Fix pseudo-class specificity calculation per CSS spec (#76)

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Author: Copilot

cssutils/css/selector.py

@@ -132,7 +132,7 @@ def append(self, seq, val, typ=None, token=None):  # noqa: C901
         if not context or context == 'negation':
             if 'id' == typ:
                 self.specificity[1] += 1
-            elif 'class' == typ or '[' == val:
+            elif 'class' == typ or '[' == val or 'pseudo-class' == typ:
                 self.specificity[2] += 1
             elif typ in (
                 'type-selector',

newsfragments/76.minor.rst

@@ -0,0 +1 @@
+Fixed pseudo-class specificity calculation. Pseudo-classes (e.g. ``:hover``, ``:last-child``, ``:nth-child()``) now correctly contribute to the class-weight column per the CSS Selectors spec.

tests/test_selector.py

@@ -410,11 +410,16 @@ def test_specificity(self):
             '* a': (0, 0, 0, 1),
             'a *': (0, 0, 0, 1),
             'a * b': (0, 0, 0, 2),
-            'a:hover': (0, 0, 0, 1),
+            'a:hover': (0, 0, 1, 1),
             'a:first-line': (0, 0, 0, 2),
             'a:first-letter': (0, 0, 0, 2),
             'a:before': (0, 0, 0, 2),
             'a:after': (0, 0, 0, 2),
+            # pseudo-classes count as class selectors (column c)
+            ':last-child': (0, 0, 1, 0),
+            'tr:last-child': (0, 0, 1, 1),
+            ':nth-child(2)': (0, 0, 1, 0),
+            '.table > :last-child > tr:last-child > *': (0, 0, 3, 1),
             # classes and attributes
             '.a': (0, 0, 1, 0),
             '*.a': (0, 0, 1, 0),