[Sass] Deprecate '@import foo' translating to '@import foo.css;'.

doc-src/SASS_CHANGELOG.md

@@ -16,6 +16,14 @@
 
 * Report the filename in warnings about selectors without properties.
 
+### Must Read!
+
+* When `@import` is given a filename without an extension,
+  the behavior of rendering a CSS `@import` if no Sass file is found
+  is deprecated.
+  In future versions, `@import foo` will either import the template
+  or raise an error.
+
 ## [2.2.16](http://github.com/nex3/haml/commit/2.2.16)
 
 * Fixed a bug where modules containing user-defined Sass functions

doc-src/SASS_REFERENCE.md

@@ -449,13 +449,16 @@ using the [`:load_paths`](#load_paths-option) option.
 
 `@import` takes a filename with or without an extension.
 If an extension isn't provided,
-Sass will try to find a Sass file with the given basename in the load paths,
-and, failing that, will assume a relevant CSS file will be available.
+Sass will try to find a Sass file with the given basename in the load paths.
 
 For example,
 
     @import foo.sass
 
+or
+
+    @import foo
+
 would compile to
 
     .foo {
@@ -469,13 +472,6 @@ would compile to
 
     @import foo.css;
 
-Finally,
-
-    @import foo
-
-might compile to either,
-depending on whether or not a file called "foo.sass" existed.
-
 #### Partials {#partials}
 
 If you have a Sass file that you want to import

lib/sass/files.rb

@@ -77,7 +77,14 @@ def find_file_to_import(filename, load_paths)
       new_filename = find_full_path("#{filename}.sass", load_paths)
 
       return new_filename if new_filename
-      return filename + '.css' unless was_sass
+      unless was_sass
+        warn <<END
+WARNING: #{filename}.sass not found. Using #{filename}.css instead.
+This behavior is deprecated and will be removed in a future version.
+If you really need #{filename}.css, import it explicitly.
+END
+        return filename + '.css'
+      end
       raise SyntaxError.new("File to import not found or unreadable: #{original_filename}.", @line)
     end
 

test/sass/engine_test.rb

@@ -211,6 +211,16 @@ def test_sass_import
     assert File.exists?(sassc_path("importee"))
   end
 
+  def test_nonexistent_extensionless_import
+    assert_warning(<<WARN) do
+WARNING: nonexistent.sass not found. Using nonexistent.css instead.
+This behavior is deprecated and will be removed in a future version.
+If you really need nonexistent.css, import it explicitly.
+WARN
+      assert_equal("@import url(nonexistent.css);\n", render("@import nonexistent"))
+    end
+  end
+
   def test_no_cache
     assert !File.exists?(sassc_path("importee"))
     renders_correctly("import", {