Merge pull request 'config: add conditions' (#287) from cond-config into master

Reviewed-on: #287

config/default.go

@@ -7,8 +7,8 @@ import (
 	"strings"
 	"time"
 
-	"github.com/google/uuid"
 	"dario.cat/mergo"
+	"github.com/google/uuid"
 	"go.unistack.org/micro/v4/options"
 	mid "go.unistack.org/micro/v4/util/id"
 	rutil "go.unistack.org/micro/v4/util/reflect"
@@ -40,6 +40,10 @@ func (c *defaultConfig) Init(opts ...options.Option) error {
 }
 
 func (c *defaultConfig) Load(ctx context.Context, opts ...options.Option) error {
+	if c.opts.SkipLoad != nil && c.opts.SkipLoad(ctx, c) {
+		return nil
+	}
+
 	if err := DefaultBeforeLoad(ctx, c); err != nil && !c.opts.AllowFail {
 		return err
 	}
@@ -292,7 +296,11 @@ func fillValues(valueOf reflect.Value, tname string) error {
 	return nil
 }
 
-func (c *defaultConfig) Save(ctx context.Context, opts ...options.Option) error {
+func (c *defaultConfig) Save(ctx context.Context, _ ...options.Option) error {
+	if c.opts.SkipSave != nil && c.opts.SkipSave(ctx, c) {
+		return nil
+	}
+
 	if err := DefaultBeforeSave(ctx, c); err != nil {
 		return err
 	}

config/options.go

@@ -43,6 +43,10 @@ type Options struct {
 	AfterInit []func(context.Context, Config) error
 	// AllowFail flag to allow fail in config source
 	AllowFail bool
+	// SkipLoad runs only if condition returns true
+	SkipLoad func(context.Context, Config) bool
+	// SkipSave runs only if condition returns true
+	SkipSave func(context.Context, Config) bool
 }
 
 // NewOptions new options struct with filed values