Merge pull request #34 from minddistrict/CB-556-FR-translation

Add support for pluralization

20 files changed, 396 insertions, 37 deletions

diff --git a/CHANGES.rst b/CHANGES.rst
index cbd6bd4..18238e6 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -5,7 +5,9 @@
 4.5 (unreleased)
 ================
 
-- Nothing changed yet.
+- Add support for pluralization. ``translate()`` now takes the
+  additional optional arguments ``msgid_plural``, ``default_plural``
+  and ``number`` in order to support it.
 
 
 4.4 (2018-10-05)
diff --git a/setup.py b/setup.py
index eac0e7d..853f686 100644
--- a/setup.py
+++ b/setup.py
@@ -101,7 +101,7 @@ setup(
         'pytz',
         'zope.deprecation',
         'zope.schema',
-        'zope.i18nmessageid',
+        'zope.i18nmessageid >= 4.3',
         'zope.component',
     ],
     extras_require={
diff --git a/src/zope/i18n/__init__.py b/src/zope/i18n/__init__.py
index 3088074..5f7d775 100644
--- a/src/zope/i18n/__init__.py
+++ b/src/zope/i18n/__init__.py
@@ -39,6 +39,7 @@ class _FallbackNegotiator(object):
     def getLanguage(self, _allowed, _context):
         return None
 
+
 _fallback_negotiator = _FallbackNegotiator()
 
 
@@ -79,8 +80,10 @@ def negotiate(context):
     negotiator = queryUtility(INegotiator, default=_fallback_negotiator)
     return negotiator.getLanguage(ALLOWED_LANGUAGES, context)
 
+
 def translate(msgid, domain=None, mapping=None, context=None,
-              target_language=None, default=None):
+              target_language=None, default=None, msgid_plural=None,
+              default_plural=None, number=None):
     """Translate text.
 
     First setup some test components:
@@ -160,6 +163,9 @@ def translate(msgid, domain=None, mapping=None, context=None,
         domain = msgid.domain
         default = msgid.default
         mapping = msgid.mapping
+        msgid_plural = msgid.msgid_plural
+        default_plural = msgid.default_plural
+        number = msgid.number
 
     if default is None:
         default = text_type(msgid)
@@ -181,7 +187,10 @@ def translate(msgid, domain=None, mapping=None, context=None,
     if target_language is None and context is not None:
         target_language = negotiate(context)
 
-    return util.translate(msgid, mapping, context, target_language, default)
+    return util.translate(
+        msgid, mapping, context, target_language, default,
+        msgid_plural, default_plural, number)
+
 
 def interpolate(text, mapping=None):
     """Insert the data passed from mapping into the text.
@@ -197,15 +206,15 @@ def interpolate(text, mapping=None):
 
     Interpolation variables can be used more than once in the text:
 
-    >>> print(interpolate(u"This is $name version ${version}. ${name} $version!",
-    ...             mapping))
+    >>> print(interpolate(
+    ...     u"This is $name version ${version}. ${name} $version!", mapping))
     This is Zope version 3. Zope 3!
 
     In case if the variable wasn't found in the mapping or '$$' form
     was used no substitution will happens:
 
-    >>> print(interpolate(u"This is $name $version. $unknown $$name $${version}.",
-    ...             mapping))
+    >>> print(interpolate(
+    ...     u"This is $name $version. $unknown $$name $${version}.", mapping))
     This is Zope 3. $unknown $$name $${version}.
 
     >>> print(interpolate(u"This is ${name}"))
diff --git a/src/zope/i18n/format.py b/src/zope/i18n/format.py
index ee2e239..96f5ef3 100644
--- a/src/zope/i18n/format.py
+++ b/src/zope/i18n/format.py
@@ -33,6 +33,7 @@ try:
 except NameError:
     pass # Py3
 
+
 def roundHalfUp(n):
     """Works like round() in python2.x
 
@@ -42,18 +43,20 @@ def roundHalfUp(n):
     """
     return math.floor(n + math.copysign(0.5, n))
 
+
 def _findFormattingCharacterInPattern(char, pattern):
     return [entry for entry in pattern
             if isinstance(entry, tuple) and entry[0] == char]
 
+
 class DateTimeParseError(Exception):
     """Error is raised when parsing of datetime failed."""
 
