Add support for :has(), :host(), and :host-context().

See #1126

lib/sass/scss/static_parser.rb

@@ -253,7 +253,7 @@ def attrib_name!
         return ns, name
       end
 
-      SELECTOR_PSEUDO_CLASSES = %w[not matches current any].to_set
+      SELECTOR_PSEUDO_CLASSES = %w[not matches current any has host host-context].to_set
 
       PREFIXED_SELECTOR_PSEUDO_CLASSES = %w[nth-child nth-last-child].to_set
 

lib/sass/selector/pseudo.rb

@@ -76,6 +76,11 @@ def with_selector(new_selector)
             # more complex cases that likely aren't worth the pain.
             next [] unless sel.name == name && sel.arg == arg
             sel.selector.members
+          when 'has', 'host', 'host-context'
+            # We can't expand nested selectors here, because each layer adds an
+            # additional layer of semantics. For example, `:has(:has(img))`
+            # doesn't match `<div><img></div>` but `:has(img)` does.
+            sel
           else
             []
           end
@@ -146,6 +151,16 @@ def superselector?(their_sseq, parents = [])
             their_seq = Sequence.new(parents + [their_sseq])
             our_seq.superselector?(their_seq)
           end
+        when 'has', 'host', 'host-context'
+          # Like :matches, :has (et al) can be a superselector of another
+          # selector if its constituent selectors are a superset of those of
+          # another :has in the other selector. However, the :matches other case
+          # doesn't work, because :has refers to nested elements.
+          (their_sseq.selector_pseudo_classes[normalized_name] || []).any? do |their_sel|
+            next false unless their_sel.is_a?(Pseudo)
+            next false unless their_sel.name == name
+            selector.superselector?(their_sel.selector)
+          end
         when 'not'
           selector.members.all? do |our_seq|
             their_sseq.members.any? do |their_sel|

test/sass/extend_test.rb

@@ -351,6 +351,9 @@ def test_extend_into_mergeable_pseudoclasses
 
     assert_extends(':-moz-any(.foo)', '.x {@extend .foo}', ':-moz-any(.foo, .x)')
     assert_extends(':current(.foo)', '.x {@extend .foo}', ':current(.foo, .x)')
+    assert_extends(':has(.foo)', '.x {@extend .foo}', ':has(.foo, .x)')
+    assert_extends(':host(.foo)', '.x {@extend .foo}', ':host(.foo, .x)')
+    assert_extends(':host-context(.foo)', '.x {@extend .foo}', ':host-context(.foo, .x)')
     assert_extends(':nth-child(n of .foo)', '.x {@extend .foo}', ':nth-child(n of .foo, .x)')
     assert_extends(
       ':nth-last-child(n of .foo)',
@@ -362,6 +365,9 @@ def test_complex_extend_into_pseudoclass
     assert_extends(':not(.bar)', '.x .y {@extend .bar}', ':not(.bar, .x .y)')
     assert_extends(':matches(.bar)', '.x .y {@extend .bar}', ':matches(.bar, .x .y)')
     assert_extends(':current(.bar)', '.x .y {@extend .bar}', ':current(.bar, .x .y)')
+    assert_extends(':has(.bar)', '.x .y {@extend .bar}', ':has(.bar, .x .y)')
+    assert_extends(':host(.bar)', '.x .y {@extend .bar}', ':host(.bar, .x .y)')
+    assert_extends(':host-context(.bar)', '.x .y {@extend .bar}', ':host-context(.bar, .x .y)')
     assert_extends(
       ':-moz-any(.bar)',
       '.x .y {@extend .bar}',
@@ -405,6 +411,15 @@ def test_pseudoclasses_merge
       ':nth-last-child(n of .foo, .bar)')
   end
 
