/
config.go
455 lines (400 loc) · 12.8 KB
/
config.go
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// Package rconfig implements a CLI configuration reader with struct-embedded
// defaults, environment variables and posix compatible flag parsing using
// the pflag library.
package rconfig
import (
"errors"
"fmt"
"os"
"reflect"
"strconv"
"strings"
"time"
"github.com/spf13/pflag"
validator "gopkg.in/validator.v2"
)
type afterFunc func() error
var (
autoEnv bool
fs *pflag.FlagSet
variableDefaults map[string]string
timeParserFormats = []string{
// Default constants
time.RFC3339Nano, time.RFC3339,
time.RFC1123Z, time.RFC1123,
time.RFC822Z, time.RFC822,
time.RFC850, time.RubyDate, time.UnixDate, time.ANSIC,
"2006-01-02 15:04:05.999999999 -0700 MST",
// More uncommon time formats
"2006-01-02 15:04:05", "2006-01-02 15:04:05Z07:00", // Simplified ISO time format
"01/02/2006 15:04:05", "01/02/2006 15:04:05Z07:00", // US time format
"02.01.2006 15:04:05", "02.01.2006 15:04:05Z07:00", // DE time format
}
)
func init() {
variableDefaults = make(map[string]string)
}
// Parse takes the pointer to a struct filled with variables which should be read
// from ENV, default or flag. The precedence in this is flag > ENV > default. So
// if a flag is specified on the CLI it will overwrite the ENV and otherwise ENV
// overwrites the default specified.
//
// For your configuration struct you can use the following struct-tags to control
// the behavior of rconfig:
//
// default: Set a default value
// vardefault: Read the default value from the variable defaults
// env: Read the value from this environment variable
// flag: Flag to read in format "long,short" (for example "listen,l")
// description: A help text for Usage output to guide your users
//
// The format you need to specify those values you can see in the example to this
// function.
func Parse(config interface{}) error {
return parse(config, nil)
}
// ParseAndValidate works exactly like Parse but implements an additional run of
// the go-validator package on the configuration struct. Therefore additional struct
// tags are supported like described in the readme file of the go-validator package:
//
// https://github.com/go-validator/validator/tree/v2#usage
func ParseAndValidate(config interface{}) error {
return parseAndValidate(config, nil)
}
// Args returns the non-flag command-line arguments.
func Args() []string {
return fs.Args()
}
// AddTimeParserFormats adds custom formats to parse time.Time fields
func AddTimeParserFormats(f ...string) {
timeParserFormats = append(timeParserFormats, f...)
}
// AutoEnv enables or disables automated env variable guessing. If no `env` struct
// tag was set and AutoEnv is enabled the env variable name is derived from the
// name of the field: `MyFieldName` will get `MY_FIELD_NAME`
func AutoEnv(enable bool) {
autoEnv = enable
}
// Usage prints a basic usage with the corresponding defaults for the flags to
// os.Stdout. The defaults are derived from the `default` struct-tag and the ENV.
func Usage() {
if fs != nil && fs.Parsed() {
fmt.Fprintf(os.Stderr, "Usage of %s:\n", os.Args[0])
fs.PrintDefaults()
}
}
// SetVariableDefaults presets the parser with a map of default values to be used
// when specifying the vardefault tag
func SetVariableDefaults(defaults map[string]string) {
variableDefaults = defaults
}
//revive:disable-next-line:confusing-naming // The public function is only a wrapper with less args
func parseAndValidate(in interface{}, args []string) (err error) {
if err = parse(in, args); err != nil {
return err
}
if err = validator.Validate(in); err != nil {
return fmt.Errorf("validating values: %w", err)
}
return nil
}
//revive:disable-next-line:confusing-naming // The public function is only a wrapper with less args
func parse(in interface{}, args []string) error {
if args == nil {
args = os.Args
}
fs = pflag.NewFlagSet(os.Args[0], pflag.ExitOnError)
afterFuncs, err := execTags(in, fs)
if err != nil {
return err
}
if err := fs.Parse(args); err != nil {
return fmt.Errorf("parsing flag-set: %w", err)
}
for _, f := range afterFuncs {
if err := f(); err != nil {
return err
}
}
return nil
}
//nolint:funlen,gocognit,gocyclo // Hard to split
func execTags(in interface{}, fs *pflag.FlagSet) ([]afterFunc, error) {
