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