Unify filter and haml_comment parsing

* Fix bug in filter parsing

    A filter with no associated block wasn't being parsed properly,
    causing issues in any following code.

  * Dispatch haml_comment direct from process_line rather than
    silent_script.

    Syntactically it is a script with a comment, but the way it is
    handled is sufficiently different (especially with a block) to be
    dispatched as its own type.

  * Unify how haml_comment and filters are handled in the parser.

    Filters and comments with blocks are basically the same, the block
    isn't parsed (and so can have arbitrary indentation), so combine how
    they are handled in the parser. Remove special handling for
    haml_comment (e.g. @haml_comment variable), it now uses the same
    as filters (e.g. @flat).

    This means the text of the comment is now included in the parse tree
    (previously it was omitted).

Fixes #840 and #838 (the latter more as a side effect).

lib/haml/parser.rb

@@ -90,7 +90,6 @@ module Haml
 
     def initialize(template, options)
       @options            = options
-      @flat               = false
       # Record the indent levels of "if" statements to validate the subsequent
       # elsif and else statements are indented at the appropriate level.
       @script_level_stack = []
@@ -109,7 +108,8 @@ module Haml
 
     def parse
       @root = @parent = ParseNode.new(:root)
-      @haml_comment = false
+      @flat = false
+      @filter_buffer = nil
       @indentation = nil
       @line = next_line
 
@@ -129,13 +129,13 @@ module Haml
         end
 
         @tab_up = nil
-        process_line(@line) unless @line.text.empty? || @haml_comment
-        if @parent.type != :haml_comment && (block_opened? || @tab_up)
+        process_line(@line) unless @line.text.empty?
+        if block_opened? || @tab_up
           @template_tabs += 1
           @parent = @parent.children.last
         end
 
-        if !@haml_comment && !flat? && @next_line.tabs - @line.tabs > 1
+        if !flat? && @next_line.tabs - @line.tabs > 1
           raise SyntaxError.new(Error.message(:deeper_indenting, @next_line.tabs - @line.tabs), @next_line.index)
         end
 
@@ -243,7 +243,9 @@ module Haml
         line.text = line.text[1..-1]
         push script(line)
       when FLAT_SCRIPT; push flat_script(line.strip!(1))
-      when SILENT_SCRIPT; push silent_script(line)
+      when SILENT_SCRIPT
+        return push haml_comment(line.text[2..-1]) if line.text[1] == SILENT_COMMENT
+        push silent_script(line)
       when FILTER; push filter(line.text[1..-1].downcase)
       when DOCTYPE
         return push doctype(line.text) if line.text[0, 3] == '!!!'
@@ -301,8 +303,6 @@ module Haml
     end
 
     def silent_script(line)
-      return haml_comment(line.text[2..-1]) if line.text[1] == SILENT_COMMENT
-
       raise SyntaxError.new(Error.message(:no_end), line.index) if line.text[1..-1].strip == 'end'
 
       line = handle_ruby_multiline(line)
@@ -343,7 +343,15 @@ module Haml
     end
 
     def haml_comment(text)
-      @haml_comment = block_opened?
+      if filter_opened?
+        @flat = true
+        @filter_buffer = String.new
+        @filter_buffer << "#{text}\n" unless text.empty?
+        text = @filter_buffer
+        # If we don't know the indentation by now, it'll be set in Line#tabs
+        @flat_spaces = @indentation * (@template_tabs+1) if @indentation
+      end
+
       ParseNode.new(:haml_comment, @line.index + 1, :text => text)
     end
 
@@ -469,10 +477,9 @@ module Haml
     def filter(name)
       raise Error.new(Error.message(:invalid_filter_name, name)) unless name =~ /^\w+$/
 
-      @filter_buffer = String.new
-
       if filter_opened?
         @flat = true
+        @filter_buffer = String.new
         # If we don't know the indentation by now, it'll be set in Line#tabs
         @flat_spaces = @indentation * (@template_tabs+1) if @indentation
       end
@@ -487,13 +494,17 @@ module Haml
     end
 
     def close_filter(_)
-      @flat = false
-      @flat_spaces = nil
-      @filter_buffer = nil
+      close_flat_section
     end
 
     def close_haml_comment(_)
-      @haml_comment = false
+      close_flat_section
+    end
+
+    def close_flat_section
+      @flat = false
+      @flat_spaces = nil
+      @filter_buffer = nil
     end
 
     def close_silent_script(node)
@@ -772,7 +783,7 @@ module Haml
     # Same semantics as block_opened?, except that block_opened? uses Line#tabs,
     # which doesn't interact well with filter lines
     def filter_opened?
-      @next_line.full =~ (@indentation ? /^#{@indentation * @template_tabs}/ : /^\s/)
+      @next_line.full =~ (@indentation ? /^#{@indentation * (@template_tabs + 1)}/ : /^\s/)
     end
 
     def flat?

test/parser_test.rb

@@ -133,6 +133,34 @@ module Haml
       end
     end
 
+    test "empty filter doesn't hide following lines" do
+      root = parse "%p\n  :plain\n  %p\n"
+      p_element = root.children[0]
+      assert_equal 2, p_element.children.size
+      assert_equal :filter, p_element.children[0].type
+      assert_equal :tag, p_element.children[1].type
+    end
+
+    # Previously blocks under a haml_comment would be rejected if any line was
+    # indented by a value that wasn't a multiple of the document indentation.
+    test "haml_comment accepts any indentation in content" do
+      begin
+        parse "-\#\n  Indented two spaces\n   Indented three spaces"
+      rescue Haml::SyntaxError
+        flunk "haml_comment should accept any combination of indentation"
+      end
+    end
+
+    test "block haml_comment includes text" do
+      root = parse "-#\n  Hello\n   Hello\n"
+      assert_equal "Hello\n Hello\n", root.children[0].value[:text]
+    end
+
+    test "block haml_comment includes first line if present" do
+      root = parse "-# First line\n  Hello\n   Hello\n"
+      assert_equal " First line\nHello\n Hello\n", root.children[0].value[:text]
+    end
+
     private
 
     def parse(haml, options = nil)