Warn about comments/blanks before shebang. Fixes #844

CHANGELOG.md

@@ -3,6 +3,7 @@
 - SC2227: Warn about redirections in the middle of 'find' commands
 - SC2224,SC2225,SC2226: Warn when using mv/cp/ln without a destination
 - SC2223: Quote warning specific to `: ${var=value}`
+- SC1128: Warn about blanks/comments before shebang
 - SC1127: Warn about C-style comments
 
 ### Fixed

ShellCheck/Parser.hs

@@ -2654,20 +2654,23 @@ prop_readShebang1 = isOk readShebang "#!/bin/sh\n"
 prop_readShebang2 = isWarning readShebang "!# /bin/sh\n"
 prop_readShebang3 = isNotOk readShebang "#shellcheck shell=/bin/sh\n"
 prop_readShebang4 = isWarning readShebang "! /bin/sh"
+prop_readShebang5 = isWarning readShebang "\n#!/bin/sh"
+prop_readShebang6 = isWarning readShebang " # Copyright \n!#/bin/bash"
+prop_readShebang7 = isNotOk readShebang "# Copyright \nfoo\n#!/bin/bash"
 readShebang = do
-    choice $ map try [
-        readCorrect,
-        readSwapped,
-        readTooManySpaces,
-        readMissingHash,
-        readMissingBang
-        ]
+    anyShebang <|> try readMissingBang <|> withHeader
     many linewhitespace
     str <- many $ noneOf "\r\n"
     optional carriageReturn
     optional linefeed
     return str
   where
+    anyShebang = choice $ map try [
+        readCorrect,
+        readSwapped,
+        readTooManySpaces,
+        readMissingHash
+        ]
     readCorrect = void $ string "#!"
 
     readSwapped = do
@@ -2705,11 +2708,22 @@ readShebang = do
         parseProblemAt pos ErrorC 1113
             "Use #!, not just #, for the shebang."
 
-
     ensurePathAhead = lookAhead $ do
         many linewhitespace
         char '/'
 
+    withHeader = try $ do
+        many1 headerLine
+        pos <- getPosition
+        anyShebang <*
+            parseProblemAt pos ErrorC 1128 "The shebang must be on the first line. Delete blanks and move comments."
+
+    headerLine = do
+        notFollowedBy2 anyShebang
+        many linewhitespace
+        optional readAnyComment
+        linefeed
+
 verifyEof = eof <|> choice [
         ifParsable g_Lparen $
             parseProblem ErrorC 1088 "Parsing stopped here. Invalid use of parentheses?",