fix: parsing into ptr fields with value (#340)

Closes #339

Author: hypnoglow

env.go

@@ -355,7 +355,7 @@ func doParseField(
 	if !refField.CanSet() {
 		return nil
 	}
-	if reflect.Ptr == refField.Kind() && !refField.IsNil() {
+	if reflect.Ptr == refField.Kind() && refField.Elem().Kind() == reflect.Struct && !refField.IsNil() {
 		return parseInternal(refField.Interface(), processField, optionsWithEnvPrefix(refTypeField, opts))
 	}
 	if reflect.Struct == refField.Kind() && refField.CanAddr() && refField.Type().Name() == "" {

env_test.go

@@ -2254,3 +2254,55 @@ func TestNoEnvKeyIgnored(t *testing.T) {
 	isEqual(t, "", cfg.Foo)
 	isEqual(t, "202", cfg.FooBar)
 }
+
+func TestIssue339(t *testing.T) {
+	t.Run("Should parse with bool ptr set and env undefined", func(t *testing.T) {
+		existingValue := true
+		cfg := Config{
+			BoolPtr: &existingValue,
+		}
+
+		isNoErr(t, Parse(&cfg))
+
+		isEqual(t, &existingValue, cfg.BoolPtr)
+	})
+
+	t.Run("Should parse with bool ptr set and env defined", func(t *testing.T) {
+		existingValue := true
+		cfg := Config{
+			BoolPtr: &existingValue,
+		}
+
+		newValue := false
+		t.Setenv("BOOL", strconv.FormatBool(newValue))
+
+		isNoErr(t, Parse(&cfg))
+
+		isEqual(t, &newValue, cfg.BoolPtr)
+	})
+
+	t.Run("Should parse with string ptr set and env undefined", func(t *testing.T) {
+		existingValue := "one"
+		cfg := Config{
+			StringPtr: &existingValue,
+		}
+
+		isNoErr(t, Parse(&cfg))
+
+		isEqual(t, &existingValue, cfg.StringPtr)
+	})
+
+	t.Run("Should parse with string ptr set and env defined", func(t *testing.T) {
+		existingValue := "one"
+		cfg := Config{
+			StringPtr: &existingValue,
+		}
+
+		newValue := "two"
+		t.Setenv("STRING", newValue)
+
+		isNoErr(t, Parse(&cfg))
+
+		isEqual(t, &newValue, cfg.StringPtr)
+	})
+}