One plugin per dir.

plugin/builtin/ConfigMapGenerator.go

@@ -1,10 +1,5 @@
-// +build plugin
-
-// Copyright 2019 The Kubernetes Authors.
-// SPDX-License-Identifier: Apache-2.0
-
-//go:generate go run sigs.k8s.io/kustomize/cmd/pluginator
-package main
+// Code generated by pluginator on ConfigMapGenerator; DO NOT EDIT.
+package builtin
 
 import (
 	"sigs.k8s.io/kustomize/pkg/ifc"
@@ -13,16 +8,18 @@ import (
 	"sigs.k8s.io/yaml"
 )
 
-type plugin struct {
+type ConfigMapGeneratorPlugin struct {
 	ldr ifc.Loader
 	rf  *resmap.Factory
 	types.GeneratorOptions
 	types.ConfigMapArgs
 }
 
-var KustomizePlugin plugin
+func NewConfigMapGeneratorPlugin() *ConfigMapGeneratorPlugin {
+  return &ConfigMapGeneratorPlugin{}
+}
 
-func (p *plugin) Config(
+func (p *ConfigMapGeneratorPlugin) Config(
 	ldr ifc.Loader, rf *resmap.Factory, config []byte) (err error) {
 	p.GeneratorOptions = types.GeneratorOptions{}
 	p.ConfigMapArgs = types.ConfigMapArgs{}
@@ -32,7 +29,7 @@ func (p *plugin) Config(
 	return
 }
 
-func (p *plugin) Generate() (resmap.ResMap, error) {
+func (p *ConfigMapGeneratorPlugin) Generate() (resmap.ResMap, error) {
 	argsList := make([]types.ConfigMapArgs, 1)
 	argsList[0] = p.ConfigMapArgs
 	return p.rf.NewResMapFromConfigMapArgs(

plugin/builtin/ImageTagTransformer.go

@@ -1,10 +1,5 @@
-// +build plugin
-
-// Copyright 2019 The Kubernetes Authors.
-// SPDX-License-Identifier: Apache-2.0
-
-//go:generate go run sigs.k8s.io/kustomize/cmd/pluginator
-package main
+// Code generated by pluginator on ImageTagTransformer; DO NOT EDIT.
+package builtin
 
 import (
 	"sigs.k8s.io/kustomize/pkg/ifc"
@@ -17,21 +12,23 @@ import (
 
 // Find matching image declarations and replace
 // the name, tag and/or digest.
-type plugin struct {
+type ImageTagTransformerPlugin struct {
 	ImageTag   image.Image        `json:"imageTag,omitempty" yaml:"imageTag,omitempty"`
 	FieldSpecs []config.FieldSpec `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
 }
 
-var KustomizePlugin plugin
+func NewImageTagTransformerPlugin() *ImageTagTransformerPlugin {
+  return &ImageTagTransformerPlugin{}
+}
 
-func (p *plugin) Config(
+func (p *ImageTagTransformerPlugin) Config(
 	ldr ifc.Loader, rf *resmap.Factory, c []byte) (err error) {
 	p.ImageTag = image.Image{}
 	p.FieldSpecs = nil
 	return yaml.Unmarshal(c, p)
 }
 
-func (p *plugin) Transform(m resmap.ResMap) error {
+func (p *ImageTagTransformerPlugin) Transform(m resmap.ResMap) error {
 	argsList := make([]image.Image, 1)
 	argsList[0] = p.ImageTag
 	t, err := transformers.NewImageTransformer(argsList, p.FieldSpecs)

plugin/builtin/NameTransformer.go

@@ -1,10 +1,5 @@
-// +build plugin
-
-// Copyright 2019 The Kubernetes Authors.
-// SPDX-License-Identifier: Apache-2.0
-
-//go:generate go run sigs.k8s.io/kustomize/cmd/pluginator
-package main
+// Code generated by pluginator on NameTransformer; DO NOT EDIT.
+package builtin
 
 import (
 	"sigs.k8s.io/kustomize/pkg/ifc"
@@ -15,15 +10,17 @@ import (
 )
 
