1// Copyright 2018 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// Package protodesc provides functionality for converting
6// FileDescriptorProto messages to/from protoreflect.FileDescriptor values.
7//
8// The google.protobuf.FileDescriptorProto is a protobuf message that describes
9// the type information for a .proto file in a form that is easily serializable.
10// The protoreflect.FileDescriptor is a more structured representation of
11// the FileDescriptorProto message where references and remote dependencies
12// can be directly followed.
13package protodesc
14
15import (
16	"google.golang.org/protobuf/internal/errors"
17	"google.golang.org/protobuf/internal/filedesc"
18	"google.golang.org/protobuf/internal/pragma"
19	"google.golang.org/protobuf/internal/strs"
20	"google.golang.org/protobuf/proto"
21	"google.golang.org/protobuf/reflect/protoreflect"
22	"google.golang.org/protobuf/reflect/protoregistry"
23
24	"google.golang.org/protobuf/types/descriptorpb"
25)
26
27// Resolver is the resolver used by NewFile to resolve dependencies.
28// The enums and messages provided must belong to some parent file,
29// which is also registered.
30//
31// It is implemented by protoregistry.Files.
32type Resolver interface {
33	FindFileByPath(string) (protoreflect.FileDescriptor, error)
34	FindDescriptorByName(protoreflect.FullName) (protoreflect.Descriptor, error)
35}
36
37// FileOptions configures the construction of file descriptors.
38type FileOptions struct {
39	pragma.NoUnkeyedLiterals
40
41	// AllowUnresolvable configures New to permissively allow unresolvable
42	// file, enum, or message dependencies. Unresolved dependencies are replaced
43	// by placeholder equivalents.
44	//
45	// The following dependencies may be left unresolved:
46	//	• Resolving an imported file.
47	//	• Resolving the type for a message field or extension field.
48	//	If the kind of the field is unknown, then a placeholder is used for both
49	//	the Enum and Message accessors on the protoreflect.FieldDescriptor.
50	//	• Resolving an enum value set as the default for an optional enum field.
51	//	If unresolvable, the protoreflect.FieldDescriptor.Default is set to the
52	//	first value in the associated enum (or zero if the also enum dependency
53	//	is also unresolvable). The protoreflect.FieldDescriptor.DefaultEnumValue
54	//	is populated with a placeholder.
55	//	• Resolving the extended message type for an extension field.
56	//	• Resolving the input or output message type for a service method.
57	//
58	// If the unresolved dependency uses a relative name,
59	// then the placeholder will contain an invalid FullName with a "*." prefix,
60	// indicating that the starting prefix of the full name is unknown.
61	AllowUnresolvable bool
62}
63
64// NewFile creates a new protoreflect.FileDescriptor from the provided
65// file descriptor message. See FileOptions.New for more information.
66func NewFile(fd *descriptorpb.FileDescriptorProto, r Resolver) (protoreflect.FileDescriptor, error) {
67	return FileOptions{}.New(fd, r)
68}
69
70// NewFiles creates a new protoregistry.Files from the provided
71// FileDescriptorSet message. See FileOptions.NewFiles for more information.
72func NewFiles(fd *descriptorpb.FileDescriptorSet) (*protoregistry.Files, error) {
73	return FileOptions{}.NewFiles(fd)
74}
75
76// New creates a new protoreflect.FileDescriptor from the provided
77// file descriptor message. The file must represent a valid proto file according
78// to protobuf semantics. The returned descriptor is a deep copy of the input.
79//
80// Any imported files, enum types, or message types referenced in the file are
81// resolved using the provided registry. When looking up an import file path,
82// the path must be unique. The newly created file descriptor is not registered
83// back into the provided file registry.
84func (o FileOptions) New(fd *descriptorpb.FileDescriptorProto, r Resolver) (protoreflect.FileDescriptor, error) {
85	if r == nil {
86		r = (*protoregistry.Files)(nil) // empty resolver
87	}
88
89	// Handle the file descriptor content.
