Add support for JSON encoding nested struct

go.mod

@@ -1,4 +1,4 @@
-module github.com/google/go-querystring
+module github.com/schmorrison/go-querystring
 
 go 1.10
 

query/encode.go

@@ -22,6 +22,7 @@ package query
 
 import (
 	"bytes"
+	"encoding/json"
 	"fmt"
 	"net/url"
 	"reflect"
@@ -119,6 +120,14 @@ type Encoder interface {
 //
 // 	"user[name]=acme&user[addr][postcode]=1234&user[addr][city]=SFO"
 //
+// Structs can be encoded as JSON by including the "json" option in that fields
+// tag. The entire struct is then passed to encoding/json.Marshal where those
+// tag signatures apply.
+//
+//  // Encoding a struct as JSON
+//  Field A `url: "myName,json"`
+//  // Result: myName={"someField": "cat", "numField": 1}
+//
 // All other values are encoded using their default string representation.
 //
 // Multiple fields that encode to the same URL parameter name will be included
@@ -252,8 +261,18 @@ func reflectValue(values url.Values, val reflect.Value, scope string) error {
 		}
 
 		if sv.Kind() == reflect.Struct {
-			if err := reflectValue(values, sv, name); err != nil {
-				return err
+			if opts.Contains("json") {
+				var b []byte
+				b, err := json.Marshal(sv.Interface())
+				if err != nil {
+					return err
+				}
+
+				values.Add(name, valueString(reflect.ValueOf(string(b)), opts, sf))
+			} else {
+				if err := reflectValue(values, sv, name); err != nil {
+					return err
+				}
 			}
 			continue
 		}

query/encode_test.go

@@ -404,6 +404,75 @@ func TestValues_EmbeddedStructs(t *testing.T) {
 	}
 }
 
+func TestValues_StructsAsJSON(t *testing.T) {
+	type Nested struct {
+		L bool `json:"l"`
+		M bool `json:"m"`
+	}
+	type Inner struct {
+		A string `json:"a"`
+		B int    `json:"b"`
+		T Nested `json:"t"`
+	}
+
+	type Outer struct {
+		S Inner  `url:"str,json"`
+		P *Inner `url:"ptr,json,omitempty"`
+	}
+
+	tests := []struct {
+		input interface{}
+		want  url.Values
+	}{
+		{
+			Outer{
+				S: Inner{
+					A: "abc",
+					B: 5,
+					T: Nested{
+						L: true,
+						M: false,
+					},
+				},
+				P: nil,
+			},
+			url.Values{
+				"str": {`{"a":"abc","b":5,"t":{"l":true,"m":false}}`},
+			},
+		},
+		{
+			Outer{
+				P: &Inner{
+					A: "def",
+					B: 22,
+					T: Nested{
+						L: true,
+						M: true,
+					},
+				},
+			},
+			url.Values{
+				"str": {`{"a":"","b":0,"t":{"l":false,"m":false}}`},
+				"ptr": {`{"a":"def","b":22,"t":{"l":true,"m":true}}`},
+			},
+		},
+		{
+			Outer{},
+			url.Values{
+				"str": {`{"a":"","b":0,"t":{"l":false,"m":false}}`},
+			},
+		},
+		{
+			nil,
+			url.Values{},
+		},
+	}
+
+	for _, tt := range tests {
+		testValue(t, tt.input, tt.want)
+	}
+}
+
 func TestValues_InvalidInput(t *testing.T) {
 	_, err := Values("")
 	if err == nil {