Support breakpoint debugger integrated to IDEs

This commit adds the IDE-integrated breakpoint debugger based on walker.
Now buildx provides DAP (Debug Adapter Protocol) API to IDEs so DAP-aware IDEs
can call buildx and allow users to perform breakpoint-based debugging on the
IDE's UI/UX.

Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>

vendor/github.com/google/go-dap/LICENSE

@@ -0,0 +1,202 @@
+
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vendor/github.com/google/go-dap/README.md

@@ -0,0 +1,20 @@
+# go-dap: Go implementation of the Debug Adapter Protocol
+
+[![PkgGoDev](https://pkg.go.dev/badge/github.com/google/go-dap)](https://pkg.go.dev/github.com/google/go-dap)
+[![Build Status](https://github.com/google/go-dap/actions/workflows/go.yml/badge.svg?branch=master)](https://github.com/google/go-dap/actions)
+[![Go Report Card](https://goreportcard.com/badge/github.com/google/go-dap)](https://goreportcard.com/report/github.com/google/go-dap)
+
+For an overview of DAP, see
+https://microsoft.github.io/debug-adapter-protocol/overview
+
+## Contributing
+
+We'd love to accept your patches and contributions to this project. See
+[docs/contributing](https://github.com/google/go-dap/blob/master/docs/contributing.md)
+for more details.
+
+## License
+
+This project is licensed under the Apache License 2.0
+
+This is not an officially supported Google product.

vendor/github.com/google/go-dap/codec.go

@@ -0,0 +1,111 @@
+// Copyright 2020 Google LLC
+//
+// 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
+//
+//     https://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.
+
+// This file contains utilities for decoding JSON-encoded bytes into DAP message.
+
+package dap
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+// DecodeProtocolMessageFieldError describes which JSON attribute
+// has an unsupported value that the decoding cannot handle.
+type DecodeProtocolMessageFieldError struct {
+	Seq        int
+	SubType    string
+	FieldName  string
+	FieldValue string
+}
+
+func (e *DecodeProtocolMessageFieldError) Error() string {
+	return fmt.Sprintf("%s %s '%s' is not supported (seq: %d)", e.SubType, e.FieldName, e.FieldValue, e.Seq)
+}
+
+// DecodeProtocolMessage parses the JSON-encoded data and returns the result of
+// the appropriate type within the ProtocolMessage hierarchy. If message type,
+// command, etc cannot be cast, returns DecodeProtocolMessageFieldError.
+// See also godoc for json.Unmarshal, which is used for underlying decoding.
+func DecodeProtocolMessage(data []byte) (Message, error) {
+	var protomsg ProtocolMessage
+	if err := json.Unmarshal(data, &protomsg); err != nil {
+		return nil, err
+	}
+	switch protomsg.Type {
+	case "request":
+		return decodeRequest(data)
+	case "response":
+		return decodeResponse(data)
+	case "event":
+		return decodeEvent(data)
+	default:
+		return nil, &DecodeProtocolMessageFieldError{protomsg.GetSeq(), "ProtocolMessage", "type", protomsg.Type}
+	}
+}
+
+type messageCtor func() Message
+
+// decodeRequest determines what request type in the ProtocolMessage hierarchy
+// data corresponds to and uses json.Unmarshal to populate the corresponding
+// struct to be returned.
+func decodeRequest(data []byte) (Message, error) {
+	var r Request
+	if err := json.Unmarshal(data, &r); err != nil {
+		return nil, err
+	}
+	if ctor, ok := requestCtor[r.Command]; ok {
+		requestPtr := ctor()
+		err := json.Unmarshal(data, requestPtr)
+		return requestPtr, err
+	}
+	return nil, &DecodeProtocolMessageFieldError{r.GetSeq(), "Request", "command", r.Command}
+}
+
+// decodeResponse determines what response type in the ProtocolMessage hierarchy
+// data corresponds to and uses json.Unmarshal to populate the corresponding
+// struct to be returned.
+func decodeResponse(data []byte) (Message, error) {
+	var r Response
+	if err := json.Unmarshal(data, &r); err != nil {
+		return nil, err
+	}
+	if !r.Success {
+		var er ErrorResponse
+		err := json.Unmarshal(data, &er)
+		return &er, err
+	}
+	if ctor, ok := responseCtor[r.Command]; ok {
+		responsePtr := ctor()
+		err := json.Unmarshal(data, responsePtr)
+		return responsePtr, err
+	}
+	return nil, &DecodeProtocolMessageFieldError{r.GetSeq(), "Response", "command", r.Command}
+}
+
+// decodeEvent determines what event type in the ProtocolMessage hierarchy
+// data corresponds to and uses json.Unmarshal to populate the corresponding
+// struct to be returned.
+func decodeEvent(data []byte) (Message, error) {
+	var e Event
+	if err := json.Unmarshal(data, &e); err != nil {
+		return nil, err
+	}
+	if ctor, ok := eventCtor[e.Event]; ok {
+		eventPtr := ctor()
+		err := json.Unmarshal(data, eventPtr)
+		return eventPtr, err
+	}
+	return nil, &DecodeProtocolMessageFieldError{e.GetSeq(), "Event", "event", e.Event}
+}

