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env.go
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env.go
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package env
import (
"encoding"
"fmt"
"net/url"
"os"
"reflect"
"strconv"
"strings"
"time"
"unicode"
)
// nolint: gochecknoglobals
var (
defaultBuiltInParsers = map[reflect.Kind]ParserFunc{
reflect.Bool: func(v string) (interface{}, error) {
return strconv.ParseBool(v)
},
reflect.String: func(v string) (interface{}, error) {
return v, nil
},
reflect.Int: func(v string) (interface{}, error) {
i, err := strconv.ParseInt(v, 10, 32)
return int(i), err
},
reflect.Int16: func(v string) (interface{}, error) {
i, err := strconv.ParseInt(v, 10, 16)
return int16(i), err
},
reflect.Int32: func(v string) (interface{}, error) {
i, err := strconv.ParseInt(v, 10, 32)
return int32(i), err
},
reflect.Int64: func(v string) (interface{}, error) {
return strconv.ParseInt(v, 10, 64)
},
reflect.Int8: func(v string) (interface{}, error) {
i, err := strconv.ParseInt(v, 10, 8)
return int8(i), err
},
reflect.Uint: func(v string) (interface{}, error) {
i, err := strconv.ParseUint(v, 10, 32)
return uint(i), err
},
reflect.Uint16: func(v string) (interface{}, error) {
i, err := strconv.ParseUint(v, 10, 16)
return uint16(i), err
},
reflect.Uint32: func(v string) (interface{}, error) {
i, err := strconv.ParseUint(v, 10, 32)
return uint32(i), err
},
reflect.Uint64: func(v string) (interface{}, error) {
i, err := strconv.ParseUint(v, 10, 64)
return i, err
},
reflect.Uint8: func(v string) (interface{}, error) {
i, err := strconv.ParseUint(v, 10, 8)
return uint8(i), err
},
reflect.Float64: func(v string) (interface{}, error) {
return strconv.ParseFloat(v, 64)
},
reflect.Float32: func(v string) (interface{}, error) {
f, err := strconv.ParseFloat(v, 32)
return float32(f), err
},
}
)
func defaultTypeParsers() map[reflect.Type]ParserFunc {
return map[reflect.Type]ParserFunc{
reflect.TypeOf(url.URL{}): func(v string) (interface{}, error) {
u, err := url.Parse(v)
if err != nil {
return nil, newParseValueError("unable to parse URL", err)
}
return *u, nil
},
reflect.TypeOf(time.Nanosecond): func(v string) (interface{}, error) {
s, err := time.ParseDuration(v)
if err != nil {
return nil, newParseValueError("unable to parse duration", err)
}
return s, err
},
}
}
// ParserFunc defines the signature of a function that can be used within `CustomParsers`.
type ParserFunc func(v string) (interface{}, error)
// OnSetFn is a hook that can be run when a value is set.
type OnSetFn func(tag string, value interface{}, isDefault bool)
// Options for the parser.
type Options struct {
// Environment keys and values that will be accessible for the service.
Environment map[string]string
// TagName specifies another tagname to use rather than the default env.
TagName string
// RequiredIfNoDef automatically sets all env as required if they do not
// declare 'envDefault'.
RequiredIfNoDef bool
// OnSet allows to run a function when a value is set.
OnSet OnSetFn
// Prefix define a prefix for each key.
Prefix string
// UseFieldNameByDefault defines whether or not env should use the field
// name by default if the `env` key is missing.
UseFieldNameByDefault bool
// Custom parse functions for different types.
FuncMap map[reflect.Type]ParserFunc
}
func defaultOptions() Options {
return Options{
TagName: "env",
Environment: toMap(os.Environ()),
FuncMap: defaultTypeParsers(),
}
}
func customOptions(opt Options) Options {
defOpts := defaultOptions()
if opt.TagName == "" {
opt.TagName = defOpts.TagName
}
if opt.Environment == nil {
opt.Environment = defOpts.Environment
}
if opt.FuncMap == nil {
opt.FuncMap = map[reflect.Type]ParserFunc{}
}
for k, v := range defOpts.FuncMap {
opt.FuncMap[k] = v
}
return opt
}
func optionsWithEnvPrefix(field reflect.StructField, opts Options) Options {
return Options{
Environment: opts.Environment,
TagName: opts.TagName,
RequiredIfNoDef: opts.RequiredIfNoDef,
OnSet: opts.OnSet,
Prefix: opts.Prefix + field.Tag.Get("envPrefix"),
UseFieldNameByDefault: opts.UseFieldNameByDefault,
FuncMap: opts.FuncMap,
}
}
// Parse parses a struct containing `env` tags and loads its values from
// environment variables.
