From df740f656281131043563a9a3b92f83a2e495fa7 Mon Sep 17 00:00:00 2001
From: Robert Liebowitz <rliebz@gmail.com>
Date: Fri, 11 Oct 2019 22:32:21 -0400
Subject: [PATCH 1/2] Fix infinite loop flag parsing with short options

---
 command_test.go |  5 +++++
 parse.go        | 17 ++++++++---------
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/command_test.go b/command_test.go
index 6235b41..66859c0 100644
--- a/command_test.go
+++ b/command_test.go
@@ -70,8 +70,13 @@ func TestParseAndRunShortOpts(t *testing.T) {
 		{[]string{"foo", "test", "-af"}, nil, []string{}},
 		{[]string{"foo", "test", "-cf"}, nil, []string{}},
 		{[]string{"foo", "test", "-acf"}, nil, []string{}},
+		{[]string{"foo", "test", "--acf"}, errors.New("flag provided but not defined: -acf"), nil},
 		{[]string{"foo", "test", "-invalid"}, errors.New("flag provided but not defined: -invalid"), nil},
+		{[]string{"foo", "test", "-acf", "-invalid"}, errors.New("flag provided but not defined: -invalid"), nil},
+		{[]string{"foo", "test", "--invalid"}, errors.New("flag provided but not defined: -invalid"), nil},
+		{[]string{"foo", "test", "-acf", "--invalid"}, errors.New("flag provided but not defined: -invalid"), nil},
 		{[]string{"foo", "test", "-acf", "arg1", "-invalid"}, nil, []string{"arg1", "-invalid"}},
+		{[]string{"foo", "test", "-acf", "arg1", "--invalid"}, nil, []string{"arg1", "--invalid"}},
 		{[]string{"foo", "test", "-acfi", "not-arg", "arg1", "-invalid"}, nil, []string{"arg1", "-invalid"}},
 		{[]string{"foo", "test", "-i", "ivalue"}, nil, []string{}},
 		{[]string{"foo", "test", "-i", "ivalue", "arg1"}, nil, []string{"arg1"}},
diff --git a/parse.go b/parse.go
index 2c2005c..cab99e5 100644
--- a/parse.go
+++ b/parse.go
@@ -22,28 +22,27 @@ func parseIter(set *flag.FlagSet, ip iterativeParser, args []string) error {
 		}
 
 		errStr := err.Error()
-		trimmed := strings.TrimPrefix(errStr, "flag provided but not defined: ")
+		trimmed := strings.TrimPrefix(errStr, "flag provided but not defined: -")
 		if errStr == trimmed {
 			return err
 		}
 
 		// regenerate the initial args with the split short opts
-		newArgs := []string{}
 		for i, arg := range args {
-			if arg != trimmed {
-				newArgs = append(newArgs, arg)
+			// skip args that are not part of the error message
+			if name := strings.TrimLeft(arg, "-"); name != trimmed {
 				continue
 			}
 
-			shortOpts := splitShortOptions(set, trimmed)
+			// if we can't split, the error was accurate
+			shortOpts := splitShortOptions(set, arg)
 			if len(shortOpts) == 1 {
 				return err
 			}
 
-			// add each short option and all remaining arguments
-			newArgs = append(newArgs, shortOpts...)
-			newArgs = append(newArgs, args[i+1:]...)
-			args = newArgs
+			// swap current argument with the split version
+			args = append(args[:i], append(shortOpts, args[i+1:]...)...)
+			break
 		}
 
 		// Since custom parsing failed, replace the flag set before retrying

From f5306b622f216cafde2a670b9a9e620cb6b0fad1 Mon Sep 17 00:00:00 2001
From: Robert Liebowitz <rliebz@gmail.com>
Date: Fri, 11 Oct 2019 22:57:55 -0400
Subject: [PATCH 2/2] Ensure infinite loop cannot occur in parsing

---
 parse.go | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/parse.go b/parse.go
index cab99e5..660f538 100644
--- a/parse.go
+++ b/parse.go
@@ -28,6 +28,7 @@ func parseIter(set *flag.FlagSet, ip iterativeParser, args []string) error {
 		}
 
 		// regenerate the initial args with the split short opts
+		argsWereSplit := false
 		for i, arg := range args {
 			// skip args that are not part of the error message
 			if name := strings.TrimLeft(arg, "-"); name != trimmed {
@@ -42,9 +43,16 @@ func parseIter(set *flag.FlagSet, ip iterativeParser, args []string) error {
 
 			// swap current argument with the split version
 			args = append(args[:i], append(shortOpts, args[i+1:]...)...)
+			argsWereSplit = true
 			break
 		}
 
+		// This should be an impossible to reach code path, but in case the arg
+		// splitting failed to happen, this will prevent infinite loops
+		if !argsWereSplit {
+			return err
+		}
+
 		// Since custom parsing failed, replace the flag set before retrying
 		newSet, err := ip.newFlagSet()
 		if err != nil {