 // Add the given prefix and suffix to the resource name.
-type plugin struct {
+type NameTransformerPlugin struct {
 	Prefix     string             `json:"prefix,omitempty" yaml:"prefix,omitempty"`
 	Suffix     string             `json:"suffix,omitempty" yaml:"suffix,omitempty"`
 	FieldSpecs []config.FieldSpec `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
 }
 
-var KustomizePlugin plugin
+func NewNameTransformerPlugin() *NameTransformerPlugin {
+  return &NameTransformerPlugin{}
+}
 
-func (p *plugin) Config(
+func (p *NameTransformerPlugin) Config(
 	ldr ifc.Loader, rf *resmap.Factory, c []byte) (err error) {
 	p.Prefix = ""
 	p.Suffix = ""
@@ -31,7 +28,7 @@ func (p *plugin) Config(
 	return yaml.Unmarshal(c, p)
 }
 
-func (p *plugin) Transform(m resmap.ResMap) error {
+func (p *NameTransformerPlugin) Transform(m resmap.ResMap) error {
 	t, err := transformers.NewNamePrefixSuffixTransformer(
 		p.Prefix,
 		p.Suffix,

plugin/builtin/SecretGenerator.go

@@ -1,10 +1,5 @@
-// +build plugin
-
-// Copyright 2019 The Kubernetes Authors.
-// SPDX-License-Identifier: Apache-2.0
-
-//go:generate go run sigs.k8s.io/kustomize/cmd/pluginator
-package main
+// Code generated by pluginator on SecretGenerator; DO NOT EDIT.
+package builtin
 
 import (
 	"sigs.k8s.io/kustomize/pkg/ifc"
@@ -13,16 +8,18 @@ import (
 	"sigs.k8s.io/yaml"
 )
 
-type plugin struct {
+type SecretGeneratorPlugin struct {
 	ldr ifc.Loader
 	rf  *resmap.Factory
 	types.GeneratorOptions
 	types.SecretArgs
 }
 
-var KustomizePlugin plugin
+func NewSecretGeneratorPlugin() *SecretGeneratorPlugin {
+  return &SecretGeneratorPlugin{}
+}
 
-func (p *plugin) Config(
+func (p *SecretGeneratorPlugin) Config(
 	ldr ifc.Loader, rf *resmap.Factory, config []byte) (err error) {
 	p.GeneratorOptions = types.GeneratorOptions{}
 	p.SecretArgs = types.SecretArgs{}
@@ -32,7 +29,7 @@ func (p *plugin) Config(
 	return
 }
 
-func (p *plugin) Generate() (resmap.ResMap, error) {
+func (p *SecretGeneratorPlugin) Generate() (resmap.ResMap, error) {
 	argsList := make([]types.SecretArgs, 1)
 	argsList[0] = p.SecretArgs
 	return p.rf.NewResMapFromSecretArgs(

plugin/builtin/configmapgenerator/ConfigMapGenerator.go

@@ -1,5 +1,8 @@
-// Code generated by pluginator on ConfigMapGenerator; DO NOT EDIT.
-package builtingen
+// 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"
@@ -8,18 +11,16 @@ import (
 	"sigs.k8s.io/yaml"
 )
 
-type ConfigMapGeneratorPlugin struct {
+type plugin struct {
 	ldr ifc.Loader
 	rf  *resmap.Factory
 	types.GeneratorOptions
 	types.ConfigMapArgs
 }
 
-func NewConfigMapGeneratorPlugin() *ConfigMapGeneratorPlugin {
-	return &ConfigMapGeneratorPlugin{}
-}
+var KustomizePlugin plugin
 
-func (p *ConfigMapGeneratorPlugin) Config(
+func (p *plugin) Config(
 	ldr ifc.Loader, rf *resmap.Factory, config []byte) (err error) {
 	p.GeneratorOptions = types.GeneratorOptions{}
 	p.ConfigMapArgs = types.ConfigMapArgs{}
@@ -29,7 +30,7 @@ func (p *ConfigMapGeneratorPlugin) Config(
 	return
 }
 
