feat: #94 - Support parse default value by struct tag default

README.md

@@ -26,6 +26,7 @@ Golang's application config manage tool library.
   - allow events: `set.value`, `set.data`, `load.data`, `clean.data`
 - Support data overlay and merge, automatically load by key when loading multiple copies of data
 - Support for binding all or part of the configuration data to the structure
+  - Support init default value by struct tag `default`
 - Support get sub value by path, like `map.key` `arr.2`
 - Support parse ENV name and allow with default value. like `envKey: ${SHELL|/bin/bash}` -> `envKey: /bin/zsh`
 - Generic api `Get` `Int` `Uint` `Int64` `Float` `String` `Bool` `Ints` `IntMap` `Strings` `StringMap` ...
@@ -329,9 +330,47 @@ type Options struct {
 	DecoderConfig *mapstructure.DecoderConfig
 	// HookFunc on data changed.
 	HookFunc HookFunc
+	// ParseDefault tag on binding data to struct. tag: default
+	ParseDefault bool
 }
 ```
 
+### Options: Parse default
+
+Support parse default value by struct tag `default`
+
+```go
+	// add option: config.ParseDefault
+	c := config.New("test").WithOptions(config.ParseDefault)
+
+	// only set name
+	c.SetData(map[string]interface{}{
+		"name": "inhere",
+	})
+
+	// age load from default tag
+	type User struct {
+		Age  int `default:"30"`
+		Name string
+		Tags []int
+	}
+
+	user := &User{}
+	goutil.MustOk(c.Decode(user))
+	dump.Println(user)
+```
+
+**Output**:
+
+```shell
+&config_test.User {
+  Age: int(30),
+  Name: string("inhere"), #len=6
+  Tags: []int [ #len=0
+  ],
+},
+```
+
 ## API Methods Refer
 
 ### Load Config

README.zh-CN.md

@@ -25,6 +25,7 @@
   - 可用事件: `set.value`, `set.data`, `load.data`, `clean.data`
 - 支持数据覆盖合并，加载多份数据时将按key自动合并
 - 支持将全部或部分配置数据绑定到结构体 `config.BindStruct("key", &s)`
+  - NEW: 支持通过结构标签 `default` 解析并设置默认值
 - 支持通过 `.` 分隔符来按路径获取子级值，也支持自定义分隔符。 e.g `map.key` `arr.2`
 - 支持解析ENV变量名称。 like `shell: ${SHELL}` -> `shell: /bin/zsh`
 - 简洁的使用API `Get` `Int` `Uint` `Int64` `String` `Bool` `Ints` `IntMap` `Strings` `StringMap` ...
@@ -309,9 +310,47 @@ type Options struct {
     DecoderConfig *mapstructure.DecoderConfig
     // HookFunc on data changed.
     HookFunc HookFunc
+	// ParseDefault tag on binding data to struct. tag: default
+	ParseDefault bool
 }
 ```
 
+### 选项: 解析默认值
+
+NEW: 支持通过结构标签 `default` 解析并设置默认值
+
+```go
+	// add option: config.ParseDefault
+	c := config.New("test").WithOptions(config.ParseDefault)
+
+	// only set name
+	c.SetData(map[string]interface{}{
+		"name": "inhere",
+	})
+
+	// age load from default tag
+	type User struct {
+		Age  int `default:"30"`
+		Name string
+		Tags []int
+	}
+
+	user := &User{}
+	goutil.MustOk(c.Decode(user))
+	dump.Println(user)
+```
+
+**Output**:
+
+```shell
+&config_test.User {
+  Age: int(30),
+  Name: string("inhere"), #len=6
+  Tags: []int [ #len=0
+  ],
+},
+```
+
 ## API方法参考
 
 ### 载入配置

config.go

@@ -51,11 +51,16 @@ const (
 	JSON = "json"
 	Yaml = "yaml"
 	Toml = "toml"
+	Prop = "properties"
+)
 
+const (
 	// default delimiter
 	defaultDelimiter byte = '.'
 	// default struct tag name for binding data to struct
 	defaultStructTag = "mapstructure"
+	// struct tag name for set default-value on binding data
+	defaultValueTag = "default"
 )
 
 // internal vars
@@ -70,7 +75,7 @@ var dc = New("default")
 
 // Config structure definition
 type Config struct {
-	// save latest error, will clear after read.
+	// save the latest error, will clear after read.
 	err error
 	// config instance name
 	name string

export.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"os"
 
+	"github.com/gookit/goutil/structs"
 	"github.com/mitchellh/mapstructure"
 )
 
