Handle unusual types in fishAddFileFlag [urfave#1156]

fish.go

@@ -161,7 +161,7 @@ func (a *App) prepareFishFlags(flags []Flag, previousCommands []string) []string
 func fishAddFileFlag(flag Flag, completion *strings.Builder) {
 	val := reflect.ValueOf(flag)
 	// if flag is a non-nil pointer to a struct...
-	if val.Kind() != reflect.Invalid && val.Elem().Kind() == reflect.Struct {
+	if val.Kind() == reflect.Ptr && val.Elem().Kind() == reflect.Struct {
 		field := val.Elem().FieldByName("TakesFile")
 		// if flag's underlying type has a bool field called TakesFile, whose value is true...
 		if field.Kind() == reflect.Bool && field.Bool() {

fish_test.go

@@ -1,6 +1,8 @@
 package cli
 
 import (
+	"flag"
+	"strings"
 	"testing"
 )
 
@@ -19,3 +21,80 @@ func TestFishCompletion(t *testing.T) {
 	expect(t, err, nil)
 	expectFileContent(t, "testdata/expected-fish-full.fish", res)
 }
+
+func TestFishAddFileFlag(t *testing.T) {
+	flags := []Flag{
+		&GenericFlag{
+			Name:      "jen-and-eric",
+			TakesFile: false,
+		},
+		&PathFlag{
+			Name:      "logfile",
+			TakesFile: false,
+		},
+		&BoolFlag{
+			Name: "dry-run",
+		},
+		&IntFlag{
+			Name: "depth",
+		},
+	}
+
+	for _, flag := range flags {
+		completion := &strings.Builder{}
+		fishAddFileFlag(flag, completion)
+		expect(t, completion.String(), " -f")
+	}
+
+	flags = []Flag{
+		&GenericFlag{
+			Name:      "jen-and-eric",
+			TakesFile: true,
+		},
+		&PathFlag{
+			Name:      "logfile",
+			TakesFile: true,
+		},
+	}
+
+	for _, flag := range flags {
+		completion := &strings.Builder{}
+		fishAddFileFlag(flag, completion)
+		t.Log(flag.Names())
+		expect(t, completion.String(), "")
+	}
+}
+
+type bareIntFlag int
+
+func (bareIntFlag) Apply(*flag.FlagSet) error { return nil }
+func (bareIntFlag) Names() []string           { return []string{} }
+func (bareIntFlag) IsSet() bool               { return false }
+func (bareIntFlag) String() string            { return "bareIntFlag" }
+
+type bareBoolFlag bool
+
+func (*bareBoolFlag) Apply(*flag.FlagSet) error { return nil }
+func (*bareBoolFlag) Names() []string           { return []string{} }
+func (*bareBoolFlag) IsSet() bool               { return false }
+func (*bareBoolFlag) String() string            { return "bareBoolFlag" }
+
+func TestFishAddFileFlagUnexpectedInput(t *testing.T) {
+	defer func() {
+		if err := recover(); err != nil {
+			t.Errorf("test panicked: %v", err)
+		}
+	}()
+	bareInt := bareIntFlag(5)
+	bareBool := bareBoolFlag(false)
+	flags := []Flag{
+		bareInt,
+		&bareBool,
+		(*bareBoolFlag)(nil),
+	}
+	for _, flag := range flags {
+		completion := &strings.Builder{}
+		fishAddFileFlag(flag, completion)
+		expect(t, completion.String(), " -f")
+	}
+}