[Sass] Explain how to escape pseudo-classes.

doc-src/SASS_CHANGELOG.md

@@ -3,6 +3,11 @@
 * Table of contents
 {:toc}
 
+## 2.2.11 (Unreleased)
+
+* Added a note to errors on properties that could be pseudo-classes (e.g. `:focus`)
+  indicating that they should be backslash-escaped.
+
 ## [2.2.10](http://github.com/nex3/haml/commit/2.2.10)
 
 * Add support for attribute selectors with spaces around the `=`.

lib/sass/tree/node.rb

@@ -123,7 +123,9 @@ module Sass
         result = String.new
         children.each do |child|
           if child.is_a? PropNode
-            raise Sass::SyntaxError.new('Properties aren\'t allowed at the root of a document.', child.line)
+            message = "Properties aren't allowed at the root of a document." +
+              child.pseudo_class_selector_message
+            raise Sass::SyntaxError.new(message, child.line)
           else
             next if child.invisible?
             child_str = child.to_s(1)

lib/sass/tree/prop_node.rb

@@ -54,7 +54,9 @@ module Sass::Tree
       real_name = "#{parent_name}-#{real_name}" if parent_name
       
       if value.empty? && children.empty?
-        raise Sass::SyntaxError.new("Invalid property: #{declaration.dump} (no value).", @line)
+        message = "Invalid property: #{declaration.dump} (no value)." +
+          pseudo_class_selector_message
+        raise Sass::SyntaxError.new(message, @line)
       end
       
       join_string = case style
@@ -76,6 +78,16 @@ module Sass::Tree
       (style == :compressed && parent_name) ? to_return : to_return[0...-1]
     end
 
+    # Returns a appropriate message indicating how to escape pseudo-class selectors.
+    # This only applies for old-style properties with no value,
+    # so returns the empty string if this is new-style.
+    #
+    # @return [String] The message
+    def pseudo_class_selector_message
+      return "" if @prop_syntax == :new || !value.empty?
+      "\nIf #{declaration.dump} should be a selector, use \"\\#{declaration}\" instead."
+    end
+
     protected
 
     # Runs any SassScript that may be embedded in the property.
@@ -103,7 +115,7 @@ module Sass::Tree
     private
 
     def declaration
-      @prop_syntax == :new ? "#{name}: #{value}" : ":#{name} #{value}"
+      (@prop_syntax == :new ? "#{name}: #{value}" : ":#{name} #{value}").strip
     end
   end
 end

test/sass/engine_test.rb

@@ -18,8 +18,11 @@ class SassEngineTest < Test::Unit::TestCase
     ":" => 'Invalid property: ":".',
     ": a" => 'Invalid property: ": a".',
     ":= a" => 'Invalid property: ":= a".',
-    "a\n  :b" => 'Invalid property: ":b " (no value).',
-    "a\n  b:" => 'Invalid property: "b: " (no value).',
+    "a\n  :b" => <<MSG,
+Invalid property: ":b" (no value).
+If ":b" should be a selector, use "\\:b" instead.
+MSG
+    "a\n  b:" => 'Invalid property: "b:" (no value).',
     "a\n  :b: c" => 'Invalid property: ":b: c".',
     "a\n  :b:c d" => 'Invalid property: ":b:c d".',
     "a\n  :b=c d" => 'Invalid property: ":b=c d".',
@@ -27,7 +30,12 @@ class SassEngineTest < Test::Unit::TestCase
     "a\n  b: c;" => 'Invalid property: "b: c;" (no ";" required at end-of-line).',
     "a\n  b : c" => 'Invalid property: "b : c".',
     "a\n  b=c: d" => 'Invalid property: "b=c: d".',
-    ":a" => 'Properties aren\'t allowed at the root of a document.',
+    ":a b" => 'Properties aren\'t allowed at the root of a document.',
+    "a:" => 'Properties aren\'t allowed at the root of a document.',
+    ":a" => <<MSG,
+Properties aren't allowed at the root of a document.
+If ":a" should be a selector, use "\\:a" instead.
+MSG
     "!" => 'Invalid variable: "!".',
     "!a" => 'Invalid variable: "!a".',
     "! a" => 'Invalid variable: "! a".',
@@ -134,7 +142,7 @@ class SassEngineTest < Test::Unit::TestCase
       rescue Sass::SyntaxError => err
         value = [value] unless value.is_a?(Array)
 
-        assert_equal(value.first, err.message, "Line: #{key}")
+        assert_equal(value.first.rstrip, err.message, "Line: #{key}")
         assert_equal(__FILE__, err.sass_filename)
         assert_equal((value[1] || key.split("\n").length) + line - 1, err.sass_line, "Line: #{key}")
         assert_match(/#{Regexp.escape(__FILE__)}:[0-9]+/, err.backtrace[0], "Line: #{key}")