Allow extends that match but don't unify.

Closes #2250

doc-src/SASS_CHANGELOG.md

@@ -10,6 +10,9 @@
 * Combine ids and `:root` when unifying selectors with `@extend` and selector
   functions.
 
+* It's no longer an error to `@extend` a selector that exists in the stylesheet,
+  but for which unification fails.
+
 * Add a `$weight` parameter to `invert()`.
 
 * The last argument in an argument list can now have a trailing comma.

lib/sass/selector/comma_sequence.rb

@@ -129,7 +129,7 @@ def populate_extends(extends, extendee, extend_node = nil, parent_directives = [
             end
 
             extends[sel] = Sass::Tree::Visitors::Cssize::Extend.new(
-              member, sel, extend_node, parent_directives, :not_found)
+              member, sel, extend_node, parent_directives, false)
           end
         end
       end

lib/sass/selector/simple_sequence.rb

@@ -191,10 +191,9 @@ def do_extend(extends, parent_directives, replace, seen)
           # seq is A, sels is B, and self is C
 
           self_without_sel = Sass::Util.array_minus(members, sels)
-          group.each {|e| e.result = :failed_to_unify unless e.result == :succeeded}
+          group.each {|e| e.success = true}
           unified = seq.members.last.unify(SimpleSequence.new(self_without_sel, subject?))
           next unless unified
-          group.each {|e| e.result = :succeeded}
           group.each {|e| check_directives_match!(e, parent_directives)}
           new_seq = Sequence.new(seq.members[0...-1] + [unified])
           new_seq.add_sources!(sources + [seq])

lib/sass/tree/visitors/cssize.rb

@@ -106,11 +106,9 @@ def visit_root(node)
   # @attr node [Sass::Tree::ExtendNode] The node that produced this extend.
   # @attr directives [Array<Sass::Tree::DirectiveNode>]
   #   The directives containing the `@extend`.
-  # @attr result [Symbol]
-  #   The result of this extend. One of `:not_found` (the target doesn't exist
-  #   in the document), `:failed_to_unify` (the target exists but cannot be
-  #   unified with the extender), or `:succeeded`.
-  Extend = Struct.new(:extender, :target, :node, :directives, :result)
+  # @attr success [Boolean]
+  #   Whether this extend successfully matched a selector.
+  Extend = Struct.new(:extender, :target, :node, :directives, :success)
 
   # Registers an extension in the `@extends` subset map.
   def visit_extend(node)

lib/sass/tree/visitors/extend.rb

@@ -49,19 +49,13 @@ class << self
 
     def check_extends_fired!(extends)
       extends.each_value do |ex|
-        next if ex.result == :succeeded || ex.node.optional?
+        next if ex.success || ex.node.optional?
         message = "\"#{ex.extender}\" failed to @extend \"#{ex.target.join}\"."
-        reason =
-          if ex.result == :not_found
-            "The selector \"#{ex.target.join}\" was not found."
-          else
-            "No selectors matching \"#{ex.target.join}\" could be unified with \"#{ex.extender}\"."
-          end
 
         # TODO(nweiz): this should use the Sass stack trace of the extend node.
         raise Sass::SyntaxError.new(<<MESSAGE, :filename => ex.node.filename, :line => ex.node.line)
 #{message}
-#{reason}
+The selector "#{ex.target.join}" was not found.
 Use "@extend #{ex.target.join} !optional" if the extend should be able to fail.
 MESSAGE
       end

test/sass/extend_test.rb

@@ -152,10 +152,7 @@ def test_class_unification
   def test_id_unification
     assert_unification '.foo.bar', '#baz {@extend .foo}', '.foo.bar, .bar#baz'
     assert_unification '.foo#baz', '#baz {@extend .foo}', '#baz'
-
-    assert_extend_doesnt_match('#bar', '.foo', :failed_to_unify, 2) do
-      render_unification '.foo#baz', '#bar {@extend .foo}'
-    end
+    assert_unification '.foo#baz', '#bar {@extend .foo}', '.foo#baz'
   end
 
   def test_universal_unification_with_simple_target
@@ -167,10 +164,7 @@ def test_universal_unification_with_simple_target
   end
 
   def test_universal_unification_with_namespaceless_universal_target
-    assert_extend_doesnt_match('ns|*', '.foo', :failed_to_unify, 2) do
-      render_unification '*.foo', 'ns|* {@extend .foo}'
-    end
-
+    assert_unification '*.foo', 'ns|* {@extend .foo}', '*.foo'
     assert_unification '*.foo', '* {@extend .foo}', '*'
     assert_unification '*.foo', '*|* {@extend .foo}', '*'
     assert_unification '*|*.foo', '* {@extend .foo}', '*|*.foo, *'
@@ -179,23 +173,14 @@ def test_universal_unification_with_namespaceless_universal_target
   end
 
