Ignore 'Language' header in PO-templates

The tools 'xgettext' from GNU gettext and 'pot-create' from lingua
both produce PO-template files containing a 'Language' header with
an empty string as value.

Babel has issues creating catalogs out of such templates.

It wants to parse the PO-template as a normal PO-catalog using the
locale of the target catalog, because it helps producing the correct
plurals. But it overwrites this locale when parsing the 'Language'
header and then it can not produce a valid catalog.

Ignoring the 'Language' header when it is known that the file being
processed is a template avoids this issue.

GitHub: #665

babel/messages/catalog.py

@@ -246,7 +246,7 @@ def __init__(self, locale=None, domain=None, header_comment=DEFAULT_HEADER,
                  project=None, version=None, copyright_holder=None,
                  msgid_bugs_address=None, creation_date=None,
                  revision_date=None, last_translator=None, language_team=None,
-                 charset=None, fuzzy=True):
+                 charset=None, fuzzy=True, is_template=False):
         """Initialize the catalog object.
 
         :param locale: the locale identifier or `Locale` object, or `None`
@@ -300,6 +300,8 @@ def __init__(self, locale=None, domain=None, header_comment=DEFAULT_HEADER,
         self._num_plurals = None
         self._plural_expr = None
 
+        self._is_template = is_template
+
     def _set_locale(self, locale):
         if locale is None:
             self._locale_identifier = None
@@ -424,7 +426,7 @@ def _set_mime_headers(self, headers):
                 self.msgid_bugs_address = value
             elif name == 'last-translator':
                 self.last_translator = value
-            elif name == 'language':
+            elif name == 'language' and not self._is_template:
                 value = value.replace('-', '_')
                 self._set_locale(value)
             elif name == 'language-team':

babel/messages/frontend.py

@@ -619,7 +619,7 @@ def run(self):
         with open(self.input_file, 'rb') as infile:
             # Although reading from the catalog template, read_po must be fed
             # the locale in order to correctly calculate plurals
-            catalog = read_po(infile, locale=self.locale)
+            catalog = read_po(infile, locale=self.locale, is_template=True)
 
         catalog.locale = self._locale
         catalog.revision_date = datetime.now(LOCALTZ)
@@ -738,7 +738,7 @@ def run(self):
             domain = os.path.splitext(os.path.basename(self.input_file))[0]
 
         with open(self.input_file, 'rb') as infile:
-            template = read_po(infile)
+            template = read_po(infile, is_template=True)
 
         for locale, filename in po_files:
             self.log.info('updating catalog %s based on %s', filename, self.input_file)

babel/messages/pofile.py

@@ -325,7 +325,8 @@ def _invalid_pofile(self, line, lineno, msg):
         print(u"WARNING: Problem on line {0}: {1}".format(lineno + 1, line))
 
 
-def read_po(fileobj, locale=None, domain=None, ignore_obsolete=False, charset=None, abort_invalid=False):
+def read_po(fileobj, locale=None, domain=None, ignore_obsolete=False,
+        charset=None, abort_invalid=False, is_template=False):
     """Read messages from a ``gettext`` PO (portable object) file from the given
     file-like object and return a `Catalog`.
 
@@ -372,7 +373,8 @@ def read_po(fileobj, locale=None, domain=None, ignore_obsolete=False, charset=No
     :param charset: the character set of the catalog.
     :param abort_invalid: abort read if po file is invalid
     """
-    catalog = Catalog(locale=locale, domain=domain, charset=charset)
+    catalog = Catalog(locale=locale, domain=domain, charset=charset,
+            is_template=is_template)
     parser = PoFileParser(catalog, ignore_obsolete, abort_invalid=abort_invalid)
     parser.parse(fileobj)
     return catalog

tests/messages/data/project/i18n/messages.pot

@@ -13,6 +13,7 @@ msgstr ""
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
+"Language: Non existent language\n"
 "MIME-Version: 1.0\n"
 "Content-Type: text/plain; charset=utf-8\n"
 "Content-Transfer-Encoding: 8bit\n"

tests/messages/data/project/i18n/messages_non_fuzzy.pot

@@ -12,6 +12,7 @@ msgstr ""
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
+"Language: \n"
 "MIME-Version: 1.0\n"
 "Content-Type: text/plain; charset=utf-8\n"
 "Content-Transfer-Encoding: 8bit\n"