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Use fromMaybes to clean up the FromJSON instance for BlobPair.

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Rob Rix 2019-10-18 12:25:09 -04:00
parent fc93bb4b4d
commit fecb0d8f1f
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1 changed files with 1 additions and 5 deletions
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6
src/Data/Blob.hs
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@ -105,11 +105,7 @@ instance FromJSON BlobPair where
parseJSON = withObject "BlobPair" $ \o -> do
before <- o .:? "before"
after <- o .:? "after"
case (before, after) of
(Just b, Just a) -> pure $ Compare b a
(Just b, Nothing) -> pure $ Delete b
(Nothing, Just a) -> pure $ Insert a
_ -> Prelude.fail "Expected object with 'before' and/or 'after' keys only"
maybeM (Prelude.fail "Expected object with 'before' and/or 'after' keys only") (fromMaybes before after)
maybeBlobPair :: MonadFail m => Maybe Blob -> Maybe Blob -> m BlobPair
maybeBlobPair a b = case (a, b) of