js/k6/exec: Allow to set state's Tags

Extended the k6/execution API to allow the get or set of a Tag in the VU state.

js/modules/k6/execution/execution.go

@@ -193,7 +193,19 @@ func (mi *ModuleInstance) newVUInfo() (*goja.Object, error) {
 		},
 	}
 
-	return newInfoObj(rt, vi)
+	o, err := newInfoObj(rt, vi)
+	if err != nil {
+		return nil, err
+	}
+
+	err = o.Set("tags", rt.NewDynamicObject(&tagsDynamicObject{
+		Runtime: rt,
+		Tags:    vuState.Tags,
+	}))
+	if err != nil {
+		return nil, err
+	}
+	return o, nil
 }
 
 func newInfoObj(rt *goja.Runtime, props map[string]func() interface{}) (*goja.Object, error) {
@@ -208,3 +220,49 @@ func newInfoObj(rt *goja.Runtime, props map[string]func() interface{}) (*goja.Ob
 
 	return o, nil
 }
+
+type tagsDynamicObject struct {
+	Runtime *goja.Runtime
+	Tags    *lib.TagMap
+}
+
+// Get a property value for the key. May return nil if the property does not exist.
+func (o *tagsDynamicObject) Get(key string) goja.Value {
+	tag, ok := o.Tags.Get(key)
+	if !ok {
+		return nil
+	}
+	return o.Runtime.ToValue(tag)
+}
+
+// Set a property value for the key. Return true if succeed.
+func (o *tagsDynamicObject) Set(key string, val goja.Value) bool {
+	o.Tags.Set(key, val.String())
+	return true
+}
+
+// Has returns true if the property exists.
+func (o *tagsDynamicObject) Has(key string) bool {
+	_, ok := o.Tags.Get(key)
+	return ok
+}
+
+// Delete deletes the property for the key. It returns true on success (note, that includes missing property).
+func (o *tagsDynamicObject) Delete(key string) bool {
+	o.Tags.Delete(key)
+	return true
+}
+
+// Keys returns a slice with all existing property keys. The order is not deterministic.
+func (o *tagsDynamicObject) Keys() []string {
+	if o.Tags.Len() < 1 {
+		return nil
+	}
+
+	tags := o.Tags.Clone()
+	keys := make([]string, 0, len(tags))
+	for k := range tags {
+		keys = append(keys, k)
+	}
+	return keys
+}

js/modules/k6/execution/execution_test.go

@@ -0,0 +1,79 @@
+/*
+ *
+ * k6 - a next-generation load testing tool
+ * Copyright (C) 2021 Load Impact
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+package execution
+
+import (
+	"context"
+	"testing"
+
+	"github.com/dop251/goja"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.k6.io/k6/js/common"
+	"go.k6.io/k6/js/modulestest"
+	"go.k6.io/k6/lib"
+	"go.k6.io/k6/stats"
+)
+
+func TestVUTags(t *testing.T) {
+	t.Parallel()
+
+	rt := goja.New()
+	ctx := common.WithRuntime(context.Background(), rt)
+	ctx = lib.WithState(ctx, &lib.State{
+		Options: lib.Options{
+			SystemTags: stats.NewSystemTagSet(stats.TagVU),
+		},
+		Tags: lib.NewTagMap(map[string]string{
+			"vu": "42",
+		}),
+	})
+	m, ok := New().NewModuleInstance(
+		&modulestest.InstanceCore{
+			Runtime: rt,
+			InitEnv: &common.InitEnvironment{},
+			Ctx:     ctx,
+		},
+	).(*ModuleInstance)
+	require.True(t, ok)
+	require.NoError(t, rt.Set("exec", m.GetExports().Default))
+
+	// overwrite a system tag is allowed
+	_, err := rt.RunString(`exec.vu.tags["vu"] = 101`)
+	require.NoError(t, err)
+	val, err := rt.RunString(`exec.vu.tags["vu"]`)
+	require.NoError(t, err)
+	assert.Equal(t, "101", val.String())
+
+	// not found
+	tag, err := rt.RunString(`exec.vu.tags["not-existing-tag"]`)
+	require.NoError(t, err)
+	assert.Equal(t, "undefined", tag.String())
+
+	// set
+	_, err = rt.RunString(`exec.vu.tags["custom-tag"] = "mytag"`)
+	require.NoError(t, err)
+
+	// get
+	tag, err = rt.RunString(`exec.vu.tags["custom-tag"]`)
+	require.NoError(t, err)
+	assert.Equal(t, "mytag", tag.String())
+}