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// Copyright 2015 The etcd 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 flags implements command-line flag parsing.
package flags
import (
"flag"
"fmt"
"os"
"strings"
"github.com/spf13/pflag"
"go.uber.org/zap"
)
// SetFlagsFromEnv parses all registered flags in the given flagset,
// and if they are not already set it attempts to set their values from
// environment variables. Environment variables take the name of the flag but
// are UPPERCASE, have the given prefix and any dashes are replaced by
// underscores - for example: some-flag => ETCD_SOME_FLAG
func SetFlagsFromEnv(lg *zap.Logger, prefix string, fs *flag.FlagSet) error {
var err error
alreadySet := make(map[string]bool)
fs.Visit(func(f *flag.Flag) {
alreadySet[FlagToEnv(prefix, f.Name)] = true
})
usedEnvKey := make(map[string]bool)
fs.VisitAll(func(f *flag.Flag) {
if serr := setFlagFromEnv(lg, fs, prefix, f.Name, usedEnvKey, alreadySet, true); serr != nil {
err = serr
}
})
verifyEnv(lg, prefix, usedEnvKey, alreadySet)
return err
}
// SetPflagsFromEnv is similar to SetFlagsFromEnv. However, the accepted flagset type is pflag.FlagSet
// and it does not do any logging.
func SetPflagsFromEnv(lg *zap.Logger, prefix string, fs *pflag.FlagSet) error {
var err error
alreadySet := make(map[string]bool)
usedEnvKey := make(map[string]bool)
fs.VisitAll(func(f *pflag.Flag) {
if f.Changed {
alreadySet[FlagToEnv(prefix, f.Name)] = true
}
if serr := setFlagFromEnv(lg, fs, prefix, f.Name, usedEnvKey, alreadySet, false); serr != nil {
err = serr
}
})
verifyEnv(lg, prefix, usedEnvKey, alreadySet)
return err
}
// FlagToEnv converts flag string to upper-case environment variable key string.
func FlagToEnv(prefix, name string) string {
return prefix + "_" + strings.ToUpper(strings.Replace(name, "-", "_", -1))
}
func verifyEnv(lg *zap.Logger, prefix string, usedEnvKey, alreadySet map[string]bool) {
for _, env := range os.Environ() {
kv := strings.SplitN(env, "=", 2)
if len(kv) != 2 {
if lg != nil {
lg.Warn("found invalid environment variable", zap.String("environment-variable", env))
}
}
if usedEnvKey[kv[0]] {
continue
}
if alreadySet[kv[0]] {
if lg != nil {
lg.Fatal(
"conflicting environment variable is shadowed by corresponding command-line flag (either unset environment variable or disable flag))",
zap.String("environment-variable", kv[0]),
)
}
}
if strings.HasPrefix(env, prefix+"_") {
if lg != nil {
lg.Warn("unrecognized environment variable", zap.String("environment-variable", env))
}
}
}
}
type flagSetter interface {
Set(fk string, fv string) error
}
func setFlagFromEnv(lg *zap.Logger, fs flagSetter, prefix, fname string, usedEnvKey, alreadySet map[string]bool, log bool) error {
key := FlagToEnv(prefix, fname)
if !alreadySet[key] {
val := os.Getenv(key)
if val != "" {
usedEnvKey[key] = true
if serr := fs.Set(fname, val); serr != nil {
return fmt.Errorf("invalid value %q for %s: %v", val, key, serr)
}
if log && lg != nil {
lg.Info(
"recognized and used environment variable",
zap.String("variable-name", key),
zap.String("variable-value", val),
)
}
}
}
return nil
}
func IsSet(fs *flag.FlagSet, name string) bool {
set := false
fs.Visit(func(f *flag.Flag) {
if f.Name == name {
set = true
}
})
return set
}
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