Flag Binding Refactor

This patch alters the way flags are handled to coincide with the
documentation on the Viper README. The documentation indicated that flag
bindings were late, when in fact they were very, very early. This patch
changes flag bindings to behave as late bindings.

viper.go

diff --git a/viper.go b/viper.go
index d9c5e67..af6e5ed 100644
--- a/viper.go
+++ b/viper.go
@@ -405,15 +405,33 @@
 
 	if val == nil {
 		source := v.find(path[0])
-		if source == nil {
-			return nil
+		if source != nil {
+			if reflect.TypeOf(source).Kind() == reflect.Map {
+				val = v.searchMap(cast.ToStringMap(source), path[1:])
+			}
 		}
+	}
 
-		if reflect.TypeOf(source).Kind() == reflect.Map {
-			val = v.searchMap(cast.ToStringMap(source), path[1:])
+	// if no other value is returned and a flag does exist for the value,
+	// get the flag's value even if the flag's value has not changed
+	if val == nil {
+		if flag, exists := v.pflags[lcaseKey]; exists {
+			jww.TRACE.Println(key, "get pflag default", val)
+			switch flag.Value.Type() {
+			case "int", "int8", "int16", "int32", "int64":
+				val = cast.ToInt(flag.Value.String())
+			case "bool":
+				val = cast.ToBool(flag.Value.String())
+			default:
+				val = flag.Value.String()
+			}
 		}
 	}
 
+	if val == nil {
+		return nil
+	}
+
 	var valType interface{}
 	if !v.typeByDefValue {
 		valType = val
@@ -539,22 +557,11 @@
 func BindPFlags(flags *pflag.FlagSet) (err error) { return v.BindPFlags(flags) }
 func (v *Viper) BindPFlags(flags *pflag.FlagSet) (err error) {
 	flags.VisitAll(func(flag *pflag.Flag) {
-		if err != nil {
-			// an error has been encountered in one of the previous flags
+		if err = v.BindPFlag(flag.Name, flag); err != nil {
 			return
 		}
-
-		err = v.BindPFlag(flag.Name, flag)
-		switch flag.Value.Type() {
-		case "int", "int8", "int16", "int32", "int64":
-			v.SetDefault(flag.Name, cast.ToInt(flag.Value.String()))
-		case "bool":
-			v.SetDefault(flag.Name, cast.ToBool(flag.Value.String()))
-		default:
-			v.SetDefault(flag.Name, flag.Value.String())
-		}
 	})
-	return
+	return nil
 }
 
 // Bind a specific key to a flag (as used by cobra)
@@ -569,15 +576,6 @@
 		return fmt.Errorf("flag for %q is nil", key)
 	}
 	v.pflags[strings.ToLower(key)] = flag
-
-	switch flag.Value.Type() {
-	case "int", "int8", "int16", "int32", "int64":
-		v.SetDefault(key, cast.ToInt(flag.Value.String()))
-	case "bool":
-		v.SetDefault(key, cast.ToBool(flag.Value.String()))
-	default:
-		v.SetDefault(key, flag.Value.String())
-	}
 	return nil
 }
 
@@ -618,9 +616,14 @@
 
 	// PFlag Override first
 	flag, exists := v.pflags[key]
-	if exists {
-		if flag.Changed {
-			jww.TRACE.Println(key, "found in override (via pflag):", val)
+	if exists && flag.Changed {
+		jww.TRACE.Println(key, "found in override (via pflag):", flag.Value)
+		switch flag.Value.Type() {
+		case "int", "int8", "int16", "int32", "int64":
+			return cast.ToInt(flag.Value.String())
+		case "bool":
+			return cast.ToBool(flag.Value.String())
+		default:
 			return flag.Value.String()
 		}
 	}