-func (p *ConfigMapGeneratorPlugin) Generate() (resmap.ResMap, error) {
+func (p *plugin) Generate() (resmap.ResMap, error) {
 	argsList := make([]types.ConfigMapArgs, 1)
 	argsList[0] = p.ConfigMapArgs
 	return p.rf.NewResMapFromConfigMapArgs(

plugin/builtin/configmapgenerator/ConfigMapGenerator_test.go

@@ -11,7 +11,7 @@ import (
 )
 
 func TestConfigMapGenerator(t *testing.T) {
-	tc := plugin.NewPluginTestEnv(t).Set()
+	tc := plugin.NewEnvForTest(t).Set()
 	defer tc.Reset()
 
 	tc.BuildGoPlugin(

plugin/builtin/imagetagtransformer/ImageTagTransformer.go

@@ -1,5 +1,8 @@
-// Code generated by pluginator on ImageTagTransformer; DO NOT EDIT.
-package builtingen
+// 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"
@@ -12,23 +15,21 @@ import (
 
 // Find matching image declarations and replace
 // the name, tag and/or digest.
-type ImageTagTransformerPlugin struct {
+type plugin struct {
 	ImageTag   image.Image        `json:"imageTag,omitempty" yaml:"imageTag,omitempty"`
 	FieldSpecs []config.FieldSpec `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
 }
 
-func NewImageTagTransformerPlugin() *ImageTagTransformerPlugin {
-	return &ImageTagTransformerPlugin{}
-}
+var KustomizePlugin plugin
 
-func (p *ImageTagTransformerPlugin) Config(
+func (p *plugin) Config(
 	ldr ifc.Loader, rf *resmap.Factory, c []byte) (err error) {
 	p.ImageTag = image.Image{}
 	p.FieldSpecs = nil
 	return yaml.Unmarshal(c, p)
 }
 
-func (p *ImageTagTransformerPlugin) Transform(m resmap.ResMap) error {
+func (p *plugin) Transform(m resmap.ResMap) error {
 	argsList := make([]image.Image, 1)
 	argsList[0] = p.ImageTag
 	t, err := transformers.NewImageTransformer(argsList, p.FieldSpecs)

plugin/builtin/imagetagtransformer/ImageTagTransformer_test.go

@@ -11,7 +11,7 @@ import (
 )
 
 func TestImageTagTransformer(t *testing.T) {
-	tc := plugin.NewPluginTestEnv(t).Set()
+	tc := plugin.NewEnvForTest(t).Set()
 	defer tc.Reset()
 
 	tc.BuildGoPlugin(

plugin/builtin/nametransformer/NameTransformer.go

@@ -1,5 +1,8 @@
-// Code generated by pluginator on NameTransformer; DO NOT EDIT.
-package builtingen
+// 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"
@@ -10,17 +13,15 @@ import (
 )
 
 // Add the given prefix and suffix to the resource name.
-type NameTransformerPlugin struct {
+type plugin struct {
 	Prefix     string             `json:"prefix,omitempty" yaml:"prefix,omitempty"`
 	Suffix     string             `json:"suffix,omitempty" yaml:"suffix,omitempty"`
 	FieldSpecs []config.FieldSpec `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
 }
 
-func NewNameTransformerPlugin() *NameTransformerPlugin {
-	return &NameTransformerPlugin{}
-}
+var KustomizePlugin plugin
 
-func (p *NameTransformerPlugin) Config(
+func (p *plugin) Config(
 	ldr ifc.Loader, rf *resmap.Factory, c []byte) (err error) {
 	p.Prefix = ""
 	p.Suffix = ""
@@ -28,7 +29,7 @@ func (p *NameTransformerPlugin) Config(
 	return yaml.Unmarshal(c, p)
 }
 
-func (p *NameTransformerPlugin) Transform(m resmap.ResMap) error {
+func (p *plugin) Transform(m resmap.ResMap) error {
 	t, err := transformers.NewNamePrefixSuffixTransformer(
 		p.Prefix,
 		p.Suffix,

plugin/builtin/nametransformer/NameTransformer_test.go

@@ -11,7 +11,7 @@ import (
 )
 
 func TestNameTransformer(t *testing.T) {
-	tc := plugin.NewPluginTestEnv(t).Set()
+	tc := plugin.NewEnvForTest(t).Set()
 	defer tc.Reset()
 
 	tc.BuildGoPlugin(

plugin/builtin/secretgenerator/SecretGenerator.go

@@ -1,5 +1,8 @@
-// Code generated by pluginator on SecretGenerator; DO NOT EDIT.
-package builtingen
+// 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"
@@ -8,18 +11,16 @@ import (
 	"sigs.k8s.io/yaml"
 )
 
