Patch mongo (add omitalways)

mongo/bson/bsoncodec/struct_codec.go

@@ -122,6 +122,10 @@ func (sc *StructCodec) EncodeValue(r EncodeContext, vw bsonrw.ValueWriter, val r
 	}
 	var rv reflect.Value
 	for _, desc := range sd.fl {
+		if desc.omitAlways {
+			continue
+		}
+
 		if desc.inline == nil {
 			rv = val.Field(desc.idx)
 		} else {
@@ -400,15 +404,16 @@ type structDescription struct {
 }
 
 type fieldDescription struct {
-	name      string // BSON key name
-	fieldName string // struct field name
-	idx       int
-	omitEmpty bool
-	minSize   bool
-	truncate  bool
-	inline    []int
-	encoder   ValueEncoder
-	decoder   ValueDecoder
+	name       string // BSON key name
+	fieldName  string // struct field name
+	idx        int
+	omitEmpty  bool
+	omitAlways bool
+	minSize    bool
+	truncate   bool
+	inline     []int
+	encoder    ValueEncoder
+	decoder    ValueDecoder
 }
 
 type byIndex []fieldDescription
@@ -491,6 +496,7 @@ func (sc *StructCodec) describeStruct(r *Registry, t reflect.Type) (*structDescr
 		}
 		description.name = stags.Name
 		description.omitEmpty = stags.OmitEmpty
+		description.omitAlways = stags.OmitAlways
 		description.minSize = stags.MinSize
 		description.truncate = stags.Truncate
 

mongo/bson/bsoncodec/struct_tag_parser.go

@@ -52,12 +52,13 @@ func (stpf StructTagParserFunc) ParseStructTags(sf reflect.StructField) (StructT
 //
 // TODO(skriptble): Add tags for undefined as nil and for null as nil.
 type StructTags struct {
-	Name      string
-	OmitEmpty bool
-	MinSize   bool
-	Truncate  bool
-	Inline    bool
-	Skip      bool
+	Name       string
+	OmitEmpty  bool
+	OmitAlways bool
+	MinSize    bool
+	Truncate   bool
+	Inline     bool
+	Skip       bool
 }
 
 // DefaultStructTagParser is the StructTagParser used by the StructCodec by default.
@@ -108,6 +109,8 @@ func parseTags(key string, tag string) (StructTags, error) {
 		switch str {
 		case "omitempty":
 			st.OmitEmpty = true
+		case "omitalways":
+			st.OmitAlways = true
 		case "minsize":
 			st.MinSize = true
 		case "truncate":