test: read_html() rewinding after parse errors

Author: erinzm

pandas/tests/io/test_html.py

@@ -990,3 +990,30 @@ def seekable(self):
                        match='passed a non-rewindable file object'):
         read_html(bad)
 
+
+def test_parse_failure_rewinds():
+    _skip_if_no('lxml')
+
+    # Issue #17975
+
+    class MockFile(object):
+        def __init__(self, data):
+            self.data = data
+            self.at_end = False
+
+        def read(self, size=None):
+            data = '' if self.at_end else self.data
+            self.at_end = True
+            return data
+
+        def seek(self, offset):
+            self.at_end = False
+
+        def seekable(self):
+            return True
+
+    good = MockFile('<table><tr><td>spam<br />eggs</td></tr></table>')
+    bad = MockFile('<table><tr><td>spam<foobr />eggs</td></tr></table>')
+
+    assert read_html(good)
+    assert read_html(bad)