support json schema

pkg/app/schema.go

@@ -0,0 +1,40 @@
+package app
+
+import (
+	"encoding/json"
+
+	js "github.com/swaggest/jsonschema-go"
+)
+
+// Generates json schema for app's config.AppConfig
+func (app *App) Schema() ([]byte, error) {
+	r := js.Reflector{}
+
+	s, err := r.Reflect(*app.cfg)
+	if err != nil {
+		return nil, err
+	}
+
+	return json.MarshalIndent(s, "", "  ")
+}
+
+// Generates json schema for custom config
+// which embeds *config.AppConfig into it
+// Panics if no *config.AppConfig is embedded into custom
+// config type
+//
+// See swaggest/jsonschema-go for struct tag docs
+func CustomSchema[T any](target T) ([]byte, error) {
+	if err := HasAppConfig(target); err != nil {
+		panic(err.Error())
+	}
+
+	r := js.Reflector{}
+
+	s, err := r.Reflect(target)
+	if err != nil {
+		return nil, err
+	}
+
+	return json.MarshalIndent(s, "", "  ")
+}

pkg/app/setup_custom.go

@@ -19,7 +19,7 @@ import (
 // are up to the caller.
 func MustLoadConfigInto[T any](ctx context.Context, into T) (context.Context, T) {
 	// Step 1: Check our custom type for required *config.AppConfig
-	if err := hasAppConfig(into); err != nil {
+	if err := HasAppConfig(into); err != nil {
 		panic(err)
 	}
 
@@ -66,7 +66,7 @@ func setAppConfig[T any](target T, appConfig *config.AppConfig) error {
 	}
 
 	// Replace *config.AppConfig
-	for i := 0; i < v.NumField(); i++ {
+	for i := range v.NumField() {
 		field := v.Field(i)
 		if field.Type() == reflect.TypeOf((*config.AppConfig)(nil)) {
 			if !field.CanSet() {
@@ -80,7 +80,7 @@ func setAppConfig[T any](target T, appConfig *config.AppConfig) error {
 	return errors.New("no *config.AppConfig field found in target struct")
 }
 
-func hasAppConfig[T any](target T) error {
+func HasAppConfig[T any](target T) error {
 	v := reflect.ValueOf(target)
 	if v.Kind() != reflect.Ptr || v.IsNil() {
 		return errors.New("target must be a non-nil pointer to a struct")
@@ -92,7 +92,7 @@ func hasAppConfig[T any](target T) error {
 	}
 
 	hasAppConfig := false
-	for i := 0; i < v.NumField(); i++ {
+	for i := range v.NumField() {
 		field := v.Type().Field(i)
 		if field.Type == reflect.TypeOf((*config.AppConfig)(nil)) {
 			hasAppConfig = true