Add vendor folder to git

vendor/github.com/grpc-ecosystem/grpc-gateway/protoc-gen-swagger/genswagger/template.go

@@ -0,0 +1,708 @@
+package genswagger
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"reflect"
+	"regexp"
+	"strconv"
+	"strings"
+
+	pbdescriptor "github.com/golang/protobuf/protoc-gen-go/descriptor"
+	"github.com/grpc-ecosystem/grpc-gateway/protoc-gen-grpc-gateway/descriptor"
+)
+
+// findServicesMessagesAndEnumerations discovers all messages and enums defined in the RPC methods of the service.
+func findServicesMessagesAndEnumerations(s []*descriptor.Service, reg *descriptor.Registry, m messageMap, e enumMap) {
+	for _, svc := range s {
+		for _, meth := range svc.Methods {
+			m[fullyQualifiedNameToSwaggerName(meth.RequestType.FQMN(), reg)] = meth.RequestType
+			findNestedMessagesAndEnumerations(meth.RequestType, reg, m, e)
+			m[fullyQualifiedNameToSwaggerName(meth.ResponseType.FQMN(), reg)] = meth.ResponseType
+			findNestedMessagesAndEnumerations(meth.ResponseType, reg, m, e)
+		}
+	}
+}
+
+// findNestedMessagesAndEnumerations those can be generated by the services.
+func findNestedMessagesAndEnumerations(message *descriptor.Message, reg *descriptor.Registry, m messageMap, e enumMap) {
+	// Iterate over all the fields that
+	for _, t := range message.Fields {
+		fieldType := t.GetTypeName()
+		// If the type is an empty string then it is a proto primitive
+		if fieldType != "" {
+			if _, ok := m[fieldType]; !ok {
+				msg, err := reg.LookupMsg("", fieldType)
+				if err != nil {
+					enum, err := reg.LookupEnum("", fieldType)
+					if err != nil {
+						panic(err)
+					}
+					e[fieldType] = enum
+					continue
+				}
+				m[fieldType] = msg
+				findNestedMessagesAndEnumerations(msg, reg, m, e)
+			}
+		}
+	}
+}
+
+func renderMessagesAsDefinition(messages messageMap, d swaggerDefinitionsObject, reg *descriptor.Registry) {
+	for name, msg := range messages {
+		switch name {
+		case ".google.protobuf.Timestamp":
+			continue
+		}
+		if opt := msg.GetOptions(); opt != nil && opt.MapEntry != nil && *opt.MapEntry {
+			continue
+		}
+		schema := swaggerSchemaObject{
+			schemaCore: schemaCore{
+				Type: "object",
+			},
+			Properties: make(map[string]swaggerSchemaObject),
+		}
+		msgComments := protoComments(reg, msg.File, msg.Outers, "MessageType", int32(msg.Index))
+		if err := updateSwaggerDataFromComments(&schema, msgComments); err != nil {
+			panic(err)
+		}
+
+		for i, f := range msg.Fields {
+			fieldValue := schemaOfField(f, reg)
+
+			fieldProtoPath := protoPathIndex(reflect.TypeOf((*pbdescriptor.DescriptorProto)(nil)), "Field")
+			fieldProtoComments := protoComments(reg, msg.File, msg.Outers, "MessageType", int32(msg.Index), fieldProtoPath, int32(i))
+			if err := updateSwaggerDataFromComments(&fieldValue, fieldProtoComments); err != nil {
+				panic(err)
+			}
+
+			schema.Properties[f.GetName()] = fieldValue
+		}
+		d[fullyQualifiedNameToSwaggerName(msg.FQMN(), reg)] = schema
+	}
+}
+
+// schemaOfField returns a swagger Schema Object for a protobuf field.
