Restrict substitution of copyright years (#12516)

Only substitute copyright notice years with values from ``SOURCE_DATE_EPOCH`` for entries that match the current system clock year, and disallow substitution of future years. Co-authored-by: Adam Turner <[email protected]>
sphinx-doc · Oct 4, 2024 · a84f700 · a84f700
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diff --git a/CHANGES.rst b/CHANGES.rst
@@ -110,6 +110,10 @@ Bugs fixed
 * #12916: Restore support for custom templates named with the legacy ``_t``
   suffix during ``apidoc`` RST rendering (regression in 7.4.0).
   Patch by James Addison.
+* #12451: Only substitute copyright notice years with values from
+  ``SOURCE_DATE_EPOCH`` for entries that match the current system clock year,
+  and disallow substitution of future years.
+  Patch by James Addison and Adam Turner.
 
 Testing
 -------

diff --git a/sphinx/config.py b/sphinx/config.py
@@ -625,22 +625,34 @@ def correct_copyright_year(_app: Sphinx, config: Config) -> None:
 
     See https://reproducible-builds.org/specs/source-date-epoch/
     """
-    if (source_date_epoch := getenv('SOURCE_DATE_EPOCH')) is None:
+    if source_date_epoch := int(getenv('SOURCE_DATE_EPOCH', '0')):
+        source_date_epoch_year = time.gmtime(source_date_epoch).tm_year
+    else:
         return
 
-    source_date_epoch_year = str(time.gmtime(int(source_date_epoch)).tm_year)
+    # If the current year is the replacement year, there's no work to do.
+    # We also skip replacement years that are in the future.
+    current_year = time.localtime().tm_year
+    if current_year <= source_date_epoch_year:
+        return
 
+    current_yr = str(current_year)
+    replace_yr = str(source_date_epoch_year)
     for k in ('copyright', 'epub_copyright'):
         if k in config:
             value: str | Sequence[str] = config[k]
             if isinstance(value, str):
-                config[k] = _substitute_copyright_year(value, source_date_epoch_year)
+                config[k] = _substitute_copyright_year(value, current_yr, replace_yr)
             else:
-                items = (_substitute_copyright_year(x, source_date_epoch_year) for x in value)
+                items = (
+                    _substitute_copyright_year(x, current_yr, replace_yr) for x in value
+                )
                 config[k] = type(value)(items)  # type: ignore[call-arg]
 
 
-def _substitute_copyright_year(copyright_line: str, replace_year: str) -> str:
+def _substitute_copyright_year(
+    copyright_line: str, current_year: str, replace_year: str
+) -> str:
     """Replace the year in a single copyright line.
 
     Legal formats are:
@@ -657,13 +669,17 @@ def _substitute_copyright_year(copyright_line: str, replace_year: str) -> str:
     if len(copyright_line) < 4 or not copyright_line[:4].isdigit():
         return copyright_line
 
-    if copyright_line[4:5] in {'', ' ', ','}:
+    if copyright_line[:4] == current_year and copyright_line[4:5] in {'', ' ', ','}:
         return replace_year + copyright_line[4:]
 
-    if copyright_line[4] != '-':
+    if copyright_line[4:5] != '-':
         return copyright_line
 
-    if copyright_line[5:9].isdigit() and copyright_line[9:10] in {'', ' ', ','}:
+    if (
+        copyright_line[5:9].isdigit()
+        and copyright_line[5:9] == current_year
+        and copyright_line[9:10] in {'', ' ', ','}
+    ):
         return copyright_line[:5] + replace_year + copyright_line[9:]
 
     return copyright_line

diff --git a/tests/test_builders/test_build_html_copyright.py b/tests/test_builders/test_build_html_copyright.py
@@ -2,16 +2,21 @@
 
 import pytest
 
+LT = time.localtime()
+LT_NEW = (2009, *LT[1:], LT.tm_zone, LT.tm_gmtoff)
+LOCALTIME_2009 = type(LT)(LT_NEW)
+
 
 @pytest.fixture(
     params=[
-        1293840000,  # 2011-01-01 00:00:00
-        1293839999,  # 2010-12-31 23:59:59
+        1199145600,  # 2008-01-01 00:00:00
+        1199145599,  # 2007-12-31 23:59:59
     ]
 )
 def source_date_year(request, monkeypatch):
     source_date_epoch = request.param
     with monkeypatch.context() as m:
+        m.setattr(time, 'localtime', lambda *a: LOCALTIME_2009)
         m.setenv('SOURCE_DATE_EPOCH', str(source_date_epoch))
         yield time.gmtime(source_date_epoch).tm_year
 