   def test_universal_unification_with_namespaced_universal_target
-    assert_extend_doesnt_match('*', '.foo', :failed_to_unify, 2) do
-      render_unification 'ns|*.foo', '* {@extend .foo}'
-    end
-
-    assert_extend_doesnt_match('ns2|*', '.foo', :failed_to_unify, 2) do
-      render_unification 'ns1|*.foo', 'ns2|* {@extend .foo}'
-    end
-
+    assert_unification 'ns|*.foo', '* {@extend .foo}', 'ns|*.foo'
+    assert_unification 'ns1|*.foo', 'ns2|* {@extend .foo}', 'ns1|*.foo'
     assert_unification 'ns|*.foo', '*|* {@extend .foo}', 'ns|*'
     assert_unification 'ns|*.foo', 'ns|* {@extend .foo}', 'ns|*'
   end
 
   def test_universal_unification_with_namespaceless_element_target
-    assert_extend_doesnt_match('ns|*', '.foo', :failed_to_unify, 2) do
-      render_unification 'a.foo', 'ns|* {@extend .foo}'
-    end
-
+    assert_unification 'a.foo', 'ns|* {@extend .foo}', 'a.foo'
     assert_unification 'a.foo', '* {@extend .foo}', 'a'
     assert_unification 'a.foo', '*|* {@extend .foo}', 'a'
     assert_unification '*|a.foo', '* {@extend .foo}', '*|a.foo, a'
@@ -204,14 +189,8 @@ def test_universal_unification_with_namespaceless_element_target
   end
 
   def test_universal_unification_with_namespaced_element_target
-    assert_extend_doesnt_match('*', '.foo', :failed_to_unify, 2) do
-      render_unification 'ns|a.foo', '* {@extend .foo}'
-    end
-
-    assert_extend_doesnt_match('ns2|*', '.foo', :failed_to_unify, 2) do
-      render_unification 'ns1|a.foo', 'ns2|* {@extend .foo}'
-    end
-
+    assert_unification 'ns|a.foo', '* {@extend .foo}', 'ns|a.foo'
+    assert_unification 'ns1|a.foo', 'ns2|* {@extend .foo}', 'ns1|a.foo'
     assert_unification 'ns|a.foo', '*|* {@extend .foo}', 'ns|a'
     assert_unification 'ns|a.foo', 'ns|* {@extend .foo}', 'ns|a'
   end
@@ -224,10 +203,7 @@ def test_element_unification_with_simple_target
   end
 
   def test_element_unification_with_namespaceless_universal_target
-    assert_extend_doesnt_match('ns|a', '.foo', :failed_to_unify, 2) do
-      render_unification '*.foo', 'ns|a {@extend .foo}'
-    end
-
+    assert_unification '*.foo', 'ns|a {@extend .foo}', '*.foo'
     assert_unification '*.foo', 'a {@extend .foo}', '*.foo, a'
     assert_unification '*.foo', '*|a {@extend .foo}', '*.foo, a'
     assert_unification '*|*.foo', 'a {@extend .foo}', '*|*.foo, a'
@@ -236,27 +212,15 @@ def test_element_unification_with_namespaceless_universal_target
   end
 
   def test_element_unification_with_namespaced_universal_target
-    assert_extend_doesnt_match('a', '.foo', :failed_to_unify, 2) do
-      render_unification 'ns|*.foo', 'a {@extend .foo}'
-    end
-
-    assert_extend_doesnt_match('ns2|a', '.foo', :failed_to_unify, 2) do
-      render_unification 'ns1|*.foo', 'ns2|a {@extend .foo}'
-    end
-
+    assert_unification 'ns|*.foo', 'a {@extend .foo}', 'ns|*.foo'
+    assert_unification 'ns1|*.foo', 'ns2|a {@extend .foo}', 'ns1|*.foo'
     assert_unification 'ns|*.foo', '*|a {@extend .foo}', 'ns|*.foo, ns|a'
     assert_unification 'ns|*.foo', 'ns|a {@extend .foo}', 'ns|*.foo, ns|a'
   end
 
   def test_element_unification_with_namespaceless_element_target
-    assert_extend_doesnt_match('ns|a', '.foo', :failed_to_unify, 2) do
-      render_unification 'a.foo', 'ns|a {@extend .foo}'
-    end
-
-    assert_extend_doesnt_match('h1', '.foo', :failed_to_unify, 2) do
-      render_unification 'a.foo', 'h1 {@extend .foo}'
-    end
-
+    assert_unification 'a.foo', 'ns|a {@extend .foo}', 'a.foo'
+    assert_unification 'a.foo', 'h1 {@extend .foo}', 'a.foo'
     assert_unification 'a.foo', 'a {@extend .foo}', 'a'
     assert_unification 'a.foo', '*|a {@extend .foo}', 'a'
     assert_unification '*|a.foo', 'a {@extend .foo}', '*|a.foo, a'
@@ -265,14 +229,8 @@ def test_element_unification_with_namespaceless_element_target
   end
 