-type SecretGeneratorPlugin struct {
+type plugin struct {
 	ldr ifc.Loader
 	rf  *resmap.Factory
 	types.GeneratorOptions
 	types.SecretArgs
 }
 
-func NewSecretGeneratorPlugin() *SecretGeneratorPlugin {
-	return &SecretGeneratorPlugin{}
-}
+var KustomizePlugin plugin
 
-func (p *SecretGeneratorPlugin) Config(
+func (p *plugin) Config(
 	ldr ifc.Loader, rf *resmap.Factory, config []byte) (err error) {
 	p.GeneratorOptions = types.GeneratorOptions{}
 	p.SecretArgs = types.SecretArgs{}
@@ -29,7 +30,7 @@ func (p *SecretGeneratorPlugin) Config(
 	return
 }
 
-func (p *SecretGeneratorPlugin) Generate() (resmap.ResMap, error) {
+func (p *plugin) Generate() (resmap.ResMap, error) {
 	argsList := make([]types.SecretArgs, 1)
 	argsList[0] = p.SecretArgs
 	return p.rf.NewResMapFromSecretArgs(

plugin/builtin/secretgenerator/SecretGenerator_test.go

@@ -11,7 +11,7 @@ import (
 )
 
 func TestSecretGenerator(t *testing.T) {
-	tc := plugin.NewPluginTestEnv(t).Set()
+	tc := plugin.NewEnvForTest(t).Set()
 	defer tc.Reset()
 
