReplaceUpdate(line, invoiceLineReplaceUpdateForMergeTest(t, period, line.UsageBased.FeatureKey, "1", func(update *api.InvoiceLineReplaceUpdate) {
+		update.RateCard.TaxConfig = &api.TaxConfig{
+			Behavior: &taxBehavior,
+		}
+		update.TaxConfig = update.RateCard.TaxConfig
+	}))
+	require.NoError(t, err)
+	require.NotNil(t, mergedLine.TaxConfig)
+	require.Nil(t, mergedLine.TaxConfig.TaxCodeID)
+	require.Nil(t, mergedLine.TaxConfig.TaxCode)
+}
+
+func TestMergeStandardLineFromInvoiceLineReplaceUpdateDoesNotPreserveExplicitTaxCodeWhenPayloadOmitsTaxCodeIdentity(t *testing.T) {
+	period := invoiceLineTestPeriod()
+	line := standardInvoiceLineForMergeTest(t, period)
+
+	explicitTaxCodeID := "explicit-tax-code-id"
+	productCatalogTaxBehavior := productcatalog.ExclusiveTaxBehavior
+	line.TaxConfig = &billing.TaxConfig{
+		TaxConfig: productcatalog.TaxConfig{
+			Behavior:  &productCatalogTaxBehavior,
+			TaxCodeID: &explicitTaxCodeID,
+		},
+		TaxCode: &taxcode.TaxCode{
+			NamespacedID: models.NamespacedID{
+				Namespace: "ns",
+				ID:        explicitTaxCodeID,
+			},
+			Name: "Explicit Tax Code",
+		},
+	}
+
+	taxBehavior := api.TaxBehaviorExclusive
+	mergedLine, err := mergeStandardLineFromInvoiceLineReplaceUpdate(line, invoiceLineReplaceUpdateForMergeTest(t, period, line.UsageBased.FeatureKey, "1", func(update *api.InvoiceLineReplaceUpdate) {
+		update.RateCard.TaxConfig = &api.TaxConfig{
+			Behavior: &taxBehavior,
+		}
+		update.TaxConfig = update.RateCard.TaxConfig
+	}))
+	require.NoError(t, err)
+	require.NotNil(t, mergedLine.TaxConfig)
+	require.Nil(t, mergedLine.TaxConfig.TaxCodeID)
+	require.Nil(t, mergedLine.TaxConfig.TaxCode)
 }
 
 func TestMergeStandardLineFromInvoiceLineReplaceUpdateDropsResolvedTaxCodeWhenTaxConfigChanges(t *testing.T) {

openmeter/billing/service/gatheringinvoice.go

@@ -72,7 +72,7 @@ func (s *Service) UpdateGatheringInvoice(ctx context.Context, input billing.Upda
 			return billing.GatheringInvoice{}, fmt.Errorf("normalizing lines: %w", err)
 		}
 
-		lineDiff, err := s.diffMutableInvoiceLines(originalInvoice, invoice, input.ChangeSource)
+		lineDiff, err := s.diffMutableInvoiceLines(ctx, originalInvoice, invoice, input.ChangeSource)
 		if err != nil {
 			return billing.GatheringInvoice{}, billing.ValidationError{
 				Err: fmt.Errorf("collecting mutable invoice line changes: %w", err),