Compatibility issue with native JSON encoder: failed to convert `null` of string field to pointer of integer

[zhenchangxc]

The below code works well with native encoder but not the json-iterator. When running with json-iterator, similar error will be returned when trying to unmarshal null into integer pointer:

stringModeNumberDecoder: expect ", but found n, ......

import (
	"encoding/json"
	"fmt"
)

type Adhoc struct {
	ID *int64 `json:"id,string"`
}

func main() {
	fmt.Println("Hello, playground")
	target := &Adhoc{}
	if err := json.Unmarshal([]byte("{\"any\": 123, \"id\": null}"), target); err != nil {
		fmt.Print(err)
		return
	}
	fmt.Println(target.ID)
	if err := json.Unmarshal([]byte(`{"any": null}`), target); err != nil {
		fmt.Print(err)
		return
	}
	fmt.Println(target.ID)
	if err := json.Unmarshal([]byte(`{"id": "123"}`), target); err != nil {
		fmt.Print(err)
		return
	}
	fmt.Println(*target.ID)
}

[nikolaydubina]

Based on example above, here is example when jsoniter fails. Playground.

package main

import (
	"encoding/json"
	"fmt"
	
	jsoniter "github.com/json-iterator/go"
)

var ji = jsoniter.ConfigCompatibleWithStandardLibrary

type Adhoc struct {
	ID *int64 `json:"id,string"`
}

func main() {
	target := &Adhoc{}
	
	if err := json.Unmarshal([]byte("{\"any\": 123, \"id\": null}"), target); err != nil {
		fmt.Print(err)
		return
	}
	fmt.Println(target.ID)
	if err := json.Unmarshal([]byte(`{"any": null}`), target); err != nil {
		fmt.Print(err)
		return
	}
	fmt.Println(target.ID)
	if err := json.Unmarshal([]byte(`{"id": "123"}`), target); err != nil {
		fmt.Print(err)
		return
	}
	fmt.Println(*target.ID)
	
	// jsoniter
	if err := ji.Unmarshal([]byte("{\"any\": 123, \"id\": null}"), target); err != nil {
		fmt.Print(err)
		return
	}
	fmt.Println(target.ID)
	if err := ji.Unmarshal([]byte(`{"any": null}`), target); err != nil {
		fmt.Print(err)
		return
	}
	fmt.Println(target.ID)
	if err := ji.Unmarshal([]byte(`{"id": "123"}`), target); err != nil {
		fmt.Print(err)
		return
	}
	fmt.Println(*target.ID)
}

[nikolaydubina]

Output error,

[nikolaydubina]

cc: @taowen

[nikolaydubina]

@zhenchangxc feel free to try again ;)