config: copyright correction logic: handle year-to-year ranges without trailing authorship info

sphinx/config.py

@@ -610,7 +610,7 @@ def _substitute_copyright_year(copyright_line: str, replace_year: str) -> str:
     if copyright_line[4] != '-':
         return copyright_line
 
-    if copyright_line[5:9].isdigit() and copyright_line[9] in ' ,':
+    if copyright_line[5:9].isdigit() and copyright_line[9:10] in {'', ' ', ','}:
         return copyright_line[:5] + replace_year + copyright_line[9:]
 
     return copyright_line

tests/test_config/test_config.py

@@ -8,7 +8,13 @@
 
 import sphinx
 from sphinx.builders.gettext import _gettext_compact_validator
-from sphinx.config import ENUM, Config, _Opt, check_confval_types
+from sphinx.config import (
+    ENUM,
+    Config,
+    _Opt,
+    check_confval_types,
+    correct_copyright_year,
+)
 from sphinx.deprecation import RemovedInSphinx90Warning
 from sphinx.errors import ConfigError, ExtensionError, VersionRequirementError
 
@@ -556,6 +562,23 @@ def test_multi_line_copyright(source_date_year, app, monkeypatch):
         ) in content
 
 
+@pytest.mark.parametrize('copyright_line', [
+    # '1970',
+    '1970-1990',  # https://github.com/sphinx-doc/sphinx/issues/11913
+    '1970-1990 Alice',
+])
+def test_correct_copyright_year(copyright_line, source_date_year):
+    config = Config({}, {'copyright': copyright_line})
+    correct_copyright_year(_app=None, config=config)
+    corrected_copyright_line = config['copyright']
+
+    assert '1970' in corrected_copyright_line
+    if source_date_year is None:
+        assert corrected_copyright_line == copyright_line
+    else:
+        assert str(source_date_year) in corrected_copyright_line
+
+
 def test_gettext_compact_command_line_true():
     config = Config({}, {'gettext_compact': '1'})
     config.add('gettext_compact', True, '', {bool, str})