Skip indentation for empty line in multiline encoding

This change prevents yamllint error when encoding multilines
that contains empty lines.

Signed-off-by: Tristan Cacqueray <[email protected]>

src/Data/Aeson/Yaml.hs

@@ -158,8 +158,14 @@ encodeLines :: Int -> [Text] -> Builder
 encodeLines level ls =
   mconcat $
   (prefix :) $
-  intersperse (bs "\n" <> indent level) $ map (b . Text.Encoding.encodeUtf8) ls
+  intersperseOn (/= "") (bs "\n" <> indent level) (bs "\n") $ map Text.Encoding.encodeUtf8 ls
   where
+    intersperseOn _ _ _ [] = []
+    intersperseOn cond thenClause elseClause (x:xs) = b x : map go xs
+      where
+        go x'
+          | cond x' = thenClause <> b x'
+          | otherwise = elseClause <> b x'
     prefix =
       mconcat
         [ bs "|"

test/Test/Data/Aeson/Yaml.hs

@@ -62,6 +62,7 @@ tcDataTypes =
    "leadingSymbol" : "!leading symbol",
    "asteriskString": "*",
    "multiLine": "The first line is followed by the\nsecond line\n",
+   "multiLineWithEmptyLines": "The first line is followed by an empty line\n\nthird line\n",
    "multiLineWithSpaces": "         This has extra\n     spaces at the beginning\n",
    "notMultiline": "This won't be\nmulti-lined",
    "list": ["foo", "bar", "baz"],
@@ -86,6 +87,10 @@ listEmpty: []
 multiLine: |
   The first line is followed by the
   second line
+multiLineWithEmptyLines: |
+  The first line is followed by an empty line
+
+  third line
 multiLineWithSpaces: |2
            This has extra
        spaces at the beginning