274 lines
7.4 KiB
Go
274 lines
7.4 KiB
Go
// Copyright 2013 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
// Package query implements encoding of structs into URL query parameters.
|
|
//
|
|
// As a simple example:
|
|
//
|
|
// type Options struct {
|
|
// Query string `url:"q"`
|
|
// ShowAll bool `url:"all"`
|
|
// Page int `url:"page"`
|
|
// }
|
|
//
|
|
// opt := Options{ "foo", true, 2 }
|
|
// v, _ := query.Values(opt)
|
|
// fmt.Print(v.Encode()) // will output: "q=foo&all=true&page=2"
|
|
//
|
|
// The exact mapping between Go values and url.Values is described in the
|
|
// documentation for the Values() function.
|
|
package query
|
|
|
|
import (
|
|
"bytes"
|
|
"errors"
|
|
"fmt"
|
|
"net/url"
|
|
"reflect"
|
|
"strconv"
|
|
"strings"
|
|
"time"
|
|
)
|
|
|
|
var timeType = reflect.TypeOf(time.Time{})
|
|
|
|
var encoderType = reflect.TypeOf(new(Encoder)).Elem()
|
|
|
|
// Encoder is an interface implemented by any type that wishes to encode
|
|
// itself into URL values in a non-standard way.
|
|
type Encoder interface {
|
|
EncodeValues(key string, v *url.Values) error
|
|
}
|
|
|
|
// Values returns the url.Values encoding of v.
|
|
//
|
|
// Values expects to be passed a struct, and traverses it recursively using the
|
|
// following encoding rules.
|
|
//
|
|
// Each exported struct field is encoded as a URL parameter unless
|
|
//
|
|
// - the field's tag is "-", or
|
|
// - the field is empty and its tag specifies the "omitempty" option
|
|
//
|
|
// The empty values are false, 0, any nil pointer or interface value, any array
|
|
// slice, map, or string of length zero, and any time.Time that returns true
|
|
// for IsZero().
|
|
//
|
|
// The URL parameter name defaults to the struct field name but can be
|
|
// specified in the struct field's tag value. The "url" key in the struct
|
|
// field's tag value is the key name, followed by an optional comma and
|
|
// options. For example:
|
|
//
|
|
// // Field is ignored by this package.
|
|
// Field int `url:"-"`
|
|
//
|
|
// // Field appears as URL parameter "myName".
|
|
// Field int `url:"myName"`
|
|
//
|
|
// // Field appears as URL parameter "myName" and the field is omitted if
|
|
// // its value is empty
|
|
// Field int `url:"myName,omitempty"`
|
|
//
|
|
// // Field appears as URL parameter "Field" (the default), but the field
|
|
// // is skipped if empty. Note the leading comma.
|
|
// Field int `url:",omitempty"`
|
|
//
|
|
// For encoding individual field values, the following type-dependent rules
|
|
// apply:
|
|
//
|
|
// Boolean values default to encoding as the strings "true" or "false".
|
|
// Including the "int" option signals that the field should be encoded as the
|
|
// strings "1" or "0".
|
|
//
|
|
// time.Time values default to encoding as RFC3339 timestamps. Including the
|
|
// "unix" option signals that the field should be encoded as a Unix time (see
|
|
// time.Unix())
|
|
//
|
|
// Slice and Array values default to encoding as multiple URL values of the
|
|
// same name. Including the "comma" option signals that the field should be
|
|
// encoded as a single comma-delimited value. Including the "space" option
|
|
// similarly encodes the value as a single space-delimited string.
|
|
//
|
|
// Anonymous struct fields are usually encoded as if their inner exported
|
|
// fields were fields in the outer struct, subject to the standard Go
|
|
// visibility rules. An anonymous struct field with a name given in its URL
|
|
// tag is treated as having that name, rather than being anonymous.
|
|
//
|
|
// Non-nil pointer values are encoded as the value pointed to.
|
|
//
|
|
// All other values are encoded using their default string representation.
|
|
//
|
|
// Multiple fields that encode to the same URL parameter name will be included
|
|
// as multiple URL values of the same name.
|
|
func Values(v interface{}) (url.Values, error) {
|
|
val := reflect.ValueOf(v)
|
|
for val.Kind() == reflect.Ptr {
|
|
if val.IsNil() {
|
|
return nil, errors.New("query: Values() expects non-nil value")
|
|
}
|
|
val = val.Elem()
|
|
}
|
|
|
|
if val.Kind() != reflect.Struct {
|
|
return nil, fmt.Errorf("query: Values() expects struct input. Got %v", val.Kind())
|
|
}
|
|
|
|
values := make(url.Values)
|
|
err := reflectValue(values, val)
|
|
return values, err
|
|
}
|
|
|
|
// reflectValue populates the values parameter from the struct fields in val.
