Reintroduce error

Author: isovector

src/Distribution/Server/Features/PackageInfoJSON.hs

@@ -38,7 +38,7 @@ import qualified Distribution.Server.Framework                as Framework
 import           Distribution.Server.Features.Core            (CoreFeature(..),
                                                                CoreResource(..))
 import qualified Distribution.Server.Features.PreferredVersions as Preferred
-import           Distribution.Server.Packages.Types           (CabalFileText(..), pkgSpecificRevision, pkgLatestRevision, pkgMaxRevision)
+import           Distribution.Server.Packages.Types           (CabalFileText(..), pkgSpecificRevision, pkgLatestRevision, pkgMaxRevision, pkgNumRevisions)
 
 import Distribution.Utils.ShortText (fromShortText)
 import Data.Foldable (toList)
@@ -245,11 +245,19 @@ servePackageBasicDescription resource userFeature preferred dpath = do
       guardValidPackageId resource pkgid
       pkg <- lookupPackageId resource pkgid
 
-      let (metadataInd, (cabalFile, uploadInfo)) =
-            fromMaybe (pkgMaxRevision pkg, pkgLatestRevision pkg) $ do
-              ix <- metadataRev
-              rev <- pkgSpecificRevision pkg ix
-              pure (ix, rev)
+      (metadataInd, (cabalFile, uploadInfo)) <- do
+        case metadataRev of
+          Nothing ->
+            pure (pkgMaxRevision pkg, pkgLatestRevision pkg)
+          Just ix ->
+            case pkgSpecificRevision pkg ix of
+              Nothing ->
+                Framework.errNotFound "Revision not found"
+                  [Framework.MText
+                    $ "There are " <> show (pkgNumRevisions pkg) <> " metadata revisions. Index "
+                    <> show ix <> " is out of bounds."]
+              Just rev -> pure (ix, rev)
+
       descr <- getPackageDescr cabalFile uploadInfo metadataInd
       return $ Framework.toResponse $ Aeson.toJSON descr