// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// This file enables an external tool to intercept package requests.
// If the tool is present then its results are used in preference to
// the go list command.
package packages
import (
"bytes"
"encoding/json"
"fmt"
"os/exec"
"strings"
)
// Driver
type driverRequest struct {
Command string `json:"command"`
Mode LoadMode `json:"mode"`
Env []string `json:"env"`
BuildFlags []string `json:"build_flags"`
Tests bool `json:"tests"`
Overlay map[string][]byte `json:"overlay"`
}
// findExternalDriver returns the file path of a tool that supplies
// the build system package structure, or "" if not found."
// If GOPACKAGESDRIVER is set in the environment findExternalTool returns its
// value, otherwise it searches for a binary named gopackagesdriver on the PATH.
func findExternalDriver(cfg *Config) driver {
const toolPrefix = "GOPACKAGESDRIVER="
tool := ""
for _, env := range cfg.Env {
if val := strings.TrimPrefix(env, toolPrefix); val != env {
tool = val
}
}
if tool != "" && tool == "off" {
return nil
}
if tool == "" {
var err error
tool, err = exec.LookPath("gopackagesdriver")
if err != nil {
return nil
}
}
return func(cfg *Config, words ...string) (*driverResponse, error) {
req, err := json.Marshal(driverRequest{
Mode: cfg.Mode,
Env: cfg.Env,
BuildFlags: cfg.BuildFlags,
Tests: cfg.Tests,
Overlay: cfg.Overlay,
})
if err != nil {
return nil, fmt.Errorf("failed to encode message to driver tool: %v", err)
}
buf := new(bytes.Buffer)
cmd := exec.CommandContext(cfg.Context, tool, words...)
cmd.Dir = cfg.Dir
cmd.Env = cfg.Env
cmd.Stdin = bytes.NewReader(req)
cmd.Stdout = buf
cmd.Stderr = new(bytes.Buffer)
if err := cmd.Run(); err != nil {
return nil, fmt.Errorf("%v: %v: %s", tool, err, cmd.Stderr)
}
var response driverResponse
if err := json.Unmarshal(buf.Bytes(), &response); err != nil {
return nil, err
}
return &response, nil
}
}
