Add support for TextUnmarshaler (#424)

* Add support for TextUnmarshaler

* Fix TextUnmarshaler handling

* Remove unused global

* Handle pointers at a different layer

Author: chadweimer

conf/conf.go

@@ -1,6 +1,7 @@
 package conf
 
 import (
+	"encoding"
 	"errors"
 	"fmt"
 	"log/slog"
@@ -30,26 +31,50 @@ func Bind(ptr any) error {
 		return errors.New("bind requires struct types")
 	}
 
-	return bindValue(val)
+	return bindStruct(val)
 }
 
-func bindValue(objVal reflect.Value) error {
+func bindStruct(objVal reflect.Value) error {
+	setValue := func(field reflect.StructField, fieldVal reflect.Value) error {
+		if err := setToDefault(field, fieldVal); err != nil {
+			return err
+		}
+		setFromEnv(field, fieldVal)
+
+		return nil
+	}
+
 	for i := 0; i < objVal.NumField(); i++ {
 		field := objVal.Type().Field(i)
 		if !field.IsExported() {
 			continue
 		}
 
 		fieldVal := objVal.Field(i)
+
+		// Walk through any pointer layers
+		for fieldVal.Type().Kind() == reflect.Pointer {
+			if fieldVal.IsNil() {
+				ptrType := fieldVal.Type().Elem()
+				fieldVal.Set(reflect.New(ptrType))
+			}
+			fieldVal = fieldVal.Elem()
+		}
+
+		var err error
+		// If this is a struct, we need to recurse
 		if fieldVal.Kind() == reflect.Struct {
-			if err := bindValue(fieldVal); err != nil {
-				return err
+			// Unless this is a TextUnmarshaler
+			if _, ok := fieldVal.Addr().Interface().(encoding.TextUnmarshaler); ok {
+				err = setValue(field, fieldVal)
+			} else {
+				err = bindStruct(fieldVal)
 			}
 		} else {
-			if err := setToDefault(field, fieldVal); err != nil {
-				return err
-			}
-			setFromEnv(field, fieldVal)
+			err = setValue(field, fieldVal)
+		}
+		if err != nil {
+			return err
 		}
 	}
 
@@ -95,6 +120,12 @@ func setFromEnv(field reflect.StructField, val reflect.Value) {
 
 func set(val reflect.Value, str string) error {
 	switch val.Type().Kind() {
+	case reflect.Struct:
+		if unmarshaler, ok := val.Addr().Interface().(encoding.TextUnmarshaler); ok {
+			return unmarshaler.UnmarshalText([]byte(str))
+		}
+		return errUnsupportedType{val.Type()}
+
 	case reflect.String:
 		val.SetString(str)
 
@@ -146,13 +177,6 @@ func set(val reflect.Value, str string) error {
 		}
 		val.Set(newVal)
 
-	case reflect.Pointer:
-		ptrType := val.Type().Elem()
-		if val.IsNil() {
-			val.Set(reflect.New(ptrType))
-		}
-		return set(val.Elem(), str)
-
 	default:
 		return errUnsupportedType{val.Type()}
 	}

conf/conf_test.go

@@ -3,6 +3,7 @@ package conf
 import (
 	"reflect"
 	"testing"
+	"time"
 
 	"github.com/chadweimer/gomp/utils"
 )
@@ -40,6 +41,8 @@ func TestBind_Defaults(t *testing.T) {
 		TestBoolArray []bool `default:"true,false"`
 
 		TestString string `default:"Hello, Tests!"`
+
+		TestTime time.Time `default:"2000-01-02T03:04:05Z"`
 	}
 	tests := []struct {
 		name string
@@ -78,6 +81,8 @@ func TestBind_Defaults(t *testing.T) {
 				TestBoolArray: []bool{true, false},
 
 				TestString: "Hello, Tests!",
+
+				TestTime: time.Date(2000, 1, 2, 3, 4, 5, 0, time.UTC),
 			},
 		},
 	}