+func schemaOfField(f *descriptor.Field, reg *descriptor.Registry) swaggerSchemaObject {
+	const (
+		singular = 0
+		array    = 1
+		object   = 2
+	)
+	var (
+		core      schemaCore
+		aggregate int
+	)
+
+	fd := f.FieldDescriptorProto
+	if m, err := reg.LookupMsg("", f.GetTypeName()); err == nil {
+		if opt := m.GetOptions(); opt != nil && opt.MapEntry != nil && *opt.MapEntry {
+			fd = m.GetField()[1]
+			aggregate = object
+		}
+	}
+	if fd.GetLabel() == pbdescriptor.FieldDescriptorProto_LABEL_REPEATED {
+		aggregate = array
+	}
+
+	switch ft := fd.GetType(); ft {
+	case pbdescriptor.FieldDescriptorProto_TYPE_ENUM, pbdescriptor.FieldDescriptorProto_TYPE_MESSAGE, pbdescriptor.FieldDescriptorProto_TYPE_GROUP:
+		if fd.GetTypeName() == ".google.protobuf.Timestamp" && pbdescriptor.FieldDescriptorProto_TYPE_MESSAGE == ft {
+			core = schemaCore{
+				Type:   "string",
+				Format: "date-time",
+			}
+		} else {
+			core = schemaCore{
+				Ref: "#/definitions/" + fullyQualifiedNameToSwaggerName(fd.GetTypeName(), reg),
+			}
+		}
+	default:
+		ftype, format, ok := primitiveSchema(ft)
+		if ok {
+			core = schemaCore{Type: ftype, Format: format}
+		} else {
+			core = schemaCore{Type: ft.String(), Format: "UNKNOWN"}
+		}
+	}
+	switch aggregate {
+	case array:
+		return swaggerSchemaObject{
+			schemaCore: schemaCore{
+				Type: "array",
+			},
+			Items: (*swaggerItemsObject)(&core),
+		}
+	case object:
+		return swaggerSchemaObject{
+			schemaCore: schemaCore{
+				Type: "object",
+			},
+			AdditionalProperties: &swaggerSchemaObject{schemaCore: core},
+		}
+	default:
+		return swaggerSchemaObject{schemaCore: core}
+	}
+}
+
+// primitiveSchema returns a pair of "Type" and "Format" in JSON Schema for
+// the given primitive field type.
+// The last return parameter is true iff the field type is actually primitive.
+func primitiveSchema(t pbdescriptor.FieldDescriptorProto_Type) (ftype, format string, ok bool) {
+	switch t {
+	case pbdescriptor.FieldDescriptorProto_TYPE_DOUBLE:
+		return "number", "double", true
+	case pbdescriptor.FieldDescriptorProto_TYPE_FLOAT:
+		return "number", "float", true
+	case pbdescriptor.FieldDescriptorProto_TYPE_INT64:
+		return "string", "int64", true
+	case pbdescriptor.FieldDescriptorProto_TYPE_UINT64:
+		// 64bit integer types are marshaled as string in the default JSONPb marshaler.
+		// TODO(yugui) Add an option to declare 64bit integers as int64.
+		//
+		// NOTE: uint64 is not a predefined format of integer type in Swagger spec.
+		// So we cannot expect that uint64 is commonly supported by swagger processor.
+		return "string", "uint64", true
+	case pbdescriptor.FieldDescriptorProto_TYPE_INT32:
+		return "integer", "int32", true
+	case pbdescriptor.FieldDescriptorProto_TYPE_FIXED64:
+		// Ditto.
+		return "string", "uint64", true
+	case pbdescriptor.FieldDescriptorProto_TYPE_FIXED32:
+		// Ditto.
+		return "integer", "int64", true
+	case pbdescriptor.FieldDescriptorProto_TYPE_BOOL:
+		return "boolean", "boolean", true
+	case pbdescriptor.FieldDescriptorProto_TYPE_STRING:
+		return "string", "string", true
+	case pbdescriptor.FieldDescriptorProto_TYPE_BYTES:
+		return "string", "byte", true
+	case pbdescriptor.FieldDescriptorProto_TYPE_UINT32:
+		// Ditto.
