Skip SC2214 if variable is modified in loop (fixes koalaman#2351)

src/ShellCheck/Analytics.hs

@@ -1957,17 +1957,9 @@ subshellAssignmentCheck params t =
 
 findSubshelled [] _ _ = return ()
 findSubshelled (Assignment x@(_, _, str, data_):rest) scopes@((reason,scope):restscope) deadVars =
-    if isTrueAssignment data_
+    if isTrueAssignmentSource data_
     then findSubshelled rest ((reason, x:scope):restscope) $ Map.insert str Alive deadVars
     else findSubshelled rest scopes deadVars
-  where
-    isTrueAssignment c =
-        case c of
-            DataString SourceChecked -> False
-            DataString SourceDeclaration -> False
-            DataArray SourceChecked -> False
-            DataArray SourceDeclaration -> False
-            _ -> True
 
 findSubshelled (Reference (_, readToken, str):rest) scopes deadVars = do
     unless (shouldIgnore str) $ case Map.findWithDefault Alive str deadVars of

src/ShellCheck/AnalyzerLib.hs

@@ -1005,6 +1005,23 @@ isUnmodifiedParameterExpansion t =
             in getBracedReference str == str
         _ -> False
 
+isTrueAssignmentSource c =
+    case c of
+        DataString SourceChecked -> False
+        DataString SourceDeclaration -> False
+        DataArray SourceChecked -> False
+        DataArray SourceDeclaration -> False
+        _ -> True
+
+modifiesVariable params token name =
+    or $ map check flow
+  where
+    flow = getVariableFlow params token
+    check t =
+        case t of
+            Assignment (_, _, n, source) -> isTrueAssignmentSource source && n == name
+            _ -> False
+
 
 return []
 runTests =  $( [| $(forAllProperties) (quickCheckWithResult (stdArgs { maxSuccess = 1 }) ) |])

src/ShellCheck/Checks/Commands.hs

@@ -961,11 +961,13 @@ prop_checkWhileGetoptsCase4 = verifyNot checkWhileGetoptsCase "while getopts 'a:
 prop_checkWhileGetoptsCase5 = verifyNot checkWhileGetoptsCase "while getopts 'a:' x; do case $x in a) foo;; \\?) bar;; *) baz;; esac; done"
 prop_checkWhileGetoptsCase6 = verifyNot checkWhileGetoptsCase "while getopts 'a:b' x; do case $y in a) foo;; esac; done"
 prop_checkWhileGetoptsCase7 = verifyNot checkWhileGetoptsCase "while getopts 'a:b' x; do case x$x in xa) foo;; xb) foo;; esac; done"
+prop_checkWhileGetoptsCase8 = verifyNot checkWhileGetoptsCase "while getopts 'a:b' x; do x=a; case $x in a) foo;; esac; done"
 checkWhileGetoptsCase = CommandCheck (Exactly "getopts") f
   where
     f :: Token -> Analysis
     f t@(T_SimpleCommand _ _ (cmd:arg1:name:_))  = do
         path <- getPathM t
+        params <- ask
         sequence_ $ do
             options <- getLiteralString arg1
             getoptsVar <- getLiteralString name
@@ -977,6 +979,9 @@ checkWhileGetoptsCase = CommandCheck (Exactly "getopts") f
             [T_Literal _ caseVar] <- return $ getWordParts bracedWord
             guard $ caseVar == getoptsVar
 
+            -- Make sure the variable isn't modified
+            guard . not $ modifiesVariable params (T_BraceGroup (Id 0) body) getoptsVar
+
             return $ check (getId arg1) (map (:[]) $ filter (/= ':') options) caseCmd
     f _ = return ()