|
|
// Embedded structs are followed recursively (using the rules defined in the
|
|
// Values function documentation) breadth-first.
|
|
func reflectValue(values url.Values, val reflect.Value) error {
|
|
var embedded []reflect.Value
|
|
|
|
typ := val.Type()
|
|
for i := 0; i < typ.NumField(); i++ {
|
|
sf := typ.Field(i)
|
|
if sf.PkgPath != "" { // unexported
|
|
continue
|
|
}
|
|
|
|
sv := val.Field(i)
|
|
tag := sf.Tag.Get("url")
|
|
if tag == "-" {
|
|
continue
|
|
}
|
|
name, opts := parseTag(tag)
|
|
if name == "" {
|
|
if sf.Anonymous && sv.Kind() == reflect.Struct {
|
|
// save embedded struct for later processing
|
|
embedded = append(embedded, sv)
|
|
continue
|
|
}
|
|
|
|
name = sf.Name
|
|
}
|
|
|
|
if opts.Contains("omitempty") && isEmptyValue(sv) {
|
|
continue
|
|
}
|
|
|
|
if sv.Type().Implements(encoderType) {
|
|
m := sv.Interface().(Encoder)
|
|
if err := m.EncodeValues(name, &values); err != nil {
|
|
return err
|
|
}
|
|
continue
|
|
}
|
|
|
|
if sv.Kind() == reflect.Slice || sv.Kind() == reflect.Array {
|
|
var del byte
|
|
if opts.Contains("comma") {
|
|
del = ','
|
|
} else if opts.Contains("space") {
|
|
del = ' '
|
|
}
|
|
|
|
if del != 0 {
|
|
s := new(bytes.Buffer)
|
|
first := true
|
|
for i := 0; i < sv.Len(); i++ {
|
|
if first {
|
|
first = false
|
|
} else {
|
|
s.WriteByte(del)
|
|
}
|
|
s.WriteString(valueString(sv.Index(i), opts))
|
|
}
|
|
values.Add(name, s.String())
|
|
} else {
|
|
for i := 0; i < sv.Len(); i++ {
|
|
values.Add(name, valueString(sv.Index(i), opts))
|
|
}
|
|
}
|
|
continue
|
|
}
|
|
|
|
values.Add(name, valueString(sv, opts))
|
|
}
|
|
|
|
for _, f := range embedded {
|
|
if err := reflectValue(values, f); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
// valueString returns the string representation of a value.
|
|
func valueString(v reflect.Value, opts tagOptions) string {
|
|
for v.Kind() == reflect.Ptr {
|
|
if v.IsNil() {
|
|
return ""
|
|
}
|
|
v = v.Elem()
|
|
}
|
|
|
|
if v.Kind() == reflect.Bool && opts.Contains("int") {
|
|
if v.Bool() {
|
|
return "1"
|
|
}
|
|
return "0"
|
|
}
|
|
|
|
if v.Type() == timeType {
|
|
t := v.Interface().(time.Time)
|
|
if opts.Contains("unix") {
|
|
return strconv.FormatInt(t.Unix(), 10)
|
|
}
|
|
return t.Format(time.RFC3339)
|
|
}
|
|
|
|
return fmt.Sprint(v.Interface())
|
|
}
|
|
|
|
// isEmptyValue checks if a value should be considered empty for the purposes
|
|
// of omitting fields with the "omitempty" option.
|
|
func isEmptyValue(v reflect.Value) bool {
|
|
switch v.Kind() {
|
|
case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
|
|
return v.Len() == 0
|
|
case reflect.Bool:
|
|
return !v.Bool()
|
|
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
|
|
return v.Int() == 0
|
|
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
|
|
return v.Uint() == 0
|
|
case reflect.Float32, reflect.Float64:
|
|
return v.Float() == 0
|
|
case reflect.Interface, reflect.Ptr:
|
|
return v.IsNil()
|
|
}
|
|
|
|
if v.Type() == timeType {
|
|
return v.Interface().(time.Time).IsZero()
|
|
}
|
|
|
|
return false
|
|
}
|
|
|
|
// tagOptions is the string following a comma in a struct field's "url" tag, or
|
|
// the empty string. It does not include the leading comma.
|
|
type tagOptions []string
|
|
|
|
// parseTag splits a struct field's url tag into its name and comma-separated
|
|
// options.
|
|
func parseTag(tag string) (string, tagOptions) {
|
|
s := strings.Split(tag, ",")
|
|
return s[0], s[1:]
|
|
}
|
|
|
|
// Contains checks whether the tagOptions contains the specified option.
|
|
func (o tagOptions) Contains(option string) bool {
|
|
for _, s := range o {
|
|
if s == option {
|
|
return true
|
|
}
|
|
}
|
|
return false
|
|
}
|