wire: output diffs to stdout, and return 1 for diffs and 2 for troubl…

…e from diff subcommand (#90)

cmd/wire/main.go

@@ -38,7 +38,10 @@ import (
 const usage = "usage: wire [gen|diff|show|check] [...]"
 
 func main() {
- var err error
+ var (
+ exitCode = 0
+ err error
+ )
  switch {
  case len(os.Args) == 2 && (os.Args[1] == "help" || os.Args[1] == "-h" || os.Args[1] == "-help" || os.Args[1] == "--help"):
  fmt.Fprintln(os.Stderr, usage)
@@ -52,9 +55,9 @@ func main() {
  case len(os.Args) > 2 && os.Args[1] == "check":
  err = check(os.Args[2:]...)
  case len(os.Args) == 2 && os.Args[1] == "diff":
- err = diff(".")
+ exitCode, err = diff(".")
  case len(os.Args) > 2 && os.Args[1] == "diff":
- err = diff(os.Args[2:]...)
+ exitCode, err = diff(os.Args[2:]...)
  case len(os.Args) == 2 && os.Args[1] == "gen":
  err = generate(".")
  case len(os.Args) > 2 && os.Args[1] == "gen":
@@ -66,12 +69,17 @@ func main() {
  err = generate(os.Args[1:]...)
  default:
  fmt.Fprintln(os.Stderr, usage)
- os.Exit(64)
+ exitCode = 64
  }
  if err != nil {
  fmt.Fprintln(os.Stderr, "wire:", err)
- os.Exit(1)
+ // Don't override more specific error codes from above
+ // (e.g., diff returns 2 on error).
+ if exitCode == 0 {
+ exitCode = 1
+ }
  }
+ os.Exit(exitCode)
 }
 
 // generate runs the gen subcommand.
@@ -118,20 +126,33 @@ func generate(pkgs ...string) error {
 //
 // Given one or more packages, diff will generate the content for the
 // wire_gen.go file, and output the diff against the existing file.
-func diff(pkgs ...string) error {
+//
+// Similar to the diff command, it returns 0 if no diff, 1 if different, 2
+// plus an error if trouble.
+func diff(pkgs ...string) (int, error) {
+ errReturn := func(err error) (int, error) {
+ return 2, err
+ }
+ okReturn := func(hadDiff bool) (int, error) {
+ if hadDiff {
+ return 1, nil
+ }
+ return 0, nil
+ }
  wd, err := os.Getwd()
  if err != nil {
- return err
+ return errReturn(err)
  }
  outs, errs := wire.Generate(context.Background(), wd, os.Environ(), pkgs)
  if len(errs) > 0 {
  logErrors(errs)
- return errors.New("generate failed")
+ return errReturn(errors.New("generate failed"))
  }
  if len(outs) == 0 {
- return nil
+ return okReturn(false)
  }
  success := true
+ hadDiff := false
  for _, out := range outs {
  if len(out.Errs) > 0 {
  fmt.Fprintf(os.Stderr, "%s: generate failed\n", out.PkgPath)
@@ -149,17 +170,18 @@ func diff(pkgs ...string) error {
  B: difflib.SplitLines(string(out.Content)),
  }); err == nil {
  if diff != "" {
- fmt.Fprintf(os.Stderr, "%s: diff from %s:\n%s", out.PkgPath, out.OutputPath, diff)
+ fmt.Fprintf(os.Stdout, "%s: diff from %s:\n%s", out.PkgPath, out.OutputPath, diff)
+ hadDiff = true
  }
  } else {
  fmt.Fprintf(os.Stderr, "%s: failed to diff %s: %v\n", out.PkgPath, out.OutputPath, err)
  success = false
  }
  }
  if !success {
- return errors.New("at least one generate failure")
+ return errReturn(errors.New("at least one generate failure"))
  }
- return nil
+ return okReturn(hadDiff)
 }
 
 // show runs the show subcommand.