Add --context flag (#81)

This limits the context to the specified number of characters/words/lines Fixes #42 Fixes #80
Gabriella439 · Mar 2, 2024 · 126fb40 · 126fb40
1 parent 872cac9
commit 126fb40
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Showing 5 changed files with 46 additions and 23 deletions.
diff --git a/app/Main.hs b/app/Main.hs
@@ -10,20 +10,21 @@
 
 module Main where
 
-import Control.Applicative ((<|>))
+import Control.Applicative ((<|>), optional)
 import Data.Text (Text)
 import Options.Applicative (Parser, ParserInfo)
+import Numeric.Natural (Natural)
 
 import qualified Control.Monad.Reader
 import qualified Control.Monad.State
+import qualified Data.Aeson
+import qualified Data.ByteString.Lazy.Char8
 import qualified Data.Set
+import qualified Data.Text.IO as Text.IO
 import qualified GHC.IO.Encoding
 import qualified Options.Applicative
 import qualified System.Posix.IO
 import qualified System.Posix.Terminal
-import qualified Data.Aeson
-import qualified Data.ByteString.Lazy.Char8
-import qualified Data.Text.IO as Text.IO
 
 import Nix.Diff
 import Nix.Diff.Types
@@ -71,6 +72,14 @@ parseLineOriented =
             <>  Options.Applicative.help ("Display textual differences on a per-" <> x <> " basis")
             )
 
+parseContext :: Parser Natural
+parseContext =
+    Options.Applicative.option
+        Options.Applicative.auto
+        (   Options.Applicative.long "context"
+        <>  Options.Applicative.help "Limit context to N lines/words/characters (depending on mode)"
+        )
+
 parseEnvironment :: Parser Bool
 parseEnvironment =
     Options.Applicative.switch
@@ -115,17 +124,19 @@ data Options = Options
     , environment      :: Bool
     , renderRunner     :: RenderRunner
     , transformOptions :: TransformOptions
+    , context          :: Maybe Natural
     }
 
 parseOptions :: Parser Options
 parseOptions = do
-    left        <- parseLeft
-    right       <- parseRight
-    color       <- parseColor
-    orientation <- parseLineOriented
-    environment <- parseEnvironment
-    renderRunner <- parseRenderRunner
+    left             <- parseLeft
+    right            <- parseRight
+    color            <- parseColor
+    orientation      <- parseLineOriented
+    environment      <- parseEnvironment
+    renderRunner     <- parseRenderRunner
     transformOptions <- parseTransformOptions
+    context          <- optional parseContext
 
     return (Options { .. })
   where

diff --git a/src/Nix/Diff.hs b/src/Nix/Diff.hs
@@ -179,9 +179,7 @@ getGroupedDiff oldList newList = go $ Patience.diff oldList newList
         let (fs, rest) = goNews xs
          in Patience.New (x : fs) : go rest
       Patience.Both x y : xs ->
-        let (fs, rest) = goBoth xs
-            (fxs, fys) = unzip fs
-         in Patience.Both (x : fxs) (y : fys) : go rest
+        Patience.Both [x] [y] : go xs
       [] -> []
 
     goOlds = \case
@@ -196,12 +194,6 @@ getGroupedDiff oldList newList = go $ Patience.diff oldList newList
          in (x : fs, rest)
       xs -> ([], xs)
 
-    goBoth = \case
-      Patience.Both x y : xs ->
-        let (fs, rest) = goBoth xs
-         in ((x, y) : fs, rest)
-      xs -> ([], xs)
-
 -- | Diff two outputs
 diffOutput
     :: Text

diff --git a/src/Nix/Diff/Render/HumanReadable.hs b/src/Nix/Diff/Render/HumanReadable.hs
@@ -35,6 +35,7 @@ data RenderContext = RenderContext
   { orientation :: Orientation
   , tty         :: TTY
   , indent      :: Natural
+  , context     :: Maybe Natural
   }
 
 newtype Render a = Render { unRender :: ReaderT RenderContext (Writer Text) a}
@@ -253,7 +254,7 @@ renderDiffHumanReadable = \case
 
     renderText :: TextDiff -> Render Text
     renderText (TextDiff chunks) = do
-      RenderContext{ indent, orientation, tty } <- ask
+      RenderContext{ indent, orientation, tty, context } <- ask
 
       let n = fromIntegral indent
 
@@ -276,6 +277,25 @@ renderDiffHumanReadable = \case
           renderChunk (Patience.Both l _) =
               grey            orientation tty l
 
-      return (format (Text.concat (fmap renderChunk chunks)))
+      let windowedChunks = case context of
+              Nothing -> chunks
+              Just m  -> fmap middle (filter predicate (zippers chunks))
+                where
+                  notBoth (Patience.Both _ _) = False
+                  notBoth  _                  = True
+
+                  nat = fromIntegral m
+
+                  predicate (before, line, after) =
+                      any notBoth (line : take nat before ++ take nat after)
+
+                  middle (_, line, _) = line
+      return (format (Text.concat (fmap renderChunk windowedChunks)))
 
     ifExist m l = maybe (pure ()) l m
+
+zippers :: [a] -> [([a], a, [a])]
+zippers = go []
+  where
+    go _           []  = []
+    go prefix (x : xs) = (prefix, x, xs) : go (x : prefix) xs
diff --git a/test/Golden/Tests.hs b/test/Golden/Tests.hs
@@ -36,7 +36,7 @@ goldenTests simpleTd complexTd = testGroup "Golden tests"
   where
     toJson drv = (<> "\n") . decodeUtf8 . BS.toStrict $ (Data.Aeson.encode drv)
 
-    humanReadable_words = toHumanReadable (renderContext Word)
+    humanReadable_words = toHumanReadable (renderContext Word Nothing)
     toHumanReadable ctx drv = runRender' (renderDiffHumanReadable drv) ctx
 
     simple_env_words = mkDTSimple (diffContextEnv Word)

diff --git a/test/Golden/Utils.hs b/test/Golden/Utils.hs
@@ -44,7 +44,7 @@ nixInstantiate :: FilePath -> ProcessConfig () () ()
 nixInstantiate fp = shell ("nix-instantiate " <> fp)
 
 nixPathInfo :: FilePath -> ProcessConfig () () ()
-nixPathInfo fp = shell ("nix path-info --experimental-features 'nix-command flakes' --derivation " <> fp)
+nixPathInfo fp = shell ("nix path-info --experimental-features 'nix-command flakes' --derivation " <> fp <> "#packages.x86_64-linux.default")
 
 makeDiffTree :: TestableDerivations -> DiffContext -> IO DerivationDiff
 makeDiffTree TestableDerivations{..} diffContext = do