gh-130647: Add --omit-header option to pygettext

Lib/test/test_tools/i18n_data/noheader.pot

@@ -0,0 +1,8 @@
+#: noheader.py:3
+msgid "Foo"
+msgstr ""
+
+#: noheader.py:5
+msgid "Bar"
+msgstr ""
+

Lib/test/test_tools/i18n_data/noheader.py

@@ -0,0 +1,5 @@
+from gettext import gettext as _
+
+_('Foo')
+
+_('Bar')

Lib/test/test_tools/test_i18n.py

@@ -526,6 +526,7 @@ def extract_from_snapshots():
         'custom_keywords.py': ('--keyword=foo', '--keyword=nfoo:1,2',
                                '--keyword=pfoo:1c,2',
                                '--keyword=npfoo:1c,2,3', '--keyword=_:1,2'),
+        'noheader.py': ('--omit-header',),
     }
 
     for filename, args in snapshots.items():

Misc/NEWS.d/next/Tools-Demos/2025-02-27-19-00-00.gh-issue-130647.uwda2h.rst

@@ -0,0 +1 @@
+Add ``--omit-header`` option to :program:`pygettext`.

Tools/i18n/pygettext.py

@@ -124,6 +124,15 @@
     --width=columns
         Set width of output to columns.
 
+    --omit-header
+        Do not write header to file.
+
+        This is useful for testing purposes because it eliminates a source of
+        variance for generated .mo files.
+
+        Note: Using this option will lead to an error during compilation or other
+        manipulation if the resulting file is not entirely in ASCII.
+
     -x filename
     --exclude-file=filename
         Specify a file that contains a list of strings that are not be
@@ -574,9 +583,11 @@ def _is_string_const(self, node):
 def write_pot_file(messages, options, fp):
     timestamp = time.strftime('%Y-%m-%d %H:%M%z')
     encoding = fp.encoding if fp.encoding else 'UTF-8'
-    print(pot_header % {'time': timestamp, 'version': __version__,
-                        'charset': encoding,
-                        'encoding': '8bit'}, file=fp)
+
+    if not options.omit_header:
+        print(pot_header % {'time': timestamp, 'version': __version__,
+                            'charset': encoding,
+                            'encoding': '8bit'}, file=fp)
 
     # Sort locations within each message by filename and lineno
     sorted_keys = [
@@ -636,7 +647,7 @@ def main():
             ['extract-all', 'add-comments=?', 'default-domain=', 'escape',
              'help', 'keyword=', 'no-default-keywords',
              'add-location', 'no-location', 'output=', 'output-dir=',
-             'style=', 'verbose', 'version', 'width=', 'exclude-file=',
+             'style=', 'verbose', 'version', 'width=', 'omit-header', 'exclude-file=',
              'docstrings', 'no-docstrings',
              ])
     except getopt.error as msg:
@@ -657,6 +668,7 @@ class Options:
         locationstyle = GNU
         verbose = 0
         width = 78
+        omit_header = False
         excludefilename = ''
         docstrings = 0
         nodocstrings = {}
@@ -709,6 +721,8 @@ class Options:
                 options.width = int(arg)
             except ValueError:
                 usage(1, f'--width argument must be an integer: {arg}')
+        elif opt in ('--omit-header',):
+            options.omit_header = True
         elif opt in ('-x', '--exclude-file'):
             options.excludefilename = arg
         elif opt in ('-X', '--no-docstrings'):