Handle properly stringifying multiline macro expressions

spec/compiler/parser/parser_spec.cr

@@ -1118,7 +1118,7 @@ module Crystal
     it_parses "puts {{**1}}", Call.new(nil, "puts", MacroExpression.new(DoubleSplat.new(1.int32)))
     it_parses "{{a = 1 if 2}}", MacroExpression.new(If.new(2.int32, Assign.new("a".var, 1.int32)))
     it_parses "{% a = 1 %}", MacroExpression.new(Assign.new("a".var, 1.int32), output: false)
-    it_parses "{%\na = 1\n%}", MacroExpression.new(Assign.new("a".var, 1.int32), output: false)
+    it_parses "{%\n  a = 1\n%}", MacroExpression.new(Assign.new("a".var, 1.int32), output: false, multiline: true)
     it_parses "{% a = 1 if 2 %}", MacroExpression.new(If.new(2.int32, Assign.new("a".var, 1.int32)), output: false)
     it_parses "{% if 1; 2; end %}", MacroExpression.new(If.new(1.int32, 2.int32), output: false)
     it_parses "{%\nif 1; 2; end\n%}", MacroExpression.new(If.new(1.int32, 2.int32), output: false)
@@ -1128,7 +1128,8 @@ module Crystal
     it_parses "{% unless 1; 2; else 3; end %}", MacroExpression.new(Unless.new(1.int32, 2.int32, 3.int32), output: false)
     it_parses "{% unless 1\n  x\nend %}", MacroExpression.new(Unless.new(1.int32, "x".var), output: false)
     it_parses "{% x unless 1 %}", MacroExpression.new(Unless.new(1.int32, "x".var), output: false)
-    it_parses "{%\n1\n2\n3\n%}", MacroExpression.new(Expressions.new([1.int32, 2.int32, 3.int32] of ASTNode), output: false)
+    it_parses "{%\n  x unless 1\n%}", MacroExpression.new(Unless.new(1.int32, "x".var), output: false, multiline: true)
+    it_parses "{%\n  1\n  2\n  3\n%}", MacroExpression.new(Expressions.new([1.int32, 2.int32, 3.int32] of ASTNode), output: false, multiline: true)
 
     assert_syntax_error "{% unless 1; 2; elsif 3; 4; end %}"
     assert_syntax_error "{% unless 1 %} 2 {% elsif 3 %} 3 {% end %}"

spec/compiler/parser/to_s_spec.cr

@@ -248,6 +248,12 @@ describe "ASTNode#to_s" do
   expect_to_s "1.//(2, &block)"
   expect_to_s %({% verbatim do %}\n  1{{ 2 }}\n  3{{ 4 }}\n{% end %})
   expect_to_s %({% for foo in bar %}\n  {{ if true\n  foo\n  bar\nend }}\n{% end %})
+  expect_to_s "{% a = 1 %}"
+  expect_to_s "{{ a = 1 }}"
+  expect_to_s "{%\n  1\n  2\n  3\n%}"
+  expect_to_s "{%\n  1\n%}"
+  expect_to_s "{%\n  2 + 2\n%}"
+
   expect_to_s %(asm("nop" ::::))
   expect_to_s %(asm("nop" : "a"(1), "b"(2) : "c"(3), "d"(4) : "e", "f" : "volatile", "alignstack", "intel"))
   expect_to_s %(asm("nop" :: "c"(3), "d"(4) ::))

src/compiler/crystal/syntax/ast.cr

@@ -2187,24 +2187,32 @@ module Crystal
   end
 
   # A macro expression,
-  # surrounded by {{ ... }} (output = true)
-  # or by {% ... %} (output = false)
+  # surrounded by {{ ... }}` (output = true, multiline = false)
+  # or by `{% ... %}` (output = false, multiline = false)
+  #
+  # ```
+  # # (output = false, multiline = true)
+  # {%
+  #   ...
+  # %}
+  # ```
   class MacroExpression < ASTNode
     property exp : ASTNode
     property? output : Bool
+    property? multiline : Bool
 
-    def initialize(@exp : ASTNode, @output = true)
+    def initialize(@exp : ASTNode, @output = true, @multiline : Bool = false)
     end
 
     def accept_children(visitor)
       @exp.accept visitor
     end
 
     def clone_without_location
-      MacroExpression.new(@exp.clone, @output)
+      MacroExpression.new(@exp.clone, @output, @multiline)
     end
 
-    def_equals_and_hash exp, output?
+    def_equals_and_hash exp, output?, multiline?
   end
 
   # Free text that is part of a macro

src/compiler/crystal/syntax/parser.cr

@@ -3353,7 +3353,13 @@ module Crystal
 
     def parse_macro_control(start_location, macro_state = Token::MacroState.default)
       location = @token.location
-      next_token_skip_space_or_newline
+      next_token_skip_space
+      multiline = false
+
+      if @token.type.newline?
+        multiline = true
+        next_token_skip_space_or_newline
+      end
 
       case @token.value
       when Keyword::FOR
@@ -3440,7 +3446,7 @@ module Crystal
       exps = parse_expressions
       @in_macro_expression = false
 
-      MacroExpression.new(exps, output: false).at(location).at_end(token_end_location)
+      MacroExpression.new(exps, output: false, multiline: multiline).at(location).at_end(token_end_location)
     end
 
     def parse_macro_if(start_location, macro_state, check_end = true, is_unless = false)

src/compiler/crystal/syntax/to_s.cr

@@ -728,13 +728,29 @@ module Crystal
     end
 
     def visit(node : MacroExpression)
-      @str << (node.output? ? "{{" : "{% ")
-      @str << ' ' if node.output?
+      @str << (node.output? ? "{{ " : node.multiline? ? "{%" : "{% ")
+
+      if node.multiline?
+        newline
+        @indent += 1
+      end
+
       outside_macro do
+        # If the MacroExpression consists of a single node we need to manually handle appending indent and trailing newline if #multiline?
+        # Otherwise, the Expressions logic handles that for us
+        if !node.exp.is_a? Expressions
+          append_indent
+        end
+
         node.exp.accept self
       end
-      @str << ' ' if node.output?
-      @str << (node.output? ? "}}" : " %}")
+
+      if node.multiline?
+        @indent -= 1
+        newline if !node.exp.is_a? Expressions
+      end
+
+      @str << (node.output? ? " }}" : node.multiline? ? "%}" : " %}")
       false
     end