+		return "integer", "int64", true
+	case pbdescriptor.FieldDescriptorProto_TYPE_SFIXED32:
+		return "integer", "int32", true
+	case pbdescriptor.FieldDescriptorProto_TYPE_SFIXED64:
+		return "string", "int64", true
+	case pbdescriptor.FieldDescriptorProto_TYPE_SINT32:
+		return "integer", "int32", true
+	case pbdescriptor.FieldDescriptorProto_TYPE_SINT64:
+		return "string", "int64", true
+	default:
+		return "", "", false
+	}
+}
+
+// renderEnumerationsAsDefinition inserts enums into the definitions object.
+func renderEnumerationsAsDefinition(enums enumMap, d swaggerDefinitionsObject, reg *descriptor.Registry) {
+	valueProtoPath := protoPathIndex(reflect.TypeOf((*pbdescriptor.EnumDescriptorProto)(nil)), "Value")
+	for _, enum := range enums {
+		enumComments := protoComments(reg, enum.File, enum.Outers, "EnumType", int32(enum.Index))
+
+		var enumNames []string
+		// it may be necessary to sort the result of the GetValue function.
+		var defaultValue string
+		var valueDescriptions []string
+		for valueIdx, value := range enum.GetValue() {
+			enumNames = append(enumNames, value.GetName())
+			if defaultValue == "" && value.GetNumber() == 0 {
+				defaultValue = value.GetName()
+			}
+
+			valueDescription := protoComments(reg, enum.File, enum.Outers, "EnumType", int32(enum.Index), valueProtoPath, int32(valueIdx))
+			if valueDescription != "" {
+				valueDescriptions = append(valueDescriptions, value.GetName()+": "+valueDescription)
+			}
+		}
+
+		if len(valueDescriptions) > 0 {
+			enumComments += "\n\n - " + strings.Join(valueDescriptions, "\n - ")
+		}
+		enumSchemaObject := swaggerSchemaObject{
+			schemaCore: schemaCore{
+				Type: "string",
+			},
+			Enum:    enumNames,
+			Default: defaultValue,
+		}
+		if err := updateSwaggerDataFromComments(&enumSchemaObject, enumComments); err != nil {
+			panic(err)
+		}
+
+		d[fullyQualifiedNameToSwaggerName(enum.FQEN(), reg)] = enumSchemaObject
+	}
+}
+
+// Take in a FQMN or FQEN and return a swagger safe version of the FQMN
+func fullyQualifiedNameToSwaggerName(fqn string, reg *descriptor.Registry) string {
+	return resolveFullyQualifiedNameToSwaggerName(fqn, append(reg.GetAllFQMNs(), reg.GetAllFQENs()...))
+}
+
+// Take the names of every proto and "uniq-ify" them. The idea is to produce a
+// set of names that meet a couple of conditions. They must be stable, they
+// must be unique, and they must be shorter than the FQN.
+//
+// This likely could be made better. This will always generate the same names
+// but may not always produce optimal names. This is a reasonably close
+// approximation of what they should look like in most cases.
+func resolveFullyQualifiedNameToSwaggerName(fqn string, messages []string) string {
+	packagesByDepth := make(map[int][][]string)
+	uniqueNames := make(map[string]string)
+
+	hierarchy := func(pkg string) []string {
+		return strings.Split(pkg, ".")
+	}
+
+	for _, p := range messages {
+		h := hierarchy(p)
+		for depth := range h {
+			if _, ok := packagesByDepth[depth]; !ok {
+				packagesByDepth[depth] = make([][]string, 0)
+			}
+			packagesByDepth[depth] = append(packagesByDepth[depth], h[len(h)-depth:])
+		}
+	}
+
+	count := func(list [][]string, item []string) int {
+		i := 0
+		for _, element := range list {
+			if reflect.DeepEqual(element, item) {
+				i++
+			}
+		}
+		return i
+	}
+
+	for _, p := range messages {
+		h := hierarchy(p)
+		for depth := 0; depth < len(h); depth++ {
+			if count(packagesByDepth[depth], h[len(h)-depth:]) == 1 {
+				uniqueNames[p] = strings.Join(h[len(h)-depth-1:], "")
+				break
+			}
+			if depth == len(h)-1 {
+				uniqueNames[p] = strings.Join(h, "")
+			}
+		}
+	}
+	return uniqueNames[fqn]
+}
+
+// Swagger expects paths of the form /path/{string_value} but grpc-gateway paths are expected to be of the form /path/{string_value=strprefix/*}. This should reformat it correctly.
