Warn when commands start with dashes (#938)

ShellCheck/ASTLib.hs

@@ -125,6 +125,11 @@ isFlag token =
         T_Literal _ ('-':_) : _ -> True
         _ -> False
 
+-- Is this token a flag where the - is unquoted?
+isUnquotedFlag token = fromMaybe False $ do
+    str <- getLeadingUnquotedString token
+    return $ "-" `isPrefixOf` str
+
 -- Given a T_DollarBraced, return a simplified version of the string contents.
 bracedString (T_DollarBraced _ l) = concat $ oversimplify l
 bracedString _ = error "Internal shellcheck error, please report! (bracedString on non-variable)"
@@ -194,6 +199,13 @@ getTrailingUnquotedLiteral t =
             T_Literal {} -> return t
             _ -> Nothing
 
+-- Get the leading, unquoted, literal string of a token (if any).
+getLeadingUnquotedString :: Token -> Maybe String
+getLeadingUnquotedString t =
+    case t of
+        T_NormalWord _ ((T_Literal _ s) : _) -> return s
+        _ -> Nothing
+
 -- Maybe get the literal string of this token and any globs in it.
 getGlobOrLiteralString = getLiteralStringExt f
   where

ShellCheck/Analytics.hs

@@ -162,6 +162,7 @@ nodeChecks = [
     ,checkSplittingInArrays
     ,checkRedirectionToNumber
     ,checkGlobAsCommand
+    ,checkFlagAsCommand
     ,checkEmptyCondition
     ]
 
@@ -275,10 +276,7 @@ checkAssignAteCommand _ (T_SimpleCommand id (T_Assignment _ _ _ _ assignmentTerm
     isCommonCommand _ = False
     firstWordIsArg list = fromMaybe False $ do
         head <- list !!! 0
-        return . or $ mapMaybe ($ head) [return . isGlob, isFlag]
+        return $ isGlob head || isUnquotedFlag head
-    isFlag word = do
-        first <- (concat $ oversimplify word) !!! 0
-        return $ first == '-'
 
 checkAssignAteCommand _ _ = return ()
 
@@ -2770,6 +2768,18 @@ checkGlobAsCommand _ t = case t of
             warn (getId first) 2211 "This is a glob used as a command name. Was it supposed to be in ${..}, array, or is it missing quoting?"
     _ -> return ()
 
+
+prop_checkFlagAsCommand1 = verify checkFlagAsCommand "-e file"
+prop_checkFlagAsCommand2 = verify checkFlagAsCommand "foo\n  --bar=baz"
+prop_checkFlagAsCommand3 = verifyNot checkFlagAsCommand "'--myexec--' args"
+prop_checkFlagAsCommand4 = verifyNot checkFlagAsCommand "var=cmd --arg"  -- Handled by SC2037
+checkFlagAsCommand _ t = case t of
+    T_SimpleCommand _ [] (first:_) ->
+        when (isUnquotedFlag first) $
+            warn (getId first) 2215 "This flag is used as a command name. Bad line break or missing [ .. ]?"
+    _ -> return ()
+
+
 prop_checkEmptyCondition1 = verify checkEmptyCondition "if [ ]; then ..; fi"
 prop_checkEmptyCondition2 = verifyNot checkEmptyCondition "[ foo -o bar ]"
 checkEmptyCondition _ t = case t of