feat: support ignored value "-" for env tag (#338)

* feat: support ignored value "-" for env tag

* fix test

Author: sv-kozlov

env.go

@@ -367,6 +367,10 @@ func doParseField(
 		return err
 	}
 
+	if params.Ignored {
+		return nil
+	}
+
 	if err := processField(refField, refTypeField, opts, params); err != nil {
 		return err
 	}
@@ -533,6 +537,7 @@ type FieldParams struct {
 	NotEmpty        bool
 	Expand          bool
 	Init            bool
+	Ignored         bool
 }
 
 func parseFieldParams(field reflect.StructField, opts Options) (FieldParams, error) {
@@ -549,6 +554,7 @@ func parseFieldParams(field reflect.StructField, opts Options) (FieldParams, err
 		Required:        opts.RequiredIfNoDef,
 		DefaultValue:    defaultValue,
 		HasDefaultValue: hasDefaultValue,
+		Ignored:         ownKey == "-",
 	}
 
 	for _, tag := range tags {
@@ -567,6 +573,8 @@ func parseFieldParams(field reflect.StructField, opts Options) (FieldParams, err
 			result.Expand = true
 		case "init":
 			result.Init = true
+		case "-":
+			result.Ignored = true
 		default:
 			return FieldParams{}, newNoSupportedTagOptionError(tag)
 		}

env_test.go

@@ -2214,3 +2214,43 @@ func TestParseWithOptionsRenamedPrefix(t *testing.T) {
 	isNoErr(t, Parse(cfg))
 	isEqual(t, "101", cfg.Foo.Str)
 }
+
+func TestFieldIgnored(t *testing.T) {
+	type Test struct {
+		Foo string `env:"FOO"`
+		Bar string `env:"BAR,-"`
+	}
+	type ComplexConfig struct {
+		Str string `env:"STR"`
+		Foo Test   `env:"FOO" envPrefix:"FOO_"`
+		Bar Test   `env:"-" envPrefix:"BAR_"`
+	}
+	t.Setenv("STR", "101")
+	t.Setenv("FOO_FOO", "202")
+	t.Setenv("FOO_BAR", "303")
+	t.Setenv("BAR_FOO", "404")
+	t.Setenv("BAR_BAR", "505")
+
+	var cfg ComplexConfig
+	isNoErr(t, Parse(&cfg))
+	isEqual(t, "101", cfg.Str)
+	isEqual(t, "202", cfg.Foo.Foo)
+	isEqual(t, "", cfg.Foo.Bar)
+	isEqual(t, "", cfg.Bar.Foo)
+	isEqual(t, "", cfg.Bar.Bar)
+}
+
+func TestNoEnvKeyIgnored(t *testing.T) {
+	type Config struct {
+		Foo    string `env:"-"`
+		FooBar string
+	}
+
+	t.Setenv("FOO", "101")
+	t.Setenv("FOO_BAR", "202")
+
+	var cfg Config
+	isNoErr(t, ParseWithOptions(&cfg, Options{UseFieldNameByDefault: true}))
+	isEqual(t, "", cfg.Foo)
+	isEqual(t, "202", cfg.FooBar)
+}