Unmarshal doesn't work for json keys with _

[kubaugustyn]

Hi, so it seems that Unmarshal won't work with JSON keys, that have underscores. Here's some code:

package main

import (
	"bytes"
	"fmt"

	"github.com/spf13/viper"
)

type ConfigUnderscores struct {
	FooBar string `json:"foo_bar"`
}

type Config struct {
	FooBar string `json:"fooBar"`
}

var content1 = []byte(`
{
	"foo_bar": "foo"
}`)

var content2 = []byte(`
{
	"fooBar": "foo"
}`)

func main() {
	var c1 ConfigUnderscores
	var c2 Config

	viper.SetConfigType("json")
	viper.ReadConfig(bytes.NewReader(content1))

	viper.Unmarshal(&c1)
	fmt.Printf("ConfigUnderscores: %v\n", c1)

	viper.ReadConfig(bytes.NewReader(content2))
	viper.Unmarshal(&c2)
	fmt.Printf("Config: %v\n", c2)
}

Output:

ConfigUnderscores: {}
Config: {foo}

[cbroglie]

Try using mapstructure instead of json in the struct tags

[kubaugustyn]

Actually works! Thanks!

[vanugrah]

A quick not here about the use of json vs mapstructure. While you can create a struct with json tags like this:

type Config struct {
    FormalChicken string `json: "formal_chicken"`
    WaterPankcake string `json: "water_pancake"`
    TreeFloof     string `json: "tree_floof"`
    DangerNoodle  string `json: "danger_noodle"`
}

Doing the same with mapstructure will result in an empty config:

type Config struct {
    FormalChicken string `mapstructure: "formal_chicken"`
    WaterPankcake string `mapstructure: "water_pancake"`
    TreeFloof     string `mapstructure: "tree_floof"`
    DangerNoodle  string `mapstructure: "danger_noodle"`
}

For this to work there cannot be any spaces between the tag and the key name. For example:

type Config struct {
    FormalChicken string `mapstructure:"formal_chicken"`
    WaterPankcake string `mapstructure:"water_pancake"`
    TreeFloof     string `mapstructure:"tree_floof"`
    DangerNoodle  string `mapstructure:"danger_noodle"`
}

I wish not to disclose the amount of time I spent on that haha

[pindamonhangaba]

You can also change the tag used in mapstructure:

type ConfigUnderscores struct {
	FooBar string `json:"foo_bar"`
}
config := ConfigUnderscores{}
err := v.Unmarshal(*config , func(c *mapstructure.DecoderConfig) {
    c.TagName = "json"
})

[sagikazarmark]

This is already covered in the troubleshooting guide: https://github.com/spf13/viper/blob/master/TROUBLESHOOTING.md#unmarshaling-doesnt-work