90	f := &filedesc.File{L2: &filedesc.FileL2{}}
91	switch fd.GetSyntax() {
92	case "proto2", "":
93		f.L1.Syntax = protoreflect.Proto2
94	case "proto3":
95		f.L1.Syntax = protoreflect.Proto3
96	default:
97		return nil, errors.New("invalid syntax: %q", fd.GetSyntax())
98	}
99	f.L1.Path = fd.GetName()
100	if f.L1.Path == "" {
101		return nil, errors.New("file path must be populated")
102	}
103	f.L1.Package = protoreflect.FullName(fd.GetPackage())
104	if !f.L1.Package.IsValid() && f.L1.Package != "" {
105		return nil, errors.New("invalid package: %q", f.L1.Package)
106	}
107	if opts := fd.GetOptions(); opts != nil {
108		opts = proto.Clone(opts).(*descriptorpb.FileOptions)
109		f.L2.Options = func() protoreflect.ProtoMessage { return opts }
110	}
111
112	f.L2.Imports = make(filedesc.FileImports, len(fd.GetDependency()))
113	for _, i := range fd.GetPublicDependency() {
114		if !(0 <= i && int(i) < len(f.L2.Imports)) || f.L2.Imports[i].IsPublic {
115			return nil, errors.New("invalid or duplicate public import index: %d", i)
116		}
117		f.L2.Imports[i].IsPublic = true
118	}
119	for _, i := range fd.GetWeakDependency() {
120		if !(0 <= i && int(i) < len(f.L2.Imports)) || f.L2.Imports[i].IsWeak {
121			return nil, errors.New("invalid or duplicate weak import index: %d", i)
122		}
123		f.L2.Imports[i].IsWeak = true
124	}
125	imps := importSet{f.Path(): true}
126	for i, path := range fd.GetDependency() {
127		imp := &f.L2.Imports[i]
128		f, err := r.FindFileByPath(path)
129		if err == protoregistry.NotFound && (o.AllowUnresolvable || imp.IsWeak) {
130			f = filedesc.PlaceholderFile(path)
131		} else if err != nil {
132			return nil, errors.New("could not resolve import %q: %v", path, err)
133		}
134		imp.FileDescriptor = f
135
136		if imps[imp.Path()] {
137			return nil, errors.New("already imported %q", path)
138		}
139		imps[imp.Path()] = true
140	}
141	for i := range fd.GetDependency() {
142		imp := &f.L2.Imports[i]
143		imps.importPublic(imp.Imports())
144	}
145
146	// Handle source locations.
147	f.L2.Locations.File = f
148	for _, loc := range fd.GetSourceCodeInfo().GetLocation() {
149		var l protoreflect.SourceLocation
150		// TODO: Validate that the path points to an actual declaration?
151		l.Path = protoreflect.SourcePath(loc.GetPath())
152		s := loc.GetSpan()
153		switch len(s) {
154		case 3:
155			l.StartLine, l.StartColumn, l.EndLine, l.EndColumn = int(s[0]), int(s[1]), int(s[0]), int(s[2])
156		case 4:
157			l.StartLine, l.StartColumn, l.EndLine, l.EndColumn = int(s[0]), int(s[1]), int(s[2]), int(s[3])
158		default:
159			return nil, errors.New("invalid span: %v", s)
160		}
161		// TODO: Validate that the span information is sensible?
162		// See https://github.com/protocolbuffers/protobuf/issues/6378.
163		if false && (l.EndLine < l.StartLine || l.StartLine < 0 || l.StartColumn < 0 || l.EndColumn < 0 ||
164			(l.StartLine == l.EndLine && l.EndColumn <= l.StartColumn)) {
165			return nil, errors.New("invalid span: %v", s)
166		}
167		l.LeadingDetachedComments = loc.GetLeadingDetachedComments()
168		l.LeadingComments = loc.GetLeadingComments()
169		l.TrailingComments = loc.GetTrailingComments()
170		f.L2.Locations.List = append(f.L2.Locations.List, l)
171	}
172
173	// Step 1: Allocate and derive the names for all declarations.
