Trim leading whitespace before doctest flags (#13164)

sphinx/ext/doctest.py

@@ -38,7 +38,7 @@ if TYPE_CHECKING:
 logger = logging.getLogger(__name__)
 
 blankline_re = re.compile(r'^\s*<BLANKLINE>', re.MULTILINE)
-doctestopt_re = re.compile(r'#\s*doctest:.+$', re.MULTILINE)
+doctestopt_re = re.compile(r'[ \t]*#\s*doctest:.+$', re.MULTILINE)
 
 
 def is_allowed_version(spec: str, version: str) -> bool:

tests/test_transforms/test_transforms_post_transforms_code.py

@@ -15,6 +15,8 @@ def test_trim_doctest_flags_html(app):
     assert 'QUUX' not in result
     assert 'CORGE' not in result
     assert 'GRAULT' in result
+    assert '<span class="n">now</span><span class="p">()</span>   \n' not in result
+    assert '<span class="n">now</span><span class="p">()</span>\n' in result
 
 
 @pytest.mark.sphinx(