   def test_element_unification_with_namespaced_element_target
-    assert_extend_doesnt_match('a', '.foo', :failed_to_unify, 2) do
-      render_unification 'ns|a.foo', 'a {@extend .foo}'
-    end
-
-    assert_extend_doesnt_match('ns2|a', '.foo', :failed_to_unify, 2) do
-      render_unification 'ns1|a.foo', 'ns2|a {@extend .foo}'
-    end
-
+    assert_unification 'ns|a.foo', 'a {@extend .foo}', 'ns|a.foo'
+    assert_unification 'ns1|a.foo', 'ns2|a {@extend .foo}', 'ns1|a.foo'
     assert_unification 'ns|a.foo', '*|a {@extend .foo}', 'ns|a'
     assert_unification 'ns|a.foo', 'ns|a {@extend .foo}', 'ns|a'
   end
@@ -288,15 +246,8 @@ def test_attribute_unification
   def test_pseudo_unification
     assert_unification ':foo.baz', ':foo(2n+1) {@extend .baz}', ':foo.baz, :foo:foo(2n+1)'
     assert_unification ':foo.baz', '::foo {@extend .baz}', ':foo.baz, :foo::foo'
-
-    assert_extend_doesnt_match('::bar', '.baz', :failed_to_unify, 2) do
-      render_unification '::foo.baz', '::bar {@extend .baz}'
-    end
-
-    assert_extend_doesnt_match('::foo(2n+1)', '.baz', :failed_to_unify, 2) do
-      render_unification '::foo.baz', '::foo(2n+1) {@extend .baz}'
-    end
-
+    assert_unification '::foo.baz', '::bar {@extend .baz}', '::foo.baz'
+    assert_unification '::foo.baz', '::foo(2n+1) {@extend .baz}', '::foo.baz'
     assert_unification '::foo.baz', '::foo {@extend .baz}', '::foo'
     assert_unification '::foo(2n+1).baz', '::foo(2n+1) {@extend .baz}', '::foo(2n+1)'
     assert_unification ':foo.baz', ':bar {@extend .baz}', ':foo.baz, :foo:bar'
@@ -618,14 +569,9 @@ def test_long_extender_runs_unification
     assert_extends 'ns|*.foo.bar', '*|a.baz {@extend .foo}', 'ns|*.foo.bar, ns|a.bar.baz'
   end
 
-  def test_long_extender_aborts_unification
-    assert_extend_doesnt_match('h1.baz', '.foo', :failed_to_unify, 2) do
-      render_extends 'a.foo#bar', 'h1.baz {@extend .foo}'
-    end
-
-    assert_extend_doesnt_match('.bang#baz', '.foo', :failed_to_unify, 2) do
-      render_extends 'a.foo#bar', '.bang#baz {@extend .foo}'
-    end
+  def test_long_extender_doesnt_unify
+    assert_extends 'a.foo#bar', 'h1.baz {@extend .foo}', 'a.foo#bar'
+    assert_extends 'a.foo#bar', '.bang#baz {@extend .foo}', 'a.foo#bar'
   end
 
   ## Nested Extenders
@@ -638,10 +584,8 @@ def test_nested_extender_runs_unification
     assert_extends '.foo.bar', 'foo bar {@extend .foo}', '.foo.bar, foo bar.bar'
   end
 
-  def test_nested_extender_aborts_unification
-    assert_extend_doesnt_match('foo bar', '.foo', :failed_to_unify, 2) do
-      render_extends 'baz.foo', 'foo bar {@extend .foo}'
-    end
+  def test_nested_extender_doesnt_unify
+    assert_extends 'baz.foo', 'foo bar {@extend .foo}', 'baz.foo'
   end
 
   def test_nested_extender_alternates_parents
@@ -1069,13 +1013,14 @@ def test_placeholder_selector_with_multiple_extenders
   end
 
   def test_placeholder_selector_as_modifier
-    assert_extend_doesnt_match('div', '%foo', :failed_to_unify, 3) do
-      render(<<SCSS)
+    assert_equal <<CSS, render(<<SCSS)
+a.baz.bar {
+  color: blue; }
+CSS
 a%foo.baz {color: blue}
 .bar {@extend %foo}
 div {@extend %foo}
 SCSS
-    end
   end
 
   def test_placeholder_interpolation
@@ -1343,17 +1288,6 @@ def test_extend_warns_when_extendee_doesnt_exist
 SCSS
   end
 
-  def test_extend_warns_when_extension_fails
-    assert_raise_message(Sass::SyntaxError, <<ERR) {render(<<SCSS)}
-"b.foo" failed to @extend ".bar".
-No selectors matching ".bar" could be unified with "b.foo".
-Use "@extend .bar !optional" if the extend should be able to fail.
-ERR
-a.bar {a: b}
-b.foo {@extend .bar}
-SCSS
-  end
-
   def test_extend_succeeds_when_one_extension_fails_but_others_dont
     assert_equal(<<CSS, render(<<SCSS))
 a.bar {