Add support for custom boolean flags through IsBoolFlag()

This is consistent with Go's native flag parsing module and can be used to implement custom boolean/tri-state flags.

Signed-off-by: Filipe Brandenburger <[email protected]>

1 files changed, 9 insertions, 0 deletions

diff --git a/bool.go b/bool.go
index 60beb54..617971a 100644
--- a/bool.go
+++ b/bool.go
@@ -5,6 +5,13 @@ import (
 	"strconv"
 )
 
+// optional interface to indicate boolean flags that can be
+// supplied without "=value" text
+type boolFlag interface {
+	Value
+	IsBoolFlag() bool
+}
+
 // -- bool Value
 type boolValue bool
 
@@ -21,6 +28,8 @@ func (b *boolValue) Set(s string) error {
 
 func (b *boolValue) String() string { return fmt.Sprintf("%v", *b) }
 
+func (b *boolValue) IsBoolFlag() bool { return true }
+
 // BoolVar defines a bool flag with specified name, default value, and usage string.
 // The argument p points to a bool variable in which to store the value of the flag.
 func (f *FlagSet) BoolVar(p *bool, name string, value bool, usage string) {