Basic implementation of variant 2 from #1802

In this case we give the Module a function to get the context and it
needs to that whenever it needs it instead of just caching it's value
... Especially between function call or something like that

js/initcontext.go

@@ -147,6 +147,14 @@ func (i *InitContext) requireModule(name string) (goja.Value, error) {
 	if perInstance, ok := mod.(modules.HasModuleInstancePerVU); ok {
 		mod = perInstance.NewModuleInstancePerVU()
 	}
+
+	if withContext, ok := mod.(modules.HasWithContext); ok {
+		withContext.WithContext(func() context.Context {
+			return *i.ctxPtr
+		})
+		return i.runtime.ToValue(mod), nil
+	}
+
 	return i.runtime.ToValue(common.Bind(i.runtime, mod, i.ctxPtr)), nil
 }
 

js/modules/k6/metrics/metrics.go

@@ -43,32 +43,39 @@ func checkName(name string) bool {
 }
 
 type Metric struct {
-	metric *stats.Metric
+	metric     *stats.Metric
+	getContext func() context.Context
 }
 
 // ErrMetricsAddInInitContext is error returned when adding to metric is done in the init context
 var ErrMetricsAddInInitContext = common.NewInitContextError("Adding to metrics in the init context is not supported")
 
-func newMetric(ctxPtr *context.Context, name string, t stats.MetricType, isTime []bool) (interface{}, error) {
-	if lib.GetState(*ctxPtr) != nil {
+func (m *MetricsModule) newMetric(call goja.ConstructorCall, t stats.MetricType) (*goja.Object, error) {
+	ctx := m.getContext()
+	if lib.GetState(ctx) != nil {
 		return nil, errors.New("metrics must be declared in the init context")
 	}
+	rt := common.GetRuntime(ctx) // NOTE we can get this differently as well
 
+	// TODO this kind of conversions can possibly be automated by the parts of common.Bind that are curently automating
+	// it and some wrapping
+	name := call.Argument(0).String()
+	isTime := call.Argument(1).ToBoolean()
 	// TODO: move verification outside the JS
 	if !checkName(name) {
 		return nil, common.NewInitContextError(fmt.Sprintf("Invalid metric name: '%s'", name))
 	}
 
 	valueType := stats.Default
-	if len(isTime) > 0 && isTime[0] {
+	if isTime {
 		valueType = stats.Time
 	}
 
-	rt := common.GetRuntime(*ctxPtr)
-	return common.Bind(rt, Metric{stats.New(name, t, valueType)}, ctxPtr), nil
+	return rt.ToValue(Metric{metric: stats.New(name, t, valueType), getContext: m.getContext}).ToObject(rt), nil
 }
 
-func (m Metric) Add(ctx context.Context, v goja.Value, addTags ...map[string]string) (bool, error) {
+func (m Metric) Add(v goja.Value, addTags ...map[string]string) (bool, error) {
+	ctx := m.getContext()
 	state := lib.GetState(ctx)
 	if state == nil {
 		return false, ErrMetricsAddInInitContext
@@ -96,24 +103,52 @@ func (m Metric) GetName() string {
 	return m.metric.Name
 }
 
-type Metrics struct{}
+type MetricsModule struct {
+	getContext func() context.Context
+}
 
-func New() *Metrics {
-	return &Metrics{}
+func (m *MetricsModule) WithContext(getContext func() context.Context) {
+	m.getContext = getContext
 }
 
-func (*Metrics) XCounter(ctx *context.Context, name string, isTime ...bool) (interface{}, error) {
-	return newMetric(ctx, name, stats.Counter, isTime)
+func New() *MetricsModule {
+	return &MetricsModule{}
 }
 
-func (*Metrics) XGauge(ctx *context.Context, name string, isTime ...bool) (interface{}, error) {
-	return newMetric(ctx, name, stats.Gauge, isTime)
+// This is not possible after common.Bind as it wraps the object and doesn't return the original one.
+func (m *MetricsModule) ReturnMetricType(metric Metric) string {
+	return metric.metric.Type.String()
 }
 
-func (*Metrics) XTrend(ctx *context.Context, name string, isTime ...bool) (interface{}, error) {
-	return newMetric(ctx, name, stats.Trend, isTime)
+// Counter ... // NOTE we still need to use goja.ConstructorCall  somewhere to have access to the
+func (m *MetricsModule) XCounter(call goja.ConstructorCall, rt *goja.Runtime) *goja.Object {
+	v, err := m.newMetric(call, stats.Counter)
+	if err != nil {
+		common.Throw(rt, err)
+	}
+	return v
+}
+
+func (m *MetricsModule) XGauge(call goja.ConstructorCall, rt *goja.Runtime) *goja.Object {
+	v, err := m.newMetric(call, stats.Gauge)
+	if err != nil {
+		common.Throw(rt, err)
+	}
+	return v
 }
 
-func (*Metrics) XRate(ctx *context.Context, name string, isTime ...bool) (interface{}, error) {
-	return newMetric(ctx, name, stats.Rate, isTime)
+func (m *MetricsModule) XTrend(call goja.ConstructorCall, rt *goja.Runtime) *goja.Object {
+	v, err := m.newMetric(call, stats.Trend)
+	if err != nil {
+		common.Throw(rt, err)
+	}
+	return v
+}
+
+func (m *MetricsModule) XRate(call goja.ConstructorCall, rt *goja.Runtime) *goja.Object {
+	v, err := m.newMetric(call, stats.Rate)
+	if err != nil {
+		common.Throw(rt, err)
+	}
+	return v
 }

js/modules/k6/metrics/metrics_test.go

@@ -64,8 +64,9 @@ func TestMetrics(t *testing.T) {
 
 					ctxPtr := new(context.Context)
 					*ctxPtr = common.WithRuntime(context.Background(), rt)
-					rt.Set("metrics", common.Bind(rt, New(), ctxPtr))
-
+					m := New()
+					m.WithContext(func() context.Context { return *ctxPtr })
+					rt.Set("metrics", m)
 					root, _ := lib.NewGroup("", nil)
 					child, _ := root.Group("child")
 					samples := make(chan stats.SampleContainer, 1000)
@@ -86,7 +87,7 @@ func TestMetrics(t *testing.T) {
 					t.Run("ExitInit", func(t *testing.T) {
 						*ctxPtr = lib.WithState(*ctxPtr, state)
 						_, err := rt.RunString(fmt.Sprintf(`new metrics.%s("my_metric")`, fn))
-						assert.EqualError(t, err, "metrics must be declared in the init context at apply (native)")
+						assert.Contains(t, err.Error(), "metrics must be declared in the init context")
 					})
 
 					groups := map[string]*lib.Group{

js/modules/modules.go

@@ -21,6 +21,7 @@
 package modules
 
 import (
+	"context"
 	"fmt"
 	"strings"
 	"sync"
@@ -69,6 +70,12 @@ type HasModuleInstancePerVU interface {
 	NewModuleInstancePerVU() interface{}
 }
 
+// HasWithContext should be implemented by modules that need access to the context, which should be all of them
+type HasWithContext interface { // TODO rename?
+	// This specifically is a function *returning* context as it can change between invocations
+	WithContext(func() context.Context) // this can be a different object that just has a context getter
+}
+
 // checks that modules implement HasModuleInstancePerVU
 // this is done here as otherwise there will be a loop if the module imports this package
 var _ HasModuleInstancePerVU = http.New()