From 73102bddabb369a1e7c02cb9ea9a26ee8ab2bcfc Mon Sep 17 00:00:00 2001
From: lit <litlighilit@foxmail.com>
Date: Sun, 12 Apr 2026 18:32:25 +0800
Subject: [PATCH] fixes #25738; std/parseopt: `-` causes IndexDefect (#25739)

(cherry picked from commit cf3c28c2236c77bed267720bce3a5576680dc50b)
---
 lib/pure/parseopt.nim    | 4 +++-
 tests/misc/tparseopt.nim | 9 +++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/lib/pure/parseopt.nim b/lib/pure/parseopt.nim
index 52c26d5a35..5b57c9a746 100644
--- a/lib/pure/parseopt.nim
+++ b/lib/pure/parseopt.nim
@@ -588,7 +588,9 @@ proc handleShortOption(p: var OptParser; cmd: string) =
     
   template next(): untyped = p.cmds[p.idx + 1]
 
-  let canTakeVal = card(p.shortNoVal) > 0 and p.key[0] notin p.shortNoVal 
+  let canTakeVal = card(p.shortNoVal) > 0 and
+    p.key.len > 0 and p.key[0] notin p.shortNoVal
+
   if i < cmd.len and cmd[i] in p.separators:
     # separator case
     if prShortAllowSep in p.rules:
diff --git a/tests/misc/tparseopt.nim b/tests/misc/tparseopt.nim
index 47be05bac9..eb1eb3c89a 100644
--- a/tests/misc/tparseopt.nim
+++ b/tests/misc/tparseopt.nim
@@ -31,6 +31,9 @@ cmdShortOption key: v value: ''
 cmdArgument key: ABC value: ''
 cmdShortOption key: j value: '4'
 cmdArgument key: ok value: ''
+parseopt stdin
+cmdShortOption key: j value: '4'
+cmdShortOption key:  value: ''
 '''
 joinable: false
 """
@@ -154,3 +157,9 @@ arg 6 ai.len:4 :{a7'b}"""
     var n = parseopt.initOptParser("-j4 ok", shortnoVal = {'n'}, longnoVal = @["novalue"])
     for kind, key, val in parseopt.getopt(n):
       echo kind," key: ", key, " value: '", val, "'"
+
+  block: # fix #25738
+    echo "parseopt stdin"
+    var p = parseopt.initOptParser("-j4 -", shortNoVal = {'n'})
+    for kind, key, val in parseopt.getopt(p):
+      echo kind," key: ", key, " value: '", val, "'"