From 733f7c060c8bd08a79329e107a49978cd7b9d62b Mon Sep 17 00:00:00 2001
From: Eljees <3.14hell@gmail.com>
Date: Sun, 9 Aug 2026 12:29:38 +0000
Subject: [PATCH] Accept an escaped ! as negation in [ ] test expressions

readCondGroup already reads its parentheses with
`readRegularOrEscaped (string "(")`, so `[ \( x \) ]` parses, and SC1028 tells
users to write them that way. readCondNot, however, matched a bare `char '!'`,
so the equally valid `[ \! x ]` was not recognised as a negation: on its own it
produced a bogus SC2057 "Unknown binary operator", and combined with escaped
parentheses it failed to parse at all (SC1072/SC1073).

Both bash and dash treat `!`, `\!` and `"!"` alike in `[ ]`, because test
simply receives the argument `!`. Inside `[[ ]]` they do not: bash rejects
`[[ \! -e foo ]]` with "conditional binary operator expected". The escaped form
is therefore accepted only when parsing `[ ]`, leaving `[[ ]]` as it was.

Fixes #3475
---
 src/ShellCheck/Analytics.hs | 1 +
 src/ShellCheck/Parser.hs    | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/ShellCheck/Analytics.hs b/src/ShellCheck/Analytics.hs
index f6208e72b..2ae3a12de 100644
--- a/src/ShellCheck/Analytics.hs
+++ b/src/ShellCheck/Analytics.hs
@@ -1710,6 +1710,7 @@ prop_checkValidCondOps2 = verify checkValidCondOps "[ -M a ]"
 prop_checkValidCondOps2a = verifyNot checkValidCondOps "[ 3 \\> 2 ]"
 prop_checkValidCondOps3 = verifyNot checkValidCondOps "[ 1 = 2 -a 3 -ge 4 ]"
 prop_checkValidCondOps4 = verifyNot checkValidCondOps "[[ ! -v foo ]]"
+prop_checkValidCondOps5 = verifyNot checkValidCondOps "[ \\! -e foo ]"
 checkValidCondOps _ (TC_Binary id _ s _ _)
     | s `notElem` binaryTestOps =
         warn id 2057 "Unknown binary operator."
diff --git a/src/ShellCheck/Parser.hs b/src/ShellCheck/Parser.hs
index 2902f9b99..b8a64608b 100644
--- a/src/ShellCheck/Parser.hs
+++ b/src/ShellCheck/Parser.hs
@@ -696,7 +696,7 @@ readConditionContents single =
 
     readCondNot = do
         start <- startSpan
-        char '!'
+        if single then void (try (readRegularOrEscaped (string "!"))) else void (char '!')
         id <- endSpan start
         spacingOrLf
         expr <- readCondExpr
@@ -947,6 +947,7 @@ prop_readCondition26 = isOk readScript "[[ foo ]]\\\n && bar"
 prop_readCondition27 = not $ isOk readConditionCommand "[[ x ]] foo"
 prop_readCondition28 = isOk readCondition "[[ x = [\"$1\"] ]]"
 prop_readCondition29 = isOk readCondition "[[ x = [*] ]]"
+prop_readCondition30 = isOk readCondition "[ \\! \\( -e foo -a -e bar \\) ]"
 
 readCondition = called "test expression" $ do
     opos <- getPosition