Config: native 'SOURCE_DATE_EPOCH' pattern-replacement support

CHANGES.rst

@@ -89,6 +89,9 @@ Bugs fixed
   Patch by Jean-François B.
 * #13685: gettext: Correctly ignore trailing backslashes.
   Patch by Bénédikt Tran.
+* #13526: Improve ``SOURCE_DATE_EPOCH`` support during ``%Y`` pattern
+  substition in :confval:`copyright` (and :confval:`project_copyright`).
+  Patch by James Addison.
 
 Testing
 -------

sphinx/builders/gettext.py

@@ -7,7 +7,7 @@
 import os.path
 import time
 from collections import defaultdict
-from os import getenv, walk
+from os import walk
 from pathlib import Path
 from typing import TYPE_CHECKING
 from uuid import uuid4
@@ -20,6 +20,7 @@
 from sphinx.errors import ThemeError
 from sphinx.locale import __
 from sphinx.util import logging
+from sphinx.util._timestamps import _get_publication_time
 from sphinx.util.display import status_iterator
 from sphinx.util.i18n import docname_to_domain
 from sphinx.util.index_entries import split_index_msg
@@ -199,11 +200,7 @@ def write_doc(self, docname: str, doctree: nodes.document) -> None:
 
 # If set, use the timestamp from SOURCE_DATE_EPOCH
 # https://reproducible-builds.org/specs/source-date-epoch/
-if (source_date_epoch := getenv('SOURCE_DATE_EPOCH')) is not None:
-    timestamp = time.gmtime(float(source_date_epoch))
-else:
-    # determine timestamp once to remain unaffected by DST changes during build
-    timestamp = time.localtime()
+timestamp = _get_publication_time()
 ctime = time.strftime('%Y-%m-%d %H:%M%z', timestamp)
 
 

sphinx/config.py

@@ -15,6 +15,7 @@
 from sphinx.errors import ConfigError, ExtensionError
 from sphinx.locale import _, __
 from sphinx.util import logging
+from sphinx.util._timestamps import _get_publication_time
 
 if TYPE_CHECKING:
     import os
@@ -707,7 +708,8 @@ def init_numfig_format(app: Sphinx, config: Config) -> None:
 
 def evaluate_copyright_placeholders(_app: Sphinx, config: Config) -> None:
     """Replace copyright year placeholders (%Y) with the current year."""
-    replace_yr = str(time.localtime().tm_year)
+    publication_time = _get_publication_time()
+    replace_yr = str(publication_time.tm_year)
     for k in ('copyright', 'epub_copyright'):
         if k in config:
             value: str | Sequence[str] = config[k]

sphinx/util/_timestamps.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import time
+from os import getenv
 
 
 def _format_rfc3339_microseconds(timestamp: int, /) -> str:
@@ -11,3 +12,19 @@ def _format_rfc3339_microseconds(timestamp: int, /) -> str:
     seconds, fraction = divmod(timestamp, 10**6)
     time_tuple = time.gmtime(seconds)
     return time.strftime('%Y-%m-%d %H:%M:%S', time_tuple) + f'.{fraction // 1_000}'
+
+
+def _get_publication_time() -> time.struct_time:
+    """Return the publication time to use for the current build.
+
+    If set, use the timestamp from SOURCE_DATE_EPOCH
+    https://reproducible-builds.org/specs/source-date-epoch/
+
+    Publication time cannot be projected into the future (beyond the local system
+    clock time).
+    """
+    system_time = time.localtime()
+    if (source_date_epoch := getenv('SOURCE_DATE_EPOCH')) is not None:
+        if (rebuild_time := time.localtime(float(source_date_epoch))) < system_time:
+            return rebuild_time
+    return system_time

tests/test_config/test_copyright.py

@@ -43,7 +43,8 @@ def expect_date(
 ) -> Iterator[int | None]:
     sde, expect = request.param
     with monkeypatch.context() as m:
-        m.setattr(time, 'localtime', lambda *a: LOCALTIME_2009)
+        lt_orig = time.localtime
+        m.setattr(time, 'localtime', lambda *a: lt_orig(*a) if a else LOCALTIME_2009)
         if sde:
             m.setenv('SOURCE_DATE_EPOCH', sde)
         else:
@@ -129,7 +130,6 @@ def test_correct_year_placeholder(expect_date: int | None) -> None:
     cfg = Config({'copyright': copyright_date}, {})
     assert cfg.copyright == copyright_date
     evaluate_copyright_placeholders(None, cfg)  # type: ignore[arg-type]
-    correct_copyright_year(None, cfg)  # type: ignore[arg-type]
     if expect_date and expect_date <= LOCALTIME_2009.tm_year:
         assert cfg.copyright == f'2006-{expect_date}, Alice'
     else:
@@ -203,11 +203,12 @@ def test_correct_year_multi_line_all_formats_placeholder(
         # other format codes are left as-is
         '2006-%y, Eve',
         '%Y-%m-%d %H:%M:S %z, Francis',
+        # non-ascii range patterns are supported
+        '2000–%Y Guinevere',
     )
     cfg = Config({'copyright': copyright_dates}, {})
     assert cfg.copyright == copyright_dates
     evaluate_copyright_placeholders(None, cfg)  # type: ignore[arg-type]
-    correct_copyright_year(None, cfg)  # type: ignore[arg-type]
     if expect_date and expect_date <= LOCALTIME_2009.tm_year:
         assert cfg.copyright == (
             f'{expect_date}',
@@ -217,7 +218,8 @@ def test_correct_year_multi_line_all_formats_placeholder(
             f'2006-{expect_date} Charlie',
             f'2006-{expect_date}, David',
             '2006-%y, Eve',
-            '2009-%m-%d %H:%M:S %z, Francis',
+            f'{expect_date}-%m-%d %H:%M:S %z, Francis',
+            f'2000–{expect_date} Guinevere',
         )
     else:
         assert cfg.copyright == (
@@ -229,6 +231,7 @@ def test_correct_year_multi_line_all_formats_placeholder(
             '2006-2009, David',
             '2006-%y, Eve',
             '2009-%m-%d %H:%M:S %z, Francis',
+            '2000–2009 Guinevere',
         )