Fix enum's from envars not validating (fixes #107).

Also added a mapper for `*os.File`.

README.md

@@ -382,11 +382,21 @@ Slices and maps treat type tags specially. For slices, the `type:""` tag
 specifies the element type. For maps, the tag has the format
 `tag:"[<key>]:[<value>]"` where either may be omitted.
 
+## Supported field types
+
 
 ## Custom decoders (mappers)
 
+
 Any field implementing `encoding.TextUnmarshaler` or `json.Unmarshaler` will use those interfaces
-for decoding values.
+for decoding values. Kong also includes builtin support for many common Go types:
+
+| Type                | Description
+|---------------------|--------------------------------------------
+| `time.Duration`     | Populated using `time.ParseDuration()`.
+| `time.Time`         | Populated using `time.Parse()`. Format defaults to RFC3339 but can be overridden with the `format:"X"` tag.
+| `*os.File`          | Path to a file that will be opened, or `-` for `os.Stdin`. File must be closed by the user.
+| `*url.URL`          | Populated with `url.Parse()`.
 
 For more fine-grained control, if a field implements the
 [MapperValue](https://godoc.org/github.com/alecthomas/kong#MapperValue)

context.go

@@ -2,6 +2,7 @@ package kong
 
 import (
 	"fmt"
+	"os"
 	"reflect"
 	"sort"
 	"strconv"
@@ -136,7 +137,8 @@ func (c *Context) Empty() bool {
 func (c *Context) Validate() error { // nolint: gocyclo
 	err := Visit(c.Model, func(node Visitable, next Next) error {
 		if value, ok := node.(*Value); ok {
-			if value.Enum != "" && (!value.Required || value.Default != "") {
+			_, ok := os.LookupEnv(value.Tag.Env)
+			if value.Enum != "" && (!value.Required || value.Default != "" || (value.Tag.Env != "" && ok)) {
 				if err := checkEnum(value, value.Target); err != nil {
 					return err
 				}

hooks.go

@@ -1,6 +1,6 @@
 package kong
 
-// BeforeResolve is a documentation-only interface describing hooks that run before values are set.
+// BeforeResolve is a documentation-only interface describing hooks that run before resolvers are applied.
 type BeforeResolve interface {
 	// This is not the correct signature - see README for details.
 	BeforeResolve(args ...interface{}) error

kong_test.go

@@ -743,7 +743,7 @@ func TestEnvarEnumValidated(t *testing.T) {
 	})
 	defer restore()
 	var cli struct {
-		Flag string `env:"FLAG" enum:"valid" default:"valid"`
+		Flag string `env:"FLAG" required:"" enum:"valid"`
 	}
 	p := mustNew(t, &cli)
 	_, err := p.Parse(nil)
@@ -798,7 +798,7 @@ func TestIssue40EnumAcrossCommands(t *testing.T) {
 			OneArg string `arg:"" required:""`
 		} `cmd:""`
 		Two struct {
-			TwoArg string `arg:"" enum:"a,b,c" required:""`
+			TwoArg string `arg:"" enum:"a,b,c" required:"" env:"FOO"`
 		} `cmd:""`
 		Three struct {
 			ThreeArg string `arg:"" optional:"" default:"a" enum:"a,b,c"`

mapper.go

@@ -231,8 +231,8 @@ func (r *Registry) RegisterDefaults() *Registry {
 		RegisterKind(reflect.Int16, intDecoder(16)).
 		RegisterKind(reflect.Int32, intDecoder(32)).
 		RegisterKind(reflect.Int64, intDecoder(64)).
-		RegisterKind(reflect.Uint, uintDecoder(64)).
+		RegisterKind(reflect.Uint, uintDecoder(bits.UintSize)).
-		RegisterKind(reflect.Uint8, uintDecoder(bits.UintSize)).
+		RegisterKind(reflect.Uint8, uintDecoder(8)).
 		RegisterKind(reflect.Uint16, uintDecoder(16)).
 		RegisterKind(reflect.Uint32, uintDecoder(32)).
 		RegisterKind(reflect.Uint64, uintDecoder(64)).
@@ -248,6 +248,7 @@ func (r *Registry) RegisterDefaults() *Registry {
 		RegisterType(reflect.TypeOf(time.Time{}), timeDecoder()).
 		RegisterType(reflect.TypeOf(time.Duration(0)), durationDecoder()).
 		RegisterType(reflect.TypeOf(&url.URL{}), urlMapper()).
+		RegisterType(reflect.TypeOf(&os.File{}), fileMapper(r)).
 		RegisterName("path", pathMapper(r)).
 		RegisterName("existingfile", existingFileMapper(r)).
 		RegisterName("existingdir", existingDirMapper(r)).
@@ -541,6 +542,31 @@ func pathMapper(r *Registry) MapperFunc {
 	}
 }
 
+func fileMapper(r *Registry) MapperFunc {
+	return func(ctx *DecodeContext, target reflect.Value) error {
+		if target.Kind() == reflect.Slice {
+			return sliceDecoder(r)(ctx, target)
+		}
+		var path string
+		err := ctx.Scan.PopValueInto("file", &path)
+		if err != nil {
+			return err
+		}
+		var file *os.File
+		if path == "-" {
+			file = os.Stdin
+		} else {
+			path = ExpandPath(path)
+			file, err = os.Open(path) // nolint: gosec
+			if err != nil {
+				return err
+			}
+		}
+		target.Set(reflect.ValueOf(file))
+		return nil
+	}
+}
+
 func existingFileMapper(r *Registry) MapperFunc {
 	return func(ctx *DecodeContext, target reflect.Value) error {
 		if target.Kind() == reflect.Slice {

mapper_test.go

@@ -345,3 +345,21 @@ func TestNumbers(t *testing.T) {
 		}, cli)
 	})
 }
+
+func TestFileMapper(t *testing.T) {
+	type CLI struct {
+		File *os.File `arg:""`
+	}
+	var cli CLI
+	p := mustNew(t, &cli)
+	_, err := p.Parse([]string{"testdata/file.txt"})
+	require.NoError(t, err)
+	require.NotNil(t, cli.File)
+	_ = cli.File.Close()
+	_, err = p.Parse([]string{"testdata/missing.txt"})
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "missing.txt: no such file or directory")
+	_, err = p.Parse([]string{"-"})
+	require.NoError(t, err)
+	require.Equal(t, os.Stdin, cli.File)
+}

testdata/file.txt

@@ -0,0 +1 @@
+Hello world.