func Parse(v interface{}) error {
return parseInternal(v, defaultOptions())
}
// Parse parses a struct containing `env` tags and loads its values from
// environment variables.
func ParseWithOptions(v interface{}, opts Options) error {
return parseInternal(v, customOptions(opts))
}
func parseInternal(v interface{}, opts Options) error {
ptrRef := reflect.ValueOf(v)
if ptrRef.Kind() != reflect.Ptr {
return newAggregateError(NotStructPtrError{})
}
ref := ptrRef.Elem()
if ref.Kind() != reflect.Struct {
return newAggregateError(NotStructPtrError{})
}
return doParse(ref, opts)
}
func doParse(ref reflect.Value, opts Options) error {
refType := ref.Type()
var agrErr AggregateError
for i := 0; i < refType.NumField(); i++ {
refField := ref.Field(i)
refTypeField := refType.Field(i)
if err := doParseField(refField, refTypeField, opts); err != nil {
if val, ok := err.(AggregateError); ok {
agrErr.Errors = append(agrErr.Errors, val.Errors...)
} else {
agrErr.Errors = append(agrErr.Errors, err)
}
}
}
if len(agrErr.Errors) == 0 {
return nil
}
return agrErr
}
func doParseField(refField reflect.Value, refTypeField reflect.StructField, opts Options) error {
if !refField.CanSet() {
return nil
}
if reflect.Ptr == refField.Kind() && !refField.IsNil() {
return parseInternal(refField.Interface(), optionsWithEnvPrefix(refTypeField, opts))
}
if reflect.Struct == refField.Kind() && refField.CanAddr() && refField.Type().Name() == "" {
return parseInternal(refField.Addr().Interface(), optionsWithEnvPrefix(refTypeField, opts))
}
value, err := get(refTypeField, opts)
if err != nil {
return err
}
if value != "" {
return set(refField, refTypeField, value, opts.FuncMap)
}
if reflect.Struct == refField.Kind() {
return doParse(refField, optionsWithEnvPrefix(refTypeField, opts))
}
return nil
}
const underscore rune = '_'
func toEnvName(input string) string {
var output []rune
for i, c := range input {
if i > 0 && output[i-1] != underscore && c != underscore && unicode.ToUpper(c) == c {
output = append(output, underscore)
}
output = append(output, unicode.ToUpper(c))
}
return string(output)
}
func get(field reflect.StructField, opts Options) (val string, err error) {
var exists bool
var isDefault bool
var loadFile bool
var unset bool
var notEmpty bool
var expand bool
required := opts.RequiredIfNoDef
ownKey, tags := parseKeyForOption(field.Tag.Get(opts.TagName))
if ownKey == "" && opts.UseFieldNameByDefault {
ownKey = toEnvName(field.Name)
}
for _, tag := range tags {
switch tag {
case "":
continue
case "file":
loadFile = true
case "required":
required = true
case "unset":
unset = true
case "notEmpty":
notEmpty = true
case "expand":
expand = true
default:
return "", newNoSupportedTagOptionError(tag)
}
}
prefix := opts.Prefix
key := prefix + ownKey
defaultValue, defExists := field.Tag.Lookup("envDefault")
val, exists, isDefault = getOr(key, defaultValue, defExists, opts.Environment)
if expand {
val = os.ExpandEnv(val)
}
if unset {
defer os.Unsetenv(key)
}
if required && !exists && len(ownKey) > 0 {
return "", newEnvVarIsNotSet(key)
}
if notEmpty && val == "" {
return "", newEmptyEnvVarError(key)
}
if loadFile && val != "" {
filename := val
val, err = getFromFile(filename)
if err != nil {
return "", newLoadFileContentError(filename, key, err)
}
}
if opts.OnSet != nil {
if ownKey != "" {
opts.OnSet(key, val, isDefault)
}
}
return val, err
}
// split the env tag's key into the expected key and desired option, if any.
