383 lines
9.3 KiB
Go
383 lines
9.3 KiB
Go
// Copyright (c) 2013 Kelsey Hightower. All rights reserved.
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// Use of this source code is governed by the MIT License that can be found in
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// the LICENSE file.
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package envconfig
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import (
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"encoding"
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"errors"
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"fmt"
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"os"
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"reflect"
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"regexp"
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"strconv"
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"strings"
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"time"
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)
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// ErrInvalidSpecification indicates that a specification is of the wrong type.
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var ErrInvalidSpecification = errors.New("specification must be a struct pointer")
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var gatherRegexp = regexp.MustCompile("([^A-Z]+|[A-Z]+[^A-Z]+|[A-Z]+)")
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var acronymRegexp = regexp.MustCompile("([A-Z]+)([A-Z][^A-Z]+)")
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// A ParseError occurs when an environment variable cannot be converted to
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// the type required by a struct field during assignment.
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type ParseError struct {
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KeyName string
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FieldName string
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TypeName string
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Value string
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Err error
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}
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// Decoder has the same semantics as Setter, but takes higher precedence.
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// It is provided for historical compatibility.
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type Decoder interface {
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Decode(value string) error
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}
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// Setter is implemented by types can self-deserialize values.
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// Any type that implements flag.Value also implements Setter.
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type Setter interface {
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Set(value string) error
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}
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func (e *ParseError) Error() string {
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return fmt.Sprintf("envconfig.Process: assigning %[1]s to %[2]s: converting '%[3]s' to type %[4]s. details: %[5]s", e.KeyName, e.FieldName, e.Value, e.TypeName, e.Err)
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}
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// varInfo maintains information about the configuration variable
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type varInfo struct {
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Name string
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Alt string
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Key string
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Field reflect.Value
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Tags reflect.StructTag
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}
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// GatherInfo gathers information about the specified struct
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func gatherInfo(prefix string, spec interface{}) ([]varInfo, error) {
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s := reflect.ValueOf(spec)
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if s.Kind() != reflect.Ptr {
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return nil, ErrInvalidSpecification
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}
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s = s.Elem()
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if s.Kind() != reflect.Struct {
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return nil, ErrInvalidSpecification
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}
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typeOfSpec := s.Type()
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// over allocate an info array, we will extend if needed later
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infos := make([]varInfo, 0, s.NumField())
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for i := 0; i < s.NumField(); i++ {
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f := s.Field(i)
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ftype := typeOfSpec.Field(i)
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if !f.CanSet() || isTrue(ftype.Tag.Get("ignored")) {
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continue
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}
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for f.Kind() == reflect.Ptr {
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if f.IsNil() {
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if f.Type().Elem().Kind() != reflect.Struct {
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// nil pointer to a non-struct: leave it alone
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break
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}
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// nil pointer to struct: create a zero instance
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f.Set(reflect.New(f.Type().Elem()))
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}
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f = f.Elem()
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}
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// Capture information about the config variable
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info := varInfo{
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Name: ftype.Name,
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Field: f,
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Tags: ftype.Tag,
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Alt: strings.ToUpper(ftype.Tag.Get("envconfig")),
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}
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// Default to the field name as the env var name (will be upcased)
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info.Key = info.Name
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// Best effort to un-pick camel casing as separate words
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if isTrue(ftype.Tag.Get("split_words")) {
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words := gatherRegexp.FindAllStringSubmatch(ftype.Name, -1)
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if len(words) > 0 {
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var name []string
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for _, words := range words {
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if m := acronymRegexp.FindStringSubmatch(words[0]); len(m) == 3 {
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name = append(name, m[1], m[2])
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} else {
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name = append(name, words[0])
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}
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}
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info.Key = strings.Join(name, "_")
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}
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}
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if info.Alt != "" {
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info.Key = info.Alt
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}
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if prefix != "" {
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info.Key = fmt.Sprintf("%s_%s", prefix, info.Key)
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}
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info.Key = strings.ToUpper(info.Key)
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infos = append(infos, info)
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if f.Kind() == reflect.Struct {
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// honor Decode if present
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if decoderFrom(f) == nil && setterFrom(f) == nil && textUnmarshaler(f) == nil && binaryUnmarshaler(f) == nil {
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innerPrefix := prefix
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if !ftype.Anonymous {
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innerPrefix = info.Key
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}
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embeddedPtr := f.Addr().Interface()
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embeddedInfos, err := gatherInfo(innerPrefix, embeddedPtr)
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if err != nil {
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return nil, err
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}
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infos = append(infos[:len(infos)-1], embeddedInfos...)
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continue
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}
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}
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}
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return infos, nil
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}
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// CheckDisallowed checks that no environment variables with the prefix are set
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// that we don't know how or want to parse. This is likely only meaningful with
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// a non-empty prefix.
