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response_writer.go
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/
response_writer.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 bufprotoplugin
import (
"bufio"
"bytes"
"context"
"io"
"io/fs"
"unicode"
"unicode/utf8"
"github.com/bufbuild/buf/private/pkg/storage"
"go.uber.org/multierr"
"go.uber.org/zap"
"google.golang.org/protobuf/types/pluginpb"
)
type responseWriter struct {
logger *zap.Logger
}
func newResponseWriter(
logger *zap.Logger,
) *responseWriter {
return &responseWriter{
logger: logger,
}
}
func (h *responseWriter) WriteResponse(
ctx context.Context,
writeBucket storage.WriteBucket,
response *pluginpb.CodeGeneratorResponse,
options ...WriteResponseOption,
) error {
writeResponseOptions := newWriteResponseOptions()
for _, option := range options {
option(writeResponseOptions)
}
for _, file := range response.File {
if file.GetInsertionPoint() != "" {
if writeResponseOptions.insertionPointReadBucket == nil {
return &fs.PathError{Op: "stat", Path: file.GetName(), Err: fs.ErrNotExist}
}
if err := applyInsertionPoint(ctx, file, writeResponseOptions.insertionPointReadBucket, writeBucket); err != nil {
return err
}
} else if err := storage.PutPath(ctx, writeBucket, file.GetName(), []byte(file.GetContent())); err != nil {
return err
}
}
return nil
}
// applyInsertionPoint inserts the content of the given file at the insertion point that it specfiies.
// For more details on insertion points, see the following:
//
// https://github.com/protocolbuffers/protobuf/blob/f5bdd7cd56aa86612e166706ed8ef139db06edf2/src/google/protobuf/compiler/plugin.proto#L135-L171
func applyInsertionPoint(
ctx context.Context,
file *pluginpb.CodeGeneratorResponse_File,
readBucket storage.ReadBucket,
writeBucket storage.WriteBucket,
) (retErr error) {
targetReadObjectCloser, err := readBucket.Get(ctx, file.GetName())
if err != nil {
return err
}
defer func() {
retErr = multierr.Append(retErr, targetReadObjectCloser.Close())
}()
resultData, err := writeInsertionPoint(ctx, file, targetReadObjectCloser)
if err != nil {
return err
}
// This relies on storageos buckets maintaining existing file permissions
return storage.PutPath(ctx, writeBucket, file.GetName(), resultData)
}
// writeInsertionPoint writes the insertion point defined in insertionPointFile
// to the targetFile and returns the result as []byte. The caller must ensure the
// provided targetFile matches the file requested in insertionPointFile.Name.
func writeInsertionPoint(
ctx context.Context,
insertionPointFile *pluginpb.CodeGeneratorResponse_File,
targetFile io.Reader,
) (_ []byte, retErr error) {
targetScanner := bufio.NewScanner(targetFile)
match := []byte("@@protoc_insertion_point(" + insertionPointFile.GetInsertionPoint() + ")")
postInsertionContent := bytes.NewBuffer(nil)
postInsertionContent.Grow(averageGeneratedFileSize)
// TODO: We should respect the line endings in the generated file. This would
// require either targetFile being an io.ReadSeeker and in the worst case
// doing 2 full scans of the file (if it is a single line), or implementing
// bufio.Scanner.Scan() inline
newline := []byte{'\n'}
for targetScanner.Scan() {
targetLine := targetScanner.Bytes()
if !bytes.Contains(targetLine, match) {
// these writes cannot fail, they will panic if they cannot
// allocate
_, _ = postInsertionContent.Write(targetLine)
_, _ = postInsertionContent.Write(newline)
continue
}
// For each line in then new content, apply the
// same amount of whitespace. This is important
// for specific languages, e.g. Python.
whitespace := leadingWhitespace(targetLine)
// Create another scanner so that we can seamlessly handle
// newlines in a platform-agnostic manner.
insertedContentScanner := bufio.NewScanner(bytes.NewBufferString(insertionPointFile.GetContent()))
insertedContent := scanWithPrefixAndLineEnding(insertedContentScanner, whitespace, newline)
// This write cannot fail, it will panic if it cannot
// allocate
_, _ = postInsertionContent.Write(insertedContent)
// Code inserted at this point is placed immediately
// above the line containing the insertion point, so
// we include it last.
// These writes cannot fail, they will panic if they cannot
// allocate
_, _ = postInsertionContent.Write(targetLine)
_, _ = postInsertionContent.Write(newline)
}
if err := targetScanner.Err(); err != nil {
return nil, err
}
// trim the trailing newline
postInsertionBytes := postInsertionContent.Bytes()
return postInsertionBytes[:len(postInsertionBytes)-1], nil
}
// leadingWhitespace iterates through the given string,
// and returns the leading whitespace substring, if any,
// respecting utf-8 encoding.
//
// leadingWhitespace("\u205F foo ") -> "\u205F "
func leadingWhitespace(buf []byte) []byte {
leadingSize := 0
iterBuf := buf
for len(iterBuf) > 0 {
r, size := utf8.DecodeRune(iterBuf)
// protobuf strings must always be valid UTF8
// https://developers.google.com/protocol-buffers/docs/proto3#scalar
// Additionally, utf8.RuneError is not a space so we'll terminate
// and return the leading, valid, UTF8 whitespace sequence.
if !unicode.IsSpace(r) {
out := make([]byte, leadingSize)
copy(out, buf)
return out
}
leadingSize += size
iterBuf = iterBuf[size:]
}
return buf
}
// scanWithPrefixAndLineEnding iterates over each of the given scanner's lines
// prepends prefix, and appends the newline sequence.
func scanWithPrefixAndLineEnding(scanner *bufio.Scanner, prefix []byte, newline []byte) []byte {
result := bytes.NewBuffer(nil)
result.Grow(averageInsertionPointSize)
for scanner.Scan() {
// These writes cannot fail, they will panic if they cannot
// allocate
_, _ = result.Write(prefix)
_, _ = result.Write(scanner.Bytes())
_, _ = result.Write(newline)
}
return result.Bytes()
}
type writeResponseOptions struct {
insertionPointReadBucket storage.ReadBucket
}
func newWriteResponseOptions() *writeResponseOptions {
return &writeResponseOptions{}
}