Merge pull request #18 from o3LL/fix/duplicate-keyframes

fix(css): collapse duplicate @keyframes names to the definition that wins

tests/test_stylesheet_keyframe_uniqueness.py

@@ -0,0 +1,52 @@
+"""No two @keyframes may share a name across the app's stylesheets.
+
+Duplicate names resolve last-wins across the whole cascade, so an earlier
+definition is dead code that still looks live at its call site. Two of them
+existed and differed from the definition that actually won, which also blocked
+moving either animation during the stylesheet decomposition: relocating one
+changes which is last and therefore changes rendered behaviour.
+"""
+
+import collections
+import re
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+STATIC = ROOT / "static"
+
+
+def _stylesheets() -> list[Path]:
+    """App-owned stylesheets, in no particular order. Vendored CSS is excluded."""
+    sheets = [STATIC / "style.css"]
+    sheets.extend(sorted((STATIC / "css").glob("*.css")))
+    return [s for s in sheets if s.exists()]
+
+
+def _keyframe_names(text: str) -> list[str]:
+    without_comments = re.sub(r"/\*.*?\*/", "", text, flags=re.S)
+    return re.findall(
+        r"@(?:-webkit-)?keyframes\s+([A-Za-z0-9_-]+)\s*\{", without_comments
+    )
+
+
+def test_app_stylesheets_exist() -> None:
+    """Guard the guard: a rename must not turn this file into a no-op."""
+    assert _stylesheets(), "no app stylesheets found to check"
+
+
+def test_no_keyframes_name_is_declared_twice() -> None:
+    counts: collections.Counter[str] = collections.Counter()
+    where: dict[str, list[str]] = collections.defaultdict(list)
+
+    for sheet in _stylesheets():
+        for name in _keyframe_names(sheet.read_text(encoding="utf-8")):
+            counts[name] += 1
+            where[name].append(sheet.relative_to(ROOT).as_posix())
+
+    duplicates = {name: where[name] for name, n in counts.items() if n > 1}
+
+    assert duplicates == {}, (
+        "duplicate @keyframes names resolve last-wins, so every definition but "
+        f"the last is dead: {duplicates}"
+    )