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// Copyright 2020 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.
// Package gocommand is a helper for calling the go command.
package gocommand
import (
"bytes"
"context"
"fmt"
"io"
"os"
"os/exec"
"regexp"
"strconv"
"strings"
"sync"
"time"
"golang.org/x/tools/internal/event"
)
// An Runner will run go command invocations and serialize
// them if it sees a concurrency error.
type Runner struct {
// once guards the runner initialization.
once sync.Once
// inFlight tracks available workers.
inFlight chan struct{}
// serialized guards the ability to run a go command serially,
// to avoid deadlocks when claiming workers.
serialized chan struct{}
}
const maxInFlight = 10
func (runner *Runner) initialize() {
runner.once.Do(func() {
runner.inFlight = make(chan struct{}, maxInFlight)
runner.serialized = make(chan struct{}, 1)
})
}
// 1.13: go: updates to go.mod needed, but contents have changed
// 1.14: go: updating go.mod: existing contents have changed since last read
var modConcurrencyError = regexp.MustCompile(`go:.*go.mod.*contents have changed`)
// Run is a convenience wrapper around RunRaw.
// It returns only stdout and a "friendly" error.
func (runner *Runner) Run(ctx context.Context, inv Invocation) (*bytes.Buffer, error) {
stdout, _, friendly, _ := runner.RunRaw(ctx, inv)
return stdout, friendly
}
// RunPiped runs the invocation serially, always waiting for any concurrent
// invocations to complete first.
func (runner *Runner) RunPiped(ctx context.Context, inv Invocation, stdout, stderr io.Writer) error {
_, err := runner.runPiped(ctx, inv, stdout, stderr)
return err
}
// RunRaw runs the invocation, serializing requests only if they fight over
// go.mod changes.
func (runner *Runner) RunRaw(ctx context.Context, inv Invocation) (*bytes.Buffer, *bytes.Buffer, error, error) {
// Make sure the runner is always initialized.
runner.initialize()
// First, try to run the go command concurrently.
stdout, stderr, friendlyErr, err := runner.runConcurrent(ctx, inv)
// If we encounter a load concurrency error, we need to retry serially.
if friendlyErr == nil || !modConcurrencyError.MatchString(friendlyErr.Error()) {
return stdout, stderr, friendlyErr, err
}
event.Error(ctx, "Load concurrency error, will retry serially", err)
// Run serially by calling runPiped.
stdout.Reset()
stderr.Reset()
friendlyErr, err = runner.runPiped(ctx, inv, stdout, stderr)
return stdout, stderr, friendlyErr, err
}
func (runner *Runner) runConcurrent(ctx context.Context, inv Invocation) (*bytes.Buffer, *bytes.Buffer, error, error) {
// Wait for 1 worker to become available.
select {
case <-ctx.Done():
return nil, nil, nil, ctx.Err()
case runner.inFlight <- struct{}{}:
defer func() { <-runner.inFlight }()
}
stdout, stderr := &bytes.Buffer{}, &bytes.Buffer{}
friendlyErr, err := inv.runWithFriendlyError(ctx, stdout, stderr)
return stdout, stderr, friendlyErr, err
}
func (runner *Runner) runPiped(ctx context.Context, inv Invocation, stdout, stderr io.Writer) (error, error) {
// Make sure the runner is always initialized.
runner.initialize()
// Acquire the serialization lock. This avoids deadlocks between two
// runPiped commands.
select {
case <-ctx.Done():
return nil, ctx.Err()
case runner.serialized <- struct{}{}:
defer func() { <-runner.serialized }()
}
// Wait for all in-progress go commands to return before proceeding,
// to avoid load concurrency errors.
for i := 0; i < maxInFlight; i++ {
select {
case <-ctx.Done():
return nil, ctx.Err()
case runner.inFlight <- struct{}{}:
// Make sure we always "return" any workers we took.
defer func() { <-runner.inFlight }()
}
}
return inv.runWithFriendlyError(ctx, stdout, stderr)
}
// An Invocation represents a call to the go command.
type Invocation struct {
Verb string
Args []string
BuildFlags []string
ModFlag string
ModFile string
Overlay string
// If CleanEnv is set, the invocation will run only with the environment
// in Env, not starting with os.Environ.
