Make plugin utils package.

api/internal/plugins/compiler/compiler.go

@@ -13,6 +13,7 @@ import (
 	"strings"
 
 	"github.com/pkg/errors"
+	"sigs.k8s.io/kustomize/api/internal/plugins/utils"
 )
 
 // Compiler creates Go plugin object files.
@@ -64,7 +65,7 @@ func (b *Compiler) Cleanup() {
 // ${pluginRoot}/${g}/${v}/$lower(${k} and places
 // object code next to source code.
 func (b *Compiler) Compile() error {
-	if !FileExists(b.srcPath()) {
+	if !utils.FileExists(b.srcPath()) {
 		return fmt.Errorf("cannot find source at '%s'", b.srcPath())
 	}
 	// If you use an IDE, make sure it's go build and test flags
@@ -77,8 +78,8 @@ func (b *Compiler) Compile() error {
 		"plugin",
 		"-o", b.objFile(),
 	}
-	goBin := goBin()
-	if !FileExists(goBin) {
+	goBin := utils.GoBin()
+	if !utils.FileExists(goBin) {
 		return fmt.Errorf(
 			"cannot find go compiler %s", goBin)
 	}
@@ -95,7 +96,7 @@ func (b *Compiler) Compile() error {
 			err, "cannot compile %s:\nSTDERR\n%s\n",
 			b.srcPath(), b.stderr.String())
 	}
-	if result := filepath.Join(b.workDir, b.objFile()); !FileExists(result) {
+	if result := filepath.Join(b.workDir, b.objFile()); !utils.FileExists(result) {
 		return fmt.Errorf("post compile, cannot find '%s'", result)
 	}
 	return nil

api/internal/plugins/compiler/compiler_test.go

@@ -9,11 +9,12 @@ import (
 
 	"sigs.k8s.io/kustomize/api/filesys"
 	. "sigs.k8s.io/kustomize/api/internal/plugins/compiler"
+	"sigs.k8s.io/kustomize/api/internal/plugins/utils"
 )
 
 // Regression coverage over compiler behavior.
 func TestCompiler(t *testing.T) {
-	srcRoot, err := DeterminePluginSrcRoot(filesys.MakeFsOnDisk())
+	srcRoot, err := utils.DeterminePluginSrcRoot(filesys.MakeFsOnDisk())
 	if err != nil {
 		t.Error(err)
 	}
@@ -29,11 +30,11 @@ func TestCompiler(t *testing.T) {
 	if err != nil {
 		t.Error(err)
 	}
-	if !FileExists(expectObj) {
+	if !utils.FileExists(expectObj) {
 		t.Errorf("didn't find expected obj file %s", expectObj)
 	}
 	c.Cleanup()
-	if FileExists(expectObj) {
+	if utils.FileExists(expectObj) {
 		t.Errorf("obj file '%s' should be gone", expectObj)
 	}
 
@@ -48,11 +49,11 @@ func TestCompiler(t *testing.T) {
 	if err != nil {
 		t.Error(err)
 	}
-	if !FileExists(expectObj) {
+	if !utils.FileExists(expectObj) {
 		t.Errorf("didn't find expected obj file %s", expectObj)
 	}
 	c.Cleanup()
-	if FileExists(expectObj) {
+	if utils.FileExists(expectObj) {
 		t.Errorf("obj file '%s' should be gone", expectObj)
 	}
 }

api/internal/plugins/loader/loader.go

@@ -15,6 +15,7 @@ import (
 	"sigs.k8s.io/kustomize/api/ifc"
 	"sigs.k8s.io/kustomize/api/internal/plugins/builtinhelpers"
 	"sigs.k8s.io/kustomize/api/internal/plugins/execplugin"
+	"sigs.k8s.io/kustomize/api/internal/plugins/utils"
 	"sigs.k8s.io/kustomize/api/konfig"
 	"sigs.k8s.io/kustomize/api/resid"
 	"sigs.k8s.io/kustomize/api/resmap"
@@ -202,8 +203,11 @@ func (l *Loader) loadGoPlugin(id resid.ResId) (resmap.Configurable, error) {
 	if c, ok := registry[regId]; ok {
 		return copyPlugin(c), nil
 	}
-	absPath := l.absolutePluginPath(id)
-	p, err := plugin.Open(absPath + ".so")
+	absPath := l.absolutePluginPath(id) + ".so"
+	if !utils.FileExists(absPath) {
+		return nil, fmt.Errorf("cannot find Go object code '%s'", absPath)
+	}
+	p, err := plugin.Open(absPath)
 	if err != nil {
 		return nil, errors.Wrapf(err, "plugin %s fails to load", absPath)
 	}

api/internal/plugins/utils/utils.go

@@ -1,7 +1,7 @@
 // Copyright 2020 The Kubernetes Authors.
 // SPDX-License-Identifier: Apache-2.0
 
-package compiler
+package utils
 
 import (
 	"os"
@@ -13,7 +13,7 @@ import (
 	"sigs.k8s.io/kustomize/api/konfig"
 )
 
-func goBin() string {
+func GoBin() string {
 	return filepath.Join(runtime.GOROOT(), "bin", "go")
 }
 

api/internal/plugins/utils/utils_test.go

@@ -1,7 +1,7 @@
 // Copyright 2020 The Kubernetes Authors.
 // SPDX-License-Identifier: Apache-2.0
 
-package compiler
+package utils
 
 import (
 	"path/filepath"