+
 @implementer(IDateTimeFormat)
 class DateTimeFormat(object):
     __doc__ = IDateTimeFormat.__doc__
 
-
     _DATETIMECHARS = "aGyMdEDFwWhHmsSkKz"
 
     calendar = None
@@ -486,11 +489,11 @@ class NumberFormat(object):
         return text_type(text)
 
 
-
 DEFAULT = 0
 IN_QUOTE = 1
 IN_DATETIMEFIELD = 2
 
+
 class DateTimePatternParseError(Exception):
     """DateTime Pattern Parse Error"""
 
@@ -760,6 +763,7 @@ SUFFIX = 7
 PADDING4 = 8
 GROUPING = 9
 
+
 class NumberPatternParseError(Exception):
     """Number Pattern Parse Error"""
 
diff --git a/src/zope/i18n/gettextmessagecatalog.py b/src/zope/i18n/gettextmessagecatalog.py
index 307e5be..8e1272b 100644
--- a/src/zope/i18n/gettextmessagecatalog.py
+++ b/src/zope/i18n/gettextmessagecatalog.py
@@ -14,6 +14,7 @@
 """A simple implementation of a Message Catalog.
 """
 
+from functools import wraps
 from gettext import GNUTranslations
 from zope.i18n.interfaces import IGlobalMessageCatalog
 from zope.interface import implementer
@@ -22,7 +23,31 @@ from zope.interface import implementer
 class _KeyErrorRaisingFallback(object):
     def ugettext(self, message):
         raise KeyError(message)
+
+    def ungettext(self, singular, plural, n):
+        raise KeyError(singular)
+
     gettext = ugettext
+    ngettext = ungettext
+
+
+def plural_formatting(func):
+    """This decorator interpolates the possible formatting marker.
+    This interpolation marker is usally present for plurals.
+    Example: `There are %d apples` or `They have %s pies.`
+
+    Please note that the interpolation can be done, alternatively,
+    using the mapping. This is only present as a conveniance.
+    """
+    @wraps(func)
+    def pformat(catalog, singular, plural, n, *args, **kwargs):
+        msg = func(catalog, singular, plural, n, *args, **kwargs)
+        try:
+            return msg % n
+        except TypeError:
+            # The message cannot be formatted : return it "raw".
+            return msg
+    return pformat
 
 
 @implementer(IGlobalMessageCatalog)
@@ -33,13 +58,20 @@ class GettextMessageCatalog(object):
 
     def __init__(self, language, domain, path_to_file):
         """Initialize the message catalog"""
-        self.language = language.decode('utf-8') if isinstance(language, bytes) else language
-        self.domain = domain.decode("utf-8") if isinstance(domain, bytes) else domain
+        self.language = (
+            language.decode('utf-8') if isinstance(language, bytes)
+            else language)
+        self.domain = (
+            domain.decode("utf-8") if isinstance(domain, bytes)
+            else domain)
         self._path_to_file = path_to_file
         self.reload()
         catalog = self._catalog
         catalog.add_fallback(_KeyErrorRaisingFallback())
-        self._gettext = catalog.gettext if str is not bytes else catalog.ugettext
+        self._gettext = (
+            catalog.gettext if str is not bytes else catalog.ugettext)
+        self._ngettext = (
+            catalog.ngettext if str is not bytes else catalog.ungettext)
 
     def reload(self):
         'See IMessageCatalog'
@@ -50,6 +82,23 @@ class GettextMessageCatalog(object):
         'See IMessageCatalog'
         return self._gettext(id)
 
