Log warning when unknown rendering option is given

tests/test_api.py

@@ -305,6 +305,15 @@ def test_python_render(assert_pixels_equal, tmp_path):
     ).write_png() == rotated_png_bytes
 
 
+@assert_no_logs
+def test_unknown_options():
+    with capture_logs() as logs:
+        pdf_bytes = FakeHTML(string='test').write_pdf(zoom=2, unknown=True)
+    assert len(logs) == 1
+    assert 'unknown' in logs[0]
+    assert pdf_bytes
+
+
 @assert_no_logs
 def test_command_line_render(tmp_path):
     css = b'''

weasyprint/__init__.py

@@ -210,6 +210,8 @@ class HTML:
         :returns: A :class:`document.Document` object.
 
         """
+        for unknown in set(options) - set(DEFAULT_OPTIONS):
+            LOGGER.warning('Unknown rendering option: %s.', unknown)
         new_options = DEFAULT_OPTIONS.copy()
         new_options.update(options)
         options = new_options

weasyprint/__main__.py

@@ -165,7 +165,8 @@ def main(argv=None, stdout=None, stdin=None, HTML=HTML):  # noqa: N803
     if args.timeout is not None:
         url_fetcher = partial(default_url_fetcher, timeout=args.timeout)
 
-    options = vars(args)
+    options = {
+        key: value for key, value in vars(args).items() if key in DEFAULT_OPTIONS}
 
     # Default to logging to stderr.
     if args.debug: