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package docopt
import (
"fmt"
"reflect"
"strconv"
"strings"
"unicode"
)
func errKey(key string) error {
return fmt.Errorf("no such key: %q", key)
}
func errType(key string) error {
return fmt.Errorf("key: %q failed type conversion", key)
}
func errStrconv(key string, convErr error) error {
return fmt.Errorf("key: %q failed type conversion: %s", key, convErr)
}
// Opts is a map of command line options to their values, with some convenience
// methods for value type conversion (bool, float64, int, string). For example,
// to get an option value as an int:
//
// opts, _ := docopt.ParseDoc("Usage: sleep <seconds>")
// secs, _ := opts.Int("<seconds>")
//
// Additionally, Opts.Bind allows you easily populate a struct's fields with the
// values of each option value. See below for examples.
//
// Lastly, you can still treat Opts as a regular map, and do any type checking
// and conversion that you want to yourself. For example:
//
// if s, ok := opts["<binary>"].(string); ok {
// if val, err := strconv.ParseUint(s, 2, 64); err != nil { ... }
// }
//
// Note that any non-boolean option / flag will have a string value in the
// underlying map.
type Opts map[string]interface{}
func (o Opts) String(key string) (s string, err error) {
v, ok := o[key]
if !ok {
err = errKey(key)
return
}
s, ok = v.(string)
if !ok {
err = errType(key)
}
return
}
func (o Opts) Bool(key string) (b bool, err error) {
v, ok := o[key]
if !ok {
err = errKey(key)
return
}
b, ok = v.(bool)
if !ok {
err = errType(key)
}
return
}
func (o Opts) Int(key string) (i int, err error) {
s, err := o.String(key)
if err != nil {
return
}
i, err = strconv.Atoi(s)
if err != nil {
err = errStrconv(key, err)
}
return
}
func (o Opts) Float64(key string) (f float64, err error) {
s, err := o.String(key)
if err != nil {
return
}
f, err = strconv.ParseFloat(s, 64)
if err != nil {
err = errStrconv(key, err)
}
return
}
// Bind populates the fields of a given struct with matching option values.
// Each key in Opts will be mapped to an exported field of the struct pointed
// to by `v`, as follows:
//
// abc int // Unexported field, ignored
// Abc string // Mapped from `--abc`, `<abc>`, or `abc`
// // (case insensitive)
// A string // Mapped from `-a`, `<a>` or `a`
// // (case insensitive)
// Abc int `docopt:"XYZ"` // Mapped from `XYZ`
// Abc bool `docopt:"-"` // Mapped from `-`
// Abc bool `docopt:"-x,--xyz"` // Mapped from `-x` or `--xyz`
// // (first non-zero value found)
//
// Tagged (annotated) fields will always be mapped first. If no field is tagged
// with an option's key, Bind will try to map the option to an appropriately
// named field (as above).
//
// Bind also handles conversion to bool, float, int or string types.
func (o Opts) Bind(v interface{}) error {
structVal := reflect.ValueOf(v)
if structVal.Kind() != reflect.Ptr {
return newError("'v' argument is not pointer to struct type")
}
for structVal.Kind() == reflect.Ptr {
structVal = structVal.Elem()
}
if structVal.Kind() != reflect.Struct {
return newError("'v' argument is not pointer to struct type")
}
structType := structVal.Type()
tagged := make(map[string]int) // Tagged field tags
untagged := make(map[string]int) // Untagged field names
for i := 0; i < structType.NumField(); i++ {
field := structType.Field(i)
if isUnexportedField(field) || field.Anonymous {
continue
}
tag := field.Tag.Get("docopt")
if tag == "" {
untagged[field.Name] = i
continue
}
for _, t := range strings.Split(tag, ",") {
tagged[t] = i
}
}
// Get the index of the struct field to use, based on the option key.
// Second argument is true/false on whether something was matched.
getFieldIndex := func(key string) (int, bool) {
if i, ok := tagged[key]; ok {
return i, true
}
if i, ok := untagged[guessUntaggedField(key)]; ok {
return i, true
}
return -1, false
}
indexMap := make(map[string]int) // Option keys to field index
// Pre-check that option keys are mapped to fields and fields are zero valued, before populating them.
for k := range o {
i, ok := getFieldIndex(k)
if !ok {
if k == "--help" || k == "--version" { // Don't require these to be mapped.
continue
}
return newError("mapping of %q is not found in given struct, or is an unexported field", k)
}
fieldVal := structVal.Field(i)
zeroVal := reflect.Zero(fieldVal.Type())
if !reflect.DeepEqual(fieldVal.Interface(), zeroVal.Interface()) {
return newError("%q field is non-zero, will be overwritten by value of %q", structType.Field(i).Name, k)
}
indexMap[k] = i
}
// Populate fields with option values.
for k, v := range o {
i, ok := indexMap[k]
if !ok {
continue // Not mapped.
}
field := structVal.Field(i)
if !reflect.DeepEqual(field.Interface(), reflect.Zero(field.Type()).Interface()) {
// The struct's field is already non-zero (by our doing), so don't change it.
// This happens with comma separated tags, e.g. `docopt:"-h,--help"` which is a
// convenient way of checking if one of multiple boolean flags are set.
continue
}
optVal := reflect.ValueOf(v)
// Option value is the zero Value, so we can't get its .Type(). No need to assign anyway, so move along.
if !optVal.IsValid() {
continue
}
if !field.CanSet() {
return newError("%q field cannot be set", structType.Field(i).Name)
}
// Try to assign now if able. bool and string values should be assignable already.
if optVal.Type().AssignableTo(field.Type()) {
field.Set(optVal)
continue
}
// Try to convert the value and assign if able.
switch field.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
if x, err := o.Int(k); err == nil {
field.SetInt(int64(x))
continue
}
case reflect.Float32, reflect.Float64:
if x, err := o.Float64(k); err == nil {
field.SetFloat(x)
continue
}
}
// TODO: Something clever (recursive?) with non-string slices.
// case reflect.Slice:
// if optVal.Kind() == reflect.Slice {
// for i := 0; i < optVal.Len(); i++ {
// sliceVal := optVal.Index(i)
// fmt.Printf("%v", sliceVal)
// }
// fmt.Printf("\n")
// }
return newError("value of %q is not assignable to %q field", k, structType.Field(i).Name)
}
return nil
}
// isUnexportedField returns whether the field is unexported.
// isUnexportedField is to avoid the bug in versions older than Go1.3.
// See following links:
// https://code.google.com/p/go/issues/detail?id=7247
// http://golang.org/ref/spec#Exported_identifiers
func isUnexportedField(field reflect.StructField) bool {
return !(field.PkgPath == "" && unicode.IsUpper(rune(field.Name[0])))
}
// Convert a string like "--my-special-flag" to "MySpecialFlag".
func titleCaseDashes(key string) string {
nextToUpper := true
mapFn := func(r rune) rune {
if r == '-' {
nextToUpper = true
return -1
}
if nextToUpper {
nextToUpper = false
return unicode.ToUpper(r)
}
return r
}
return strings.Map(mapFn, key)
}
// Best guess which field.Name in a struct to assign for an option key.
func guessUntaggedField(key string) string {
switch {
case strings.HasPrefix(key, "--") && len(key[2:]) > 1:
return titleCaseDashes(key[2:])
case strings.HasPrefix(key, "-") && len(key[1:]) == 1:
return titleCaseDashes(key[1:])
case strings.HasPrefix(key, "<") && strings.HasSuffix(key, ">"):
key = key[1 : len(key)-1]
}
return strings.Title(strings.ToLower(key))
}
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