 	tc.BuildGoPlugin(

plugin/doc.go

@@ -0,0 +1,237 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+/*
+Package plugin contains builtin and example
+plugins, tests and test libraries, and a code
+generator for converting a plugin to statically
+loadable code (see pluginator).
+
+
+HOW PLUGINS RUN
+
+Assume a file 'secGen.yaml' containing
+
+   apiVersion: someteam.example.com/v1
+   kind: SecretGenerator
+   metadata:
+     name: makesecrets
+   name: mySecret
+   behavior: merge
+   envs:
+   - db.env
+   - fruit.env
+
+If this file were referenced by a kustomization
+file in its 'generators' field, kustomize would
+
+ * Read 'secGen.yaml'.
+
+ * Use the value of $XGD_CONFIG_HOME and
+   'apiversion' and to find an executable
+   named 'SecretGenerator' to use as
+   an exec plugin, or failing that,
+
+ * use the same info to load a Go plugin
+   object file called 'SecretGenerator.so'.
+
+ * Send either the file name 'secGen.yaml' as
+   the first arg to the exec plugin, or send its
+   contents to the go plugin's Config method.
+
+ * Use the plugin to generate and/or transform.
+
+
+GO PLUGINS
+
+A .go file can be a Go plugin if it declares
+'main' as it's package, and exports a symbol to
+which useful functions are attached.
+
+It can further be used as a _kustomize_ plugin if
+the symbol is named 'KustomizePlugin' and the
+attached functions implement the Configurable,
+Generator and Transformer interfaces.
+
+A plugin won't load into some program foo/main.go
+if there is any package version mismatch in the
+dependencies of the plugin and the dependencies of
+foo/main.go.  Control this with matching
+declarations in go.mod files.  The versions of the
+builtin packages "fmt", "io", "os" (not normally
+listed in go.mod) etc have the same version as the
+compiler.
+
+
+ONE PLUGIN PER DIRECTORY
+
+For kustomize (and perhaps anyone), it's simplest
+to put each plugin into its own directory.
+
+Go plugins must be in package `main`, and so
+having more than one plugin in a directory means
+their loading symbols have to differ, which makes
+it hard to standardize around how they get loaded,
+or it means one must use build tags to suppress
+full directory compilation - which creates
+difficulties using IDEs, the `go mod` tool, `go
+test ./...`, etc.
+
+A one plugin per directory policy makes it easy to
+define the plugin as a module, with its own
+`go.mod` file - which is vital for resolving
+package version dependency mismatches at load
+time.  It also makes it easy to create a plugin
+tarball (source, test, go.mod, plugin data files,
+etc.) for distribution.
+
+
+BUILTIN PLUGIN CONFIGURATION
+
+For performance reasons, all builting plugins are
+Go plugins (not exec plugins).
+
+Using "SecretGenerator" as an example in what
+follows.
+
+The plugin config file looks like
+
+  ---------------------------------------------
+  apiVersion: builtin
+  kind: SecretGenerator
+  metadata:
+    name: whatever
+  otherField1: whatever
+  otherField2: whatever
+  ...
+  ---------------------------------------------
+
+The apiVersion must be 'builtin'.  The kind is the
+CamelCase name of the plugin.
+
+For non-builtins the apiVersion can be any legal
+apiVersion value, e.g. 'someteam.example.com/v1beta1'
+
+The builtin source must be at:
+
+  repo=$GOPATH/src/sigs.k8s.io/kustomize
+  ${repo}/plugin/${apiVersion}/LOWERCASE(${kind})/${kind}.go
+
+(dropping the ".go" for exec plugins).
+
+k8s wants 'kind' values to follow CamelCase, while
+Go style doesn't like but does allow such names.
+
+The lowercased value of kind is used as the name of the
+directory holding the plugin, its test, and any
+optional associated files (possibly a go.mod file).
+
+
+PLUGIN SOURCE
+
+ * Pattern
+
+   secretgenerator.go
+   ---------------------------------------------
+   //go:generate go run sigs.k8s.io/kustomize/cmd/pluginator
+   package main
+   import ...
+   type plugin struct{...}
+   var KustomizePlugin plugin
+   func (p *plugin) Config(
+      ldr ifc.Loader,
+      rf *resmap.Factory,
+      c []byte) error {...}
+   func (p *plugin) Generate(
+      ) (resmap.ResMap, error) {...}
+   func (p *plugin) Transform(
+      m resmap.ResMap) error {...}
+   ---------------------------------------------
+
+   The plugin name doesn't appear in the file itself.
+
+ * Compilation
+
+     repo=$GOPATH/src/sigs.k8s.io/kustomize
+     dir=$repo/plugin/builtin
+     go build -buildmode plugin \
+         -o $dir/secretgenerator.so \
+         $dir/secretgenerator.go
+
+
+
+BUILTIN PLUGIN GENERATION
+
+The pluginator program is a code generator that
+converts kustomize generator (G) and/or
+transformer (T) Go plugins to statically linkable
+code.
+
+It arises from following requirements:
+
+ * extension
+
+     kustomize does two things - generate or
+     transform k8s resources.  Plugins let
+     users write their own G&T's without
+     having to fork kustomize and learn its
+     internals.
+
+ * dogfooding
+
+     A G&T extension framework one can trust
+     should be used by its authors to deliver
+     builtin G&T's.
+
+ * distribution
+
+     kustomize should be distributable via
+     `go get` and should run where Go
+     programs are expected to run.
+
+ The extension requirement led to the creation
+ of a framework that accommodates writing a
+ G or T as either
+
+   * an 'exec' plugin (any executable file
+     runnable as a kustomize subprocess), or
+
+   * as a Go plugin - see
+     https://golang.org/pkg/plugin.
+
+ The dogfooding (and an implicit performance
+ requirement) requires a 'builtin' G or T to
+ be written as a Go plugin.
+
+ The distribution ('go get') requirement demands
+ conversion of Go plugins to statically linked
+ code, hence this program.
+
+
+TO GENERATE CODE
+
+  repo=$GOPATH/src/sigs.k8s.io/kustomize
+  cd $repo/plugin/builtin
+  go generate ./...
+
+This creates
+
+  $repo/plugin/builtin/SecretGenerator.go
+
+etc.
+
+Generated plugins are used in kustomize via
+
+  ---------------------------------------------
+  package whatever
+  import "sigs.k8s.io/kustomize/plugin/builtin
+  ...
+  g := builtin.NewSecretGenerator()
+  g.Config(l, rf, k)
+  resources, err := g.Generate()
+  err = g.Transform(resources)
+  // Eventually emit resources.
+  ---------------------------------------------
+
+*/
+package plugin

plugin/envfortest.go

@@ -8,15 +8,16 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"sigs.k8s.io/kustomize/pkg/pgmconfig"
 	"sigs.k8s.io/kustomize/pkg/plugins"
 )
 
