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// Copyright 2013, 2014 Canonical Ltd.
// Licensed under the LGPLv3, see LICENCE file for details.
package testing
import (
"os"
"reflect"
"strings"
)
// Restorer holds a function that can be used
// to restore some previous state.
type Restorer func()
// Add returns a Restorer that restores first f1
// and then f. It is valid to call this on a nil
// Restorer.
func (f Restorer) Add(f1 Restorer) Restorer {
return func() {
f1.Restore()
if f != nil {
f.Restore()
}
}
}
// Restore restores some previous state.
func (r Restorer) Restore() {
r()
}
// PatchValue sets the value pointed to by the given destination to the given
// value, and returns a function to restore it to its original value. The
// value must be assignable to the element type of the destination.
func PatchValue(dest, value interface{}) Restorer {
destv := reflect.ValueOf(dest).Elem()
oldv := reflect.New(destv.Type()).Elem()
oldv.Set(destv)
valuev := reflect.ValueOf(value)
if !valuev.IsValid() {
// This isn't quite right when the destination type is not
// nilable, but it's better than the complex alternative.
valuev = reflect.Zero(destv.Type())
}
destv.Set(valuev)
return func() {
destv.Set(oldv)
}
}
// PatchEnvironment provides a test a simple way to override a single
// environment variable. A function is returned that will return the
// environment to what it was before.
func PatchEnvironment(name, value string) Restorer {
oldValue, oldValueSet := os.LookupEnv(name)
_ = os.Setenv(name, value)
return func() {
if oldValueSet {
_ = os.Setenv(name, oldValue)
} else {
_ = os.Unsetenv(name)
}
}
}
// PatchEnvPathPrepend provides a simple way to prepend path to the start of the
// PATH environment variable. Returns a function that restores the environment
// to what it was before.
func PatchEnvPathPrepend(dir string) Restorer {
return PatchEnvironment("PATH", joinPathLists(dir, os.Getenv("PATH")))
}
func joinPathLists(paths ...string) string {
return strings.Join(paths, string(os.PathListSeparator))
}
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