@@ -53,24 +58,24 @@ def test_html_multi_line_copyright_sde(source_date_year, app):
     content = (app.outdir / 'index.html').read_text(encoding='utf-8')
 
     # check the copyright footer line by line (empty lines ignored)
-    assert f'  &#169; Copyright {source_date_year}.<br/>\n' in content
+    assert '  &#169; Copyright 2006.<br/>\n' in content
     assert f'  &#169; Copyright 2006-{source_date_year}, Alice.<br/>\n' in content
-    assert f'  &#169; Copyright 2010-{source_date_year}, Bob.<br/>\n' in content
-    assert f'  &#169; Copyright 2014-{source_date_year}, Charlie.<br/>\n' in content
-    assert f'  &#169; Copyright 2018-{source_date_year}, David.<br/>\n' in content
-    assert f'  &#169; Copyright 2022-{source_date_year}, Eve.' in content
+    assert '  &#169; Copyright 2010-2013, Bob.<br/>\n' in content
+    assert '  &#169; Copyright 2014-2017, Charlie.<br/>\n' in content
+    assert '  &#169; Copyright 2018-2021, David.<br/>\n' in content
+    assert '  &#169; Copyright 2022-2025, Eve.' in content
 
     # check the raw copyright footer block (empty lines included)
     assert (
-        f'      &#169; Copyright {source_date_year}.<br/>\n'
-        f'    \n'
+        '      &#169; Copyright 2006.<br/>\n'
+        '    \n'
         f'      &#169; Copyright 2006-{source_date_year}, Alice.<br/>\n'
-        f'    \n'
-        f'      &#169; Copyright 2010-{source_date_year}, Bob.<br/>\n'
-        f'    \n'
-        f'      &#169; Copyright 2014-{source_date_year}, Charlie.<br/>\n'
-        f'    \n'
-        f'      &#169; Copyright 2018-{source_date_year}, David.<br/>\n'
-        f'    \n'
-        f'      &#169; Copyright 2022-{source_date_year}, Eve.'
+        '    \n'
+        '      &#169; Copyright 2010-2013, Bob.<br/>\n'
+        '    \n'
+        '      &#169; Copyright 2014-2017, Charlie.<br/>\n'
+        '    \n'
+        '      &#169; Copyright 2018-2021, David.<br/>\n'
+        '    \n'
+        '      &#169; Copyright 2022-2025, Eve.'
     ) in content
diff --git a/tests/test_config/test_correct_year.py b/tests/test_config/test_correct_year.py
@@ -14,12 +14,13 @@
 @pytest.fixture(
     params=[
         # test with SOURCE_DATE_EPOCH unset: no modification
-        (None, ''),
-        # test with SOURCE_DATE_EPOCH set: copyright year should be updated
-        ('1293840000', '2011'),
-        ('1293839999', '2010'),
-        ('1199145600', '2008'),
-        ('1199145599', '2007'),
+        (None, None),
+        # test with post-2009 SOURCE_DATE_EPOCH set: copyright year should not be updated
+        ('1293840000', 2011),
+        ('1293839999', 2010),
+        # test with pre-2009 SOURCE_DATE_EPOCH set: copyright year should be updated
+        ('1199145600', 2008),
+        ('1199145599', 2007),
     ],
 )
 def expect_date(request, monkeypatch):
@@ -39,7 +40,7 @@ def test_correct_year(expect_date):
     cfg = Config({'copyright': copyright_date}, {})
     assert cfg.copyright == copyright_date
     correct_copyright_year(None, cfg)  # type: ignore[arg-type]
-    if expect_date:
+    if expect_date and expect_date <= LOCALTIME_2009.tm_year:
         assert cfg.copyright == f'2006-{expect_date}, Alice'
     else:
         assert cfg.copyright == copyright_date
@@ -51,7 +52,7 @@ def test_correct_year_space(expect_date):
     cfg = Config({'copyright': copyright_date}, {})
     assert cfg.copyright == copyright_date
     correct_copyright_year(None, cfg)  # type: ignore[arg-type]
-    if expect_date:
+    if expect_date and expect_date <= LOCALTIME_2009.tm_year:
         assert cfg.copyright == f'2006-{expect_date} Alice'
     else:
         assert cfg.copyright == copyright_date
