Unexpected encoding with interface{} key using Canonical and MapKeyAsString.

[winder]

Problem statement

When MapKeyAsString and Canonical are true, integer map keys are not quoted.

Expected behavior

Setting MapKeyAsString should ensure all map keys are quoted.

Example

These examples show the unexpected behavior using github.com/ugorji/go/codec v1.2.9.

Snippet

	handle := new(codec.JsonHandle)
	handle.MapKeyAsString = true
	handle.Canonical = true

	var b []byte
	enc := codec.NewEncoderBytes(&b, handle)
	enc.MustEncode(map[interface{}]interface{}{0: "int key"})
	if strings.Contains(string(b), "0:") {
		fmt.Printf("   * ERROR: unquoted key in \"%s\"\n", b)
	}

Standalone program:

package main

import (
	"fmt"
	"strings"

	"github.com/ugorji/go/codec"
)

func test(name string, canonical bool, mapType interface{}) {
	fmt.Printf("* %s, canonical = %t\n", name, canonical)

	handle := new(codec.JsonHandle)
	handle.MapKeyAsString = true
	handle.Canonical = canonical

	var b []byte
	enc := codec.NewEncoderBytes(&b, handle)
	enc.MustEncode(mapType)
	if strings.Contains(string(b), "0:") {
		fmt.Printf("   * ERROR: unquoted key in \"%s\"\n", b)
	}
}

func main() {
	test("map[int]interface{}", true, map[int]interface{}{0: "int key"})
	test("map[int]interface{}", false, map[int]interface{}{0: "int key"})
	test("map[interface{}]interface{}", true, map[interface{}]interface{}{0: "interface{} key"})
	test("map[interface{}]interface{}", false, map[interface{}]interface{}{0: "interface{} key"})
}

Output:

* map[int]interface{}, canonical = true
* map[int]interface{}, canonical = false
* map[interface{}]interface{}, canonical = true
   * ERROR: unquoted key in "{0:"interface{} key"}"
* map[interface{}]interface{}, canonical = false