+func templateToSwaggerPath(path string) string {
+	// It seems like the right thing to do here is to just use
+	// strings.Split(path, "/") but that breaks badly when you hit a url like
+	// /{my_field=prefix/*}/ and end up with 2 sections representing my_field.
+	// Instead do the right thing and write a small pushdown (counter) automata
+	// for it.
+	var parts []string
+	depth := 0
+	buffer := ""
+	for _, char := range path {
+		switch char {
+		case '{':
+			// Push on the stack
+			depth++
+			buffer += string(char)
+			break
+		case '}':
+			if depth == 0 {
+				panic("Encountered } without matching { before it.")
+			}
+			// Pop from the stack
+			depth--
+			buffer += "}"
+		case '/':
+			if depth == 0 {
+				parts = append(parts, buffer)
+				buffer = ""
+				// Since the stack was empty when we hit the '/' we are done with this
+				// section.
+				continue
+			}
+		default:
+			buffer += string(char)
+			break
+		}
+	}
+
+	// Now append the last element to parts
+	parts = append(parts, buffer)
+
+	// Parts is now an array of segments of the path. Interestingly, since the
+	// syntax for this subsection CAN be handled by a regexp since it has no
+	// memory.
+	re := regexp.MustCompile("{([a-zA-Z][a-zA-Z0-9_.]*).*}")
+	for index, part := range parts {
+		parts[index] = re.ReplaceAllString(part, "{$1}")
+	}
+
+	return strings.Join(parts, "/")
+}
+
+func renderServices(services []*descriptor.Service, paths swaggerPathsObject, reg *descriptor.Registry) error {
+	// Correctness of svcIdx and methIdx depends on 'services' containing the services in the same order as the 'file.Service' array.
+	for svcIdx, svc := range services {
+		for methIdx, meth := range svc.Methods {
+			for _, b := range meth.Bindings {
+				// Iterate over all the swagger parameters
+				parameters := swaggerParametersObject{}
+				for _, parameter := range b.PathParams {
+
+					var paramType, paramFormat string
+					switch pt := parameter.Target.GetType(); pt {
+					case pbdescriptor.FieldDescriptorProto_TYPE_GROUP, pbdescriptor.FieldDescriptorProto_TYPE_MESSAGE:
+						return fmt.Errorf("only primitive types are allowed in path parameters")
+					case pbdescriptor.FieldDescriptorProto_TYPE_ENUM:
+						paramType = fullyQualifiedNameToSwaggerName(parameter.Target.GetTypeName(), reg)
+						paramFormat = ""
+					default:
+						var ok bool
+						paramType, paramFormat, ok = primitiveSchema(pt)
+						if !ok {
+							return fmt.Errorf("unknown field type %v", pt)
+						}
+					}
+
+					parameters = append(parameters, swaggerParameterObject{
+						Name:     parameter.String(),
+						In:       "path",
+						Required: true,
+						// Parameters in gRPC-Gateway can only be strings?
