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// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
package main
import (
"fmt"
"os"
"sort"
"strings"
)
// Environment starts from an initial set of environment variables, and tracks
// mutations to the environment. It can then apply those mutations to the
// environment, or produce debugging output that illustrates the changes it
// would make.
type Environment struct {
init map[string]string
set map[string]string
unset map[string]bool
setenv func(string, string) error
unsetenv func(string) error
}
// NewEnvironment returns an Environment initialized from os.Environ.
func NewEnvironment() *Environment {
init := map[string]string{}
for _, env := range os.Environ() {
fs := strings.SplitN(env, "=", 2)
if len(fs) != 2 {
panic("bad environ provided")
}
init[fs[0]] = fs[1]
}
return newEnvironmentForTest(init, os.Setenv, os.Unsetenv)
}
func newEnvironmentForTest(init map[string]string, setenv func(string, string) error, unsetenv func(string) error) *Environment {
return &Environment{
init: init,
set: map[string]string{},
unset: map[string]bool{},
setenv: setenv,
unsetenv: unsetenv,
}
}
// Set sets the environment variable k to v.
func (e *Environment) Set(k, v string) {
e.set[k] = v
delete(e.unset, k)
}
// Unset removes the environment variable k.
func (e *Environment) Unset(k string) {
delete(e.set, k)
e.unset[k] = true
}
// IsSet reports whether the environment variable k is set.
func (e *Environment) IsSet(k string) bool {
if e.unset[k] {
return false
}
if _, ok := e.init[k]; ok {
return true
}
if _, ok := e.set[k]; ok {
return true
}
return false
}
// Get returns the value of the environment variable k, or defaultVal if it is
// not set.
func (e *Environment) Get(k, defaultVal string) string {
if e.unset[k] {
return defaultVal
}
if v, ok := e.set[k]; ok {
return v
}
if v, ok := e.init[k]; ok {
return v
}
return defaultVal
}
// Apply applies all pending mutations to the environment.
func (e *Environment) Apply() error {
for k, v := range e.set {
if err := e.setenv(k, v); err != nil {
return fmt.Errorf("setting %q: %v", k, err)
}
e.init[k] = v
delete(e.set, k)
}
for k := range e.unset {
if err := e.unsetenv(k); err != nil {
return fmt.Errorf("unsetting %q: %v", k, err)
}
delete(e.init, k)
delete(e.unset, k)
}
return nil
}
// Diff returns a string describing the pending mutations to the environment.
func (e *Environment) Diff() string {
lines := make([]string, 0, len(e.set)+len(e.unset))
for k, v := range e.set {
old, ok := e.init[k]
if ok {
lines = append(lines, fmt.Sprintf("%s=%s (was %s)", k, v, old))
} else {
lines = append(lines, fmt.Sprintf("%s=%s (was <nil>)", k, v))
}
}
for k := range e.unset {
old, ok := e.init[k]
if ok {
lines = append(lines, fmt.Sprintf("%s=<nil> (was %s)", k, old))
} else {
lines = append(lines, fmt.Sprintf("%s=<nil> (was <nil>)", k))
}
}
sort.Strings(lines)
return strings.Join(lines, "\n")
}
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