Introduces highlighting package version differences

src/Stackage/Snapshot/Diff.hs

@@ -4,10 +4,12 @@ module Stackage.Snapshot.Diff
   , snapshotDiff
   , SnapshotDiff()
   , toDiffList
+  , toVersionedDiffList
   , VersionChange(..)
   , WithSnapshotNames(..)
   ) where
 
+import qualified Data.Text as T(commonPrefixes)
 import           Data.Align
 import           Data.Aeson
 import qualified Data.HashMap.Strict as HashMap
@@ -36,6 +38,20 @@ instance ToJSON (WithSnapshotNames SnapshotDiff) where
 toDiffList :: SnapshotDiff -> [(PackageName, VersionChange)]
 toDiffList = sortOn (toCaseFold . unPackageName . fst) . HashMap.toList . unSnapshotDiff
 
+versionPrefix :: VersionChange -> Maybe (Text,Text,Text)
+versionPrefix vc = case unVersionChange vc of
+        These (Version a) (Version b) -> T.commonPrefixes a b
+        _ -> Nothing
+
+versionedDiffList :: [(PackageName, VersionChange)] -> [(PackageName, VersionChange, Maybe (Text,Text,Text))]
+versionedDiffList = map withPrefixedVersion
+  where
+    withPrefixedVersion (packageName, versionChange) = (packageName, versionChange, versionPrefix versionChange)
+
+
+toVersionedDiffList :: SnapshotDiff -> [(PackageName, VersionChange, Maybe (Text, Text, Text))]
+toVersionedDiffList = versionedDiffList . toDiffList
+
 -- | Versions of a package as it occurs in the listings provided to `snapshotDiff`.
 --
 --   Would be represented with `These v1 v2` if the package is present in both listings,

templates/package-list.lucius

@@ -2,4 +2,13 @@
   .table th, .table td {
     padding-left: 0;
   }
+
+  .table span.version-removed {
+    background-color: red;
+    text-decoration: line-through;
+  }
+
+  .table span.version-added {
+    background-color: green;
+  }
 }

templates/stackage-diff.hamlet

@@ -33,7 +33,7 @@
                 $else
                   <option value=@{StackageDiffR name1 name2'}>#{toPathPiece name2'}
       <tbody>
-        $forall (pkgname, VersionChange verChange) <- toDiffList snapDiff
+        $forall (pkgname, VersionChange verChange, versionDiff) <- toVersionedDiffList snapDiff
           <tr>
             $case verChange
               $of This oldVersion
@@ -47,9 +47,19 @@
                   <a href=@{packageUrl name2 pkgname newVersion}#changes>
                     #{pkgname}-#{newVersion}
               $of These oldVersion newVersion
-                <td>
+                $maybe (common, old, new) <- versionDiff
-                  <a href=@{packageUrl name1 pkgname oldVersion}#changes>
+                  <td>
-                    #{pkgname}-#{oldVersion}
+                    <a href=@{packageUrl name1 pkgname oldVersion}#changes>
-                <td>
+                      #{pkgname}-#{common}#
-                  <a href=@{packageUrl name2 pkgname newVersion}#changes>
+                      <span .version-removed>#{old}
-                    #{pkgname}-#{newVersion}
+                  <td>
+                    <a href=@{packageUrl name2 pkgname newVersion}#changes>
+                      #{pkgname}-#{common}#
+                      <span .version-added>#{new}
+                $nothing
+                  <td>
+                    <a href=@{packageUrl name1 pkgname oldVersion}#changes>
+                      #{pkgname}-#{oldVersion}
+                  <td>
+                    <a href=@{packageUrl name2 pkgname newVersion}#changes>
+                      #{pkgname}-#{newVersion}