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run.go
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99 lines (89 loc) · 2.18 KB
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package run
import (
"bytes"
"fmt"
"io"
"os"
"os/exec"
"path/filepath"
"strings"
)
// Runnable is typically an exec.Cmd or its stub in tests
type Runnable interface {
Output() ([]byte, error)
Run() error
}
// PrepareCmd extends exec.Cmd with extra error reporting features and provides a
// hook to stub command execution in tests
var PrepareCmd = func(cmd *exec.Cmd) Runnable {
return &cmdWithStderr{cmd}
}
// SetPrepareCmd overrides PrepareCmd and returns a func to revert it back
func SetPrepareCmd(fn func(*exec.Cmd) Runnable) func() {
origPrepare := PrepareCmd
PrepareCmd = func(cmd *exec.Cmd) Runnable {
// normalize git executable name for consistency in tests
if baseName := filepath.Base(cmd.Args[0]); baseName == "git" || baseName == "git.exe" {
cmd.Args[0] = "git"
}
return fn(cmd)
}
return func() {
PrepareCmd = origPrepare
}
}
// cmdWithStderr augments exec.Cmd by adding stderr to the error message
type cmdWithStderr struct {
*exec.Cmd
}
func (c cmdWithStderr) Output() ([]byte, error) {
if os.Getenv("DEBUG") != "" {
_ = printArgs(os.Stderr, c.Cmd.Args)
}
if c.Cmd.Stderr != nil {
return c.Cmd.Output()
}
errStream := &bytes.Buffer{}
c.Cmd.Stderr = errStream
out, err := c.Cmd.Output()
if err != nil {
err = &CmdError{errStream, c.Cmd.Args, err}
}
return out, err
}
func (c cmdWithStderr) Run() error {
if os.Getenv("DEBUG") != "" {
_ = printArgs(os.Stderr, c.Cmd.Args)
}
if c.Cmd.Stderr != nil {
return c.Cmd.Run()
}
errStream := &bytes.Buffer{}
c.Cmd.Stderr = errStream
err := c.Cmd.Run()
if err != nil {
err = &CmdError{errStream, c.Cmd.Args, err}
}
return err
}
// CmdError provides more visibility into why an exec.Cmd had failed
type CmdError struct {
Stderr *bytes.Buffer
Args []string
Err error
}
func (e CmdError) Error() string {
msg := e.Stderr.String()
if msg != "" && !strings.HasSuffix(msg, "\n") {
msg += "\n"
}
return fmt.Sprintf("%s%s: %s", msg, e.Args[0], e.Err)
}
func printArgs(w io.Writer, args []string) error {
if len(args) > 0 {
// print commands, but omit the full path to an executable
args = append([]string{filepath.Base(args[0])}, args[1:]...)
}
_, err := fmt.Fprintf(w, "%v\n", args)
return err
}