feat(unmarshal): add Unmarshal and UnmarshalKey methods

Add struct unmarshaling support via JSON round-trip:
- Unmarshal() unmarshals full combined config into a struct
- UnmarshalKey() unmarshals a specific key (supports dot notation)
- Package-level convenience functions for default manager
- Comprehensive tests covering JSON, TOML, YAML, nested keys, scalars
- Bump Go to 1.26.2
- Fix stale Delete reference in README API table
- Add .gitignore for cover.out

.gitignore

@@ -0,0 +1 @@
+cover.out

README.md

@@ -15,7 +15,7 @@ Originally built to support [grlx](http://github.com/gogrlx/grlx).
 go get github.com/taigrr/jety
 ```
 
-Requires Go 1.26.1 or later.
+Requires Go 1.26.2 or later.
 
 ## Quick Start
 
@@ -133,7 +133,6 @@ export MYAPP_SERVICES_CLOUD_VAR=override_value
 | ------------------------ | ------------------------ |
 | `Set(key, value)`        | Set a value              |
 | `SetDefault(key, value)` | Set a default value      |
-| `Delete(key)`            | Remove a key             |
 | `Sub(key)`               | Get scoped sub-config    |
 | `Get(key)`               | Get raw value            |
 | `GetString(key)`         | Get as string            |
@@ -148,6 +147,8 @@ export MYAPP_SERVICES_CLOUD_VAR=override_value
 | `IsSet(key)`             | Check if key has a value |
 | `AllKeys()`              | List all known keys      |
 | `AllSettings()`          | Get all values as a map  |
+| `Unmarshal(target)`      | Unmarshal config to struct |
+| `UnmarshalKey(key, target)` | Unmarshal a key to struct |
 
 ### Environment
 
@@ -156,6 +157,45 @@ export MYAPP_SERVICES_CLOUD_VAR=override_value
 | `WithEnvPrefix(prefix)` | Filter env vars by prefix (strips prefix from keys) |
 | `SetEnvPrefix(prefix)`  | Set prefix for env var lookups                      |
 
+## Struct Unmarshaling
+
+Unmarshal your configuration directly into Go structs:
+
+```go
+type Config struct {
+    Host    string `json:"host"`
+    Port    int    `json:"port"`
+    Debug   bool   `json:"debug"`
+}
+
+jety.SetConfigFile("config.json")
+jety.SetConfigType("json")
+jety.ReadInConfig()
+
+var cfg Config
+if err := jety.Unmarshal(&cfg); err != nil {
+    log.Fatal(err)
+}
+```
+
+For nested sections, use `UnmarshalKey`:
+
+```go
+type DatabaseConfig struct {
+    Host string `json:"host"`
+    Port int    `json:"port"`
+    Name string `json:"name"`
+}
+
+var dbCfg DatabaseConfig
+if err := jety.UnmarshalKey("database", &dbCfg); err != nil {
+    log.Fatal(err)
+}
+```
+
+Struct tags use `json:"..."` since the unmarshaling uses JSON round-trip internally.
+Dot notation works with `UnmarshalKey` for deeply nested values (e.g., `"services.api"`).
+
 ## License
 
 See [LICENSE](LICENSE) file.

default.go

@@ -111,3 +111,11 @@ func AllKeys() []string {
 func AllSettings() map[string]any {
 	return defaultConfigManager.AllSettings()
 }
+
+func Unmarshal(target any) error {
+	return defaultConfigManager.Unmarshal(target)
+}
+
+func UnmarshalKey(key string, target any) error {
+	return defaultConfigManager.UnmarshalKey(key, target)
+}

go.mod

@@ -1,6 +1,6 @@
 module github.com/taigrr/jety
 
-go 1.26.1
+go 1.26.2
 
 require (
 	github.com/BurntSushi/toml v1.6.0

unmarshal.go

@@ -0,0 +1,49 @@
+package jety
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+// Unmarshal unmarshals the full combined configuration into the provided
+// struct pointer. It works by marshaling the settings map to JSON and then
+// unmarshaling into the target, so struct field tags should use `json:"key"`.
+// The target must be a non-nil pointer to a struct.
+func (c *ConfigManager) Unmarshal(target any) error {
+	settings := c.AllSettings()
+	return mapToStruct(settings, target)
+}
+
+// UnmarshalKey unmarshals a specific key's value into the provided struct
+// pointer. The key must refer to a map value (e.g., a nested TOML/YAML/JSON
+// section). Supports dot notation for nested keys.
+func (c *ConfigManager) UnmarshalKey(key string, target any) error {
+	c.mutex.RLock()
