Fix printing of indented block comments (#3225)

- Closes #3143 

The formatting of block comments has changed slightly.
A comment block has the syntax `{- multi-line-text -}`.
The rules are:
1. The first line, i.e. the line that starts with `{-` is trimmed of
trailing space.
2. The last line, i.e. the line that ends with `-}` is trimmed of prefix
space.
3. Lines in the middle are trimmed of prefix and trailing space.

This makes it impossible to have such a comment:
```
{-
  indented
-}
```
The reasoning is that if we don't want to have an indentation sensitive
parser we have two choices.
1. Print all comments flushed to the left
2. Do not have indentation in the middle lines.

I thought 2. was better

---------

Co-authored-by: Łukasz Czajka <62751+lukaszcz@users.noreply.github.com>

src/Juvix/Data/Comment.hs

@@ -1,10 +1,12 @@
 module Juvix.Data.Comment where
 
 import Data.HashMap.Strict qualified as HashMap
+import Data.Text qualified as Text
+import Juvix.Data.CodeAnn (CodeAnn (..), PrettyCodeAnn, ppCodeAnn)
 import Juvix.Data.Loc
 import Juvix.Extra.Strings qualified as Str
 import Juvix.Prelude.Base
-import Prettyprinter
+import Prettyprinter hiding (concatWith)
 
 newtype Comments = Comments
   { _commentsByFile :: HashMap (Path Abs File) FileComments
@@ -99,14 +101,48 @@ instance HasLoc SpaceSection where
 instance HasLoc Comment where
   getLoc = (^. commentInterval)
 
+instance PrettyCodeAnn Comment where
+  ppCodeAnn = annotate AnnComment . pretty
+
 instance Pretty Comment where
   pretty :: Comment -> Doc ann
-  pretty c = delim (pretty (c ^. commentText))
+  pretty c = delim (c ^. commentText)
     where
-      delim :: Doc ann -> Doc ann
+      delim :: Text -> Doc ann
       delim = case c ^. commentType of
-        CommentOneLine -> (Str.commentLineStart <>)
-        CommentBlock -> enclose Str.commentBlockStart Str.commentBlockEnd
+        CommentOneLine -> (Str.commentLineStart <>) . pretty
+        CommentBlock ->
+          enclose Str.commentBlockStart Str.commentBlockEnd
+            . pretty
+            . trimPrefixSpace
+
+      trimPrefixSpace :: Text -> Text
+      trimPrefixSpace txt = case Text.unsnoc txt of
+        Nothing -> ""
+        Just (_, l) ->
+          appendNl
+            . striplines
+            $ txt
+          where
+            striplines :: Text -> Text
+            striplines =
+              concatWith (\a b -> a <> "\n" <> b)
+                . run
+                . execOutputList
+                . go True
+                . Text.lines
+            go :: (Members '[Output Text] r) => Bool -> [Text] -> Sem r ()
+            go isFirst = \case
+              [] -> return ()
+              a : as
+                | isFirst && isLast -> output a
+                | isFirst -> output (Text.stripEnd a) >> go False as
+                | isLast -> output (Text.stripStart a)
+                | otherwise -> output (Text.strip a) >> go False as
+                where
+                  isLast = null as
+            lastnl = '\n' == l
+            appendNl = if lastnl then (<> "\n") else id
 
 allComments :: Comments -> [Comment]
 allComments c =

src/Juvix/Data/Effect/ExactPrint/Base.hs

@@ -154,7 +154,7 @@ printSpaceSpan = mapM_ printSpaceSection . (^. spaceSpan)
 
 printComment :: (Members '[State Builder] r) => Comment -> Sem r ()
 printComment c = do
-  append' (annotate AnnComment (P.pretty c))
+  append' (ppCodeAnn c)
   hardline'
 
 popQueue :: (Members '[State Builder] r) => Sem r ()

tests/positive/Format.juvix

@@ -534,6 +534,22 @@ module MultiIf;
       | else := 2;
 end;
 
+{-hi
+
+-}
+module CommentAfterFun;
+  myfun (a : Nat) : Nat :=
+    {-
+    My comment.
+    -}
+    {-nospaces-}
+    {-    somespaces   -}
+    {-    first line
+
+    last line  -}
+    1;
+end;
+
 module PublicImports;
 
   module Inner;