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func CheckDisallowed(prefix string, spec interface{}) error {
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infos, err := gatherInfo(prefix, spec)
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if err != nil {
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return err
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}
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vars := make(map[string]struct{})
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for _, info := range infos {
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vars[info.Key] = struct{}{}
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}
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if prefix != "" {
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prefix = strings.ToUpper(prefix) + "_"
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}
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for _, env := range os.Environ() {
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if !strings.HasPrefix(env, prefix) {
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continue
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}
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v := strings.SplitN(env, "=", 2)[0]
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if _, found := vars[v]; !found {
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return fmt.Errorf("unknown environment variable %s", v)
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}
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}
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return nil
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}
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// Process populates the specified struct based on environment variables
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func Process(prefix string, spec interface{}) error {
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infos, err := gatherInfo(prefix, spec)
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for _, info := range infos {
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// `os.Getenv` cannot differentiate between an explicitly set empty value
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// and an unset value. `os.LookupEnv` is preferred to `syscall.Getenv`,
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// but it is only available in go1.5 or newer. We're using Go build tags
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// here to use os.LookupEnv for >=go1.5
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value, ok := lookupEnv(info.Key)
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if !ok && info.Alt != "" {
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value, ok = lookupEnv(info.Alt)
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}
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def := info.Tags.Get("default")
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if def != "" && !ok {
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value = def
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}
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req := info.Tags.Get("required")
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if !ok && def == "" {
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if isTrue(req) {
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key := info.Key
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if info.Alt != "" {
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key = info.Alt
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}
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return fmt.Errorf("required key %s missing value", key)
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}
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continue
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}
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err = processField(value, info.Field)
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if err != nil {
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return &ParseError{
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KeyName: info.Key,
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FieldName: info.Name,
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TypeName: info.Field.Type().String(),
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Value: value,
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Err: err,
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}
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}
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}
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return err
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}
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// MustProcess is the same as Process but panics if an error occurs
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func MustProcess(prefix string, spec interface{}) {
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if err := Process(prefix, spec); err != nil {
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panic(err)
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}
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}
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func processField(value string, field reflect.Value) error {
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typ := field.Type()
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decoder := decoderFrom(field)
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if decoder != nil {
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return decoder.Decode(value)
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}
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// look for Set method if Decode not defined
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setter := setterFrom(field)
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if setter != nil {
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return setter.Set(value)
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}
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if t := textUnmarshaler(field); t != nil {
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return t.UnmarshalText([]byte(value))
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}
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if b := binaryUnmarshaler(field); b != nil {
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return b.UnmarshalBinary([]byte(value))
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}
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if typ.Kind() == reflect.Ptr {
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typ = typ.Elem()
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if field.IsNil() {
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field.Set(reflect.New(typ))
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}
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field = field.Elem()
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}
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switch typ.Kind() {
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case reflect.String:
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field.SetString(value)
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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var (
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val int64
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err error
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)
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if field.Kind() == reflect.Int64 && typ.PkgPath() == "time" && typ.Name() == "Duration" {
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var d time.Duration
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d, err = time.ParseDuration(value)
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val = int64(d)
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} else {
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val, err = strconv.ParseInt(value, 0, typ.Bits())
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}
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if err != nil {
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return err
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}
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field.SetInt(val)
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
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val, err := strconv.ParseUint(value, 0, typ.Bits())
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if err != nil {
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return err
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}
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field.SetUint(val)
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case reflect.Bool:
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val, err := strconv.ParseBool(value)
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if err != nil {
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return err
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}
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field.SetBool(val)
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case reflect.Float32, reflect.Float64:
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val, err := strconv.ParseFloat(value, typ.Bits())
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if err != nil {
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return err
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}
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field.SetFloat(val)
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case reflect.Slice:
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sl := reflect.MakeSlice(typ, 0, 0)
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if typ.Elem().Kind() == reflect.Uint8 {
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sl = reflect.ValueOf([]byte(value))
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} else if len(strings.TrimSpace(value)) != 0 {
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vals := strings.Split(value, ",")
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sl = reflect.MakeSlice(typ, len(vals), len(vals))
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for i, val := range vals {
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err := processField(val, sl.Index(i))
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if err != nil {
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return err
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}
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}
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}
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field.Set(sl)
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case reflect.Map:
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mp := reflect.MakeMap(typ)
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if len(strings.TrimSpace(value)) != 0 {
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pairs := strings.Split(value, ",")
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for _, pair := range pairs {
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kvpair := strings.Split(pair, ":")
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if len(kvpair) != 2 {
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return fmt.Errorf("invalid map item: %q", pair)
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}
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k := reflect.New(typ.Key()).Elem()
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err := processField(kvpair[0], k)
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if err != nil {
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return err
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}
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v := reflect.New(typ.Elem()).Elem()
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err = processField(kvpair[1], v)
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if err != nil {
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return err
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}
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mp.SetMapIndex(k, v)
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}
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}
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field.Set(mp)
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}
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return nil
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}
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func interfaceFrom(field reflect.Value, fn func(interface{}, *bool)) {
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// it may be impossible for a struct field to fail this check
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if !field.CanInterface() {
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return
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}
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var ok bool
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fn(field.Interface(), &ok)
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if !ok && field.CanAddr() {
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fn(field.Addr().Interface(), &ok)
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}
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}
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func decoderFrom(field reflect.Value) (d Decoder) {
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interfaceFrom(field, func(v interface{}, ok *bool) { d, *ok = v.(Decoder) })
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return d
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}
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func setterFrom(field reflect.Value) (s Setter) {
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interfaceFrom(field, func(v interface{}, ok *bool) { s, *ok = v.(Setter) })
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return s
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}
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func textUnmarshaler(field reflect.Value) (t encoding.TextUnmarshaler) {
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interfaceFrom(field, func(v interface{}, ok *bool) { t, *ok = v.(encoding.TextUnmarshaler) })
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return t
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}
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func binaryUnmarshaler(field reflect.Value) (b encoding.BinaryUnmarshaler) {
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interfaceFrom(field, func(v interface{}, ok *bool) { b, *ok = v.(encoding.BinaryUnmarshaler) })
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return b
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}
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func isTrue(s string) bool {
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b, _ := strconv.ParseBool(s)
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return b
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}
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