Fixes #285 - Avoid crashing when handling @import rule

CHANGELOG.rst

@@ -3,6 +3,11 @@
 ChangeLog
 =========
 
+Unreleased
+----------
+- Avoid crash on ``@import`` rules in stylesheets. The rules are simply ignored
+  (#285).
+
 1.4.1 (2022-08-05)
 ------------------
 - No source code changes, only fixed a leftover set_trace() in the released code

README.rst

@@ -83,8 +83,8 @@ Features
 Known limitations
 -----------------
 
-- support for stylesheets is still experimental. Please report any
-  bug or shortcoming on the `svglib issue tracker`_.
+- @import rules in stylesheets are ignored. CSS is supported, but the range
+  of supported attributes is still limited
 - clipping is limited to single paths, no mask support
 - color gradients are not supported (limitation of reportlab)
 - SVG ``ForeignObject`` elements are not supported.

svglib/svglib.py

@@ -133,7 +133,7 @@ def add_styles(self, style_content):
         )
 
         for rule in rules:
-            if not rule.prelude:
+            if not rule.prelude or rule.type == 'at-rule':
                 continue
             selectors = cssselect2.compile_selector_list(rule.prelude)
             selector_string = tinycss2.serialize(rule.prelude)

tests/test_basic.py

@@ -566,6 +566,18 @@ def test_css_nth_of_type(self):
         assert main_group.contents[0].contents[1].contents[0].fontName == 'Helvetica-Bold'
         assert main_group.contents[0].contents[2].contents[0].fontName == 'Helvetica'
 
+    def test_import_rule_no_crash(self):
+        # Just test that svglib does not crash. Import rules are currently ignored.
+        drawing = drawing_from_svg('''
+            <svg>
+              <defs>
+                <style type="text/css">
+                  @import url('https://fonts.example.org/css2?family=Ubuntu+Condensed');
+                </style>
+              </defs>
+            </svg>
+        ''')
+
 
 class TestGroupNode:
     def test_svg_groups_have_svgid(self):