allow to pass additional options

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

flag.go

@@ -28,6 +28,7 @@ var (
 */
 
 type flagConfig struct {
+	fset *flag.FlagSet
 	opts config.Options
 }
 
@@ -45,7 +46,7 @@ func (c *flagConfig) Init(opts ...config.Option) error {
 		return err
 	}
 
-	flag.CommandLine.Init(os.Args[0], flag.ContinueOnError)
+	// flag.CommandLine.Init(os.Args[0], flag.ContinueOnError)
 	for _, sf := range fields {
 		tf, ok := sf.Field.Tag.Lookup(c.opts.StructTag)
 		if !ok {
@@ -65,6 +66,8 @@ func (c *flagConfig) Init(opts ...config.Option) error {
 		if f := flag.Lookup(fn); f != nil {
 			return nil
 		}
+
+		fmt.Printf("register %s flag\n", fn)
 		switch vi.(type) {
 		case time.Duration:
 			err = c.flagDuration(sf.Value, fn, fv, fd)
@@ -151,5 +154,37 @@ func NewConfig(opts ...config.Option) config.Config {
 	if len(options.StructTag) == 0 {
 		options.StructTag = DefaultStructTag
 	}
-	return &flagConfig{opts: options}
+	flagSet := flag.CommandLine
+	flagSetName := os.Args[0]
+	flagSetErrorHandling := flag.ExitOnError
+	var flagUsage func()
+	var isSet bool
+
+	if options.Context != nil {
+		if v, ok := options.Context.Value(flagSetNameKey{}).(string); ok {
+			isSet = true
+			flagSetName = v
+		}
+		if v, ok := options.Context.Value(flagSetErrorHandlingKey{}).(flag.ErrorHandling); ok {
+			isSet = true
+			flagSetErrorHandling = v
+		}
+		if v, ok := options.Context.Value(flagSetKey{}).(*flag.FlagSet); ok {
+			flagSet = v
+		}
+		if v, ok := options.Context.Value(flagSetUsageKey{}).(func()); ok {
+			flagUsage = v
+		}
+	}
+
+	if isSet {
+		flagSet.Init(flagSetName, flagSetErrorHandling)
+	}
+	if flagUsage != nil {
+		flagSet.Usage = flagUsage
+	}
+
+	c := &flagConfig{opts: options, fset: flagSet}
+
+	return c
 }

flag_test.go

@@ -2,6 +2,7 @@ package flag
 
 import (
 	"context"
+	"flag"
 	"os"
 	"testing"
 	"time"
@@ -40,7 +41,7 @@ func TestLoad(t *testing.T) {
 	ctx := context.Background()
 	cfg := &Config{Nested: &NestedConfig{}}
 
-	c := NewConfig(config.Struct(cfg), TimeFormat(time.RFC822))
+	c := NewConfig(config.Struct(cfg), TimeFormat(time.RFC822), FlagErrorHandling(flag.ContinueOnError))
 	if err := c.Init(); err != nil {
 		t.Fatalf("init failed: %v", err)
 	}

options.go

@@ -1,6 +1,8 @@
 package flag
 
 import (
+	"flag"
+
 	"go.unistack.org/micro/v3/config"
 )
 
@@ -24,3 +26,31 @@ type timeFormatKey struct{}
 func TimeFormat(s string) config.Option {
 	return config.SetOption(timeFormatKey{}, s)
 }
+
+type flagSetKey struct{}
+
+// FlagSet set flag set name
+func FlagSet(f *flag.FlagSet) config.Option {
+	return config.SetOption(flagSetKey{}, f)
+}
+
+type flagSetNameKey struct{}
+
+// FlagSetName set flag set name
+func FlagSetName(n string) config.Option {
+	return config.SetOption(flagSetNameKey{}, n)
+}
+
+type flagSetErrorHandlingKey struct{}
+
+// FlagErrorHandling set flag set error handling
+func FlagErrorHandling(eh flag.ErrorHandling) config.Option {
+	return config.SetOption(flagSetErrorHandlingKey{}, eh)
+}
+
+type flagSetUsageKey struct{}
+
+// FlagUsage set flag set usage func
+func FlagUsage(fn func()) config.Option {
+	return config.SetOption(flagSetUsageKey{}, fn)
+}