check emptiness

geval.cabal

@@ -32,6 +32,7 @@ library
                      , resourcet
                      , split
                      , text
+                     , unix
   default-language:    Haskell2010
 
 executable geval

src/GEval/Core.hs

@@ -26,9 +26,11 @@ import Data.Text
 import Data.Text.Read as TR
 import Control.Applicative
 import Control.Exception
-import Control.Conditional (unlessM)
+import Control.Conditional (unlessM, whenM)
 import qualified System.Directory as D
 
+import System.Posix
+
 import System.FilePath
 import Data.Maybe
 
@@ -79,6 +81,7 @@ data GEvalException = NoExpectedFile FilePath
                       | FileAlreadyThere FilePath
                       | TooFewLines
                       | TooManyLines
+                      | EmptyOutput
                       deriving (Eq)
 
 instance Exception GEvalException
@@ -93,6 +96,7 @@ instance Show GEvalException where
   show (FileAlreadyThere filePath) = somethingWrongWithFilesMessage "File already there" filePath
   show TooFewLines = "Too few lines in the output file"
   show TooManyLines = "Too many lines in the output file"
+  show EmptyOutput = "The output file is empty"
 
 somethingWrongWithFilesMessage :: String -> FilePath -> String
 somethingWrongWithFilesMessage msg filePath = Prelude.concat
@@ -106,6 +110,10 @@ defaultGEvalSpecification = GEvalSpecification {
   gesExpectedFile = defaultExpectedFile,
   gesMetric = defaultMetric }
 
+isEmptyFile :: FilePath -> IO (Bool)
+isEmptyFile path = do
+    stat <- getFileStatus path
+    return ((fileSize stat) == 0)
 
 geval :: GEvalSpecification -> IO (MetricValue)
 geval gevalSpec = do
@@ -131,6 +139,7 @@ gevalCore RMSE expectedFilePath outFilePath = do
 gevalCore metric expectedFilePath outFilePath = do
   unlessM (D.doesFileExist expectedFilePath) $ throwM $ NoExpectedFile expectedFilePath
   unlessM (D.doesFileExist outFilePath) $ throwM $ NoOutFile outFilePath
+  whenM (isEmptyFile outFilePath) $ throwM $ EmptyOutput
   gevalCore' metric expectedFilePath outFilePath
 
 gevalCore' :: Metric -> String -> String -> IO (MetricValue)

test/Spec.hs

@@ -38,7 +38,8 @@ main = hspec $ do
       runGEvalTest "error-too-few-lines" `shouldThrow` (== TooFewLines)
     it "too many lines are handled" $ do
       runGEvalTest "error-too-many-lines" `shouldThrow` (== TooManyLines)
-
+    it "empty output is handled" $ do
+      runGEvalTest "empty-output" `shouldThrow` (== EmptyOutput)
 
 extractVal :: (Either (ParserResult GEvalOptions) (Maybe MetricValue)) -> IO MetricValue
 extractVal (Right (Just val)) = return val

test/empty-output/empty-output/config.txt

@@ -0,0 +1 @@
+--metric BLEU

test/empty-output/empty-output/test-A/expected.tsv

@@ -0,0 +1,2 @@
+Alice has a cat.
+Basia has a dog.

test/empty-output/empty-output/test-A/in.tsv

@@ -0,0 +1,2 @@
+Ala ma kota.
+Basia ma psa.