shfmt/interp/handler.go at master · patrickvane/shfmt · GitHub

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// See LICENSE for licensing information

package interp

import (

"context"

"fmt"

"io"

"os"

"os/exec"

"path/filepath"

"runtime"

"strings"

"syscall"

"time"

"mvdan.cc/sh/v3/expand"

)

// HandlerCtx returns HandlerContext value stored in ctx.

// It panics if ctx has no HandlerContext stored.

func HandlerCtx(ctx context.Context) HandlerContext {

hc, ok := ctx.Value(handlerCtxKey{}).(HandlerContext)

if !ok {

panic("interp.HandlerCtx: no HandlerContext in ctx")

}

return hc

}

type handlerCtxKey struct{}

// HandlerContext is the data passed to all the handler functions via a context value.

// It contains some of the current state of the Runner.

type HandlerContext struct {

// Env is a read-only version of the interpreter's environment,

// including environment variables, global variables, and local function

// variables.

Env expand.Environ

// Dir is the interpreter's current directory.

Dir string

// Stdin is the interpreter's current standard input reader.

Stdin io.Reader

// Stdout is the interpreter's current standard output writer.

Stdout io.Writer

// Stderr is the interpreter's current standard error writer.

Stderr io.Writer

}

// ExecHandlerFunc is a handler which executes simple command. It is

// called for all CallExpr nodes where the first argument is neither a

// declared function nor a builtin.

// Returning nil error sets commands exit status to 0. Other exit statuses

// can be set with NewExitStatus. Any other error will halt an interpreter.

type ExecHandlerFunc func(ctx context.Context, args []string) error

// DefaultExecHandler returns an ExecHandlerFunc used by default.

// It finds binaries in PATH and executes them.

// When context is cancelled, interrupt signal is sent to running processes.

// KillTimeout is a duration to wait before sending kill signal.

// A negative value means that a kill signal will be sent immediately.

// On Windows, the kill signal is always sent immediately,

// because Go doesn't currently support sending Interrupt on Windows.

// Runner.New sets killTimeout to 2 seconds by default.

func DefaultExecHandler(killTimeout time.Duration) ExecHandlerFunc {

return func(ctx context.Context, args []string) error {

hc := HandlerCtx(ctx)

path, err := LookPath(hc.Env, args[0])

if err != nil {

fmt.Fprintln(hc.Stderr, err)

return NewExitStatus(127)

}

cmd := exec.Cmd{

Path: path,

Args: args,

Env: execEnv(hc.Env),

Dir: hc.Dir,

Stdin: hc.Stdin,

Stdout: hc.Stdout,

Stderr: hc.Stderr,

}

err = cmd.Start()

if err == nil {

if done := ctx.Done(); done != nil {

go func() {

<-done

if killTimeout <= 0 || runtime.GOOS == "windows" {

_ = cmd.Process.Signal(os.Kill)

return

}

// TODO: don't temporarily leak this goroutine

// if the program stops itself with the

// interrupt.

go func() {

time.Sleep(killTimeout)

_ = cmd.Process.Signal(os.Kill)

}()

_ = cmd.Process.Signal(os.Interrupt)

}()

}

err = cmd.Wait()

}

switch x := err.(type) {

case *exec.ExitError:

// started, but errored - default to 1 if OS

// doesn't have exit statuses

if status, ok := x.Sys().(syscall.WaitStatus); ok {

if status.Signaled() {

if ctx.Err() != nil {

return ctx.Err()

}

return NewExitStatus(uint8(128 + status.Signal()))

}

return NewExitStatus(uint8(status.ExitStatus()))

}

return NewExitStatus(1)

case *exec.Error:

// did not start

fmt.Fprintf(hc.Stderr, "%v\n", err)

return NewExitStatus(127)

default:

return err

}

func checkStat(dir, file string) (string, error) {

if !filepath.IsAbs(file) {

file = filepath.Join(dir, file)

}

info, err := os.Stat(file)

if err != nil {

return "", err

}

m := info.Mode()

if m.IsDir() {

return "", fmt.Errorf("is a directory")