+    @plural_formatting
+    def getPluralMessage(self, singular, plural, n):
+        'See IMessageCatalog'
+        return self._ngettext(singular, plural, n)
+
+    @plural_formatting
+    def queryPluralMessage(self, singular, plural, n, dft1=None, dft2=None):
+        'See IMessageCatalog'
+        try:
+            return self._ngettext(singular, plural, n)
+        except KeyError:
+            # Here, we use the catalog plural function to determine
+            # if `n` triggers a plural form or not.
+            if self._catalog.plural(n):
+                return dft2
+            return dft1
+
     def queryMessage(self, id, default=None):
         'See IMessageCatalog'
         try:
diff --git a/src/zope/i18n/interfaces/__init__.py b/src/zope/i18n/interfaces/__init__.py
index 397c8f5..11d8c21 100644
--- a/src/zope/i18n/interfaces/__init__.py
+++ b/src/zope/i18n/interfaces/__init__.py
@@ -60,13 +60,30 @@ class IMessageCatalog(Interface):
 
         An exception is raised if the message id is not found.
         """
-
+        
     def queryMessage(msgid, default=None):
         """Look for the appropriate text for the given message id.
 
         If the message id is not found, default is returned.
         """
 
+    def getPluralMessage(self, singular, plural, n):
+        """Get the appropriate text for the given message id and the
+        plural id.
+
+        An exception is raised if nothing was found.
+        """
+
+    def queryPluralMessage(singular, plural, n, dft1=None, dft2=None):
+        """Look for the appropriate text for the given message id and the
+        plural id.
+
+        If `n` is evaluated as a singular and the id is not found,
+        `dft1` is returned.
+        If `n` is evaluated as a plural and the plural id is not found,
+        `dft2` is returned.
+        """
+
     language = TextLine(
         title=u"Language",
         description=u"The language the catalog translates to.",
@@ -118,6 +135,10 @@ class ITranslationDomain(Interface):
 
         target_language -- The language to translate to.
 
+        msgid_plural -- The id of the plural message that should be translated.
+
+        number -- The number of items linked to the plural of the message.
+
         context -- An object that provides contextual information for
                    determining client language preferences.  It must implement
                    or have an adapter that implements IUserPreferredLanguages.
@@ -133,7 +154,8 @@ class ITranslationDomain(Interface):
         required=True)
 
     def translate(msgid, mapping=None, context=None, target_language=None,
-                  default=None):
+                  default=None, msgid_plural=None, default_plural=None,
+                  number=None):
         """Return the translation for the message referred to by msgid.
 
         Return the default if no translation is found.
@@ -147,6 +169,7 @@ class ITranslationDomain(Interface):
 
         """
 
+
 class IFallbackTranslationDomainFactory(Interface):
     """Factory for creating fallback translation domains
 
@@ -158,6 +181,7 @@ class IFallbackTranslationDomainFactory(Interface):
         """Return a fallback translation domain for the given domain id.
         """
 
+
 class ITranslator(Interface):
     """A collaborative object which contains the domain, context, and locale.
 
@@ -165,7 +189,8 @@ class ITranslator(Interface):
     the domain, context, and target language.
     """
 
-    def translate(msgid, mapping=None, default=None):
+    def translate(msgid, mapping=None, default=None,
+                  msgid_plural=None, default_plural=None, number=None):
         """Translate the source msgid using the given mapping.
 
         See ITranslationService for details.
@@ -212,6 +237,7 @@ class IUserPreferredLanguages(Interface):
         languages first.
         """
 
+
 class IModifiableUserPreferredLanguages(IUserPreferredLanguages):
 
     def setPreferredLanguages(languages):
diff --git a/src/zope/i18n/negotiator.py b/src/zope/i18n/negotiator.py
index 66417c0..3c5fa17 100644
--- a/src/zope/i18n/negotiator.py
+++ b/src/zope/i18n/negotiator.py
@@ -14,16 +14,17 @@
 """Language Negotiator
 """
 from zope.interface import implementer
-
 from zope.i18n.interfaces import INegotiator
 from zope.i18n.interfaces import IUserPreferredLanguages
 
