fix: this assert is possible, remove it. #1891

CHANGES.rst

@@ -23,7 +23,10 @@ upgrading your version of coverage.py.
 Unreleased
 ----------
 
-Nothing yet.
+- One of the new asserts from 7.6.5 caused problems in real projects, as
+  reported in `issue 1891`_.  The assert has been removed.
+
+.. _issue 1891: https://github.com/nedbat/coveragepy/issues/1891
 
 
 .. start-releases

coverage/parser.py

@@ -437,14 +437,14 @@ def _line_numbers(self) -> Iterable[TLineNo]:
             byte_num = 0
             for byte_incr, line_incr in zip(byte_increments, line_increments):
                 if byte_incr:
-                    assert line_num != last_line_num, f"Oops, {byte_incr = }, {line_incr = }"
-                    yield line_num
-                    last_line_num = line_num
+                    if line_num != last_line_num:
+                        yield line_num
+                        last_line_num = line_num
                     byte_num += byte_incr
                 if line_incr >= 0x80:
                     line_incr -= 0x100
                 line_num += line_incr
-            assert line_num != last_line_num
+            assert line_num != last_line_num, f"Oops: {self.code.co_name}@{linenum}"
             yield line_num
 
     def _find_statements(self) -> Iterable[TLineNo]:

tests/test_parser.py

@@ -197,6 +197,13 @@ def test_fuzzed_double_parse(self) -> None:
         with pytest.raises(NotPython, match=msg):
             self.parse_text("]")
 
+    def test_bug_1891(self) -> None:
+        # This code exercises a code path I thought was impossible.
+        parser = self.parse_text("""\
+            res = siblings('configure', **ca)
+            """)
+        assert parser.exit_counts() == { 1:1 }
+
 
 class ExclusionParserTest(PythonParserTestBase):
     """Tests for the exclusion code in PythonParser."""