Don't require InstanceCore to be embeded

Also rename it as it now makes less sense to be called that way. As well
as remove GenerateExports and make module authors to actually specify
exactly what they will export.

js/modules/k6/execution/execution.go

@@ -40,7 +40,7 @@ type (
 
 	// ModuleInstance represents an instance of the execution module.
 	ModuleInstance struct {
-		modules.InstanceCore
+		modules.InstanceParams
 		obj *goja.Object
 	}
 )
@@ -57,8 +57,8 @@ func New() *RootModule {
 
 // NewModuleInstance implements the modules.IsModuleV2 interface to return
 // a new instance for each VU.
-func (*RootModule) NewModuleInstance(m modules.InstanceCore) modules.Instance {
-	mi := &ModuleInstance{InstanceCore: m}
+func (*RootModule) NewModuleInstance(m modules.InstanceParams) modules.Instance {
+	mi := &ModuleInstance{InstanceParams: m}
 	rt := m.GetRuntime()
 	o := rt.NewObject()
 	defProp := func(name string, newInfo func() (*goja.Object, error)) {

js/modules/k6/metrics/metrics.go

@@ -37,7 +37,7 @@ import (
 
 type Metric struct {
 	metric *stats.Metric
-	core   modules.InstanceCore
+	core   modules.InstanceParams
 }
 
 // ErrMetricsAddInInitContext is error returned when adding to metric is done in the init context
@@ -58,7 +58,7 @@ func (mi *ModuleInstance) newMetric(call goja.ConstructorCall, t stats.MetricTyp
 		if err != nil {
 			return nil, err
 		}
-		metric := &Metric{metric: m, core: mi.InstanceCore}
+		metric := &Metric{metric: m, core: mi.InstanceParams}
 		o := rt.NewObject()
 		err = o.DefineDataProperty("name", rt.ToValue(name), goja.FLAG_FALSE, goja.FLAG_FALSE, goja.FLAG_TRUE)
 		if err != nil {
@@ -139,7 +139,7 @@ type (
 	RootModule struct{}
 	// ModuleInstance represents an instance of the metrics module
 	ModuleInstance struct {
-		modules.InstanceCore
+		modules.InstanceParams
 	}
 )
 
@@ -149,8 +149,8 @@ var (
 )
 
 // NewModuleInstance implements modules.IsModuleV2 interface
-func (*RootModule) NewModuleInstance(m modules.InstanceCore) modules.Instance {
-	return &ModuleInstance{InstanceCore: m}
+func (*RootModule) NewModuleInstance(m modules.InstanceParams) modules.Instance {
+	return &ModuleInstance{InstanceParams: m}
 }
 
 // New returns a new RootModule.
@@ -160,7 +160,14 @@ func New() *RootModule {
 
 // Exports returns the exports of the metrics module
 func (mi *ModuleInstance) Exports() modules.Exports {
-	return modules.GenerateExports(mi)
+	return modules.Exports{
+		Named: map[string]interface{}{
+			"Counter": mi.XCounter,
+			"Gauge":   mi.XGauge,
+			"Trend":   mi.XTrend,
+			"Rate":    mi.XRate,
+		},
+	}
 }
 
 // XCounter is a counter constructor

js/modules/modules.go

@@ -70,7 +70,7 @@ type Module interface {
 	// NewModuleInstance will get InstanceCore that should provide the module with *everything* it needs and return an
 	// Instance implementation (embedding the InstanceCore).
 	// This method will be called for *each* require/import and return an object for VUs.
-	NewModuleInstance(InstanceCore) Instance
+	NewModuleInstance(InstanceParams) Instance
 }
 
 // checks that modules implement HasModuleInstancePerVU
@@ -92,7 +92,6 @@ func GetJSModules() map[string]interface{} {
 
 // Instance is what a module needs to return
 type Instance interface {
-	InstanceCore
 	Exports() Exports
 }
 
@@ -108,8 +107,9 @@ func getInterfaceMethods() []string {
 	return result
 }
 
-// InstanceCore is something that will be provided to modules and they need to embed it in ModuleInstance
-type InstanceCore interface {
+// InstanceParams is something that will be provided to module instance on initialization so that it can get access to
+// everything it needs
+type InstanceParams interface {
 	GetContext() context.Context
 
 	// GetInitEnv returns common.InitEnvironment instance if present
@@ -120,9 +120,6 @@ type InstanceCore interface {
 
 	// GetRuntime returns the goja.Runtime for the current VU
 	GetRuntime() *goja.Runtime
-
-	// sealing field will help probably with pointing users that they just need to embed this in their Instance
-	// implementations
 }
 
 // Exports is representation of ESM exports of a module
@@ -132,44 +129,3 @@ type Exports struct {
 	// Named is the named exports of a module
 	Named map[string]interface{}
 }
-
-// GenerateExports generates an Exports from a module akin to how common.Bind does now.
-// it also skips anything that is expected will not want to be exported such as methods and fields coming from
-// interfaces defined in this package.
-func GenerateExports(v interface{}) Exports {
-	exports := make(map[string]interface{})
-	val := reflect.ValueOf(v)
-	typ := val.Type()
-	badNames := getInterfaceMethods()
-outer:
-	for i := 0; i < typ.NumMethod(); i++ {
-		meth := typ.Method(i)
-		for _, badname := range badNames {
-			if meth.Name == badname {
-				continue outer
-			}
-		}
-		name := common.MethodName(typ, meth)
-
-		fn := val.Method(i)
-		exports[name] = fn.Interface()
-	}
-
-	// If v is a pointer, we need to indirect it to access its fields.
-	if typ.Kind() == reflect.Ptr {
-		val = val.Elem()
-		typ = val.Type()
-	}
-	var mic InstanceCore // TODO move this out
-	for i := 0; i < typ.NumField(); i++ {
-		field := typ.Field(i)
-		if field.Type == reflect.TypeOf(&mic).Elem() {
-			continue
-		}
-		name := common.FieldName(typ, field)
-		if name != "" {
-			exports[name] = val.Field(i).Interface()
-		}
-	}
-	return Exports{Default: exports, Named: exports}
-}

js/modulestest/modulestest.go

@@ -29,7 +29,7 @@ import (
 	"go.k6.io/k6/lib"
 )
 
-var _ modules.InstanceCore = &InstanceCore{}
+var _ modules.InstanceParams = &InstanceCore{}
 
 // InstanceCore is a modules.InstanceCore implementation meant to be used within tests
 type InstanceCore struct {