+						Type:   paramType,
+						Format: paramFormat,
+					})
+				}
+				// Now check if there is a body parameter
+				if b.Body != nil {
+					var schema swaggerSchemaObject
+
+					if len(b.Body.FieldPath) == 0 {
+						schema = swaggerSchemaObject{
+							schemaCore: schemaCore{
+								Ref: fmt.Sprintf("#/definitions/%s", fullyQualifiedNameToSwaggerName(meth.RequestType.FQMN(), reg)),
+							},
+						}
+					} else {
+						lastField := b.Body.FieldPath[len(b.Body.FieldPath) - 1]
+						schema = schemaOfField(lastField.Target, reg)
+					}
+
+					desc := ""
+					if meth.GetClientStreaming() {
+						desc = "(streaming inputs)"
+					}
+					parameters = append(parameters, swaggerParameterObject{
+						Name:        "body",
+						Description: desc,
+						In:          "body",
+						Required:    true,
+						Schema: &schema,
+					})
+				}
+
+				pathItemObject, ok := paths[templateToSwaggerPath(b.PathTmpl.Template)]
+				if !ok {
+					pathItemObject = swaggerPathItemObject{}
+				}
+
+				methProtoPath := protoPathIndex(reflect.TypeOf((*pbdescriptor.ServiceDescriptorProto)(nil)), "Method")
+				desc := ""
+				if meth.GetServerStreaming() {
+					desc += "(streaming responses)"
+				}
+				operationObject := &swaggerOperationObject{
+					Tags:        []string{svc.GetName()},
+					OperationID: fmt.Sprintf("%s", meth.GetName()),
+					Parameters:  parameters,
+					Responses: swaggerResponsesObject{
+						"200": swaggerResponseObject{
+							Description: desc,
+							Schema: swaggerSchemaObject{
+								schemaCore: schemaCore{
+									Ref: fmt.Sprintf("#/definitions/%s", fullyQualifiedNameToSwaggerName(meth.ResponseType.FQMN(), reg)),
+								},
+							},
+						},
+					},
+				}
+				methComments := protoComments(reg, svc.File, nil, "Service", int32(svcIdx), methProtoPath, int32(methIdx))
+				if err := updateSwaggerDataFromComments(operationObject, methComments); err != nil {
+					panic(err)
+				}
+
+				switch b.HTTPMethod {
+				case "DELETE":
+					pathItemObject.Delete = operationObject
+					break
+				case "GET":
+					pathItemObject.Get = operationObject
+					break
+				case "POST":
+					pathItemObject.Post = operationObject
+					break
+				case "PUT":
+					pathItemObject.Put = operationObject
+					break
+				}
+				paths[templateToSwaggerPath(b.PathTmpl.Template)] = pathItemObject
+			}
+		}
+	}
+
+	// Success! return nil on the error object
+	return nil
+}
+
+// This function is called with a param which contains the entire definition of a method.
+func applyTemplate(p param) (string, error) {
+	// Create the basic template object. This is the object that everything is
+	// defined off of.
+	s := swaggerObject{
+		// Swagger 2.0 is the version of this document
+		Swagger:     "2.0",
+		Schemes:     []string{"http", "https"},
+		Consumes:    []string{"application/json"},
+		Produces:    []string{"application/json"},
+		Paths:       make(swaggerPathsObject),
+		Definitions: make(swaggerDefinitionsObject),
+		Info: swaggerInfoObject{
+			Title:   *p.File.Name,
+			Version: "version not set",
+		},
+	}
+
+	// Loops through all the services and their exposed GET/POST/PUT/DELETE definitions
+	// and create entries for all of them.
+	renderServices(p.Services, s.Paths, p.reg)
+
+	// Find all the service's messages and enumerations that are defined (recursively) and then
+	// write their request and response types out as definition objects.
+	m := messageMap{}
+	e := enumMap{}
+	findServicesMessagesAndEnumerations(p.Services, p.reg, m, e)
+	renderMessagesAsDefinition(m, s.Definitions, p.reg)
+	renderEnumerationsAsDefinition(e, s.Definitions, p.reg)
+
+	// File itself might have some comments and metadata.
+	packageProtoPath := protoPathIndex(reflect.TypeOf((*pbdescriptor.FileDescriptorProto)(nil)), "Package")
+	packageComments := protoComments(p.reg, p.File, nil, "Package", packageProtoPath)
+	if err := updateSwaggerDataFromComments(&s, packageComments); err != nil {
+		panic(err)
+	}
+
+	// We now have rendered the entire swagger object. Write the bytes out to a
+	// string so it can be written to disk.
+	var w bytes.Buffer
+	enc := json.NewEncoder(&w)
+	enc.Encode(&s)
+
+	return w.String(), nil
+}
+
+// updateSwaggerDataFromComments updates a Swagger object based on a comment
+// from the proto file.