CleanEnv bool
Env []string
WorkingDir string
Logf func(format string, args ...interface{})
}
func (i *Invocation) runWithFriendlyError(ctx context.Context, stdout, stderr io.Writer) (friendlyError error, rawError error) {
rawError = i.run(ctx, stdout, stderr)
if rawError != nil {
friendlyError = rawError
// Check for 'go' executable not being found.
if ee, ok := rawError.(*exec.Error); ok && ee.Err == exec.ErrNotFound {
friendlyError = fmt.Errorf("go command required, not found: %v", ee)
}
if ctx.Err() != nil {
friendlyError = ctx.Err()
}
friendlyError = fmt.Errorf("err: %v: stderr: %s", friendlyError, stderr)
}
return
}
func (i *Invocation) run(ctx context.Context, stdout, stderr io.Writer) error {
log := i.Logf
if log == nil {
log = func(string, ...interface{}) {}
}
goArgs := []string{i.Verb}
appendModFile := func() {
if i.ModFile != "" {
goArgs = append(goArgs, "-modfile="+i.ModFile)
}
}
appendModFlag := func() {
if i.ModFlag != "" {
goArgs = append(goArgs, "-mod="+i.ModFlag)
}
}
appendOverlayFlag := func() {
if i.Overlay != "" {
goArgs = append(goArgs, "-overlay="+i.Overlay)
}
}
switch i.Verb {
case "env", "version":
goArgs = append(goArgs, i.Args...)
case "mod":
// mod needs the sub-verb before flags.
goArgs = append(goArgs, i.Args[0])
appendModFile()
goArgs = append(goArgs, i.Args[1:]...)
case "get":
goArgs = append(goArgs, i.BuildFlags...)
appendModFile()
goArgs = append(goArgs, i.Args...)
default: // notably list and build.
goArgs = append(goArgs, i.BuildFlags...)
appendModFile()
appendModFlag()
appendOverlayFlag()
goArgs = append(goArgs, i.Args...)
}
cmd := exec.Command("go", goArgs...)
cmd.Stdout = stdout
cmd.Stderr = stderr
// On darwin the cwd gets resolved to the real path, which breaks anything that
// expects the working directory to keep the original path, including the
// go command when dealing with modules.
// The Go stdlib has a special feature where if the cwd and the PWD are the
// same node then it trusts the PWD, so by setting it in the env for the child
// process we fix up all the paths returned by the go command.
if !i.CleanEnv {
cmd.Env = os.Environ()
}
cmd.Env = append(cmd.Env, i.Env...)
if i.WorkingDir != "" {
cmd.Env = append(cmd.Env, "PWD="+i.WorkingDir)
cmd.Dir = i.WorkingDir
}
defer func(start time.Time) { log("%s for %v", time.Since(start), cmdDebugStr(cmd)) }(time.Now())
return runCmdContext(ctx, cmd)
}
// runCmdContext is like exec.CommandContext except it sends os.Interrupt
// before os.Kill.
func runCmdContext(ctx context.Context, cmd *exec.Cmd) error {
if err := cmd.Start(); err != nil {
return err
}
resChan := make(chan error, 1)
go func() {
resChan <- cmd.Wait()
}()
select {
case err := <-resChan:
return err
case <-ctx.Done():
}
// Cancelled. Interrupt and see if it ends voluntarily.
cmd.Process.Signal(os.Interrupt)
select {
case err := <-resChan:
return err
case <-time.After(time.Second):
}
// Didn't shut down in response to interrupt. Kill it hard.
cmd.Process.Kill()
return <-resChan
}
func cmdDebugStr(cmd *exec.Cmd) string {
env := make(map[string]string)
for _, kv := range cmd.Env {
split := strings.SplitN(kv, "=", 2)
k, v := split[0], split[1]
env[k] = v
}
var args []string
for _, arg := range cmd.Args {
quoted := strconv.Quote(arg)
if quoted[1:len(quoted)-1] != arg || strings.Contains(arg, " ") {
args = append(args, quoted)
} else {
args = append(args, arg)
}
}
return fmt.Sprintf("GOROOT=%v GOPATH=%v GO111MODULE=%v GOPROXY=%v PWD=%v %v", env["GOROOT"], env["GOPATH"], env["GO111MODULE"], env["GOPROXY"], env["PWD"], strings.Join(args, " "))
}