+	v, ok := c.resolve(key)
+	c.mutex.RUnlock()
+	if !ok {
+		return fmt.Errorf("key %q not found", key)
+	}
+	m, ok := v.Value.(map[string]any)
+	if !ok {
+		// If the value is not a map, try direct JSON round-trip
+		data, err := json.Marshal(v.Value)
+		if err != nil {
+			return fmt.Errorf("cannot marshal value for key %q: %w", key, err)
+		}
+		return json.Unmarshal(data, target)
+	}
+	return mapToStruct(m, target)
+}
+
+// mapToStruct converts a map[string]any to a struct via JSON round-trip.
+func mapToStruct(m map[string]any, target any) error {
+	data, err := json.Marshal(m)
+	if err != nil {
+		return fmt.Errorf("cannot marshal config: %w", err)
+	}
+	if err := json.Unmarshal(data, target); err != nil {
+		return fmt.Errorf("cannot unmarshal config: %w", err)
+	}
+	return nil
+}

unmarshal_test.go

@@ -0,0 +1,333 @@
+package jety
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestUnmarshal(t *testing.T) {
+	type ServerConfig struct {
+		Host string `json:"host"`
+		Port int    `json:"port"`
+	}
+	type AppConfig struct {
+		Name   string       `json:"name"`
+		Debug  bool         `json:"debug"`
+		Server ServerConfig `json:"server"`
+	}
+
+	dir := t.TempDir()
+	configFile := filepath.Join(dir, "config.json")
+	err := os.WriteFile(configFile, []byte(`{
+		"name": "myapp",
+		"debug": true,
+		"server": {
+			"host": "localhost",
+			"port": 8080
+		}
+	}`), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cm := NewConfigManager()
+	cm.SetConfigFile(configFile)
+	if err := cm.SetConfigType("json"); err != nil {
+		t.Fatal(err)
+	}
+	if err := cm.ReadInConfig(); err != nil {
+		t.Fatal(err)
+	}
+
+	var cfg AppConfig
+	if err := cm.Unmarshal(&cfg); err != nil {
+		t.Fatal(err)
+	}
+
+	if cfg.Name != "myapp" {
+		t.Errorf("expected name 'myapp', got %q", cfg.Name)
+	}
+	if !cfg.Debug {
+		t.Error("expected debug to be true")
+	}
+	if cfg.Server.Host != "localhost" {
+		t.Errorf("expected host 'localhost', got %q", cfg.Server.Host)
+	}
+	if cfg.Server.Port != 8080 {
+		t.Errorf("expected port 8080, got %d", cfg.Server.Port)
+	}
+}
+
+func TestUnmarshalWithDefaults(t *testing.T) {
+	type Config struct {
+		Host    string `json:"host"`
+		Port    int    `json:"port"`
+		Timeout int    `json:"timeout"`
+	}
+
+	dir := t.TempDir()
+	configFile := filepath.Join(dir, "config.json")
+	err := os.WriteFile(configFile, []byte(`{
+		"host": "example.com"
+	}`), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cm := NewConfigManager()
+	cm.SetDefault("port", 3000)
+	cm.SetDefault("timeout", 30)
+	cm.SetConfigFile(configFile)
+	if err := cm.SetConfigType("json"); err != nil {
+		t.Fatal(err)
+	}
+	if err := cm.ReadInConfig(); err != nil {
+		t.Fatal(err)
+	}
+
+	var cfg Config
+	if err := cm.Unmarshal(&cfg); err != nil {
+		t.Fatal(err)
+	}
+
+	if cfg.Host != "example.com" {
+		t.Errorf("expected host 'example.com', got %q", cfg.Host)
+	}
+	if cfg.Port != 3000 {
+		t.Errorf("expected port 3000, got %d", cfg.Port)
+	}
+	if cfg.Timeout != 30 {
+		t.Errorf("expected timeout 30, got %d", cfg.Timeout)
+	}
+}
+
+func TestUnmarshalKey(t *testing.T) {
+	type DatabaseConfig struct {
+		Host string `json:"host"`
+		Port int    `json:"port"`
+		Name string `json:"name"`
+	}
+
+	dir := t.TempDir()
+	configFile := filepath.Join(dir, "config.json")
+	err := os.WriteFile(configFile, []byte(`{
+		"database": {
+			"host": "db.example.com",
+			"port": 5432,
+			"name": "mydb"
+		},
+		"cache": {
+			"host": "cache.example.com",
+			"port": 6379
+		}
+	}`), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cm := NewConfigManager()
+	cm.SetConfigFile(configFile)
+	if err := cm.SetConfigType("json"); err != nil {
+		t.Fatal(err)
+	}
+	if err := cm.ReadInConfig(); err != nil {
+		t.Fatal(err)
+	}
+
+	var dbCfg DatabaseConfig
+	if err := cm.UnmarshalKey("database", &dbCfg); err != nil {
+		t.Fatal(err)
+	}
+
+	if dbCfg.Host != "db.example.com" {
+		t.Errorf("expected host 'db.example.com', got %q", dbCfg.Host)
+	}
+	if dbCfg.Port != 5432 {
