UnmarshalKey looses some data if a subitem is overridden

[SVilgelm]

Expected behavior (what you expected to happen):
viper.UnmarshalKey should unmarshals whole structure, not overridden keys only

Actual behavior (what actually happened):
if viper.Set has been used to override a value of a sub item, then viper.UnmarshalKey unmarshals only overridden keys

Repl.it link:

https://replit.com/@SVilgelm/viperUnmarshalKey-bug

Code reproducing the issue:

package main

import (
	"strings"

	"github.com/spf13/viper"
)

func main() {
	config := `
resources:
  baz:
    name: "Super bazzz"
    xyz: true
    test: 123
`
	viper.Debug()
	println("########################################################################")

	viper.SetConfigType("yaml")
	viper.ReadConfig(strings.NewReader(config))
	viper.Debug()
	println("########################################################################")

	res1 := struct {
		Name string `mapstructure:"name"`
		XYZ  bool   `mapstructure:"xyz"`
	}{}
	viper.UnmarshalKey("resources.baz", &res1)
	println("res1 Name:", res1.Name, "; XYZ:", res1.XYZ)
	println("########################################################################")

	viper.Set("resources.baz.name", "override name")
	viper.Debug()
	println("########################################################################")

	res2 := struct {
		Name string `mapstructure:"name"`
		XYZ  bool   `mapstructure:"xyz"`
	}{}
	viper.UnmarshalKey("resources.baz", &res2)
	println("res2 Name:", res2.Name, "; XYZ:", res2.XYZ)
	println("########################################################################")
}

Environment:

• Viper version:v1.7.1
• Config source: any
• File format: any

[github-actions]

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[SVilgelm]

Actually the issue with viper.Get, it does not return the whole structure

[madsoigard]

any update on this?

[sagikazarmark]

The problem is that resources.baz exists as a key, so UnmashalKey won't look any further. I wonder what happens if you create a Resources struct and try to unmarshal resources instead. I think that should work.

[SVilgelm]

@sagikazarmark I have updated the repl, the problem still exists even if I unmarshal resources. I also updated th go.mod to use latest viper.

https://replit.com/@SVilgelm/viperUnmarshalKey-bug#main.go

Code:

package main

import (
	"strings"
  "fmt"

	"github.com/spf13/viper"
)

func main() {
	config := `
resources:
  baz:
    name: "Super bazzz"
    xyz: true
    test: 123
`
	viper.Debug()
	println("########################################################################")

	viper.SetConfigType("yaml")
	viper.ReadConfig(strings.NewReader(config))
	viper.Debug()
	println("########################################################################")

	res1 := struct {
		Name string `mapstructure:"name"`
		XYZ  bool   `mapstructure:"xyz"`
	}{}
	viper.UnmarshalKey("resources.baz", &res1)
	println("res1 Name:", res1.Name, "; XYZ:", res1.XYZ)
	println("########################################################################")

	viper.Set("resources.baz.name", "override name")
	viper.Debug()
	println("########################################################################")

	res2 := struct {
		Name string `mapstructure:"name"`
		XYZ  bool   `mapstructure:"xyz"`
	}{}
	viper.UnmarshalKey("resources.baz", &res2)
	println("res2 Name:", res2.Name, "; XYZ:", res2.XYZ)
	println("########################################################################")

  println("########################################################################")

  res3 := struct {
    Baz struct {
      Name string `mapstructure:"name"`
      XYZ  bool   `mapstructure:"xyz"`
    } `mapstructure:"baz"`
	}{}
	viper.UnmarshalKey("resources", &res3)
	println("res3 Name:", res3.Baz.Name, "; XYZ:", res3.Baz.XYZ)
	println("########################################################################")

  fmt.Printf("viper.Get: %+v\n", viper.Get("resources"))
  println("########################################################################")
}

Here is the output:

