flag: exit 0 when -h or -help invoked but undefined

flag treats -h or -help as a special case to print a nice help message, but exit with a status code of 2. This update makes that status code 0. Fixes #37533 Change-Id: I7e0bd29944ce46607fb7cfc6740734f7444a151a GitHub-Last-Rev: 83f64d757bc3a9957c49caa5de74d05a96724771 GitHub-Pull-Request: golang/go#37530 Reviewed-on: https://go-review.googlesource.com/c/go/+/221427 Run-TryBot: Ian Lance Taylor <[email protected]> TryBot-Result: Gobot Gobot <[email protected]> Reviewed-by: Ian Lance Taylor <[email protected]>
cloudflare · Apr 3, 2020 · dcf0929 · dcf0929
1 parent 041bcb3
commit dcf0929
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diff --git a/doc/go1.15.html b/doc/go1.15.html
@@ -119,6 +119,21 @@ <h3 id="minor_library_changes">Minor changes to the library</h3>
 TODO
 </p>
 
+<dl id="flag"><dt><a href="/pkg/flag/">flag</a></dt>
+ <dd>
+ <p><!-- CL 221427 -->
+ When the flag package sees <code>-h</code> or <code>-help</code>, and
+ those flags are not defined, the flag package prints a usage message.
+ If the <a href=/pkg/flag/#FlagSet><code>FlagSet</code></a> was created with
+ <a href=/pkg/flag/#ExitOnError><code>ExitOnError</code></a>,
+ <a href=/pkg/flag/#FlagSet.Parse><code>FlagSet.Parse</code></a> would then
+ exit with a status of 2. In this release, the exit status for <code>-h</code>
+ or <code>-help</code> has been changed to 0. In particular, this applies to
+ the default handling of command line flags.
+ </p>
+ </dd>
+</dl>
+
 <dl id="pkg-runtime"><dt><a href="/pkg/runtime/">runtime</a></dt>
  <dd>
  <p><!-- CL 221779 -->

diff --git a/src/flag/flag.go b/src/flag/flag.go
@@ -308,7 +308,7 @@ type ErrorHandling int
 // These constants cause FlagSet.Parse to behave as described if the parse fails.
 const (
  ContinueOnError ErrorHandling = iota // Return a descriptive error.
- ExitOnError // Call os.Exit(2).
+ ExitOnError // Call os.Exit(2) or for -h/-help Exit(0).
  PanicOnError // Call panic with a descriptive error.
 )
 
@@ -979,6 +979,9 @@ func (f *FlagSet) Parse(arguments []string) error {
  case ContinueOnError:
  return err
  case ExitOnError:
+ if err == ErrHelp {
+ os.Exit(0)
+ }
  os.Exit(2)
  case PanicOnError:
  panic(err)

diff --git a/src/flag/flag_test.go b/src/flag/flag_test.go
@@ -8,9 +8,11 @@ import (
  "bytes"
  . "flag"
  "fmt"
+ "internal/testenv"
  "io"
  "io/ioutil"
  "os"
+ "os/exec"
  "sort"
  "strconv"
  "strings"
@@ -544,3 +546,62 @@ func TestRangeError(t *testing.T) {
  }
  }
 }
+
+func TestExitCode(t *testing.T) {
+ testenv.MustHaveExec(t)
+
+ magic := 123
+ if os.Getenv("GO_CHILD_FLAG") != "" {
+ fs := NewFlagSet("test", ExitOnError)
+ if os.Getenv("GO_CHILD_FLAG_HANDLE") != "" {
+ var b bool
+ fs.BoolVar(&b, os.Getenv("GO_CHILD_FLAG_HANDLE"), false, "")
+ }
+ fs.Parse([]string{os.Getenv("GO_CHILD_FLAG")})
+ os.Exit(magic)
+ }
+
+ tests := []struct {
+ flag string
+ flagHandle string
+ expectExit int
+ }{
+ {
+ flag: "-h",
+ expectExit: 0,
+ },
+ {
+ flag: "-help",
+ expectExit: 0,
+ },
+ {
+ flag: "-undefined",
+ expectExit: 2,
+ },
+ {
+ flag: "-h",
+ flagHandle: "h",
+ expectExit: magic,
+ },
+ {
+ flag: "-help",
+ flagHandle: "help",
+ expectExit: magic,
+ },
+ }
+
+ for _, test := range tests {
+ cmd := exec.Command(os.Args[0], "-test.run=TestExitCode")
+ cmd.Env = append(
+ os.Environ(),
+ "GO_CHILD_FLAG="+test.flag,
+ "GO_CHILD_FLAG_HANDLE="+test.flagHandle,
+ )
+ cmd.Run()
+ got := cmd.ProcessState.ExitCode()
+ if got != test.expectExit {
+ t.Errorf("unexpected exit code for test case %+v \n: got %d, expect %d",
+ test, got, test.expectExit)
+ }
+ }
+}