+//
+// First paragraph of a comment is used for summary. Remaining paragraphs of a
+// comment are used for description. If 'Summary' field is not present on the
+// passed swaggerObject, the summary and description are joined by \n\n.
+//
+// If there is a field named 'Info', its 'Summary' and 'Description' fields
+// will be updated instead.
+//
+// If there is no 'Summary', the same behavior will be attempted on 'Title',
+// but only if the last character is not a period.
+func updateSwaggerDataFromComments(swaggerObject interface{}, comment string) error {
+	if len(comment) == 0 {
+		return nil
+	}
+
+	// Figure out what to apply changes to.
+	swaggerObjectValue := reflect.ValueOf(swaggerObject)
+	infoObjectValue := swaggerObjectValue.Elem().FieldByName("Info")
+	if !infoObjectValue.CanSet() {
+		// No such field? Apply summary and description directly to
+		// passed object.
+		infoObjectValue = swaggerObjectValue.Elem()
+	}
+
+	// Figure out which properties to update.
+	summaryValue := infoObjectValue.FieldByName("Summary")
+	descriptionValue := infoObjectValue.FieldByName("Description")
+	usingTitle := false
+	if !summaryValue.CanSet() {
+		summaryValue = infoObjectValue.FieldByName("Title")
+		usingTitle = true
+	}
+
+	// If there is a summary (or summary-equivalent), use the first
+	// paragraph as summary, and the rest as description.
+	if summaryValue.CanSet() {
+		paragraphs := strings.Split(comment, "\n\n")
+
+		summary := strings.TrimSpace(paragraphs[0])
+		description := strings.TrimSpace(strings.Join(paragraphs[1:], "\n\n"))
+		if !usingTitle || summary == "" || summary[len(summary)-1] != '.' {
+			if len(summary) > 0 {
+				summaryValue.Set(reflect.ValueOf(summary))
+			}
+			if len(description) > 0 {
+				if !descriptionValue.CanSet() {
+					return fmt.Errorf("Encountered object type with a summary, but no description")
+				}
+				descriptionValue.Set(reflect.ValueOf(description))
+			}
+			return nil
+		}
+	}
+
+	// There was no summary field on the swaggerObject. Try to apply the
+	// whole comment into description.
+	if descriptionValue.CanSet() {
+		descriptionValue.Set(reflect.ValueOf(comment))
+		return nil
+	}
+
+	return fmt.Errorf("No description nor summary property.")
+}
+
+func protoComments(reg *descriptor.Registry, file *descriptor.File, outers []string, typeName string, typeIndex int32, fieldPaths ...int32) string {
+	if file.SourceCodeInfo == nil {
+		// Curious! A file without any source code info.
+		// This could be a test that's providing incomplete
+		// descriptor.File information.
+		//
+		// We could simply return no comments, but panic
+		// could make debugging easier.
+		panic("descriptor.File should not contain nil SourceCodeInfo")
+	}
+
+	outerPaths := make([]int32, len(outers))
+	for i := range outers {
+		location := ""
+		if file.Package != nil {
+			location = file.GetPackage()
+		}
+
+		msg, err := reg.LookupMsg(location, strings.Join(outers[:i+1], "."))
+		if err != nil {
+			panic(err)
+		}
+		outerPaths[i] = int32(msg.Index)
+	}
+
+	for _, loc := range file.SourceCodeInfo.Location {
+		if !isProtoPathMatches(loc.Path, outerPaths, typeName, typeIndex, fieldPaths) {
+			continue
+		}
+		comments := ""
+		if loc.LeadingComments != nil {
+			comments = strings.TrimRight(*loc.LeadingComments, "\n")
+			comments = strings.TrimSpace(comments)
+			// TODO(ivucica): this is a hack to fix "// " being interpreted as "//".
