Warn about `read foo[i]` expanding as glob (fixes #2345)

CHANGELOG.md

@@ -17,6 +17,7 @@
 - SC2304-SC2306: Warn about unquoted globs in expr arguments
 - SC2307: Warn about insufficient number of arguments to expr
 - SC2308: Suggest other approaches for non-standard expr extensions
+- SC2313: Warn about `read` with unquoted, array indexed variable
 
 ### Fixed
 - SC2102 about repetitions in ranges no longer triggers on [[ -v arr[xx] ]]

src/ShellCheck/Analytics.hs

@@ -2689,12 +2689,13 @@ prop_checkCharRangeGlob1 = verify checkCharRangeGlob "ls *[:digit:].jpg"
 prop_checkCharRangeGlob2 = verifyNot checkCharRangeGlob "ls *[[:digit:]].jpg"
 prop_checkCharRangeGlob3 = verify checkCharRangeGlob "ls [10-15]"
 prop_checkCharRangeGlob4 = verifyNot checkCharRangeGlob "ls [a-zA-Z]"
-prop_checkCharRangeGlob5 = verifyNot checkCharRangeGlob "tr -d [a-zA-Z]" -- tr has 2060
+prop_checkCharRangeGlob5 = verifyNot checkCharRangeGlob "tr -d [aa]" -- tr has 2060
 prop_checkCharRangeGlob6 = verifyNot checkCharRangeGlob "[[ $x == [!!]* ]]"
 prop_checkCharRangeGlob7 = verifyNot checkCharRangeGlob "[[ -v arr[keykey] ]]"
 prop_checkCharRangeGlob8 = verifyNot checkCharRangeGlob "[[ arr[keykey] -gt 1 ]]"
+prop_checkCharRangeGlob9 = verifyNot checkCharRangeGlob "read arr[keykey]" -- tr has 2313
 checkCharRangeGlob p t@(T_Glob id str) |
-  isCharClass str && not (isParamTo (parentMap p) "tr" t) && not (isDereferenced t) =
+  isCharClass str && not isIgnoredCommand && not (isDereferenced t) =
     if ":" `isPrefixOf` contents
         && ":" `isSuffixOf` contents
         && contents /= ":"
@@ -2712,6 +2713,10 @@ checkCharRangeGlob p t@(T_Glob id str) |
             '^':rest -> rest
             x -> x
 
+    isIgnoredCommand = fromMaybe False $ do
+        cmd <- getClosestCommand (parentMap p) t
+        return $ isCommandMatch cmd (`elem` ["tr", "read"])
+
     -- Check if this is a dereferencing context like [[ -v array[operandhere] ]]
     isDereferenced = fromMaybe False . msum . map isDereferencingOp . getPath (parentMap p)
     isDereferencingOp t =

src/ShellCheck/Checks/Commands.hs

@@ -790,6 +790,7 @@ prop_checkReadExpansions5 = verify checkReadExpansions "read \"$var\""
 prop_checkReadExpansions6 = verify checkReadExpansions "read -a $var"
 prop_checkReadExpansions7 = verifyNot checkReadExpansions "read $1"
 prop_checkReadExpansions8 = verifyNot checkReadExpansions "read ${var?}"
+prop_checkReadExpansions9 = verify checkReadExpansions "read arr[val]"
 checkReadExpansions = CommandCheck (Exactly "read") check
   where
     options = getGnuOpts flagsForRead
@@ -797,13 +798,26 @@ checkReadExpansions = CommandCheck (Exactly "read") check
         opts <- options $ arguments cmd
         return [y | (x,(_, y)) <- opts, null x || x == "a"]
 
-    check cmd = mapM_ warning $ getVars cmd
-    warning t = sequence_ $ do
+    check cmd = do
+        mapM_ dollarWarning $ getVars cmd
+        mapM_ arrayWarning $ arguments cmd
+
+    dollarWarning t = sequence_ $ do
         name <- getSingleUnmodifiedBracedString t
         guard $ isVariableName name   -- e.g. not $1
         return . warn (getId t) 2229 $
             "This does not read '" ++ name ++ "'. Remove $/${} for that, or use ${var?} to quiet."
 
+    arrayWarning word =
+        when (any isUnquotedBracket $ getWordParts word) $
+            warn (getId word) 2313 $
+                "Quote array indices to avoid them expanding as globs."
+
+    isUnquotedBracket t =
+        case t of
+            T_Glob _ ('[':_) -> True
+            _ -> False
+
 -- Return the single variable expansion that makes up this word, if any.
 -- e.g. $foo -> $foo, "$foo"'' -> $foo , "hello $name" -> Nothing
 getSingleUnmodifiedBracedString :: Token -> Maybe String