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strip_legacy_options.go
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strip_legacy_options.go
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// Copyright 2020-2024 Buf Technologies, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package protoencoding
import (
"fmt"
"google.golang.org/protobuf/proto"
"google.golang.org/protobuf/types/descriptorpb"
)
// stripLegacyOptions modifies the given slice of file descriptors so that the slice does
// not contain legacy elements that the Go protobuf runtime does not support -- namely
// messages that use the message set wire format (and any extensions whose tags are too
// high to use outside of message set wire format) and weak fields.
//
// It does this by simply clearing any message_set_wire_format message options and weak
// field options encountered, by omitting extensions whose tags are too high, and by
// modifying extension ranges with numbers that are too high (which means omitting
// ranges whose start value is too high).
//
// This does not actually mutate the given descriptors (though it will mutate the given
// slice). If any of the descriptors needs to be modified, it is first cloned and its
// replacement will be stored in the slice. So it is safe to provide descriptor protos
// that are potentially shared with/referenced from other state.
func stripLegacyOptions(files []*descriptorpb.FileDescriptorProto) error {
for i, file := range files {
newDescriptor, err := stripLegacyOptionsFromFile(file)
if err != nil {
return err
}
if newDescriptor != nil {
files[i] = newDescriptor
}
}
return nil
}
// stripLegacyOptionsFromFile strips legacy options from the given file descriptor.
// If none are encountered this returns nil to indicate no changes were made. Otherwise,
// it returns a clone of file with legacy options removed.
func stripLegacyOptionsFromFile(file *descriptorpb.FileDescriptorProto) (*descriptorpb.FileDescriptorProto, error) {
var cloned bool
for i, message := range file.MessageType {
newDescriptor, err := stripLegacyOptionsFromMessage(message)
if err != nil {
return nil, err
}
if newDescriptor == nil {
continue
}
if !cloned {
newFile, err := clone(file)
if err != nil {
return nil, err
}
file = newFile
cloned = true
}
file.MessageType[i] = newDescriptor
}
newExts, err := stripLegacyOptionsFromExtensions(file.Extension)
if err != nil {
return nil, err
}
if newExts != nil {
if !cloned {
newFile, err := clone(file)
if err != nil {
return nil, err
}
file = newFile
cloned = true
}
file.Extension = newExts
}
if cloned {
return file, nil
}
return nil, nil // nothing changed
}
// stripLegacyOptionsFromMessage strips legacy options from the given message descriptor.
// If none are encountered this returns nil to indicate no changes were made. Otherwise,
// it returns a clone of message with legacy options removed.
func stripLegacyOptionsFromMessage(message *descriptorpb.DescriptorProto) (*descriptorpb.DescriptorProto, error) {
var cloned bool
if message.GetOptions().GetMessageSetWireFormat() {
// Strip this option since the Go runtime does not support
// creating protoreflect.Descriptor instances with this set.
newMessage, err := clone(message)
if err != nil {
return nil, err
}
message = newMessage
cloned = true
message.Options.MessageSetWireFormat = nil
}
for i, field := range message.Field {
newDescriptor, err := stripLegacyOptionsFromField(field)
if err != nil {
return nil, err
}
if newDescriptor == nil {
continue
}
if !cloned {
newMessage, err := clone(message)
if err != nil {
return nil, err
}
message = newMessage
cloned = true
}
message.Field[i] = newDescriptor
}
for i, nested := range message.NestedType {
newDescriptor, err := stripLegacyOptionsFromMessage(nested)
if err != nil {
return nil, err
}
if newDescriptor == nil {
continue
}
if !cloned {
newMessage, err := clone(message)
if err != nil {
return nil, err
}
message = newMessage
cloned = true
}
message.NestedType[i] = newDescriptor
}
newExtRanges, err := stripLegacyOptionsFromExtensionRanges(message.ExtensionRange)
if err != nil {
return nil, err
}
if newExtRanges != nil {
if !cloned {
newMessage, err := clone(message)
if err != nil {
return nil, err
}
message = newMessage
cloned = true
}
message.ExtensionRange = newExtRanges
}
newExts, err := stripLegacyOptionsFromExtensions(message.Extension)
if err != nil {
return nil, err
}
if newExts != nil {
if !cloned {
newMessage, err := clone(message)
if err != nil {
return nil, err
}
message = newMessage
cloned = true
}
message.Extension = newExts
}
if cloned {
return message, nil
}
return nil, nil // nothing changed
}
// stripLegacyOptionsFromField strips legacy options from the given field descriptor.
