Restore formatter function help texts to Transifex

We now use the form processed for easy translation. Fixes #2117352 [Translatable raw strings cause spurious newlines on Transifex](https://bugs.launchpad.net/calibre/+bug/2117352)

setup/translations.py

@@ -8,6 +8,7 @@ __docformat__ = 'restructuredtext en'
 import errno
 import glob
 import hashlib
+import inspect
 import json
 import os
 import re
@@ -28,6 +29,20 @@ from setup.iso_codes import iso_data
 from setup.parallel_build import batched_parallel_jobs
 
 
+def serialize_msgid(text):
+    '''Serialize a string in the format used by msgid in GNU POT files.'''
+    if not text:
+        return 'msgid ""\n'
+    # Escape backslashes and quotes
+    escaped = text.replace('\\', r'\\').replace('"', r'\"')
+    ans = ['msgid ""']
+    lines = escaped.splitlines()
+    for line in lines:
+        trailer = '"' if line is lines[-1] else r'\n"'
+        ans.append(f'"{line}{trailer}')
+    return '\n'.join(ans)
+
+
 def qt_sources():
     qtdir = os.environ.get('QT_SRC', '/usr/src/qt6/qtbase')
     j = partial(os.path.join, qtdir)
@@ -71,6 +86,15 @@ class POT(Command):  # {{{
                     ans.append(self.a(self.j(root, name)))
         return ans
 
+    def get_ffml_docs(self):
+        from calibre.utils.formatter_functions import _formatter_builtins as b
+        ans = []
+        for ff in b:
+            lnum = inspect.getsourcelines(ff.__doc__getter__)[1]
+            text = ff.__doc__getter__().msgid
+            ans.append(f'#: src/calibre/utils/formatter_function.py:{lnum}\n' + serialize_msgid(text) + '\nmsgstr ""\n\n')
+        return ''.join(ans)
+
     def get_tweaks_docs(self):
         path = self.a(self.j(self.SRC, '..', 'resources', 'default_tweaks.py'))
         with open(path, 'rb') as f:
@@ -218,12 +242,12 @@ class POT(Command):  # {{{
                 '--from-code=UTF-8', '--sort-by-file', '--omit-header',
                                    '--no-wrap', '-kQT_TRANSLATE_NOOP:2', '-ktr', '-ktranslate:2',
                 ] + qt_inputs)
-
             with open(out.name, 'rb') as f:
                 src = f.read().decode('utf-8')
             os.remove(out.name)
             src = pot_header + '\n' + src
             src += '\n\n' + self.get_tweaks_docs()
+            src += '\n\n' + self.get_ffml_docs()
             bdir = os.path.join(self.TRANSLATIONS, __appname__)
             if not os.path.exists(bdir):
                 os.makedirs(bdir)

src/calibre/utils/formatter_functions.py

@@ -60,20 +60,20 @@ URL_FUNCTIONS = _('URL functions')
 # Class and method to save an untranslated copy of translated strings
 class TranslatedStringWithRaw(str):
 
-    def __new__(cls, raw_english, raw_other, formatted_english, formatted_other):
+    def __new__(cls, raw_english, raw_other, formatted_english, formatted_other, msgid):
         instance = super().__new__(cls, formatted_other)
         instance.raw_english = raw_english
         instance.raw_other = raw_other
         instance.formatted_english = formatted_english
         instance.formatted_other = formatted_other
+        instance.msgid = msgid
         instance.did_format = False
         return instance
 
     def format(self, *args, **kw):
         formatted_english = self.raw_english.format(*args, **kw)
         formatted_other = self.raw_other.format(*args, **kw)
-        v = TranslatedStringWithRaw(self.raw_english, self.raw_other,
-                                       formatted_english, formatted_other)
+        v = TranslatedStringWithRaw(self.raw_english, self.raw_other, formatted_english, formatted_other, self.msgid)
         v.saved_args = args
         v.saved_kwargs = kw
         v.did_format = True
@@ -87,9 +87,11 @@ class TranslatedStringWithRaw(str):
 
 def translate_ffml(txt):
     from calibre.utils.ffml_processor import FFMLProcessor
-    lookup = FFMLProcessor().document_to_transifex(txt, '', safe=True)
-    translated = xlated(lookup)
-    return TranslatedStringWithRaw(txt, translated, txt, translated)
+    msgid = FFMLProcessor().document_to_transifex(txt, '', safe=True).strip()
+    translated = xlated(msgid)
+    if translated == msgid:
+        translated = txt
+    return TranslatedStringWithRaw(txt, translated, txt, translated, msgid)
 
 
 class StoredObjectType(Enum):