[ fix #1626 ] Empty lines are still lines

src/Idris/Desugar.idr

@@ -572,12 +572,13 @@ mutual
 
       trimLeft : Nat -> List PStr -> Core (List PStr)
       trimLeft indent [] = pure []
-      trimLeft indent [(StrLiteral fc str)]
+      trimLeft indent [StrLiteral fc str]
           = let (trimed, rest) = splitAt indent (fastUnpack str) in
             if any (not . isSpace) trimed
               then throw $ BadMultiline fc "Line is less indented than the closing delimiter"
-                   else pure $ [StrLiteral fc (fastPack rest)]
-      trimLeft indent ((StrLiteral fc str)::xs)
+              else let str = if null rest then "\n" else fastPack rest in
+                   pure [StrLiteral fc str]
+      trimLeft indent (StrLiteral fc str :: xs)
           = let (trimed, rest) = splitAt indent (fastUnpack str) in
             if any (not . isSpace) trimed || length trimed < indent
               then throw $ BadMultiline fc "Line is less indented than the closing delimiter"

tests/Main.idr

@@ -42,7 +42,8 @@ idrisTestsBasic = MkTestPool "Fundamental language features" [] Nothing
        "basic051", "basic052", "basic053", "basic054", "basic055",
        "basic056", "basic057", "basic058", "basic059", "basic060",
        "basic061", "basic062", "basic063",
-       "interpolation001", "interpolation002", "interpolation003"]
+       "interpolation001", "interpolation002", "interpolation003",
+       "interpolation004"]
 
 idrisTestsCoverage : TestPool
 idrisTestsCoverage = MkTestPool "Coverage checking" [] Nothing

tests/idris2/interpolation004/StringLiteral.idr

@@ -0,0 +1,20 @@
+module StringLiteral
+
+Str : String
+Str = """
+  First line
+
+  Third line
+  """
+
+Str2NL : String
+Str2NL = "First line\n\nThird line"
+
+sss : Str === Str2NL
+sss = Refl
+
+Str1NL : String
+Str1NL = "First line\nThird line"
+
+sss' : (Str == Str1NL) === False
+sss' = Refl

tests/idris2/interpolation004/expected

@@ -0,0 +1 @@
+1/1: Building StringLiteral (StringLiteral.idr)

tests/idris2/interpolation004/run

@@ -0,0 +1,3 @@
+rm -rf build
+
+$1 --no-color --console-width 0 --no-banner --check StringLiteral.idr