+  def test_nesting_pseudoclasses_merge
+    assert_extends(':has(.foo)', ':has(.bar) {@extend .foo}', ':has(.foo, :has(.bar))')
+    assert_extends(':host(.foo)', ':host(.bar) {@extend .foo}', ':host(.foo, :host(.bar))')
+    assert_extends(
+      ':host-context(.foo)',
+      ':host-context(.bar) {@extend .foo}',
+      ':host-context(.foo, :host-context(.bar))')
+  end
+
   def test_not_unifies_with_unique_values
     assert_unification('foo', ':not(bar) {@extend foo}', ':not(bar)')
     assert_unification('#foo', ':not(#bar) {@extend #foo}', ':not(#bar)')

test/sass/scss/css_test.rb

@@ -699,6 +699,8 @@ def test_summarized_selectors_with_element
     assert_selector_parses('E:not(s)')
     assert_selector_parses('E:not(s1, s2)')
     assert_selector_parses('E:matches(s1, s2)')
+    assert_selector_parses('E:has(s1, s2)')
+    assert_selector_parses('E:has(> s1, > s2)')
     assert_selector_parses('E.warning')
     assert_selector_parses('E#myid')
     assert_selector_parses('E[foo]')
@@ -761,6 +763,10 @@ def test_summarized_selectors_with_element
     assert_selector_parses('E! > F')
 
     assert_selector_parses('E /ns|foo/ F')
+
+    # From http://dev.w3.org/csswg/css-scoping-1/
+    assert_selector_parses('E:host(s)')
+    assert_selector_parses('E:host-context(s)')
   end
 
   # Taken from http://dev.w3.org/csswg/selectors4/#overview, but without element
@@ -769,6 +775,8 @@ def test_more_summarized_selectors
     assert_selector_parses(':not(s)')
     assert_selector_parses(':not(s1, s2)')
     assert_selector_parses(':matches(s1, s2)')
+    assert_selector_parses(':has(s1, s2)')
+    assert_selector_parses(':has(> s1, > s2)')
     assert_selector_parses('.warning')
     assert_selector_parses('#myid')
     assert_selector_parses('[foo]')
@@ -823,6 +831,10 @@ def test_more_summarized_selectors
     assert_selector_parses(':nth-last-child(n of selector)')
     assert_selector_parses(':nth-child(n)')
     assert_selector_parses(':nth-last-child(n)')
+
+    # From http://dev.w3.org/csswg/css-scoping-1/
+    assert_selector_parses(':host(s)')
+    assert_selector_parses(':host-context(s)')
   end
 
   def test_attribute_selectors_with_identifiers
@@ -865,6 +877,10 @@ def test_selectors_containing_selectors
     assert_selector_can_contain_selectors(':nth-child(n of <sel>)')
     assert_selector_can_contain_selectors(':nth-last-child(n of <sel>)')
     assert_selector_can_contain_selectors(':-moz-any(<sel>)')
+    assert_selector_can_contain_selectors(':has(<sel>)')
+    assert_selector_can_contain_selectors(':has(+ <sel>)')
+    assert_selector_can_contain_selectors(':host(<sel>)')
+    assert_selector_can_contain_selectors(':host-context(<sel>)')
   end
 
   def assert_selector_can_contain_selectors(sel)

test/sass/superselector_test.rb

@@ -143,6 +143,31 @@ def test_nth_match_can_be_subselector
     end
   end
 
+  def has_is_superselector_of_subset_host
+    assert_strict_superselector ':has(.foo, .bar, .baz)', ':has(.foo.bip, .baz.bang)'
+  end
+
+  def has_isnt_superselector_of_contained_selector
+    assert_strict_superselector ':has(.foo, .bar, .baz)', '.foo'
+  end
+
+  def host_is_superselector_of_subset_host
+    assert_strict_superselector ':host(.foo, .bar, .baz)', ':host(.foo.bip, .baz.bang)'
+  end
+
+  def host_isnt_superselector_of_contained_selector
+    assert_strict_superselector ':host(.foo, .bar, .baz)', '.foo'
+  end
+
+  def host_context_is_superselector_of_subset_host
+    assert_strict_superselector(
+      ':host-context(.foo, .bar, .baz)', ':host-context(.foo.bip, .baz.bang)')
+  end
+
+  def host_context_isnt_superselector_of_contained_selector
+    assert_strict_superselector ':host-context(.foo, .bar, .baz)', '.foo'
+  end
+
   private
 
   def assert_superselector(superselector, subselector)