if reflect.TypeOf(in).Kind() != reflect.Ptr {
return nil, errors.New("calling parser with non-pointer")
}
if reflect.ValueOf(in).Elem().Kind() != reflect.Struct {
return nil, errors.New("calling parser with pointer to non-struct")
}
afterFuncs := []afterFunc{}
st := reflect.ValueOf(in).Elem()
for i := 0; i < st.NumField(); i++ {
valField := st.Field(i)
typeField := st.Type().Field(i)
if typeField.Tag.Get("default") == "" && typeField.Tag.Get("env") == "" && typeField.Tag.Get("flag") == "" && typeField.Type.Kind() != reflect.Struct {
// None of our supported tags is present and it's not a sub-struct
continue
}
value := varDefault(typeField.Tag.Get("vardefault"), typeField.Tag.Get("default"))
value = envDefault(typeField, value)
parts := strings.Split(typeField.Tag.Get("flag"), ",")
switch typeField.Type {
case reflect.TypeOf(time.Duration(0)):
v, err := time.ParseDuration(value)
if err != nil {
if value != "" {
return nil, fmt.Errorf("parsing time.Duration: %w", err)
}
v = time.Duration(0)
}
if typeField.Tag.Get("flag") != "" {
if len(parts) == 1 {
fs.DurationVar(valField.Addr().Interface().(*time.Duration), parts[0], v, typeField.Tag.Get("description"))
} else {
fs.DurationVarP(valField.Addr().Interface().(*time.Duration), parts[0], parts[1], v, typeField.Tag.Get("description"))
}
} else {
valField.Set(reflect.ValueOf(v))
}
continue
case reflect.TypeOf(time.Time{}):
var sVar string
if typeField.Tag.Get("flag") != "" {
if len(parts) == 1 {
fs.StringVar(&sVar, parts[0], value, typeField.Tag.Get("description"))
} else {
fs.StringVarP(&sVar, parts[0], parts[1], value, typeField.Tag.Get("description"))
}
} else {
sVar = value
}
afterFuncs = append(afterFuncs, func(valField reflect.Value, sVar *string) func() error {
return func() error {
if *sVar == "" {
// No time, no problem
return nil
}
// Check whether we could have a timestamp
if ts, err := strconv.ParseInt(*sVar, 10, 64); err == nil {
t := time.Unix(ts, 0)
valField.Set(reflect.ValueOf(t))
return nil
}
// We haven't so lets walk through possible time formats
matched := false
for _, tf := range timeParserFormats {
if t, err := time.Parse(tf, *sVar); err == nil {
valField.Set(reflect.ValueOf(t))
return nil
}
}
if !matched {
return fmt.Errorf("value %q did not match expected time formats", *sVar)
}
return nil
}
}(valField, &sVar))
continue
}
switch typeField.Type.Kind() {
case reflect.String:
if typeField.Tag.Get("flag") != "" {
if len(parts) == 1 {
fs.StringVar(valField.Addr().Interface().(*string), parts[0], value, typeField.Tag.Get("description"))
} else {
fs.StringVarP(valField.Addr().Interface().(*string), parts[0], parts[1], value, typeField.Tag.Get("description"))
}
} else {
valField.SetString(value)
}
case reflect.Bool:
v := value == "true"
if typeField.Tag.Get("flag") != "" {
if len(parts) == 1 {
fs.BoolVar(valField.Addr().Interface().(*bool), parts[0], v, typeField.Tag.Get("description"))
} else {
fs.BoolVarP(valField.Addr().Interface().(*bool), parts[0], parts[1], v, typeField.Tag.Get("description"))
}
} else {
valField.SetBool(v)
}
case reflect.Int, reflect.Int8, reflect.Int32, reflect.Int64:
vt, err := strconv.ParseInt(value, 10, 64)
if err != nil {
if value != "" {
return nil, fmt.Errorf("parsing int: %w", err)
}
vt = 0
}
if typeField.Tag.Get("flag") != "" {
registerFlagInt(typeField.Type.Kind(), fs, valField.Addr().Interface(), parts, vt, typeField.Tag.Get("description"))
} else {
valField.SetInt(vt)
}
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
vt, err := strconv.ParseUint(value, 10, 64)
if err != nil {
if value != "" {
return nil, fmt.Errorf("parsing uint: %w", err)
}
vt = 0
}
if typeField.Tag.Get("flag") != "" {
registerFlagUint(typeField.Type.Kind(), fs, valField.Addr().Interface(), parts, vt, typeField.Tag.Get("description"))
} else {
valField.SetUint(vt)
}
case reflect.Float32, reflect.Float64:
vt, err := strconv.ParseFloat(value, 64)
if err != nil {
if value != "" {
return nil, fmt.Errorf("parsing float: %w", err)
}
vt = 0.0
}
if typeField.Tag.Get("flag") != "" {
registerFlagFloat(typeField.Type.Kind(), fs, valField.Addr().Interface(), parts, vt, typeField.Tag.Get("description"))
} else {
valField.SetFloat(vt)
}
case reflect.Struct:
afs, err := execTags(valField.Addr().Interface(), fs)
if err != nil {
return nil, err
}
afterFuncs = append(afterFuncs, afs...)
