Define a plugin compiler.

pkg/plugins/compiler.go

@@ -0,0 +1,146 @@
+/*
+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 plugins
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"time"
+
+	"sigs.k8s.io/kustomize/k8sdeps/kv/plugin"
+	"sigs.k8s.io/kustomize/pkg/pgmconfig"
+)
+
+// Compiler creates Go plugin object files.
+//
+// Source code is read from
+//   ${srcRoot}/${g}/${v}/${k}.go
+//
+// Object code is written to
+//   ${objRoot}/${g}/${v}/${k}.so
+type Compiler struct {
+	srcRoot string
+	objRoot string
+}
+
+// DefaultSrcRoot guesses where the user
+// has her ${g}/${v}/${k}.go files.
+func DefaultSrcRoot() (string, error) {
+	var nope []string
+	var root string
+
+	root = filepath.Join(
+		os.Getenv("GOPATH"), "src",
+		pgmconfig.DomainName,
+		pgmconfig.ProgramName, plugin.PluginRoot)
+	if FileExists(root) {
+		return root, nil
+	}
+	nope = append(nope, root)
+
+	root = filepath.Join(
+		pgmconfig.ConfigRoot(), plugin.PluginRoot)
+	if FileExists(root) {
+		return root, nil
+	}
+	nope = append(nope, root)
+
+	root = filepath.Join(
+		pgmconfig.HomeDir(),
+		pgmconfig.ProgramName, plugin.PluginRoot)
+	if FileExists(root) {
+		return root, nil
+	}
+	nope = append(nope, root)
+
+	return "", fmt.Errorf(
+		"no default src root; tried %v", nope)
+}
+
+// NewCompiler returns a new compiler instance.
+func NewCompiler(srcRoot, objRoot string) *Compiler {
+	return &Compiler{srcRoot: srcRoot, objRoot: objRoot}
+}
+
+// ObjRoot is root of compilation target tree.
+func (b *Compiler) ObjRoot() string {
+	return b.objRoot
+}
+
+func goBin() string {
+	return filepath.Join(os.Getenv("GOROOT"), "bin", "go")
+}
+
+// Compile reads ${srcRoot}/${g}/${v}/${k}.go
+//    and writes ${objRoot}/${g}/${v}/${k}.so
+func (b *Compiler) Compile(g, v, k string) error {
+	objDir := filepath.Join(b.objRoot, g, v)
+	objFile := filepath.Join(objDir, k) + ".so"
+	if RecentFileExists(objFile) {
+		// Skip rebuilding it.
+		return nil
+	}
+	err := os.MkdirAll(objDir, os.ModePerm)
+	if err != nil {
+		return err
+	}
+	srcFile := filepath.Join(b.srcRoot, g, v, k) + ".go"
+	if !FileExists(srcFile) {
+		return fmt.Errorf(
+			"cannot find source %s", srcFile)
+	}
+	commands := []string{
+		"build",
+		"-buildmode",
+		"plugin",
+		"-tags=plugin",
+		"-o", objFile, srcFile,
+	}
+	goBin := goBin()
+	if !FileExists(goBin) {
+		return fmt.Errorf(
+			"cannot find go compiler %s", goBin)
+	}
+	cmd := exec.Command(goBin, commands...)
+	cmd.Env = os.Environ()
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf(
+			"compiler error building %s: %v", srcFile, err)
+	}
+	return nil
+}
+
+// True if file less than 3 minutes old, i.e. not
+// accidentally left over from some earlier build.
+func RecentFileExists(path string) bool {
+	fi, err := os.Stat(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return false
+		}
+	}
+	age := time.Now().Sub(fi.ModTime())
+	return age.Minutes() < 3
+}
+
+func FileExists(name string) bool {
+	if _, err := os.Stat(name); err != nil {
+		if os.IsNotExist(err) {
+			return false
+		}
+	}
+	return true
+}