@@ -63,7 +64,7 @@ def test_correct_year_no_author(expect_date):
     cfg = Config({'copyright': copyright_date}, {})
     assert cfg.copyright == copyright_date
     correct_copyright_year(None, cfg)  # type: ignore[arg-type]
-    if expect_date:
+    if expect_date and expect_date <= LOCALTIME_2009.tm_year:
         assert cfg.copyright == f'2006-{expect_date}'
     else:
         assert cfg.copyright == copyright_date
@@ -75,7 +76,7 @@ def test_correct_year_single(expect_date):
     cfg = Config({'copyright': copyright_date}, {})
     assert cfg.copyright == copyright_date
     correct_copyright_year(None, cfg)  # type: ignore[arg-type]
-    if expect_date:
+    if expect_date and expect_date <= LOCALTIME_2009.tm_year:
         assert cfg.copyright == f'{expect_date}, Alice'
     else:
         assert cfg.copyright == copyright_date
@@ -87,7 +88,7 @@ def test_correct_year_single_space(expect_date):
     cfg = Config({'copyright': copyright_date}, {})
     assert cfg.copyright == copyright_date
     correct_copyright_year(None, cfg)  # type: ignore[arg-type]
-    if expect_date:
+    if expect_date and expect_date <= LOCALTIME_2009.tm_year:
         assert cfg.copyright == f'{expect_date} Alice'
     else:
         assert cfg.copyright == copyright_date
@@ -99,7 +100,7 @@ def test_correct_year_single_no_author(expect_date):
     cfg = Config({'copyright': copyright_date}, {})
     assert cfg.copyright == copyright_date
     correct_copyright_year(None, cfg)  # type: ignore[arg-type]
-    if expect_date:
+    if expect_date and expect_date <= LOCALTIME_2009.tm_year:
         assert cfg.copyright == f'{expect_date}'
     else:
         assert cfg.copyright == copyright_date
@@ -108,7 +109,7 @@ def test_correct_year_single_no_author(expect_date):
 def test_correct_year_multi_line(expect_date):
     # test that copyright is substituted
     copyright_dates = (
-        '2006',
+        '2009',
         '2006-2009, Alice',
         '2010-2013, Bob',
         '2014-2017, Charlie',
@@ -118,14 +119,15 @@ def test_correct_year_multi_line(expect_date):
     cfg = Config({'copyright': copyright_dates}, {})
     assert cfg.copyright == copyright_dates
     correct_copyright_year(None, cfg)  # type: ignore[arg-type]
-    if expect_date:
+    if expect_date and expect_date <= LOCALTIME_2009.tm_year:
         assert cfg.copyright == (
             f'{expect_date}',
             f'2006-{expect_date}, Alice',
-            f'2010-{expect_date}, Bob',
-            f'2014-{expect_date}, Charlie',
-            f'2018-{expect_date}, David',
-            f'2022-{expect_date}, Eve',
+            # post 2009-dates aren't substituted
+            '2010-2013, Bob',
+            '2014-2017, Charlie',
+            '2018-2021, David',
+            '2022-2025, Eve',
         )
     else:
         assert cfg.copyright == copyright_dates
@@ -144,7 +146,7 @@ def test_correct_year_multi_line_all_formats(expect_date):
     cfg = Config({'copyright': copyright_dates}, {})
     assert cfg.copyright == copyright_dates
     correct_copyright_year(None, cfg)  # type: ignore[arg-type]
-    if expect_date:
+    if expect_date and expect_date <= LOCALTIME_2009.tm_year:
         assert cfg.copyright == (
             f'{expect_date}',
             f'{expect_date} Alice',
@@ -166,7 +168,7 @@ def test_correct_year_app(expect_date, tmp_path, make_app):
         srcdir=tmp_path,
         confoverrides={'copyright': copyright_date},
     )
-    if expect_date:
+    if expect_date and expect_date <= LOCALTIME_2009.tm_year:
         assert app.config.copyright == f'2006-{expect_date}, Alice'
     else:
         assert app.config.copyright == copyright_date