+			// perhaps we should:
+			// - split by \n
+			// - determine if every (but first and last) line begins with " "
+			// - trim every line only if that is the case
+			// - join by \n
+			comments = strings.Replace(comments, "\n ", "\n", -1)
+		}
+		return comments
+	}
+	return ""
+}
+
+var messageProtoPath = protoPathIndex(reflect.TypeOf((*pbdescriptor.FileDescriptorProto)(nil)), "MessageType")
+var nestedProtoPath = protoPathIndex(reflect.TypeOf((*pbdescriptor.DescriptorProto)(nil)), "NestedType")
+var packageProtoPath = protoPathIndex(reflect.TypeOf((*pbdescriptor.FileDescriptorProto)(nil)), "Package")
+
+func isProtoPathMatches(paths []int32, outerPaths []int32, typeName string, typeIndex int32, fieldPaths []int32) bool {
+	if typeName == "Package" && typeIndex == packageProtoPath {
+		// path for package comments is just [2], and all the other processing
+		// is too complex for it.
+		if len(paths) == 0 || typeIndex != paths[0] {
+			return false
+		}
+		return true
+	}
+
+	if len(paths) != len(outerPaths)*2+2+len(fieldPaths) {
+		return false
+	}
+
+	typeNameDescriptor := reflect.TypeOf((*pbdescriptor.FileDescriptorProto)(nil))
+	if len(outerPaths) > 0 {
+		if paths[0] != messageProtoPath || paths[1] != outerPaths[0] {
+			return false
+		}
+		paths = paths[2:]
+		outerPaths = outerPaths[1:]
+
+		for i, v := range outerPaths {
+			if paths[i*2] != nestedProtoPath || paths[i*2+1] != v {
+				return false
+			}
+		}
+		paths = paths[len(outerPaths)*2:]
+
+		if typeName == "MessageType" {
+			typeName = "NestedType"
+		}
+		typeNameDescriptor = reflect.TypeOf((*pbdescriptor.DescriptorProto)(nil))
+	}
+
+	if paths[0] != protoPathIndex(typeNameDescriptor, typeName) || paths[1] != typeIndex {
+		return false
+	}
+	paths = paths[2:]
+
+	for i, v := range fieldPaths {
+		if paths[i] != v {
+			return false
+		}
+	}
+	return true
+}
+
+// protoPathIndex returns a path component for google.protobuf.descriptor.SourceCode_Location.
+//
+// Specifically, it returns an id as generated from descriptor proto which
+// can be used to determine what type the id following it in the path is.
+// For example, if we are trying to locate comments related to a field named
+// `Address` in a message named `Person`, the path will be:
+//
+//     [4, a, 2, b]
+//
+// While `a` gets determined by the order in which the messages appear in
+// the proto file, and `b` is the field index specified in the proto
+// file itself, the path actually needs to specify that `a` refers to a
+// message and not, say, a service; and  that `b` refers to a field and not
+// an option.
+//
+// protoPathIndex figures out the values 4 and 2 in the above example. Because
+// messages are top level objects, the value of 4 comes from field id for
+// `MessageType` inside `google.protobuf.descriptor.FileDescriptor` message.
+// This field has a message type `google.protobuf.descriptor.DescriptorProto`.
+// And inside message `DescriptorProto`, there is a field named `Field` with id
+// 2.
+//
+// Some code generators seem to be hardcoding these values; this method instead
+// interprets them from `descriptor.proto`-derived Go source as necessary.
+func protoPathIndex(descriptorType reflect.Type, what string) int32 {
+	field, ok := descriptorType.Elem().FieldByName(what)
+	if !ok {
+		panic(fmt.Errorf("Could not find protobuf descriptor type id for %s.", what))
+	}
+	pbtag := field.Tag.Get("protobuf")
+	if pbtag == "" {
+		panic(fmt.Errorf("No Go tag 'protobuf' on protobuf descriptor for %s.", what))
+	}
+	path, err := strconv.Atoi(strings.Split(pbtag, ",")[1])
+	if err != nil {
+		panic(fmt.Errorf("Protobuf descriptor id for %s cannot be converted to a number: %s", what, err.Error()))
+	}
+
+	return int32(path)
+}