// If none are encountered this returns nil to indicate no changes were made. Otherwise,
// it returns a clone of field with legacy options removed.
func stripLegacyOptionsFromField(field *descriptorpb.FieldDescriptorProto) (*descriptorpb.FieldDescriptorProto, error) {
if !field.GetOptions().GetWeak() {
return nil, nil
}
// Strip this option since the Go runtime does not support
// creating protoreflect.Descriptor instances with this set.
// Buf CLI doesn't actually support weak dependencies, so
// there should be no practical consequences of removing this.
newField, err := clone(field)
if err != nil {
return nil, err
}
newField.Options.Weak = nil
return newField, nil
}
// stripLegacyOptionsFromExtensions strips legacy options and values from the
// given slice of extension descriptor. If none are encountered this returns
// nil to indicate no changes were made. Otherwise, it returns a new slice
// that omits invalid legacy extensions (those whose tag number is too high
// because they extended a message with message set wire format) and replaces
// items that had legacy options with clones that have the options removed.
func stripLegacyOptionsFromExtensions(exts []*descriptorpb.FieldDescriptorProto) ([]*descriptorpb.FieldDescriptorProto, error) {
// We leave this nil unless we are actually changing the extensions
// (by removing one with a tag that is too high are or by stripping
// the weak option from one).
var newExts []*descriptorpb.FieldDescriptorProto
for i, ext := range exts {
// Message-set extensions could be out of range. We simply remove them.
// This could possibly
if ext.GetNumber() > maxTagNumber {
if newExts == nil {
// initialize to everything so far except current item (which we're dropping)
newExts = make([]*descriptorpb.FieldDescriptorProto, i, len(exts)-1)
copy(newExts, exts)
}
continue
}
newDescriptor, err := stripLegacyOptionsFromField(ext)
if err != nil {
return nil, err
}
if newDescriptor != nil {
if newExts == nil {
// initialize to everything so far except current item (that we're replacing)
newExts = make([]*descriptorpb.FieldDescriptorProto, i, len(exts))
copy(newExts, exts)
}
newExts = append(newExts, newDescriptor)
continue
}
if newExts != nil {
newExts = append(newExts, ext)
}
}
return newExts, nil
}
// stripLegacyOptionsFromExtensionRanges strips legacy values from the given
// slice of extension descriptor. If none are encountered this returns nil
// to indicate no changes were made. Otherwise, it returns a new slice that
// is updated to exclude invalid legacy extension ranges (those referencing
// tag numbers that are too high because they extended a message with message
// set wire format). If an extension range has a start tag that is too high,
// it is omitted entirely. If it has an end tag that is too high, the end tag
// is changed to the maximum valid end tag.
func stripLegacyOptionsFromExtensionRanges(extRanges []*descriptorpb.DescriptorProto_ExtensionRange) ([]*descriptorpb.DescriptorProto_ExtensionRange, error) {
// We leave this nil unless we are actually changing the extensions
// (by removing one with a tag that is too high are or by stripping
// the weak option from one).
var newExtRanges []*descriptorpb.DescriptorProto_ExtensionRange
for i, extRange := range extRanges {
// Message-set extensions could be out of range. We simply remove them.
// This could possibly
if extRange.GetStart() > maxTagNumber {
if newExtRanges == nil {
// initialize to everything so far except current item (which we're dropping)
newExtRanges = make([]*descriptorpb.DescriptorProto_ExtensionRange, i, len(extRanges)-1)
copy(newExtRanges, extRanges)
}
continue
}
if extRange.GetEnd() > maxTagNumber+1 /* extension range end is exclusive */ {
newExtRange, err := clone(extRange)
if err != nil {
return nil, err
}
newExtRange.End = proto.Int32(maxTagNumber + 1)
if newExtRanges == nil {
// initialize to everything so far except current item (that we're replacing)
newExtRanges = make([]*descriptorpb.DescriptorProto_ExtensionRange, i, len(extRanges))
copy(newExtRanges, extRanges)
}
newExtRanges = append(newExtRanges, newExtRange)
continue
}
if newExtRanges != nil {
newExtRanges = append(newExtRanges, extRange)
}
}
return newExtRanges, nil
}
func clone[M proto.Message](message M) (M, error) {
clone := proto.Clone(message)
newMessage, isFileProto := clone.(M)
if !isFileProto {
var zero M
return zero, fmt.Errorf("proto.Clone returned unexpected value: %T instead of %T", clone, message)
}
return newMessage, nil
}