Ignore flags after the special option delimiter argument ('--') and
interprete them as non-flag, positional arguments as getopt(3) does.

Example:

	type Foo struct {
		Force bool          `opt:"-f"`
		Name  string        `opt:"name"`
	}

Current behavior:

	$ foo -- -f
	main.Foo{Force:true, Name:"--"}

Expected behavior with this patch:

	$ foo -- -f
	main.Foo{Force:false, Name:"-f"}

and

	$ foo -f -- -f
	main.Foo{Force:true, Name:"-f"}

Signed-off-by: Koni Marti <koni.marti@gmail.com>
---
v1->v2:

 * match getopt(3) behavior: end option-scanning after -- and treat rest
   as positionals

 README.md    |  3 +++
 spec.go      | 14 ++++++++++++--
 spec_test.go |  8 ++++++++
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index b1478f4..4652a95 100644
--- a/README.md
+++ b/README.md
@@ -277,3 +277,6 @@ Short flags can be combined like with `getopt(3)`:
 
 * Flags with no value: `-abc` is equivalent to `-a -b -c`
 * Flags with a value (options): `-j9` is equivalent to `-j 9`
+
+The special argument `--` forces an end to the flag parsing. The remaining
+arguments are interpreted as positional arguments (see `getopt(3)`).
diff --git a/spec.go b/spec.go
index 323dffa..d4960d1 100644
--- a/spec.go
+++ b/spec.go
@@ -82,6 +82,8 @@ var (
 	positionalRe = regexp.MustCompile(`^([a-zA-Z][\w-]*)$`)
 )
 
+const optionDelim = "--"
+
 // Interpret all struct fields to a list of option specs
 func NewCmdSpec(name string, v any) *CmdSpec {
 	typ := reflect.TypeOf(v)
@@ -412,6 +414,7 @@ func (c *CmdSpec) parseArgs(args *Args) []*ArgError {
 		argErrors = append(argErrors, &ArgError{kind, s, detail})
 	}
 	positionals := c.positionals
+	ignoreFlags := false
 	c.seen = nil
 	args.Shift(1) // skip command name
 	i := 1
@@ -420,7 +423,7 @@ func (c *CmdSpec) parseArgs(args *Args) []*ArgError {
 		arg := args.Arg(0)
 
 		switch {
-		case c.getLongFlag(arg) != nil:
+		case c.getLongFlag(arg) != nil && !ignoreFlags:
 			if cur != nil {
 				fail(missingValue, cur.spec, nil)
 			}
@@ -443,7 +446,7 @@ func (c *CmdSpec) parseArgs(args *Args) []*ArgError {
 				cur = nil
 			}
 
-		case c.getShortFlag(arg) != nil:
+		case c.getShortFlag(arg) != nil && !ignoreFlags:
 			if cur != nil {
 				fail(missingValue, cur.spec, nil)
 			}
@@ -486,6 +489,7 @@ func (c *CmdSpec) parseArgs(args *Args) []*ArgError {
 				cur = nil
 				goto next
 			}
+
 			for len(positionals) > 0 {
 				spec := &c.opts[positionals[0]]
 				positionals = positionals[1:]
@@ -494,6 +498,12 @@ func (c *CmdSpec) parseArgs(args *Args) []*ArgError {
 					break
 				}
 			}
+
+			if arg == optionDelim {
+				ignoreFlags = true
+				goto next
+			}
+
 			if cur == nil {
 				fail(unexpectedArg, nil, errors.New(arg))
 				goto next
diff --git a/spec_test.go b/spec_test.go
index 1d0b6de..4673ed0 100644
--- a/spec_test.go
+++ b/spec_test.go
@@ -92,6 +92,14 @@ func TestArgsToStruct(t *testing.T) {
 				Name:    "n a m e",
 			},
 		},
+		{
+			cmdline: `bar -j3 -- -j7`,
+			expected: OptionStruct{
+				Jobs:  3,
+				Delay: 0.5,
+				Name:  "-j7",
+			},
+		},
 	}
 
 	for _, v := range vectors {
-- 
2.43.0

Koni Marti <koni.marti@gmail.com> wrote:
> Ignore flags after the special option delimiter argument ('--') and
> interprete them as non-flag, positional arguments as getopt(3) does.
>
> Example:
>
> 	type Foo struct {
> 		Force bool          `opt:"-f"`
> 		Name  string        `opt:"name"`
> 	}
>
> Current behavior:
>
> 	$ foo -- -f
> 	main.Foo{Force:true, Name:"--"}
>
> Expected behavior with this patch:
>
> 	$ foo -- -f
> 	main.Foo{Force:false, Name:"-f"}
>
> and
>
> 	$ foo -f -- -f
> 	main.Foo{Force:true, Name:"-f"}
>
> Signed-off-by: Koni Marti <koni.marti@gmail.com>
> ---
> v1->v2:
>
>  * match getopt(3) behavior: end option-scanning after -- and treat rest
>    as positionals

Acked-by: Robin Jarry <robin@jarry.cc>

Applied, thanks.

To 
   cb392dfc9d62..4bd5fff1499e  main -> main