}

if runtime.GOOS != "windows" && m&0o111 == 0 {

return "", fmt.Errorf("permission denied")

}

return file, nil

}

func winHasExt(file string) bool {

i := strings.LastIndex(file, ".")

if i < 0 {

return false

}

return strings.LastIndexAny(file, `:\/`) < i

}

func findExecutable(dir, file string, exts []string) (string, error) {

if len(exts) == 0 {

// non-windows

return checkStat(dir, file)

}

if winHasExt(file) {

if file, err := checkStat(dir, file); err == nil {

return file, nil

}

for _, e := range exts {

f := file + e

if f, err := checkStat(dir, f); err == nil {

return f, nil

}

return "", fmt.Errorf("not found")

}

func driveLetter(c byte) bool {

return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')

}

// splitList is like filepath.SplitList, but always using the unix path

// list separator ':'. On Windows, it also makes sure not to split

// [A-Z]:[/\].

func splitList(path string) []string {

if path == "" {

return []string{""}

}

list := strings.Split(path, ":")

if runtime.GOOS != "windows" {

return list

}

// join "C", "/foo" into "C:/foo"

var fixed []string

for i := 0; i < len(list); i++ {

s := list[i]

switch {

case len(s) != 1, !driveLetter(s[0]):

case i+1 >= len(list):

// last element

case strings.IndexAny(list[i+1], `/\`) != 0:

// next element doesn't start with / or \

default:

fixed = append(fixed, s+":"+list[i+1])

i++

continue

}

fixed = append(fixed, s)

}

return fixed

}

// LookPath is similar to os/exec.LookPath, with the difference that it uses the

// provided environment. env is used to fetch relevant environment variables

// such as PWD and PATH.

// If no error is returned, the returned path must be valid.

func LookPath(env expand.Environ, file string) (string, error) {

pathList := splitList(env.Get("PATH").String())

chars := `/`

if runtime.GOOS == "windows" {

chars = `:\/`

// so that "foo" always tries "./foo"

pathList = append([]string{"."}, pathList...)

}

exts := pathExts(env)

dir := env.Get("PWD").String()

if strings.ContainsAny(file, chars) {

return findExecutable(dir, file, exts)

}

for _, elem := range pathList {

var path string

switch elem {

case "", ".":

// otherwise "foo" won't be "./foo"

path = "." + string(filepath.Separator) + file

default:

path = filepath.Join(elem, file)

}

if f, err := findExecutable(dir, path, exts); err == nil {

return f, nil

}

return "", fmt.Errorf("%q: executable file not found in $PATH", file)

}

func pathExts(env expand.Environ) []string {

if runtime.GOOS != "windows" {

return nil

}

pathext := env.Get("PATHEXT").String()

if pathext == "" {

return []string{".com", ".exe", ".bat", ".cmd"}

}

var exts []string

for _, e := range strings.Split(strings.ToLower(pathext), `;`) {

if e == "" {

continue

}

if e[0] != '.' {

e = "." + e

}

exts = append(exts, e)

}

return exts

}

// OpenHandlerFunc is a handler which opens files. It is

// called for all files that are opened directly by the shell, such as

// in redirects. Files opened by executed programs are not included.

// The path parameter may be relative to the current directory, which can be

// fetched via HandlerCtx.

// Use a return error of type *os.PathError to have the error printed to

// stderr and the exit status set to 1. If the error is of any other type, the

// interpreter will come to a stop.

type OpenHandlerFunc func(ctx context.Context, path string, flag int, perm os.FileMode) (io.ReadWriteCloser, error)

// DefaultOpenHandler returns an OpenHandlerFunc used by default. It uses os.OpenFile to open files.

func DefaultOpenHandler() OpenHandlerFunc {

return func(ctx context.Context, path string, flag int, perm os.FileMode) (io.ReadWriteCloser, error) {

mc := HandlerCtx(ctx)

if !filepath.IsAbs(path) {

path = filepath.Join(mc.Dir, path)

}

return os.OpenFile(path, flag, perm)

}

shfmt/interp/handler.go at master · patrickvane/shfmt · GitHub

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