Allow blink as a text-decoration value

It will only be ignored while drawing, but it doesn't harm to keep the value
and makes code and tests more readable.

Also use a set instead of a frozenset to store text-decoration-line, bringing
more readability even if it may be a little, little, little bit slower.

weasyprint/css/validation/expanders.py

@@ -354,8 +354,8 @@ def expand_text_decoration(base_url, name, tokens):
 
     for token in tokens:
         keyword = get_keyword(token)
-        if keyword in ('none', 'underline', 'overline', 'line-through',
-                       'blink'):
+        if keyword in (
+                'none', 'underline', 'overline', 'line-through', 'blink'):
             text_decoration_line.add(keyword)
         elif keyword in ('solid', 'double', 'dotted', 'dashed', 'wavy'):
             if text_decoration_style is not None:
@@ -377,8 +377,6 @@ def expand_text_decoration(base_url, name, tokens):
         text_decoration_line = 'none'
     elif not(text_decoration_line):
         text_decoration_line = 'none'
-    else:
-        text_decoration_line = frozenset(text_decoration_line - set(['blink']))
 
     yield 'text_decoration_line', text_decoration_line
     yield 'text_decoration_color', text_decoration_color or 'currentColor'

weasyprint/css/validation/properties.py

@@ -980,17 +980,12 @@ def text_align(keyword):
 @property()
 def text_decoration_line(tokens):
     """``text-decoration-line`` property validation."""
-    keywords = [get_keyword(v) for v in tokens]
-    if keywords == ['none']:
+    keywords = {get_keyword(token) for token in tokens}
+    if keywords == {'none'}:
         return 'none'
-    if all(keyword in ('underline', 'overline', 'line-through', 'blink')
-            for keyword in keywords):
-        unique = set(keywords)
-        if len(unique) == len(keywords):
-            # No duplicate
-            # blink is accepted but ignored
-            # "Conforming user agents may simply not blink the text."
-            return frozenset(unique - set(['blink']))
+    allowed_values = {'underline', 'overline', 'line-through', 'blink'}
+    if len(tokens) == len(keywords) and keywords.issubset(allowed_values):
+        return keywords
 
 
 @property()

weasyprint/tests/test_css.py

@@ -136,7 +136,7 @@ def test_annotate_document():
     assert li_0['margin_bottom'] == (16, 'px')
     assert li_0['margin_left'] == (32, 'px')  # 4em
 
-    assert a['text_decoration_line'] == frozenset(['underline'])
+    assert a['text_decoration_line'] == {'underline'}
     assert a['font_weight'] == 900
     assert a['font_size'] == 24  # 300% of 8px
     assert a['padding_top'] == (1, 'px')

weasyprint/tests/test_css_validation.py

@@ -132,10 +132,9 @@ def test_spacing_invalid(rule):
 @assert_no_logs
 @pytest.mark.parametrize('rule, result', (
     ('text-decoration-line: none', {'text_decoration_line': 'none'}),
-    ('text-decoration-line: overline', {
-        'text_decoration_line': frozenset(['overline'])}),
+    ('text-decoration-line: overline', {'text_decoration_line': {'overline'}}),
     ('text-decoration-line: overline blink line-through', {
-        'text_decoration_line': frozenset(['line-through', 'overline'])}),
+        'text_decoration_line': {'blink', 'line-through', 'overline'}}),
 ))
 def test_decoration_line(rule, result):
     assert expand_to_dict(rule) == result
@@ -163,10 +162,9 @@ TEXT_DECORATION_DEFAULT = {
 @assert_no_logs
 @pytest.mark.parametrize('rule, result', (
     ('text-decoration: none', {'text_decoration_line': 'none'}),
-    ('text-decoration: overline', {
-        'text_decoration_line': frozenset(['overline'])}),
+    ('text-decoration: overline', {'text_decoration_line': {'overline'}}),
     ('text-decoration: overline blink line-through', {
-        'text_decoration_line': frozenset(['line-through', 'overline'])}),
+        'text_decoration_line': {'blink', 'line-through', 'overline'}}),
     ('text-decoration: red', {'text_decoration_color': (1, 0, 0, 1)}),
 ))
 def test_decoration(rule, result):