Aliases:
map[string]string{}
Override:
map[string]interface {}{}
PFlags:
map[string]viper.FlagValue{}
Env:
map[string]string{}
Key/Value Store:
map[string]interface {}{}
Config:
map[string]interface {}{}
Defaults:
map[string]interface {}{}
########################################################################
Aliases:
map[string]string{}
Override:
map[string]interface {}{}
PFlags:
map[string]viper.FlagValue{}
Env:
map[string]string{}
Key/Value Store:
map[string]interface {}{}
Config:
map[string]interface {}{"resources":map[string]interface {}{"baz":map[string]interface {}{"name":"Super bazzz", "test":123, "xyz":true
 go build
 ./main
Aliases:
map[string]string{}
Override:
map[string]interface {}{}
PFlags:
map[string]viper.FlagValue{}
Env:
map[string]string{}
Key/Value Store:
map[string]interface {}{}
Config:
map[string]interface {}{}
Defaults:
map[string]interface {}{}
########################################################################
Aliases:
map[string]string{}
Override:
map[string]interface {}{}
PFlags:
map[string]viper.FlagValue{}
Env:
map[string]string{}
Key/Value Store:
map[string]interface {}{}
Config:
map[string]interface {}{"resources":map[string]interface {}{"baz":map[string]interface {}{"name":"Super bazzz", "test":123, "xyz":true
 go build
 ./main
Aliases:
map[string]string{}
Override:
map[string]interface {}{}
PFlags:
map[string]viper.FlagValue{}
Env:
map[string]string{}
Key/Value Store:
map[string]interface {}{}
Config:
map[string]interface {}{}
Defaults:
map[string]interface {}{}
########################################################################
Aliases:
map[string]string{}
Override:
map[string]interface {}{}
PFlags:
map[string]viper.FlagValue{}
Env:
map[string]string{}
Key/Value Store:
map[string]interface {}{}
Config:
map[string]interface {}{"resources":map[string]interface {}{"baz":map[string]interface {}{"name":"Super bazzz", "test":123, "xyz":true
 go build
 ./main
Aliases:
map[string]string{}
Override:
map[string]interface {}{}
PFlags:
map[string]viper.FlagValue{}
Env:
map[string][]string{}
Key/Value Store:
map[string]interface {}{}
Config:
map[string]interface {}{}
Defaults:
map[string]interface {}{}
########################################################################
Aliases:
map[string]string{}
Override:
map[string]interface {}{}
PFlags:
map[string]viper.FlagValue{}
Env:
map[string][]string{}
Key/Value Store:
map[string]interface {}{}
Config:
map[string]interface {}{"resources":map[string]interface {}{"baz":map[string]interface {}{"name":"Super bazzz", "test":123, "xyz":true}}}
Defaults:
map[string]interface {}{}
########################################################################
res1 Name: Super bazzz ; XYZ: true
########################################################################
Aliases:
map[string]string{}
Override:
map[string]interface {}{"resources":map[string]interface {}{"baz":map[string]interface {}{"name":"override name"}}}
PFlags:
map[string]viper.FlagValue{}
Env:
map[string][]string{}
Key/Value Store:
map[string]interface {}{}
Config:
map[string]interface {}{"resources":map[string]interface {}{"baz":map[string]interface {}{"name":"Super bazzz", "test":123, "xyz":true}}}
Defaults:
map[string]interface {}{}
########################################################################
res2 Name: override name ; XYZ: false
########################################################################
########################################################################
res3 Name: override name ; XYZ: false
########################################################################
viper.Get: map[baz:map[name:override name]]
########################################################################

[missing1984]

running into the same issue. any workaround?

[SVilgelm]

there is no workaround, the issue is that the viper has several internal storages. In order to fix the issue, the logic of Get should be changed to merge all possible combinations, like take the baz from the loaded config, then take the baz.name from the overrides and apply it and etc...

[kasparjarek]

Hi, since the release v1.18.0 the issue is also happening for the Unmarshal() function. I suspect that the issue was introduced by this pull request #1429. FYI @krakowski @sagikazarmark