-// PluginTestEnv manages the plugin test environment.
+// EnvForTest manages the plugin test environment.
 // It sets/resets XDG_CONFIG_HOME, makes/removes a temp objRoot.
-type PluginTestEnv struct {
+type EnvForTest struct {
 	t        *testing.T
 	compiler *plugins.Compiler
 	workDir  string
@@ -24,34 +25,33 @@ type PluginTestEnv struct {
 	wasSet   bool
 }
 
-func NewPluginTestEnv(t *testing.T) *PluginTestEnv {
-	return &PluginTestEnv{t: t}
+func NewEnvForTest(t *testing.T) *EnvForTest {
+	return &EnvForTest{t: t}
 }
 
-func (x *PluginTestEnv) Set() *PluginTestEnv {
+func (x *EnvForTest) Set() *EnvForTest {
 	x.createWorkDir()
 	x.compiler = x.makeCompiler()
 	x.setEnv()
 	return x
 }
 
-func (x *PluginTestEnv) Reset() {
+func (x *EnvForTest) Reset() {
 	x.resetEnv()
 	x.removeWorkDir()
 }
 
-func (x *PluginTestEnv) BuildGoPlugin(g, v, k string) {
+func (x *EnvForTest) BuildGoPlugin(g, v, k string) {
 	err := x.compiler.Compile(g, v, k)
 	if err != nil {
 		x.t.Errorf("compile failed: %v", err)
 	}
 }
 
-func (x *PluginTestEnv) BuildExecPlugin(name ...string) {
-	obj := filepath.Join(
-		append([]string{x.compiler.ObjRoot()}, name...)...)
-	src := filepath.Join(
-		append([]string{x.compiler.SrcRoot()}, name...)...)
+func (x *EnvForTest) BuildExecPlugin(g, v, k string) {
+	lowK := strings.ToLower(k)
+	obj := filepath.Join(x.compiler.ObjRoot(), g, v, lowK, k)
+	src := filepath.Join(x.compiler.SrcRoot(), g, v, lowK, k)
 	if err := os.MkdirAll(filepath.Dir(obj), 0755); err != nil {
 		x.t.Errorf("error making directory: %s", filepath.Dir(obj))
 	}
@@ -62,7 +62,7 @@ func (x *PluginTestEnv) BuildExecPlugin(name ...string) {
 	}
 }
 
-func (x *PluginTestEnv) makeCompiler() *plugins.Compiler {
+func (x *EnvForTest) makeCompiler() *plugins.Compiler {
 	// The plugin loader wants to find object code under
 	//    $XDG_CONFIG_HOME/kustomize/plugins
 	// and the compiler writes object code to
@@ -81,7 +81,7 @@ func (x *PluginTestEnv) makeCompiler() *plugins.Compiler {
 	return plugins.NewCompiler(srcRoot, objRoot)
 }
 
-func (x *PluginTestEnv) createWorkDir() {
+func (x *EnvForTest) createWorkDir() {
 	var err error
 	x.workDir, err = ioutil.TempDir("", "kustomize-plugin-tests")
 	if err != nil {
@@ -89,7 +89,7 @@ func (x *PluginTestEnv) createWorkDir() {
 	}
 }
 
-func (x *PluginTestEnv) removeWorkDir() {
+func (x *EnvForTest) removeWorkDir() {
 	err := os.RemoveAll(x.workDir)
 	if err != nil {
 		x.t.Errorf(
@@ -97,12 +97,12 @@ func (x *PluginTestEnv) removeWorkDir() {
 	}
 }
 
-func (x *PluginTestEnv) setEnv() {
+func (x *EnvForTest) setEnv() {
 	x.oldXdg, x.wasSet = os.LookupEnv(pgmconfig.XDG_CONFIG_HOME)
 	os.Setenv(pgmconfig.XDG_CONFIG_HOME, x.workDir)
 }
 
