One plugin per dir.

plugin/builtin/configmapgenerator/ConfigMapGenerator.go

@@ -0,0 +1,38 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+//go:generate go run sigs.k8s.io/kustomize/plugin/pluginator
+package main
+
+import (
+	"sigs.k8s.io/kustomize/pkg/ifc"
+	"sigs.k8s.io/kustomize/pkg/resmap"
+	"sigs.k8s.io/kustomize/pkg/types"
+	"sigs.k8s.io/yaml"
+)
+
+type plugin struct {
+	ldr ifc.Loader
+	rf  *resmap.Factory
+	types.GeneratorOptions
+	types.ConfigMapArgs
+}
+
+var KustomizePlugin plugin
+
+func (p *plugin) Config(
+	ldr ifc.Loader, rf *resmap.Factory, config []byte) (err error) {
+	p.GeneratorOptions = types.GeneratorOptions{}
+	p.ConfigMapArgs = types.ConfigMapArgs{}
+	err = yaml.Unmarshal(config, p)
+	p.ldr = ldr
+	p.rf = rf
+	return
+}
+
+func (p *plugin) Generate() (resmap.ResMap, error) {
+	argsList := make([]types.ConfigMapArgs, 1)
+	argsList[0] = p.ConfigMapArgs
+	return p.rf.NewResMapFromConfigMapArgs(
+		p.ldr, &p.GeneratorOptions, argsList)
+}

plugin/builtin/configmapgenerator/ConfigMapGenerator_test.go

@@ -0,0 +1,54 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package main_test
+
+import (
+	"testing"
+
+	"sigs.k8s.io/kustomize/pkg/kusttest"
+	"sigs.k8s.io/kustomize/plugin"
+)
+
+func TestConfigMapGenerator(t *testing.T) {
+	tc := plugin.NewEnvForTest(t).Set()
+	defer tc.Reset()
+
+	tc.BuildGoPlugin(
+		"builtin", "", "ConfigMapGenerator")
+
+	th := kusttest_test.NewKustTestPluginHarness(t, "/app")
+
+	th.WriteF("/app/devops.env", `
+SERVICE_PORT=32
+`)
+	th.WriteF("/app/uxteam.env", `
+COLOR=red
+`)
+
+	rm := th.LoadAndRunGenerator(`
+apiVersion: builtin
+kind: ConfigMapGenerator
+metadata:
+  name: myMapGen
+name: myMap
+envs:
+- devops.env
+- uxteam.env
+literals:
+- FRUIT=apple
+- VEGETABLE=carrot
+`)
+
+	th.AssertActualEqualsExpected(rm, `
+apiVersion: v1
+data:
+  COLOR: red
+  FRUIT: apple
+  SERVICE_PORT: "32"
+  VEGETABLE: carrot
+kind: ConfigMap
+metadata:
+  name: myMap
+`)
+}