Improve config package names and reduce API exposure.

api/konfig/plugins.go

@@ -0,0 +1,150 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package konfig
+
+import (
+	"os"
+	"path/filepath"
+	"runtime"
+
+	"sigs.k8s.io/kustomize/api/filesys"
+	"sigs.k8s.io/kustomize/api/types"
+)
+
+const (
+	// Symbol that must be used inside Go plugins.
+	PluginSymbol = "KustomizePlugin"
+
+	// Name of environment variable used to set AbsPluginHome.
+	// See that variable for an explanation.
+	KustomizePluginHomeEnv = "KUSTOMIZE_PLUGIN_HOME"
+
+	// Relative path below XDG_CONFIG_HOME/kustomize to find plugins.
+	// e.g. AbsPluginHome = XDG_CONFIG_HOME/kustomize/plugin
+	RelPluginHome = "plugin"
+
+	// Location of builtin plugins below AbsPluginHome.
+	BuiltinPluginPackage = "builtin"
+
+	// The value of kubernetes ApiVersion to use in configuration
+	// files for builtin plugins.
+	// The value for non-builtins can be anything.
+	BuiltinPluginApiVersion = BuiltinPluginPackage
+
+	// Domain from which kustomize code is imported, for locating
+	// plugin source code under $GOPATH when GOPATH is defined.
+	DomainName = "sigs.k8s.io"
+)
+
+func EnabledPluginConfig() (*types.PluginConfig, error) {
+	dir, err := DefaultAbsPluginHome(filesys.MakeFsOnDisk())
+	if err != nil {
+		return nil, err
+	}
+	return MakePluginConfig(types.PluginRestrictionsNone, dir), nil
+}
+
+func DisabledPluginConfig() *types.PluginConfig {
+	return MakePluginConfig(
+		types.PluginRestrictionsBuiltinsOnly, NoPluginHomeSentinal)
+}
+
+func MakePluginConfig(
+	pr types.PluginRestrictions, home string) *types.PluginConfig {
+	return &types.PluginConfig{
+		PluginRestrictions: pr,
+		AbsPluginHome:      home,
+	}
+}
+
+// Use an obviously erroneous path, in case it's accidentally used.
+const NoPluginHomeSentinal = "/no/non-builtin/plugins!"
+
+type NotedFunc struct {
+	Note string
+	F    func() string
+}
+
+func DefaultAbsPluginHome(fSys filesys.FileSystem) (string, error) {
+	return FirstDirThatExistsElseError(
+		"plugin home directory", fSys, []NotedFunc{
+			{
+				Note: "homed in $" + KustomizePluginHomeEnv,
+				F: func() string {
+					return os.Getenv(KustomizePluginHomeEnv)
+				},
+			},
+			{
+				Note: "homed in $" + XdgConfigHomeEnv,
+				F: func() string {
+					return filepath.Join(
+						os.Getenv(XdgConfigHomeEnv),
+						ProgramName, RelPluginHome)
+				},
+			},
+			{
+				Note: "homed in default value of $" + XdgConfigHomeEnv,
+				F: func() string {
+					return filepath.Join(
+						HomeDir(), XdgConfigHomeEnvDefault,
+						ProgramName, RelPluginHome)
+				},
+			},
+			{
+				Note: "homed in home directory",
+				F: func() string {
+					return filepath.Join(
+						HomeDir(), ProgramName, RelPluginHome)
+				},
+			},
+		})
+}
+
+// FirstDirThatExistsElseError tests different path functions for
+// existence, returning the first that works, else error if all fail.
+func FirstDirThatExistsElseError(
+	what string,
+	fSys filesys.FileSystem,
+	pathFuncs []NotedFunc) (string, error) {
+	var nope []types.Pair
+	for _, dt := range pathFuncs {
+		dir := dt.F()
+		if fSys.Exists(dir) {
+			return dir, nil
+		}
+		nope = append(nope, types.Pair{Key: dt.Note, Value: dir})
+	}
+	return "", types.NewErrUnableToFind(what, nope)
+}
+
+func HomeDir() string {
+	home := os.Getenv(homeEnv())
+	if len(home) > 0 {
+		return home
+	}
+	return "~"
+}
+
+func homeEnv() string {
+	if runtime.GOOS == "windows" {
+		return "USERPROFILE"
+	}
+	return "HOME"
+}
+
+func CurrentWorkingDir() string {
+	// Try for full path first to be explicit.
+	pwd := os.Getenv(pwdEnv())
+	if len(pwd) > 0 {
+		return pwd
+	}
+	return "."
+}
+
+func pwdEnv() string {
+	if runtime.GOOS == "windows" {
+		return "CD"
+	}
+	return "PWD"
+}