LoadData doesn't merge configs like LoadFiles

[Adzikus]

System (please complete the following information):

• OS: windows
• GO Version: 1.20
• Pkg Version: 2.2.3

Describe the bug

When loading config from Files

paths := []string{"base.json", "mod.json"}
err = tmpCfg.LoadFiles(paths...)

configuration is appended but when using LoadData() is overriding by last source

To Reproduce

// MODELS

type PostgresConfig struct {
// cut for simplicity
	Postgres *Postgres
}

type Postgres struct {
	Host         string
	Port         int
	User         string
	Password     string
	PasswordFile string
	Database     string
	SearchPath   string
	MinPoolSize  int32
	MaxPoolSize  int32 
}

// GOT
initConfig := map[string]any{
 "Postgres": &Postgres{
 Host:         "init-host",
 Port:         1000,
 User:         "init-user",
 Password:     "init-password",
 PasswordFile: "init-password-file",
 Database:     "init-database",
 SearchPath:   "init-search-path",
 MinPoolSize:  10,
 MaxPoolSize:  100,
 }}
appendConfig := map[string]any{
 "Postgres": &Postgres{Host: "append-host"}}

cfg := config.New("")
result := &PostgresConfig{}
cfg.LoadData(initConfig, appendConfig)
cfg.Decode(result)

Current behavior

Expected behavior

LoadData Merges all data loaded by parameter list

Additional context

If needed some more explanation, code or screens, fell free to write.
If there is any other method to load data like from files but from source maps or maybe there is possibility to create something like Merge(any...)

[yz3358]

I don't think this is a bug. The equivalent of LoadData here should be loading map[string]any, without pointer. Becasue when you create struct, zero values are assigned automatically.

When LoadFile, contents are converted to map[string]any instead of a predefined struct.

LoadData uses mergo.Merge(..., merge.WithOverride). It will override "non-empty" attributes, which is desired in most use cases. (e.g. intentional override some int field to 0).

I did not find a way to differentiate "user assigned zero value" vs "automatic zero value" in a struct. If there is, then adding a custom mergo.Transformers might do.

[inhere]

hi @yz3358 @Adzikus On https://github.com/gookit/config/releases/tag/v2.2.5, add new option: MergeOptions support custom the data merge options