mrhwick/partialmarshal

A Go library for JSON marshaling with extra payloads

PartialMarshal

A Go library for JSON marshaling with extra payloads.

Standard Go JSON marshaling into a struct discards any unmatching fields from the JSON payload. In some use cases, the developer does not want to discard this extra payload data. This library provides a familiar interface for performing marshaling and unmarshaling while keeping any extra data for use by the calling code.

Install

go get github.com/mrhwick/partialmarshal

Usage and Examples

Just like the standard library json package, partialmarshal provides a simple pair of functions for marshaling and unmarshaling of JSON-formatted data into and out of structs.

When a user wants to use partialmarshal to hold onto extra data from a JSON payload, they may simply add the partialmarshal.Extra type as an embedded type in their struct. This embedded type is used by the partialmarshal library for storage of any data from the provided JSON that doesn't match a field of that struct.

type Person struct {
	Name string
	FavoriteFood string `json:"favorite_food"`
	partialmarshal.Extra
}

jsonData := []bytes(`{"name": "gopher", "favorite_food": "Pizza", "age": 25}`)

// Unmarshaling
// => Person{Name: "gopher", FavoriteFood: "Pizza", partialmarshal.Extra{"age":25}}
var p Person
partialmarshal.Unmarshal(jsonData, &p)

// Marshaling
// => `{"name": "gopher", "favorite_food": "Salad", "age" 25}`
p.FavoriteFood = "Salad"
result, err := partialmarshal.Marshal(p)

partialmarshal's Issues

Must support JSON lists

Currently this library is only compatible with single JSON objects. We should do some detection for lists on both Marshal and Unmarshal to correctly parse and feed the lists into the current functions for parsing objects.

Benchmark Tests

We should have benchmarks for the various external APIs of this library.

json.RawMessage might be useful to reduce complexity

The stdlib encoding/json package has the RawMessage type, which may be useful for extra payload storage.

Support nested/embedded types w/ their own partialmarshal.Extra embedded types

Currently, nested partialmarshal.Extra embedded types will not be handled correctly.

Here's a scenario:

type Address struct {
    StreetName string `json:"street_name"`
    partialmarshal.Extra
}

type Person struct {
    Name string `json:"name"`
    Age int `json:"age"`
    Address `json:"address"`
    partialmarshal.Extra
}

var p Person

JSONData := `{
    "name": "Matt",
    "age": 27,
    "address": {
        "street_name": "Market",
        "zip_code": "37402"
    },
    "favorite_food": "Pizza"
}`

partialmarshal.Unmarshal(JSONData, &p)
// Should yield that p now contains:
// => 
// Person{
//     Name: "Matt",
//     Age: 27,
//     Address: Address{StreetName: "Market", partialmarshal.Extra{"zip_code": "37402"}},
//     partialmarshal.Extra{"favorite_food": "Pizza"}
// }