+		t.Errorf("expected port 5432, got %d", dbCfg.Port)
+	}
+	if dbCfg.Name != "mydb" {
+		t.Errorf("expected name 'mydb', got %q", dbCfg.Name)
+	}
+}
+
+func TestUnmarshalKeyNotFound(t *testing.T) {
+	cm := NewConfigManager()
+	var target struct{}
+	err := cm.UnmarshalKey("nonexistent", &target)
+	if err == nil {
+		t.Error("expected error for missing key")
+	}
+}
+
+func TestUnmarshalKeyScalarValue(t *testing.T) {
+	cm := NewConfigManager()
+	cm.Set("count", 42)
+
+	var count int
+	if err := cm.UnmarshalKey("count", &count); err != nil {
+		t.Fatal(err)
+	}
+	if count != 42 {
+		t.Errorf("expected 42, got %d", count)
+	}
+}
+
+func TestUnmarshalKeyNestedDotNotation(t *testing.T) {
+	type Inner struct {
+		Value string `json:"value"`
+	}
+
+	dir := t.TempDir()
+	configFile := filepath.Join(dir, "config.json")
+	err := os.WriteFile(configFile, []byte(`{
+		"services": {
+			"api": {
+				"value": "hello"
+			}
+		}
+	}`), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cm := NewConfigManager()
+	cm.SetConfigFile(configFile)
+	if err := cm.SetConfigType("json"); err != nil {
+		t.Fatal(err)
+	}
+	if err := cm.ReadInConfig(); err != nil {
+		t.Fatal(err)
+	}
+
+	var inner Inner
+	if err := cm.UnmarshalKey("services.api", &inner); err != nil {
+		t.Fatal(err)
+	}
+	if inner.Value != "hello" {
+		t.Errorf("expected 'hello', got %q", inner.Value)
+	}
+}
+
+func TestUnmarshalTOML(t *testing.T) {
+	type Config struct {
+		Title string `json:"title"`
+		Port  int    `json:"port"`
+	}
+
+	dir := t.TempDir()
+	configFile := filepath.Join(dir, "config.toml")
+	err := os.WriteFile(configFile, []byte(`
+title = "My App"
+port = 9090
+`), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cm := NewConfigManager()
+	cm.SetConfigFile(configFile)
+	if err := cm.SetConfigType("toml"); err != nil {
+		t.Fatal(err)
+	}
+	if err := cm.ReadInConfig(); err != nil {
+		t.Fatal(err)
+	}
+
+	var cfg Config
+	if err := cm.Unmarshal(&cfg); err != nil {
+		t.Fatal(err)
+	}
+
+	if cfg.Title != "My App" {
+		t.Errorf("expected title 'My App', got %q", cfg.Title)
+	}
+	if cfg.Port != 9090 {
+		t.Errorf("expected port 9090, got %d", cfg.Port)
+	}
+}
+
+func TestUnmarshalYAML(t *testing.T) {
+	type Config struct {
+		Name    string   `json:"name"`
+		Tags    []string `json:"tags"`
+		Enabled bool     `json:"enabled"`
+	}
+
+	dir := t.TempDir()
+	configFile := filepath.Join(dir, "config.yaml")
+	err := os.WriteFile(configFile, []byte(`
+name: testapp
+tags:
+  - web
+  - api
+enabled: true
+`), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cm := NewConfigManager()
+	cm.SetConfigFile(configFile)
+	if err := cm.SetConfigType("yaml"); err != nil {
+		t.Fatal(err)
+	}
+	if err := cm.ReadInConfig(); err != nil {
+		t.Fatal(err)
+	}
+
+	var cfg Config
+	if err := cm.Unmarshal(&cfg); err != nil {
+		t.Fatal(err)
+	}
+
+	if cfg.Name != "testapp" {
+		t.Errorf("expected name 'testapp', got %q", cfg.Name)
+	}
+	if len(cfg.Tags) != 2 || cfg.Tags[0] != "web" || cfg.Tags[1] != "api" {
+		t.Errorf("expected tags [web api], got %v", cfg.Tags)
+	}
+	if !cfg.Enabled {
+		t.Error("expected enabled to be true")
+	}
+}
+
+func TestDefaultUnmarshal(t *testing.T) {
+	// Test package-level Unmarshal function
+	type Config struct {
+		Key string `json:"key"`
+	}
+
+	// Reset default manager
+	defaultConfigManager = NewConfigManager()
+	Set("key", "value")
+
+	var cfg Config
+	if err := Unmarshal(&cfg); err != nil {
+		t.Fatal(err)
+	}
+	if cfg.Key != "value" {
+		t.Errorf("expected 'value', got %q", cfg.Key)
+	}
+
+	// Restore
+	defaultConfigManager = NewConfigManager()
+}
+
+func TestDefaultUnmarshalKey(t *testing.T) {
+	defaultConfigManager = NewConfigManager()
+	Set("section", map[string]any{"field": "data"})
+
+	type Section struct {
+		Field string `json:"field"`
+	}
+	var sec Section
+	if err := UnmarshalKey("section", &sec); err != nil {
+		t.Fatal(err)
+	}
+	if sec.Field != "data" {
+		t.Errorf("expected 'data', got %q", sec.Field)
+	}
+
+	defaultConfigManager = NewConfigManager()
+}