feat: expose costs

router-tests/go.mod

@@ -26,7 +26,7 @@ require (
 	github.com/wundergraph/cosmo/demo/pkg/subgraphs/projects v0.0.0-20250715110703-10f2e5f9c79e
 	github.com/wundergraph/cosmo/router v0.0.0-20251125205644-175f80c4e6d9
 	github.com/wundergraph/cosmo/router-plugin v0.0.0-20250808194725-de123ba1c65e
-	github.com/wundergraph/graphql-go-tools/v2 v2.0.0-rc.245
+	github.com/wundergraph/graphql-go-tools/v2 v2.0.0-rc.246
 	go.opentelemetry.io/otel v1.36.0
 	go.opentelemetry.io/otel/sdk v1.36.0
 	go.opentelemetry.io/otel/sdk/metric v1.36.0

router-tests/go.sum

@@ -352,8 +352,8 @@ github.com/wk8/go-ordered-map/v2 v2.1.8 h1:5h/BUHu93oj4gIdvHHHGsScSTMijfx5PeYkE/
 github.com/wk8/go-ordered-map/v2 v2.1.8/go.mod h1:5nJHM5DyteebpVlHnWMV0rPz6Zp7+xBAnxjb1X5vnTw=
 github.com/wundergraph/astjson v0.0.0-20250106123708-be463c97e083 h1:8/D7f8gKxTBjW+SZK4mhxTTBVpxcqeBgWF1Rfmltbfk=
 github.com/wundergraph/astjson v0.0.0-20250106123708-be463c97e083/go.mod h1:eOTL6acwctsN4F3b7YE+eE2t8zcJ/doLm9sZzsxxxrE=
-github.com/wundergraph/graphql-go-tools/v2 v2.0.0-rc.245 h1:MYewlXgIhI9jusocPUeyo346J3M5cqzc6ddru1qp+S8=
-github.com/wundergraph/graphql-go-tools/v2 v2.0.0-rc.245/go.mod h1:mX25ASEQiKamxaFSK6NZihh0oDCigIuzro30up4mFH4=
+github.com/wundergraph/graphql-go-tools/v2 v2.0.0-rc.246 h1:B4/E6zJ5PbHNqcNw4Bvki7o+alcgyz8L5+Nlq1FZbLM=
+github.com/wundergraph/graphql-go-tools/v2 v2.0.0-rc.246/go.mod h1:mX25ASEQiKamxaFSK6NZihh0oDCigIuzro30up4mFH4=
 github.com/xrash/smetrics v0.0.0-20250705151800-55b8f293f342 h1:FnBeRrxr7OU4VvAzt5X7s6266i6cSVkkFPS0TuXWbIg=
 github.com/xrash/smetrics v0.0.0-20250705151800-55b8f293f342/go.mod h1:Ohn+xnUBiLI6FVj/9LpzZWtj1/D6lUovWYBkxHVV3aM=
 github.com/yosida95/uritemplate/v3 v3.0.2 h1:Ed3Oyj9yrmi9087+NczuL5BwkIc4wvTb5zIM+UJPGz4=

router-tests/modules/custom_trace_propagator_test.go

@@ -1,4 +1,4 @@
-package module
+package module_test
 
 import (
 	"encoding/json"

router-tests/modules/streams_hooks_combined_test.go

@@ -1,4 +1,4 @@
-package module
+package module_test
 
 import (
 	"encoding/json"
@@ -8,6 +8,8 @@ import (
 	"github.com/hasura/go-graphql-client"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"go.uber.org/zap/zapcore"
+
 	"github.com/wundergraph/cosmo/router-tests/events"
 	stream_publish "github.com/wundergraph/cosmo/router-tests/modules/stream-publish"
 	stream_receive "github.com/wundergraph/cosmo/router-tests/modules/stream-receive"
@@ -16,7 +18,6 @@ import (
 	"github.com/wundergraph/cosmo/router/pkg/config"
 	"github.com/wundergraph/cosmo/router/pkg/pubsub/datasource"
 	"github.com/wundergraph/cosmo/router/pkg/pubsub/kafka"
-	"go.uber.org/zap/zapcore"
 )
 
