protogen: add field number prop

internal/protogen/exporter.go

@@ -200,10 +200,10 @@ func (x *sheetExporter) exportStruct() error {
 	x.g.P("  option (tableau.struct) = {", marshalToText(opts), "};")
 	x.g.P("")
 	// generate the fields
-	depth := 1
 	for i, field := range x.ws.Fields {
 		tagid := i + 1
-		if err := x.exportField(depth, tagid, field, x.ws.Name); err != nil {
+		err := x.exportField(1, tagid, field, x.ws.Name)
+		if err != nil {
 			return err
 		}
 	}
@@ -260,10 +260,9 @@ func (x *sheetExporter) exportUnion() error {
 		}
 		x.g.P("  message ", strings.TrimSpace(msgField.Name), " {")
 		// generate the fields
-		depth := 2
 		tagid := 1
 		for _, field := range msgField.Fields {
-			if err := x.exportField(depth, tagid, field, msgField.Name); err != nil {
+			if err := x.exportField(2, tagid, field, msgField.Name); err != nil {
 				return err
 			}
 			cross := int(field.GetOptions().GetProp().GetCross())
@@ -290,11 +289,12 @@ func (x *sheetExporter) exportMessager() error {
 	x.g.P("message ", x.ws.Name, " {")
 	x.g.P("  option (tableau.worksheet) = {", marshalToText(x.ws.Options), "};")
 	x.g.P("")
+	// generate the tagids
+	tagids := genTagids(x.ws.Fields)
 	// generate the fields
-	depth := 1
 	for i, field := range x.ws.Fields {
-		tagid := i + 1
-		if err := x.exportField(depth, tagid, field, x.ws.Name); err != nil {
+		tagid := tagids[i]
+		if err := x.exportField(1, tagid, field, x.ws.Name); err != nil {
 			return err
 		}
 	}
@@ -365,8 +365,10 @@ func (x *sheetExporter) exportField(depth int, tagid int, field *internalpb.Fiel
 
 		// x.g.P("")
 		x.g.P(printer.Indent(depth), "message ", typeName, " {")
+		// generate the tagids
+		tagids := genTagids(field.Fields)
 		for i, f := range field.Fields {
-			tagid := i + 1
+			tagid := tagids[i]
 			if err := x.exportField(depth+1, tagid, f, nestedMsgName); err != nil {
 				return err
 			}
@@ -382,6 +384,7 @@ func genFieldOptionsString(opts *tableaupb.FieldOptions) string {
 	if opts.Prop != nil {
 		jsonName = opts.Prop.JsonName
 		opts.Prop.JsonName = ""
+		opts.Prop.Number = 0
 
 		// set nil if field prop is empty
 		if IsEmptyFieldProp(opts.Prop) {
@@ -424,3 +427,36 @@ func isSameFieldMessageType(left, right *internalpb.Field) bool {
 	}
 	return false
 }
+
+func genTagids(fields []*internalpb.Field) []int {
+	tagids := make([]int, 0, len(fields))
+	occupiedTagids := make(map[int]bool, len(fields))
+	for i, field := range fields {
+		if i == 0 {
+			tagids = append(tagids, 1)
+			continue
+		}
+		number := int(field.Options.GetProp().GetNumber())
+		if number > 1 && !occupiedTagids[number] {
+			tagids = append(tagids, number)
+			occupiedTagids[number] = true
+		} else {
+			tagids = append(tagids, 0)
+		}
+	}
+	autogenTagid := 1
+	nextTagid := func() int {
+		for {
+			autogenTagid++
+			if !occupiedTagids[autogenTagid] {
+				return autogenTagid
+			}
+		}
+	}
+	for i, tagid := range tagids {
+		if tagid == 0 {
+			tagids[i] = nextTagid()
+		}
+	}
+	return tagids
+}

internal/protogen/field_prop.go

@@ -26,6 +26,7 @@ func ExtractMapFieldProp(prop *tableaupb.FieldProp) *tableaupb.FieldProp {
 		Patch:    prop.Patch,
 		Sep:      prop.Sep,
 		Subsep:   prop.Subsep,
+		Number:   prop.Number,
 	}
 	if IsEmptyFieldProp(p) {
 		return nil
@@ -50,6 +51,7 @@ func ExtractListFieldProp(prop *tableaupb.FieldProp, isScalarList bool) *tableau
 		Sep:      prop.Sep,
 		Subsep:   prop.Subsep,
 		Cross:    prop.Cross,
+		Number:   prop.Number,
 	}
 	if isScalarList {
 		p.Range = prop.Range
@@ -75,6 +77,7 @@ func ExtractStructFieldProp(prop *tableaupb.FieldProp) *tableaupb.FieldProp {
 		Patch:    prop.Patch,
 		Sep:      prop.Sep,
 		Subsep:   prop.Subsep,
+		Number:   prop.Number,
 	}
 	if IsEmptyFieldProp(p) {
 		return nil
@@ -99,6 +102,7 @@ func ExtractScalarFieldProp(prop *tableaupb.FieldProp) *tableaupb.FieldProp {
 		Optional: prop.Optional,
 		Patch:    prop.Patch,
 		Pattern:  prop.Pattern,
+		Number:   prop.Number,
 	}
 	if IsEmptyFieldProp(p) {
 		return nil

proto/tableau/protobuf/tableau.proto

@@ -71,9 +71,9 @@ message OneofOptions {
 
 message WorkbookOptions {
   // filename with path, e.g.: "relative/path/BookName.suffix" (slash path)
-  string name = 1;   
+  string name = 1;
   // book alias without suffix, e.g.: "BookAlias"
-  string alias = 2;  
+  string alias = 2;
   // Exact row number of column name definition at a worksheet.
   //
   // Default: 1.
@@ -344,6 +344,15 @@ message FieldProp {
   //
   // TODO: use cases for more field types.
   string pattern = 16;
+  // Specify field number (unique numbered tag).
+  // All fields without numbers specified will use a sequence starting from 1 by default,
+  // and will not reuse explicitly specified field numbers.
+  // The first field of a message must occupy number 1 by default, and specifying other
+  // field number as 1 makes no sense since this number is reserved for the first field.
+  // If you specify same field number on multiple fields, only the first of them works.
+  //
+  // Refer to [protobuf: Assigning Field Numbers](https://protobuf.dev/programming-guides/proto3/#assigning)
+  int32 number = 17;
 }
 
 // Layout of list and map.