From 82a682ce648c48c890949ad67fc22900448dc94e Mon Sep 17 00:00:00 2001
From: Luke Lau <luke_lau@icloud.com>
Date: Tue, 31 Jul 2018 11:35:07 +0100
Subject: [PATCH] Add diff to replay error output

---
 .gitignore                                  |  2 ++
 haskell-lsp-test.cabal                      |  1 +
 src/Language/Haskell/LSP/Test/Exceptions.hs | 15 +++++++++++----
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/.gitignore b/.gitignore
index f78eac2..e6ad272 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,7 @@
 .stack-work
 dist
+.cabal-sandbox
+cabal.sandbox.config
 dist-newstyle
 cabal.project.local*
 .ghc.environment.*
diff --git a/haskell-lsp-test.cabal b/haskell-lsp-test.cabal
index d3ef940..ec769ac 100644
--- a/haskell-lsp-test.cabal
+++ b/haskell-lsp-test.cabal
@@ -33,6 +33,7 @@ library
                      , conduit-parse
                      , containers
                      , data-default
+                     , Diff
                      , directory
                      , filepath
                      , lens
diff --git a/src/Language/Haskell/LSP/Test/Exceptions.hs b/src/Language/Haskell/LSP/Test/Exceptions.hs
index b337f0b..28903dc 100644
--- a/src/Language/Haskell/LSP/Test/Exceptions.hs
+++ b/src/Language/Haskell/LSP/Test/Exceptions.hs
@@ -3,7 +3,10 @@ module Language.Haskell.LSP.Test.Exceptions where
 import Control.Exception
 import Language.Haskell.LSP.Messages
 import Language.Haskell.LSP.Types
-import Data.Aeson
+import Data.Aeson.Encode.Pretty
+import Data.Algorithm.Diff
+import Data.Algorithm.DiffOutput
+import Data.List
 import qualified Data.ByteString.Lazy.Char8 as B
 
 data SessionException = Timeout
@@ -23,10 +26,14 @@ instance Show SessionException where
     "Was parsing: " ++ expected ++ "\n" ++
     "Last message received: " ++ show lastMsg
   show (ReplayOutOfOrder received expected) =
-    "Replay is out of order:\n" ++
+    let expected' = nub expected
+        getJsonDiff = lines . B.unpack . encodePretty
+        showExp exp = B.unpack (encodePretty exp) ++ "\nDiff:\n" ++
+                ppDiff (getGroupedDiff (getJsonDiff received) (getJsonDiff exp))
+    in "Replay is out of order:\n" ++
        -- Print json so its a bit easier to update the session logs
-    "Received from server:\n" ++ B.unpack (encode received) ++ "\n" ++
-    "Expected one of:\n" ++ unlines (map (B.unpack . encode) expected)
+       "Received from server:\n" ++ B.unpack (encodePretty received) ++ "\n" ++
+       "Expected one of:\n" ++ unlines (map showExp expected')
   show UnexpectedDiagnostics = "Unexpectedly received diagnostics from the server."
   show (IncorrectApplyEditRequest msgStr) = "ApplyEditRequest didn't contain document, instead received:\n"
                                           ++ msgStr
-- 
2.30.2