fix(gcp/computeengine): follow every page of the billing SKU listing

providers/gcp/services/computeengine/client.go

@@ -29,6 +29,7 @@ import (
 
 	"github.com/LeanerCloud/cloud-commitments-go/pkg/common"
 	"github.com/LeanerCloud/cloud-commitments-go/pkg/retry"
+	"github.com/LeanerCloud/cloud-commitments-go/providers/gcp/internal/skulist"
 	"github.com/LeanerCloud/cloud-commitments-go/providers/gcp/internal/skumatch"
 )
 
@@ -335,13 +336,23 @@ func (r *realMachineTypesService) Close() error {
 
 // realBillingService wraps the real cloudbilling.APIService.
 type realBillingService struct {
+	ctx     context.Context
 	service *cloudbilling.APIService
 }
 
+// ListSKUs returns every SKU of the service: the Compute Engine catalog is
+// 33,453 SKUs over 7 pages of 5000, so a single call misses most of it.
 func (r *realBillingService) ListSKUs(serviceID string) (*cloudbilling.ListSkusResponse, error) {
-	return r.service.Services.Skus.List(serviceID).Do()
+	skus, err := skulist.All(r.ctx, r.service.Services.Skus.List(serviceID).PageSize(skuPageSize), skulist.DefaultMaxPages)
+	if err != nil {
+		return nil, fmt.Errorf("computeengine: list SKUs for %s: %w", serviceID, err)
+	}
+	return &cloudbilling.ListSkusResponse{Skus: skus}, nil
 }
 
+// skuPageSize is the largest page the catalog serves.
+const skuPageSize = 5000
+
 // realRecommenderIterator wraps the real recommender iterator.
 type realRecommenderIterator struct {
 	it *recommender.RecommendationIterator
@@ -1099,7 +1110,7 @@ func (c *Client) getOrCreateBillingService(ctx context.Context) (BillingService,
 		return nil, fmt.Errorf("failed to create billing service: %w", err)
 	}
 
-	return &realBillingService{service: service}, nil
+	return &realBillingService{ctx: ctx, service: service}, nil
 }
 
 // extractComputePricingFromSKUs extracts on-demand and commitment pricing from SKU list.

providers/gcp/services/computeengine/paging_test.go

@@ -0,0 +1,66 @@
+package computeengine
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"strconv"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/api/cloudbilling/v1"
+	"google.golang.org/api/option"
+)
+
+// catalogServer serves total synthetic SKUs in pages of pageSize and records the
+// page tokens it was asked for.
+func catalogServer(t *testing.T, total, pageSize int, tokens *[]string) *httptest.Server {
+	t.Helper()
+	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		token := r.URL.Query().Get("pageToken")
+		*tokens = append(*tokens, token)
+		start := 0
+		if token != "" {
+			start, _ = strconv.Atoi(token)
+		}
+		end := min(start+pageSize, total)
+		var body strings.Builder
+		body.WriteString(`{"skus":[`)
+		for i := start; i < end; i++ {
+			if i > start {
+				body.WriteString(",")
+			}
+			fmt.Fprintf(&body, `{"skuId":"sku-%d"}`, i)
+		}
+		body.WriteString("]")
+		if end < total {
+			fmt.Fprintf(&body, `,"nextPageToken":"%d"`, end)
+		}
+		body.WriteString("}")
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(body.String()))
+	}))
+}
+
+func billingAgainst(t *testing.T, srv *httptest.Server) *realBillingService {
+	t.Helper()
+	api, err := cloudbilling.NewService(context.Background(), option.WithEndpoint(srv.URL), option.WithoutAuthentication())
+	require.NoError(t, err)
+	return &realBillingService{ctx: context.Background(), service: api}
+}
+
+// The live Compute Engine catalog is 33,453 SKUs over 7 pages of 5000; reading
+// only the first page left the commitment SKUs unseen.
+func TestRealBillingService_ListSKUsFollowsEveryPage(t *testing.T) {
+	var tokens []string
+	srv := catalogServer(t, 33453, 5000, &tokens)
+	defer srv.Close()
+
+	resp, err := billingAgainst(t, srv).ListSKUs("services/6F81-5844-456A")
+	require.NoError(t, err)
+	assert.Len(t, resp.Skus, 33453)
+	assert.Len(t, tokens, 7)
+}