Pipe all warnings through Haml::Util.haml_warn.

lib/haml/template.rb

@@ -77,7 +77,7 @@ if Haml::Util.rails_root
       FileUtils.cp(haml_init_file, rails_init_file) unless FileUtils.cmp(rails_init_file, haml_init_file)
     end
   rescue SystemCallError
-    warn <<END
+    Haml::Util.haml_warn <<END
 HAML WARNING:
 #{rails_init_file} is out of date and couldn't be automatically updated.
 Please run `haml --rails #{File.expand_path(Haml::Util.rails_root)}' to update it.

lib/haml/util.rb

@@ -168,6 +168,26 @@ module Haml
       $stderr = the_real_stderr
     end
 
+    @@silence_warnings = false
+    # Silences all Haml warnings within a block.
+    #
+    # @yield A block in which no Haml warnings will be printed
+    def silence_haml_warnings
+      old_silence_warnings = @@silence_warnings
+      @@silence_warnings = true
+      yield
+    ensure
+      @@silence_warnings = old_silence_warnings
+    end
+
+    # The same as `Kernel#warn`, but is silenced by \{#silence\_haml\_warnings}.
+    #
+    # @param msg [String]
+    def haml_warn(msg)
+      return if @@silence_warnings
+      warn(msg)
+    end
+
     ## Cross Rails Version Compatibility
 
     # Returns the root of the Rails application,

lib/sass/engine.rb

@@ -356,7 +356,7 @@ MSG
 
     def check_for_no_children(node)
       return unless node.is_a?(Tree::RuleNode) && node.children.empty?
-      warn(<<WARNING.strip)
+      Haml::Util.haml_warn(<<WARNING.strip)
 WARNING on line #{node.line}#{" of #{node.filename}" if node.filename}:
 This selector doesn't have any properties and will not be rendered.
 WARNING

lib/sass/files.rb

@@ -81,7 +81,7 @@ module Sass
 
       return new_filename if new_filename
       unless was_sass || was_scss
-        warn <<END
+        Haml::Util.haml_warn <<END
 WARNING: Neither #{filename}.sass nor .scss 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.
@@ -116,7 +116,7 @@ END
         return Marshal.load(f.read)
       end
     rescue EOFError, TypeError, ArgumentError => e
-      warn "Warning. Error encountered while reading cache #{compiled_filename}: #{e}"
+      Haml::Util.haml_warn "Warning. Error encountered while reading cache #{compiled_filename}: #{e}"
     end
 
     def try_to_write_sassc(root, compiled_filename, sha, options)

lib/sass/script.rb

@@ -40,7 +40,7 @@ module Sass
 
     # @private
     def self.var_warning(varname, line, offset, filename)
-      warn <<MESSAGE
+      Haml::Util.haml_warn <<MESSAGE
 DEPRECATION WARNING:
 On line #{line}, character #{offset}#{" of '#{filename}'" if filename}
 Variables with ! have been deprecated and will be removed in version 3.2.
@@ -49,7 +49,7 @@ MESSAGE
     end
 
     def self.equals_warning(types, name, val, line, offset, filename)
-      warn <<MESSAGE
+      Haml::Util.haml_warn <<MESSAGE
 DEPRECATION WARNING:
 On line #{line}#{", character #{offset}" if offset}#{" of '#{filename}'" if filename}
 Setting #{types} with = has been deprecated and will be removed in version 3.2.

lib/sass/script/color.rb

@@ -184,7 +184,7 @@ module Sass::Script
     # @deprecated This will be removed in version 3.2.
     # @see #rgb
     def value
-      warn <<END
+      Haml::Util.haml_warn <<END
 DEPRECATION WARNING:
 The Sass::Script::Color #value attribute is deprecated and will be
 removed in version 3.2. Use the #rgb attribute instead.

test/haml/util_test.rb

@@ -85,6 +85,20 @@ class UtilTest < Test::Unit::TestCase
     $stderr = old_stderr
   end
 
+  def test_haml_warn
+    assert_warning("Foo!") {haml_warn "Foo!"}
+  end
+
+  def test_silence_haml_warnings
+    old_stderr, $stderr = $stderr, StringIO.new
+    silence_haml_warnings {warn "Out"}
+    assert_equal("Out\n", $stderr.string)
+    silence_haml_warnings {haml_warn "In"}
+    assert_equal("Out\n", $stderr.string)
+  ensure
+    $stderr = old_stderr
+  end
+
   def test_has
     assert(has?(:instance_method, String, :chomp!))
     assert(has?(:private_instance_method, Haml::Engine, :set_locals))