Add support for encoding.TextUnmarshaler

README.md

@@ -192,7 +192,8 @@ There are following supported types:
 - maps (of any other supported type);
 - `time.Duration`;
 - `time.Time` (layout by default is RFC3339, may be overridden by `env-layout`);
-- `*time.Location` (time zone parsing [depends](https://pkg.go.dev/time#LoadLocation) on running machine)
+- `*time.Location` (time zone parsing [depends](https://pkg.go.dev/time#LoadLocation) on running machine);
+- any type that implements `encoding.TextUnmarshaler`;
 - any type implementing `cleanenv.Setter` interface.
 
 

cleanenv.go

@@ -1,6 +1,7 @@
 package cleanenv
 
 import (
+	"encoding"
 	"encoding/json"
 	"flag"
 	"fmt"
@@ -459,15 +460,29 @@ func readEnvVars(cfg interface{}, update bool) error {
 func parseValue(field reflect.Value, value, sep string, layout *string) error {
 	// TODO: simplify recursion
 
+	valueType := field.Type()
+
+	// look for supported struct parser
+	// parsing of struct must be done before checking the implementation `encoding.TextUnmarshaler`
+	// standard struct types already have the implementation `encoding.TextUnmarshaler` (for example `time.Time`)
+	if structParser, found := validStructs[valueType]; found {
+		return structParser(&field, value, layout)
+	}
+
 	if field.CanInterface() {
+		if ct, ok := field.Interface().(encoding.TextUnmarshaler); ok {
+			return ct.UnmarshalText([]byte(value))
+		} else if ctp, ok := field.Addr().Interface().(encoding.TextUnmarshaler); ok {
+			return ctp.UnmarshalText([]byte(value))
+		}
+
 		if cs, ok := field.Interface().(Setter); ok {
 			return cs.SetValue(value)
 		} else if csp, ok := field.Addr().Interface().(Setter); ok {
 			return csp.SetValue(value)
 		}
 	}
 
-	valueType := field.Type()
 	switch valueType.Kind() {
 
 	// parse string value
@@ -542,11 +557,6 @@ func parseValue(field reflect.Value, value, sep string, layout *string) error {
 		field.Set(*mapValue)
 
 	default:
-		// look for supported struct parser
-		if structParser, found := validStructs[valueType]; found {
-			return structParser(&field, value, layout)
-		}
-
 		return fmt.Errorf("unsupported type %s.%s", valueType.PkgPath(), valueType.Name())
 	}
 

example_test.go

@@ -179,36 +179,49 @@ func ExampleReadEnvWithURL() {
 	//Output: https://images.cdn/
 }
 
-// MyField is an example type with a custom setter
-type MyField string
+// MyField1 is an example type with a custom setter
+type MyField1 string
 
-func (f *MyField) SetValue(s string) error {
+func (f *MyField1) SetValue(s string) error {
 	if s == "" {
 		return fmt.Errorf("field value can't be empty")
 	}
-	*f = MyField("my field is: " + s)
+	*f = MyField1("my field is: " + s)
 	return nil
 }
 
-func (f MyField) String() string {
+func (f MyField1) String() string {
 	return string(f)
 }
 
+// MyField2 is an example type with encoding.TextUnmarshaler implementation.
+type MyField2 string
+
+func (f *MyField2) UnmarshalText(p []byte) error {
+	if len(p) == 0 {
+		return fmt.Errorf("field value can't be empty")
+	}
+	*f = MyField2("my field is: " + string(p))
+	return nil
+}
+
 // Example_setter uses type with a custom setter to parse environment variable data
 func Example_setter() {
 	type config struct {
-		Default string  `env:"ONE"`
-		Custom  MyField `env:"TWO"`
+		Default string   `env:"ONE"`
+		Custom1 MyField1 `env:"TWO"`
+		Custom2 MyField2 `env:"THREE"`
 	}
 
 	var cfg config
 
 	os.Setenv("ONE", "test1")
 	os.Setenv("TWO", "test2")
+	os.Setenv("THREE", "test3")
 
 	cleanenv.ReadEnv(&cfg)
 	fmt.Printf("%+v\n", cfg)
-	//Output: {Default:test1 Custom:my field is: test2}
+	//Output: {Default:test1 Custom1:my field is: test2 Custom2:my field is: test3}
 }
 
 // ConfigUpdate is a type with a custom updater