+
 def normalize_lang(lang):
     lang = lang.strip().lower()
     lang = lang.replace('_', '-')
     lang = lang.replace(' ', '')
     return lang
 
+
 def normalize_langs(langs):
     # Make a mapping from normalized->original so we keep can match
     # the normalized lang and return the original string.
@@ -32,6 +33,7 @@ def normalize_langs(langs):
         n_langs[normalize_lang(l)] = l
     return n_langs
 
+
 @implementer(INegotiator)
 class Negotiator(object):
 
diff --git a/src/zope/i18n/simpletranslationdomain.py b/src/zope/i18n/simpletranslationdomain.py
index b50fb68..b093db8 100644
--- a/src/zope/i18n/simpletranslationdomain.py
+++ b/src/zope/i18n/simpletranslationdomain.py
@@ -18,8 +18,10 @@ from zope.component import getUtility
 from zope.i18n.interfaces import ITranslationDomain, INegotiator
 from zope.i18n import interpolate
 
+
 text_type = str if bytes is not str else unicode
 
+
 @implementer(ITranslationDomain)
 class SimpleTranslationDomain(object):
     """This is the simplest implementation of the ITranslationDomain I
@@ -39,12 +41,14 @@ class SimpleTranslationDomain(object):
 
     def __init__(self, domain, messages=None):
         """Initializes the object. No arguments are needed."""
-        self.domain = domain.decode("utf-8") if isinstance(domain, bytes) else domain
+        self.domain = (
+            domain.decode("utf-8") if isinstance(domain, bytes) else domain)
         self.messages = messages if messages is not None else {}
         assert self.messages is not None
 
     def translate(self, msgid, mapping=None, context=None,
-                  target_language=None, default=None):
+                  target_language=None, default=None, msgid_plural=None,
+                  default_plural=None, number=None):
         '''See interface ITranslationDomain'''
         # Find out what the target language should be
         if target_language is None and context is not None:
diff --git a/src/zope/i18n/tests/de-default.mo b/src/zope/i18n/tests/de-default.mo
index 392a0ff..f49b8da 100644
--- a/src/zope/i18n/tests/de-default.mo
+++ b/src/zope/i18n/tests/de-default.mo
diff --git a/src/zope/i18n/tests/de-default.po b/src/zope/i18n/tests/de-default.po
index 99a5f8d..7d3b2f6 100644
--- a/src/zope/i18n/tests/de-default.po
+++ b/src/zope/i18n/tests/de-default.po
@@ -6,9 +6,15 @@ msgstr ""
 "MIME-Version: 1.0\n"
 "Content-Type: text/plain; charset=ISO-8859-1\n"
 "Content-Transfer-Encoding: 8bit\n"
+"Plural-Forms: nplurals=2; plural=n != 1;\n"
 
 msgid "short_greeting"
 msgstr "Hallo!"
 
 msgid "greeting"
 msgstr "Hallo $name, wie geht es Dir?"
+
+msgid "There is one file."
+msgid_plural "There are %d files."
+msgstr[0] "Es gibt eine Datei."
+msgstr[1] "Es gibt %d Dateien."
diff --git a/src/zope/i18n/tests/en-alt.mo b/src/zope/i18n/tests/en-alt.mo
index e08bb59..2e7a16a 100644
--- a/src/zope/i18n/tests/en-alt.mo
+++ b/src/zope/i18n/tests/en-alt.mo
diff --git a/src/zope/i18n/tests/en-alt.po b/src/zope/i18n/tests/en-alt.po
index de55bbc..eb439fb 100644
--- a/src/zope/i18n/tests/en-alt.po
+++ b/src/zope/i18n/tests/en-alt.po
@@ -12,3 +12,8 @@ msgstr "Hey!"
 
