From 228181817284070efe29f64e793a531224f135b3 Mon Sep 17 00:00:00 2001
From: Joe Hermaszewski <git@monoid.al>
Date: Fri, 27 Nov 2020 11:55:48 +0800
Subject: [PATCH] Preserve the last empty comment line after eval plugin

```haskell
-- >>> foo
--
-- >>> bar
```

After running the plugin on both prompts we end up with this:

```haskell
-- >>> foo
-- foo_output
--
-- >>> bar
-- bar_output
```

instead of

```haskell
-- >>> foo
-- foo_output
-- >>> bar
-- bar_output
```
---
 plugins/default/src/Ide/Plugin/Eval.hs | 9 ++++++++-
 test/functional/Eval.hs                | 2 ++
 test/testdata/eval/T27.hs              | 4 ++++
 test/testdata/eval/T27.hs.expected     | 5 +++++
 4 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 test/testdata/eval/T27.hs
 create mode 100644 test/testdata/eval/T27.hs.expected

diff --git a/plugins/default/src/Ide/Plugin/Eval.hs b/plugins/default/src/Ide/Plugin/Eval.hs
index 28a16f383e..e91396c03d 100644
--- a/plugins/default/src/Ide/Plugin/Eval.hs
+++ b/plugins/default/src/Ide/Plugin/Eval.hs
@@ -117,7 +117,14 @@ extractMatches = goSearch 0 . maybe [] T.lines
         r = Range p p'
         p = Position line 0
         p' = Position (line + spliceLength) 0
-        spliceLength = length (takeWhile looksLikeSplice (l : ll))
+        spliceLines = takeWhile looksLikeSplice (l : ll)
+        -- Don't include the last line if it's an empty comment.
+        -- Do this to preserve spacing between consecutive splices
+        isEmptyComment = (== "--")
+        spliceLength = case spliceLines of
+                         [] -> 0
+                         ls | isEmptyComment (last ls) -> length ls - 1
+                            | otherwise -> length ls
 
 provider :: CodeLensProvider
 provider lsp _state plId CodeLensParams {_textDocument} = response $ do
diff --git a/test/functional/Eval.hs b/test/functional/Eval.hs
index 7c5e6b62c0..78762599e4 100644
--- a/test/functional/Eval.hs
+++ b/test/functional/Eval.hs
@@ -91,6 +91,8 @@ tests = testGroup
   $ goldenTest "T25.hs"
   , testCase "local imports"
   $ goldenTest "T26.hs"
+  , testCase "Preserves one empty comment line after prompt"
+  $ goldenTest "T27.hs"
   ]
 
 goldenTest :: FilePath -> IO ()
diff --git a/test/testdata/eval/T27.hs b/test/testdata/eval/T27.hs
new file mode 100644
index 0000000000..c1d68eba66
--- /dev/null
+++ b/test/testdata/eval/T27.hs
@@ -0,0 +1,4 @@
+module T27 where
+
+-- >>> ()
+--
diff --git a/test/testdata/eval/T27.hs.expected b/test/testdata/eval/T27.hs.expected
new file mode 100644
index 0000000000..e931c55c29
--- /dev/null
+++ b/test/testdata/eval/T27.hs.expected
@@ -0,0 +1,5 @@
+module T27 where
+
+-- >>> ()
+-- ()
+--