func membersToFields()

in cmd/go-to-protobuf/protobuf/generator.go [621:716]
81 lines of code
29 McCabe index (conditional complexity)

func membersToFields(locator ProtobufLocator, t *types.Type, localPackage types.Name, omitFieldTypes map[types.Name]struct{}) ([]protoField, error) {
	fields := []protoField{}

	for _, m := range t.Members {
		if namer.IsPrivateGoName(m.Name) {
			// skip private fields
			continue
		}
		if _, ok := omitFieldTypes[types.Name{Name: m.Type.Name.Name, Package: m.Type.Name.Package}]; ok {
			continue
		}
		tags := reflect.StructTag(m.Tags)
		field := protoField{
			LocalPackage: localPackage,

			Tag:    -1,
			Extras: make(map[string]string),
		}

		protobufTag := tags.Get("protobuf")
		if protobufTag == "-" {
			continue
		}

		if err := protobufTagToField(protobufTag, &field, m, t, localPackage); err != nil {
			return nil, err
		}

		// extract information from JSON field tag
		if tag := tags.Get("json"); len(tag) > 0 {
			parts := strings.Split(tag, ",")
			if len(field.Name) == 0 && len(parts[0]) != 0 {
				field.Name = parts[0]
			}
			if field.Tag == -1 && field.Name == "-" {
				continue
			}
		}

		if field.Type == nil {
			if err := memberTypeToProtobufField(locator, &field, m.Type); err != nil {
				return nil, fmt.Errorf("unable to embed type %q as field %q in %q: %v", m.Type, field.Name, t.Name, err)
			}
		}
		if len(field.Name) == 0 {
			field.Name = namer.IL(m.Name)
		}

		if field.Map && field.Repeated {
			// maps cannot be repeated
			field.Repeated = false
			field.Nullable = true
		}

		if !field.Nullable {
			field.Extras["(gogoproto.nullable)"] = "false"
		}
		if (field.Type.Name.Name == "bytes" && field.Type.Name.Package == "") || (field.Repeated && field.Type.Name.Package == "" && namer.IsPrivateGoName(field.Type.Name.Name)) {
			delete(field.Extras, "(gogoproto.nullable)")
		}
		if field.Name != m.Name {
			field.Extras["(gogoproto.customname)"] = strconv.Quote(m.Name)
		}
		field.CommentLines = m.CommentLines
		fields = append(fields, field)
	}

	// assign tags
	highest := 0
	byTag := make(map[int]*protoField)
	// fields are in Go struct order, which we preserve
	for i := range fields {
		field := &fields[i]
		tag := field.Tag
		if tag != -1 {
			if existing, ok := byTag[tag]; ok {
				return nil, fmt.Errorf("field %q and %q both have tag %d", field.Name, existing.Name, tag)
			}
			byTag[tag] = field
		}
		if tag > highest {
			highest = tag
		}
	}
	// starting from the highest observed tag, assign new field tags
	for i := range fields {
		field := &fields[i]
		if field.Tag != -1 {
			continue
		}
		highest++
		field.Tag = highest
		byTag[field.Tag] = field
	}
	return fields, nil
}