case reflect.Slice:
switch typeField.Type.Elem().Kind() {
case reflect.Int:
def := []int{}
for _, v := range strings.Split(value, ",") {
it, err := strconv.ParseInt(strings.TrimSpace(v), 10, 64)
if err != nil {
return nil, fmt.Errorf("parsing int: %w", err)
}
def = append(def, int(it))
}
if len(parts) == 1 {
fs.IntSliceVar(valField.Addr().Interface().(*[]int), parts[0], def, typeField.Tag.Get("description"))
} else {
fs.IntSliceVarP(valField.Addr().Interface().(*[]int), parts[0], parts[1], def, typeField.Tag.Get("description"))
}
case reflect.String:
del := typeField.Tag.Get("delimiter")
if len(del) == 0 {
del = ","
}
def := []string{}
if value != "" {
def = strings.Split(value, del)
}
if len(parts) == 1 {
fs.StringSliceVar(valField.Addr().Interface().(*[]string), parts[0], def, typeField.Tag.Get("description"))
} else {
fs.StringSliceVarP(valField.Addr().Interface().(*[]string), parts[0], parts[1], def, typeField.Tag.Get("description"))
}
}
}
}
return afterFuncs, nil
}
func registerFlagFloat(t reflect.Kind, fs *pflag.FlagSet, field interface{}, parts []string, vt float64, desc string) {
switch t {
case reflect.Float32:
if len(parts) == 1 {
fs.Float32Var(field.(*float32), parts[0], float32(vt), desc)
} else {
fs.Float32VarP(field.(*float32), parts[0], parts[1], float32(vt), desc)
}
case reflect.Float64:
if len(parts) == 1 {
fs.Float64Var(field.(*float64), parts[0], vt, desc)
} else {
fs.Float64VarP(field.(*float64), parts[0], parts[1], vt, desc)
}
}
}
func registerFlagInt(t reflect.Kind, fs *pflag.FlagSet, field interface{}, parts []string, vt int64, desc string) {
switch t {
case reflect.Int:
if len(parts) == 1 {
fs.IntVar(field.(*int), parts[0], int(vt), desc)
} else {
fs.IntVarP(field.(*int), parts[0], parts[1], int(vt), desc)
}
case reflect.Int8:
if len(parts) == 1 {
fs.Int8Var(field.(*int8), parts[0], int8(vt), desc)
} else {
fs.Int8VarP(field.(*int8), parts[0], parts[1], int8(vt), desc)
}
case reflect.Int32:
if len(parts) == 1 {
fs.Int32Var(field.(*int32), parts[0], int32(vt), desc)
} else {
fs.Int32VarP(field.(*int32), parts[0], parts[1], int32(vt), desc)
}
case reflect.Int64:
if len(parts) == 1 {
fs.Int64Var(field.(*int64), parts[0], vt, desc)
} else {
fs.Int64VarP(field.(*int64), parts[0], parts[1], vt, desc)
}
}
}
func registerFlagUint(t reflect.Kind, fs *pflag.FlagSet, field interface{}, parts []string, vt uint64, desc string) {
switch t {
case reflect.Uint:
if len(parts) == 1 {
fs.UintVar(field.(*uint), parts[0], uint(vt), desc)
} else {
fs.UintVarP(field.(*uint), parts[0], parts[1], uint(vt), desc)
}
case reflect.Uint8:
if len(parts) == 1 {
fs.Uint8Var(field.(*uint8), parts[0], uint8(vt), desc)
} else {
fs.Uint8VarP(field.(*uint8), parts[0], parts[1], uint8(vt), desc)
}
case reflect.Uint16:
if len(parts) == 1 {
fs.Uint16Var(field.(*uint16), parts[0], uint16(vt), desc)
} else {
fs.Uint16VarP(field.(*uint16), parts[0], parts[1], uint16(vt), desc)
}
case reflect.Uint32:
if len(parts) == 1 {
fs.Uint32Var(field.(*uint32), parts[0], uint32(vt), desc)
} else {
fs.Uint32VarP(field.(*uint32), parts[0], parts[1], uint32(vt), desc)
}
case reflect.Uint64:
if len(parts) == 1 {
fs.Uint64Var(field.(*uint64), parts[0], vt, desc)
} else {
fs.Uint64VarP(field.(*uint64), parts[0], parts[1], vt, desc)
}
}
}
func envDefault(field reflect.StructField, def string) string {
value := def
env := field.Tag.Get("env")
if env == "" && autoEnv {
env = deriveEnvVarName(field.Name)
}
if env != "" {
if e := os.Getenv(env); e != "" {
value = e
}
}
return value
}
func varDefault(name, def string) string {
value := def
if name != "" {
if v, ok := variableDefaults[name]; ok {
value = v
}
}
return value
}