-func (x *PluginTestEnv) resetEnv() {
+func (x *EnvForTest) resetEnv() {
 	if x.wasSet {
 		os.Setenv(pgmconfig.XDG_CONFIG_HOME, x.oldXdg)
 	} else {

plugin/generateBuiltins.sh

@@ -0,0 +1,37 @@
+#!/bin/bash
+#
+# This script creates the generator and
+# transformer factory functions in
+#   sigs.k8s.io/kustomize/plugin/builtin
+# by generating code based on the plugins
+# found below that directory.
+
+set -e
+
+myGoPath=$1
+if [ -z ${1+x} ]; then
+  myGoPath=$GOPATH
+fi
+
+if [ -z "$myGoPath" ]; then
+  echo "Must specify a GOPATH"
+  exit 1
+fi
+
+dir=$myGoPath/src/sigs.k8s.io/kustomize
+
+if [ ! -d "$dir" ]; then
+  echo "$dir is not a directory."
+  exit 1
+fi
+
+echo Generating linkable plugins...
+
+pushd $dir >& /dev/null
+
+GOPATH=$myGoPath go generate \
+    sigs.k8s.io/kustomize/plugin/builtin/...
+
+popd >& /dev/null
+
+echo All done.

plugin/pluginator/main.go

@@ -0,0 +1,132 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+// See plugin/doc.go for an explanation.
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"sigs.k8s.io/kustomize/pkg/pgmconfig"
+	"sigs.k8s.io/kustomize/pkg/plugins"
+)
+
+func main() {
+	root := inputFileRoot()
+	file, err := os.Open(root + ".go")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer file.Close()
+	scanner := bufio.NewScanner(file)
+	readToPackageMain(scanner, file.Name())
+
+	w := NewWriter(root)
+	defer w.close()
+
+	// This particular phrasing is required.
+	w.write(
+		fmt.Sprintf(
+			"// Code generated by pluginator on %s; DO NOT EDIT.",
+			root))
+	w.write("package builtin")
+
+	for scanner.Scan() {
+		l := scanner.Text()
+		if strings.HasPrefix(l, "//go:generate") {
+			continue
+		}
+		if l == "var "+plugins.PluginSymbol+" plugin" {
+			w.write("func New" + root + "Plugin() *" + root + "Plugin {")
+			w.write("  return &" + root + "Plugin{}")
+			w.write("}")
+			continue
+		}
+		w.write(l)
+	}
+	if err := scanner.Err(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func inputFileRoot() string {
+	n := os.Getenv("GOFILE")
+	if !strings.HasSuffix(n, ".go") {
+		log.Fatalf("expecting .go suffix on %s", n)
+	}
+	return n[:len(n)-len(".go")]
+}
+
+func readToPackageMain(s *bufio.Scanner, f string) {
+	gotMain := false
+	for !gotMain && s.Scan() {
+		gotMain = strings.HasPrefix(s.Text(), "package main")
+	}
+	if !gotMain {
+		log.Fatalf("%s missing package main", f)
+	}
+}
+
+type writer struct {
+	root string
+	f    *os.File
+}
+
+func NewWriter(r string) *writer {
+	n := makeOutputFileName(r)
+	f, err := os.Create(n)
+	if err != nil {
+		log.Fatalf("unable to create `%s`; %v", n, err)
+	}
+	return &writer{root: r, f: f}
+}
+
+func makeOutputFileName(root string) string {
+	return filepath.Join(
+		os.Getenv("GOPATH"),
+		"src",
+		pgmconfig.DomainName,
+		pgmconfig.ProgramName,
+		pgmconfig.PluginRoot,
+		"builtin",
+		root+".go")
+}
+
+func (w *writer) close() {
+	fmt.Println("Generated " + w.root)
+	w.f.Close()
+}
+
+func (w *writer) write(line string) {
+	_, err := w.f.WriteString(w.filter(line) + "\n")
+	if err != nil {
+		log.Printf("Trouble writing: %s", line)
+		log.Fatal(err)
+	}
+}
+
+func (w *writer) filter(in string) string {
+	if ok, newer := w.replace(in, "type plugin struct"); ok {
+		return newer
+	}
+	if ok, newer := w.replace(in, "*plugin)"); ok {
+		return newer
+	}
+	return in
+}
+
+// replace 'plugin' with 'FooPlugin' in context
+// sensitive manner.
+func (w *writer) replace(in, target string) (bool, string) {
+	if !strings.Contains(in, target) {
+		return false, ""
+	}
+	newer := strings.Replace(
+		target, "plugin", w.root+"Plugin", 1)
+	return true, strings.Replace(in, target, newer, 1)
+}

plugin/someteam.example.com/v1/chartinflator/ChartInflator

@@ -1,8 +1,9 @@
 #!/bin/bash
-set -e
+# Copyright 2019 The Kubernetes Authors.
+# SPDX-License-Identifier: Apache-2.0
 