func parseKeyForOption(key string) (string, []string) {
opts := strings.Split(key, ",")
return opts[0], opts[1:]
}
func getFromFile(filename string) (value string, err error) {
b, err := os.ReadFile(filename)
return string(b), err
}
func getOr(key, defaultValue string, defExists bool, envs map[string]string) (string, bool, bool) {
value, exists := envs[key]
switch {
case (!exists || key == "") && defExists:
return defaultValue, true, true
case exists && value == "" && defExists:
return defaultValue, true, true
case !exists:
return "", false, false
}
return value, true, false
}
func set(field reflect.Value, sf reflect.StructField, value string, funcMap map[reflect.Type]ParserFunc) error {
if tm := asTextUnmarshaler(field); tm != nil {
if err := tm.UnmarshalText([]byte(value)); err != nil {
return newParseError(sf, err)
}
return nil
}
typee := sf.Type
fieldee := field
if typee.Kind() == reflect.Ptr {
typee = typee.Elem()
fieldee = field.Elem()
}
parserFunc, ok := funcMap[typee]
if ok {
val, err := parserFunc(value)
if err != nil {
return newParseError(sf, err)
}
fieldee.Set(reflect.ValueOf(val))
return nil
}
parserFunc, ok = defaultBuiltInParsers[typee.Kind()]
if ok {
val, err := parserFunc(value)
if err != nil {
return newParseError(sf, err)
}
fieldee.Set(reflect.ValueOf(val).Convert(typee))
return nil
}
switch field.Kind() {
case reflect.Slice:
return handleSlice(field, value, sf, funcMap)
case reflect.Map:
return handleMap(field, value, sf, funcMap)
}
return newNoParserError(sf)
}
func handleSlice(field reflect.Value, value string, sf reflect.StructField, funcMap map[reflect.Type]ParserFunc) error {
separator := sf.Tag.Get("envSeparator")
if separator == "" {
separator = ","
}
parts := strings.Split(value, separator)
typee := sf.Type.Elem()
if typee.Kind() == reflect.Ptr {
typee = typee.Elem()
}
if _, ok := reflect.New(typee).Interface().(encoding.TextUnmarshaler); ok {
return parseTextUnmarshalers(field, parts, sf)
}
parserFunc, ok := funcMap[typee]
if !ok {
parserFunc, ok = defaultBuiltInParsers[typee.Kind()]
if !ok {
return newNoParserError(sf)
}
}
result := reflect.MakeSlice(sf.Type, 0, len(parts))
for _, part := range parts {
r, err := parserFunc(part)
if err != nil {
return newParseError(sf, err)
}
v := reflect.ValueOf(r).Convert(typee)
if sf.Type.Elem().Kind() == reflect.Ptr {
v = reflect.New(typee)
v.Elem().Set(reflect.ValueOf(r).Convert(typee))
}
result = reflect.Append(result, v)
}
field.Set(result)
return nil
}
func handleMap(field reflect.Value, value string, sf reflect.StructField, funcMap map[reflect.Type]ParserFunc) error {
keyType := sf.Type.Key()
keyParserFunc, ok := funcMap[keyType]
if !ok {
keyParserFunc, ok = defaultBuiltInParsers[keyType.Kind()]
if !ok {
return newNoParserError(sf)
}
}
elemType := sf.Type.Elem()
elemParserFunc, ok := funcMap[elemType]
if !ok {
elemParserFunc, ok = defaultBuiltInParsers[elemType.Kind()]
if !ok {
return newNoParserError(sf)
}
}
separator := sf.Tag.Get("envSeparator")
if separator == "" {
separator = ","
}
result := reflect.MakeMap(sf.Type)
for _, part := range strings.Split(value, separator) {
pairs := strings.Split(part, ":")
if len(pairs) != 2 {
return newParseError(sf, fmt.Errorf(`%q should be in "key:value" format`, part))
}
key, err := keyParserFunc(pairs[0])
if err != nil {
return newParseError(sf, err)
}
elem, err := elemParserFunc(pairs[1])
if err != nil {
return newParseError(sf, err)
}
result.SetMapIndex(reflect.ValueOf(key).Convert(keyType), reflect.ValueOf(elem).Convert(elemType))
}
field.Set(result)
return nil
}
func asTextUnmarshaler(field reflect.Value) encoding.TextUnmarshaler {
if reflect.Ptr == field.Kind() {
if field.IsNil() {
field.Set(reflect.New(field.Type().Elem()))
}
} else if field.CanAddr() {
field = field.Addr()
}
tm, ok := field.Interface().(encoding.TextUnmarshaler)
if !ok {
return nil
}
return tm
}
func parseTextUnmarshalers(field reflect.Value, data []string, sf reflect.StructField) error {
s := len(data)
elemType := field.Type().Elem()
slice := reflect.MakeSlice(reflect.SliceOf(elemType), s, s)
for i, v := range data {
sv := slice.Index(i)
kind := sv.Kind()
if kind == reflect.Ptr {
sv = reflect.New(elemType.Elem())
} else {
sv = sv.Addr()
}
tm := sv.Interface().(encoding.TextUnmarshaler)
if err := tm.UnmarshalText([]byte(v)); err != nil {
return newParseError(sf, err)
}
if kind == reflect.Ptr {
slice.Index(i).Set(sv)
}
}
field.Set(slice)
return nil
}