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