174	// This copies all fields from the descriptor proto except:
175	//	google.protobuf.FieldDescriptorProto.type_name
176	//	google.protobuf.FieldDescriptorProto.default_value
177	//	google.protobuf.FieldDescriptorProto.oneof_index
178	//	google.protobuf.FieldDescriptorProto.extendee
179	//	google.protobuf.MethodDescriptorProto.input
180	//	google.protobuf.MethodDescriptorProto.output
181	var err error
182	sb := new(strs.Builder)
183	r1 := make(descsByName)
184	if f.L1.Enums.List, err = r1.initEnumDeclarations(fd.GetEnumType(), f, sb); err != nil {
185		return nil, err
186	}
187	if f.L1.Messages.List, err = r1.initMessagesDeclarations(fd.GetMessageType(), f, sb); err != nil {
188		return nil, err
189	}
190	if f.L1.Extensions.List, err = r1.initExtensionDeclarations(fd.GetExtension(), f, sb); err != nil {
191		return nil, err
192	}
193	if f.L1.Services.List, err = r1.initServiceDeclarations(fd.GetService(), f, sb); err != nil {
194		return nil, err
195	}
196
197	// Step 2: Resolve every dependency reference not handled by step 1.
198	r2 := &resolver{local: r1, remote: r, imports: imps, allowUnresolvable: o.AllowUnresolvable}
199	if err := r2.resolveMessageDependencies(f.L1.Messages.List, fd.GetMessageType()); err != nil {
200		return nil, err
201	}
202	if err := r2.resolveExtensionDependencies(f.L1.Extensions.List, fd.GetExtension()); err != nil {
203		return nil, err
204	}
205	if err := r2.resolveServiceDependencies(f.L1.Services.List, fd.GetService()); err != nil {
206		return nil, err
207	}
208
209	// Step 3: Validate every enum, message, and extension declaration.
210	if err := validateEnumDeclarations(f.L1.Enums.List, fd.GetEnumType()); err != nil {
211		return nil, err
212	}
213	if err := validateMessageDeclarations(f.L1.Messages.List, fd.GetMessageType()); err != nil {
214		return nil, err
215	}
216	if err := validateExtensionDeclarations(f.L1.Extensions.List, fd.GetExtension()); err != nil {
217		return nil, err
218	}
219
220	return f, nil
221}
222
223type importSet map[string]bool
224
225func (is importSet) importPublic(imps protoreflect.FileImports) {
226	for i := 0; i < imps.Len(); i++ {
227		if imp := imps.Get(i); imp.IsPublic {
228			is[imp.Path()] = true
229			is.importPublic(imp.Imports())
230		}
231	}
232}
233
234// NewFiles creates a new protoregistry.Files from the provided
235// FileDescriptorSet message. The descriptor set must include only
236// valid files according to protobuf semantics. The returned descriptors
237// are a deep copy of the input.
238func (o FileOptions) NewFiles(fds *descriptorpb.FileDescriptorSet) (*protoregistry.Files, error) {
239	files := make(map[string]*descriptorpb.FileDescriptorProto)
240	for _, fd := range fds.File {
241		if _, ok := files[fd.GetName()]; ok {
242			return nil, errors.New("file appears multiple times: %q", fd.GetName())
243		}
244		files[fd.GetName()] = fd
245	}
246	r := &protoregistry.Files{}
247	for _, fd := range files {
248		if err := o.addFileDeps(r, fd, files); err != nil {
249			return nil, err
250		}
251	}
252	return r, nil
253}
254func (o FileOptions) addFileDeps(r *protoregistry.Files, fd *descriptorpb.FileDescriptorProto, files map[string]*descriptorpb.FileDescriptorProto) error {
255	// Set the entry to nil while descending into a file's dependencies to detect cycles.
256	files[fd.GetName()] = nil
257	for _, dep := range fd.Dependency {
258		depfd, ok := files[dep]
259		if depfd == nil {
260			if ok {
261				return errors.New("import cycle in file: %q", dep)
262			}
263			continue
264		}
265		if err := o.addFileDeps(r, depfd, files); err != nil {
266			return err
267		}
268	}
269	// Delete the entry once dependencies are processed.
270	delete(files, fd.GetName())
271	f, err := o.New(fd, r)
272	if err != nil {
273		return err
274	}
275	return r.RegisterFile(f)
276}
277