 # Helm chart inflator
-
+#
 # Reads a file like this
 #
 #  apiVersion: kustomize.config.k8s.io/v1
@@ -23,6 +24,7 @@ set -e
 # Example execution:
 # ./plugin/someteam.example.com/v1/ChartInflator configFile.yaml
 
+set -e
 
 # Yaml parsing is a ridiculous thing to do in bash,
 # but let's try:

plugin/someteam.example.com/v1/chartinflator/ChartInflator_test.go

@@ -19,7 +19,7 @@ import (
 // TODO: Download and inflate the chart, and check that
 // in for the test.
 func TestChartInflator(t *testing.T) {
-	tc := plugin.NewPluginTestEnv(t).Set()
+	tc := plugin.NewEnvForTest(t).Set()
 	defer tc.Reset()
 
 	tc.BuildExecPlugin(

plugin/someteam.example.com/v1/dateprefixer/DatePrefixer.go

@@ -1,20 +1,5 @@
-// +build plugin
-
-/*
-Copyright 2019 The Kubernetes Authors.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-*/
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
 
 package main
 

plugin/someteam.example.com/v1/kvMaker.go

@@ -1,43 +0,0 @@
-// +build plugin
-
-/*
-Copyright 2019 The Kubernetes Authors.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-*/
-
-package main
-
-var database = map[string]string{
-	"TREE":      "oak",
-	"ROCKET":    "Saturn V",
-	"FRUIT":     "apple",
-	"VEGETABLE": "carrot",
-	"SIMPSON":   "homer",
-}
-
-type plugin struct{}
-
-var KVSource plugin
-
-func (p plugin) Get(
-	root string, args []string) (map[string]string, error) {
-	r := make(map[string]string)
-	for _, k := range args {
-		v, ok := database[k]
-		if ok {
-			r[k] = v
-		}
-	}
-	return r, nil
-}

plugin/someteam.example.com/v1/kvmaker/kvMaker.go

@@ -0,0 +1,25 @@
+package kvmaker
+
+var database = map[string]string{
+	"TREE":      "oak",
+	"ROCKET":    "Saturn V",
+	"FRUIT":     "apple",
+	"VEGETABLE": "carrot",
+	"SIMPSON":   "homer",
+}
+
+type plugin struct{}
+
+var KVSource plugin
+
+func (p plugin) Get(
+	root string, args []string) (map[string]string, error) {
+	r := make(map[string]string)
+	for _, k := range args {
+		v, ok := database[k]
+		if ok {
+			r[k] = v
+		}
+	}
+	return r, nil
+}

plugin/someteam.example.com/v1/sedtransformer/SedTransformer_test.go

@@ -11,7 +11,7 @@ import (
 )
 
 func TestSedTransformer(t *testing.T) {
-	tc := plugin.NewPluginTestEnv(t).Set()
+	tc := plugin.NewEnvForTest(t).Set()
 	defer tc.Reset()
 
 	tc.BuildExecPlugin("someteam.example.com", "v1", "SedTransformer")

plugin/someteam.example.com/v1/someservicegenerator/SomeServiceGenerator.go

@@ -1,5 +1,3 @@
-// +build plugin
-
 // Copyright 2019 The Kubernetes Authors.
 // SPDX-License-Identifier: Apache-2.0
 

plugin/someteam.example.com/v1/someservicegenerator/SomeServiceGenerator_test.go

@@ -11,7 +11,7 @@ import (
 )
 
 func TestSomeServiceGeneratorPlugin(t *testing.T) {
-	tc := plugin.NewPluginTestEnv(t).Set()
+	tc := plugin.NewEnvForTest(t).Set()
 	defer tc.Reset()
 
 	tc.BuildGoPlugin(

plugin/someteam.example.com/v1/stringprefixer/StringPrefixer.go

@@ -1,5 +1,3 @@
-// +build plugin
-
 // Copyright 2019 The Kubernetes Authors.
 // SPDX-License-Identifier: Apache-2.0