@@ -83,6 +84,14 @@ func (c *Config) Structure(key string, dst interface{}) error {
 		}
 	}
 
+	// init default value by tag: default
+	if c.opts.ParseDefault {
+		err := structs.InitDefaults(dst)
+		if err != nil {
+			return err
+		}
+	}
+
 	bindConf := c.opts.makeDecoderConfig()
 	// set result struct ptr
 	bindConf.Result = dst

go.mod

@@ -4,7 +4,7 @@ go 1.16
 
 require (
 	github.com/BurntSushi/toml v1.2.0
-	github.com/gookit/goutil v0.5.9
+	github.com/gookit/goutil v0.5.10
 	github.com/gookit/ini/v2 v2.1.1
 	github.com/gookit/properties v0.1.0
 	github.com/hashicorp/hcl v1.0.0

go.sum

@@ -22,8 +22,9 @@ github.com/gookit/color v1.5.0/go.mod h1:43aQb+Zerm/BWh2GnrgOQm7ffz7tvQXEKV6BFMl
 github.com/gookit/color v1.5.1 h1:Vjg2VEcdHpwq+oY63s/ksHrgJYCTo0bwWvmmYWdE9fQ=
 github.com/gookit/color v1.5.1/go.mod h1:wZFzea4X8qN6vHOSP2apMb4/+w/orMznEzYsIHPaqKM=
 github.com/gookit/goutil v0.5.3/go.mod h1:W0rVeVN9EcoRV+ODq91TXvqoUA87BXGi36WFVykCKRI=
-github.com/gookit/goutil v0.5.9 h1:DBaSHaealbqxLWEZrEt/vqnPKiJHLQJau9dbcFQG/ng=
 github.com/gookit/goutil v0.5.9/go.mod h1:iZLXpRhMqKGvKtJ9+b0cdls2gXRH4HaGWQfkf2mdHRQ=
+github.com/gookit/goutil v0.5.10 h1:tKvo3LzE6j8vTXizQoPvZq9jt4VrVriuD5lQMbQbhH4=
+github.com/gookit/goutil v0.5.10/go.mod h1:rZCjNKf63zWuD5N0vyn6718utvN9m2uT0jsHBV66hAU=
 github.com/gookit/ini/v2 v2.1.1 h1:q2VtSSl/ivTOZMPvxhjWxO3f146NvWM84jBQZETj/1o=
 github.com/gookit/ini/v2 v2.1.1/go.mod h1:zkMTCrnE2QgDW0izB/pRtgEKKjXmT/22dfk5eZg+IHo=
 github.com/gookit/properties v0.1.0 h1:UHwgz0UCjxJ0q36qmvOAWNSdNh+yGIBUjUDaKzLryJY=

issues_test.go

@@ -230,6 +230,44 @@ func TestIssues_81(t *testing.T) {
 	is.Eq(wantTm, opt.IdleTime)
 }
 
+// https://github.com/gookit/config/issues/94
+func TestIssues_94(t *testing.T) {
+	is := assert.New(t)
+	// add option: config.ParseDefault
+	c := config.New("test").WithOptions(config.ParseDefault)
+
+	// only set name
+	c.SetData(map[string]interface{}{
+		"name": "inhere",
+	})
+
+	// age load from default tag
+	type User struct {
+		Age  int `json:"age" default:"30"`
+		Name string
+		Tags []int
+	}
+
+	user := &User{}
+	is.NoErr(c.Decode(user))
+	dump.Println(user)
+	is.Eq("inhere", user.Name)
+	is.Eq(30, user.Age)
+
+	// field use ptr
+	type User1 struct {
+		Age  *int `json:"age" default:"30"`
+		Name string
+		Tags []int
+	}
+
+	u1 := &User1{}
+	is.NoErr(c.Decode(u1))
+	dump.Println(u1)
+	is.Eq("inhere", u1.Name)
+	is.Eq(30, *u1.Age)
+}
+
 // https://github.com/gookit/config/issues/96
 func TestIssues_96(t *testing.T) {
 	is := assert.New(t)

util.go

@@ -10,7 +10,8 @@ import (
 	"github.com/mitchellh/mapstructure"
 )
 
-// ValDecodeHookFunc returns a mapstructure.DecodeHookFunc that parse ENV var, and more custom parse
+// ValDecodeHookFunc returns a mapstructure.DecodeHookFunc
+// that parse ENV var, and more custom parse
 func ValDecodeHookFunc(parseEnv, parseTime bool) mapstructure.DecodeHookFunc {
 	return func(f reflect.Type, t reflect.Type, data interface{}) (interface{}, error) {
 		if f.Kind() != reflect.String {