 func TestStreamsHooksCombined(t *testing.T) {

router-tests/modules/verify-cost-analysis/module.go

@@ -0,0 +1,63 @@
+package verify_cost_analysis
+
+import (
+	"net/http"
+
+	"go.uber.org/zap"
+
+	"github.com/wundergraph/cosmo/router/core"
+)
+
+const myModuleID = "verifyCost"
+
+// CapturedCost holds the captured cost from operation context
+type CapturedCost struct {
+	Cost  core.OperationCost
+	Error error
+}
+
+// VerifyCostModule captures cost for verification in tests
+type VerifyCostModule struct {
+	ResultsChan chan CapturedCost
+	Logger      *zap.Logger
+}
+
+func (m *VerifyCostModule) Provision(ctx *core.ModuleContext) error {
+	m.Logger = ctx.Logger
+	if m.ResultsChan == nil {
+		m.ResultsChan = make(chan CapturedCost, 1)
+	}
+	return nil
+}
+
+func (m *VerifyCostModule) Middleware(ctx core.RequestContext, next http.Handler) {
+	operation := ctx.Operation()
+
+	cost, err := operation.Cost()
+	captured := CapturedCost{Cost: cost, Error: err}
+
+	// Send the captured values to the test
+	select {
+	case m.ResultsChan <- captured:
+	default:
+		// Channel is full, skip
+	}
+
+	next.ServeHTTP(ctx.ResponseWriter(), ctx.Request())
+}
+
+func (m *VerifyCostModule) Module() core.ModuleInfo {
+	return core.ModuleInfo{
+		ID:       myModuleID,
+		Priority: 1,
+		New: func() core.Module {
+			return &VerifyCostModule{
+				ResultsChan: make(chan CapturedCost, 1),
+			}
+		},
+	}
+}
+
+var (
+	_ core.RouterMiddlewareHandler = (*VerifyCostModule)(nil)
+)

router-tests/modules/verify_cost_analysis_test.go

@@ -0,0 +1,103 @@
+package module_test
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	verifyModule "github.com/wundergraph/cosmo/router-tests/modules/verify-cost-analysis"
+	"github.com/wundergraph/cosmo/router-tests/testenv"
+	"github.com/wundergraph/cosmo/router/core"
+	"github.com/wundergraph/cosmo/router/pkg/config"
+)
+
+func TestCostModuleExposition(t *testing.T) {
+	t.Parallel()
+
+	t.Run("module can access cost when cost analysis is enabled", func(t *testing.T) {
+		t.Parallel()
+
+		resultsChan := make(chan verifyModule.CapturedCost, 1)
+
+		cfg := config.Config{
+			Graph: config.Graph{},
+			Modules: map[string]any{
+				"verifyCost": verifyModule.VerifyCostModule{
+					ResultsChan: resultsChan,
+				},
+			},
+		}
+
+		testenv.Run(t, &testenv.Config{
+			RouterOptions: []core.Option{
+				core.WithModulesConfig(cfg.Modules),
+				core.WithCustomModules(&verifyModule.VerifyCostModule{}),
+			},
+			ModifySecurityConfiguration: func(securityConfiguration *config.SecurityConfiguration) {
+				securityConfiguration.CostAnalysis = &config.CostAnalysis{
+					Enabled:           true,
+					Mode:              config.CostAnalysisModeMeasure,
+					EstimatedListSize: 10,
+				}
+			},
+		}, func(t *testing.T, xEnv *testenv.Environment) {
+			res, err := xEnv.MakeGraphQLRequest(testenv.GraphQLRequest{
+				Query: `query GetEmployee { employee(id: 1) { id } }`,
+			})
+			require.NoError(t, err)
+			assert.Equal(t, 200, res.Response.StatusCode)
+
+			testenv.AwaitChannelWithT(t, 10*time.Second, resultsChan, func(t *testing.T, captured verifyModule.CapturedCost) {
+				assert.NoError(t, captured.Error, "Cost() should not return an error when cost analysis is enabled")
+				assert.Greater(t, captured.Cost.Estimated, 0, "Estimated cost should be greater than 0 for a query with object fields")
+
+				// Log the cost for demonstration purposes
+				t.Logf("Query estimated cost: %d (could be used for rate limiting)", captured.Cost.Estimated)
+				// In a real module, you could use this cost for:
+				// - Rate limiting (deduct from user's cost budget)
+				// - Logging/metrics
+				// - Custom rejection logic
+				// - Billing/monetization
+
+			})
+		})
+	})
+
+	t.Run("module receives error when cost analysis is disabled", func(t *testing.T) {
+		t.Parallel()
+
+		resultsChan := make(chan verifyModule.CapturedCost, 1)
+
+		cfg := config.Config{
+			Graph: config.Graph{},
+			Modules: map[string]any{
+				"verifyCost": verifyModule.VerifyCostModule{
+					ResultsChan: resultsChan,
+				},
+			},
+		}
+
+		testenv.Run(t, &testenv.Config{
+			RouterOptions: []core.Option{
+				core.WithModulesConfig(cfg.Modules),
+				core.WithCustomModules(&verifyModule.VerifyCostModule{}),
+			},
+			ModifySecurityConfiguration: func(securityConfiguration *config.SecurityConfiguration) {
+				securityConfiguration.CostAnalysis = nil
+			},
+		}, func(t *testing.T, xEnv *testenv.Environment) {
+			res, err := xEnv.MakeGraphQLRequest(testenv.GraphQLRequest{
+				Query: `query GetEmployee { employee(id: 1) { id } }`,
+			})
+			require.NoError(t, err)
+			assert.Equal(t, 200, res.Response.StatusCode)
+
+			testenv.AwaitChannelWithT(t, 10*time.Second, resultsChan, func(t *testing.T, captured verifyModule.CapturedCost) {
+				assert.Error(t, captured.Error, "Cost() should return an error when cost analysis is disabled")
+				assert.Equal(t, 0, captured.Cost.Estimated, "Estimated cost should be 0 when cost analysis is disabled")
+			})
+		})
+	})
+}