vendor/github.com/google/go-dap/doc.go

@@ -0,0 +1,20 @@
+// Copyright 2021 Google LLC
+//
+// 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
+//
+//     https://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 dap contains data types and code for Debug Adapter Protocol (DAP) specification.
+// https://github.com/microsoft/vscode-debugadapter-node/blob/main/debugProtocol.json
+package dap
+
+//go:generate go run ./cmd/gentypes/gentypes.go -o schematypes.go -u cmd/gentypes/debugProtocol.json
+

vendor/github.com/google/go-dap/io.go

@@ -0,0 +1,137 @@
+// Copyright 2020 Google LLC
+//
+// 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
+//
+//     https://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.
+
+// This file contains utilities for DAP Base protocol I/O.
+// For additional information, see "Base protocol" section in
+// https://microsoft.github.io/debug-adapter-protocol/overview.
+
+package dap
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"io"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// BaseProtocolError represents base protocol error, which occurs when the raw
+// message does not conform to the header+content format of the base protocol.
+type BaseProtocolError struct {
+	Err string
+}
+
+func (bpe *BaseProtocolError) Error() string { return bpe.Err }
+
+var (
+	// ErrHeaderDelimiterNotCrLfCrLf is returned when only partial header
+	// delimiter \r\n\r\n is encountered.
+	ErrHeaderDelimiterNotCrLfCrLf = &BaseProtocolError{fmt.Sprintf("header delimiter is not %q", crLfcrLf)}
+
+	// ErrHeaderNotContentLength is returned when the parsed header is
+	// not of valid Content-Length format.
+	ErrHeaderNotContentLength = &BaseProtocolError{fmt.Sprintf("header format is not %q", contentLengthHeaderRegex)}
+
+	// ErrHeaderContentTooLong is returned when the content length specified in
+	// the header is above contentMaxLength.
+	ErrHeaderContentTooLong = &BaseProtocolError{fmt.Sprintf("content length over %v bytes", contentMaxLength)}
+)
+
+const (
+	crLfcrLf               = "\r\n\r\n"
+	contentLengthHeaderFmt = "Content-Length: %d\r\n\r\n"
+	contentMaxLength       = 4 * 1024 * 1024
+)
+
+var (
+	contentLengthHeaderRegex = regexp.MustCompile("^Content-Length: ([0-9]+)$")
+)
+
+// WriteBaseMessage formats content with Content-Length header and delimiters
+// as per the base protocol and writes the resulting message to w.
+func WriteBaseMessage(w io.Writer, content []byte) error {
+	header := fmt.Sprintf(contentLengthHeaderFmt, len(content))
+	if _, err := w.Write([]byte(header)); err != nil {
+		return err
+	}
+	_, err := w.Write(content)
+	return err
+}
+
+// ReadBaseMessage reads one message from r consisting of a Content-Length
+// header and a content part. It parses the header to determine the size of
+// the content part and extracts and returns the actual content of the message.
+// Returns nil bytes on error, which can be one of the standard IO errors or
+// a BaseProtocolError defined in this package.
+func ReadBaseMessage(r *bufio.Reader) ([]byte, error) {
+	contentLength, err := readContentLengthHeader(r)
+	if err != nil {
+		return nil, err
+	}
+	if contentLength > contentMaxLength {
+		return nil, ErrHeaderContentTooLong
+	}
+	content := make([]byte, contentLength)
+	if _, err = io.ReadFull(r, content); err != nil {
+		return nil, err
+	}
+	return content, nil
+}
+
+// readContentLengthHeader looks for the only header field that is supported
+// and required:
+// 		Content-Length: [0-9]+\r\n\r\n
+// Extracts and returns the content length.
+func readContentLengthHeader(r *bufio.Reader) (contentLength int64, err error) {
+	// Look for <some header>\r\n\r\n
+	headerWithCr, err := r.ReadString('\r')
+	if err != nil {
+		return 0, err
+	}
+	nextThree := make([]byte, 3)
+	if _, err = io.ReadFull(r, nextThree); err != nil {
+		return 0, err
+	}
+	if string(nextThree) != "\n\r\n" {
+		return 0, ErrHeaderDelimiterNotCrLfCrLf
+	}
+
+	// If header is in the right format, get the length
+	header := strings.TrimSuffix(headerWithCr, "\r")
+	headerAndLength := contentLengthHeaderRegex.FindStringSubmatch(header)
+	if len(headerAndLength) < 2 {
+		return 0, ErrHeaderNotContentLength
+	}
+	return strconv.ParseInt(headerAndLength[1], 10, 64)
+}
+
+// WriteProtocolMessage encodes message and writes it to w.
+func WriteProtocolMessage(w io.Writer, message Message) error {
+	b, err := json.Marshal(message)
+	if err != nil {
+		return err
+	}
+	return WriteBaseMessage(w, b)
+}
+
+// ReadProtocolMessage reads a message from r, decodes and returns it.
+func ReadProtocolMessage(r *bufio.Reader) (Message, error) {
+	content, err := ReadBaseMessage(r)
+	if err != nil {
+		return nil, err
+	}
+	return DecodeProtocolMessage(content)
+}