Don't crash on blank PO-Revision-Date / POT-Creation-Date headers

babel/messages/catalog.py

@@ -582,10 +582,16 @@ def _set_mime_headers(self, headers: Iterable[tuple[str, str]]) -> None:
                 self._num_plurals = int(params.get('nplurals', 2))
                 self._plural_expr = params.get('plural', '(n != 1)')
             elif name == 'pot-creation-date':
-                self.creation_date = _parse_datetime_header(value)
+                # Some tools (e.g. Poedit) may leave this header blank.
+                # Keep the previous/default value rather than crashing.
+                if value.strip():
+                    self.creation_date = _parse_datetime_header(value)
             elif name == 'po-revision-date':
-                # Keep the value if it's not the default one
-                if 'YEAR' not in value:
+                # Keep the value if it's not the default one.
+                # Some tools (e.g. Poedit) may also leave this header
+                # blank; keep the previous/default value in that case
+                # too, rather than crashing.
+                if 'YEAR' not in value and value.strip():
                     self.revision_date = _parse_datetime_header(value)
 
     mime_headers = property(

tests/messages/test_catalog.py

@@ -346,6 +346,36 @@ def test_catalog_stores_datetime_correctly():
             assert value == '2009-03-09 15:47-0700'
 
 
+def test_catalog_handles_blank_revision_and_creation_date():
+    """Regression test for
+    https://github.com/python-babel/babel/issues/1219
+
+    Some tools (e.g. Poedit) can leave PO-Revision-Date and/or
+    POT-Creation-Date blank in the header. Parsing such a header must
+    not raise, and must not silently store an unparseable value that
+    would corrupt the header on write-out.
+    """
+    cat = catalog.Catalog()
+    default_creation_date = cat.creation_date
+    default_revision_date = cat.revision_date
+
+    cat[''] = catalog.Message(
+        '',
+        "POT-Creation-Date: \n"
+        "PO-Revision-Date: \n",
+    )
+
+    # The blank headers should not have overwritten the defaults with
+    # an unparseable value (e.g. the raw empty string) or crashed.
+    assert cat.creation_date == default_creation_date
+    assert cat.revision_date == default_revision_date
+
+    for key, value in cat.mime_headers:
+        if key in ('POT-Creation-Date', 'PO-Revision-Date'):
+            assert value is not None
+            assert 'None' not in str(value)
+
+
 def test_catalog_mime_headers_contain_same_information_as_attributes():
     cat = catalog.Catalog()
     cat[''] = catalog.Message('',