From 640326ca5de12c21f87fe728bde69c21d8444320 Mon Sep 17 00:00:00 2001
From: Gregor Kleen <kleen@cip.ifi.lmu.de>
Date: Sun, 20 Oct 2019 11:02:32 +0200
Subject: [PATCH] fix(assign-submissions): avoid division by zero

---
 src/Handler/Utils/Submission.hs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/Handler/Utils/Submission.hs b/src/Handler/Utils/Submission.hs
index 4df32cd24..8304c1ec8 100644
--- a/src/Handler/Utils/Submission.hs
+++ b/src/Handler/Utils/Submission.hs
@@ -197,6 +197,10 @@ planSubmissions sid restriction = do
                 proportionSum = getSum . foldMap corrProportion . fromMaybe Map.empty $ correctors !? sheetId
                   where corrProportion (_, CorrectorExcused) = mempty
                         corrProportion (Load{..}, _) = Sum byProportion
+                relativeProportion :: Rational -> Rational
+                relativeProportion prop
+                  | proportionSum == 0 = 0
+                  | otherwise = prop / proportionSum
                 extra
                   | Just (Load{..}, corrState) <- correctors !? sheetId >>= Map.lookup corrector
                   = sum
@@ -208,7 +212,7 @@ planSubmissions sid restriction = do
                         return . negate . fromIntegral . Map.size $ Map.filter (\(mCorr, tutors, sheetId') -> mCorr == Just corrector && sheetId == sheetId' && Map.member corrector tutors) submissionState
                     , fromMaybe 0 $ do
                         guard $ corrState /= CorrectorExcused
-                        return . negate $ (byProportion / proportionSum) * fromIntegral sheetSize
+                        return . negate $ relativeProportion byProportion * fromIntegral sheetSize
                     ]
                   | otherwise
                   = assigned