 msgid "special"
 msgstr "Wow"
+
+msgid "apple"
+msgid_plural "apple"
+msgstr[0] "orange"
+msgstr[1] "oranges"
diff --git a/src/zope/i18n/tests/en-default.mo b/src/zope/i18n/tests/en-default.mo
index 4164029..0dc0588 100644
--- a/src/zope/i18n/tests/en-default.mo
+++ b/src/zope/i18n/tests/en-default.mo
diff --git a/src/zope/i18n/tests/en-default.po b/src/zope/i18n/tests/en-default.po
index a3d843b..2432498 100644
--- a/src/zope/i18n/tests/en-default.po
+++ b/src/zope/i18n/tests/en-default.po
@@ -6,9 +6,40 @@ msgstr ""
 "MIME-Version: 1.0\n"
 "Content-Type: text/plain; charset=ISO-8859-1\n"
 "Content-Transfer-Encoding: 8bit\n"
+"Plural-Forms: nplurals=2; plural=n != 1;\n"
 
 msgid "short_greeting"
 msgstr "Hello!"
 
 msgid "greeting"
 msgstr "Hello $name, how are you?"
+
+msgid "There is one file."
+msgid_plural "There are %d files."
+msgstr[0] "There is one file."
+msgstr[1] "There are %d files."
+
+msgid "The item is rated 1/5 star."
+msgid_plural "The item is rated %s/5 stars."
+msgstr[0] "The item is rated 1/5 star."
+msgstr[1] "The item is rated %s/5 stars."
+
+msgid "There is %d chance."
+msgid_plural "There are %f chances."
+msgstr[0] "There is %d chance."
+msgstr[1] "There are %f chances."
+
+msgid "There is %d ${type}."
+msgid_plural "There are %d ${type}."
+msgstr[0] "There is %d ${type}."
+msgstr[1] "There are %d ${type}."
+
+msgid "apple"
+msgid_plural "apples"
+msgstr[0] "apple"
+msgstr[1] "apples"
+
+msgid "banana"
+msgid_plural "bananas"
+msgstr[0] "banana"
+msgstr[1] "bananas"
diff --git a/src/zope/i18n/tests/pl-default.mo b/src/zope/i18n/tests/pl-default.mo
new file mode 100644
index 0000000..37b73fe
--- /dev/null
+++ b/src/zope/i18n/tests/pl-default.mo
diff --git a/src/zope/i18n/tests/pl-default.po b/src/zope/i18n/tests/pl-default.po
new file mode 100644
index 0000000..3951a9c
--- /dev/null
+++ b/src/zope/i18n/tests/pl-default.po
@@ -0,0 +1,22 @@
+msgid ""
+msgstr ""
+"Project-Id-Version: Zope 3\n"
+"PO-Revision-Date: 2018-09-04 11:05+0100\n"
+"Last-Translator: Zope 3 contributors\n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=utf-8\n"
+"Content-Transfer-Encoding: 8bit\n"
+"Plural-Forms: nplurals=3; plural=n==1 ? 0 : n%10>=2 && n%10<=4 && (n%100<10 || n%100>=20) ? 1 : 2;\n"
+
+
+msgid "short_greeting"
+msgstr "Cześć !"
+
+msgid "greeting"
+msgstr "Cześć $name, jak się masz?"
+
+msgid "There is one file."
+msgid_plural "There are %d files."
+msgstr[0] "Istnieje %d plik."
+msgstr[1] "Istnieją %d pliki."
+msgstr[2] "Istnieją %d plików."
diff --git a/src/zope/i18n/tests/test_imessagecatalog.py b/src/zope/i18n/tests/test_imessagecatalog.py
index 2856c67..803d4f0 100644
--- a/src/zope/i18n/tests/test_imessagecatalog.py
+++ b/src/zope/i18n/tests/test_imessagecatalog.py
@@ -43,24 +43,20 @@ class TestIMessageCatalog(unittest.TestCase):
         self.assertEqual(catalog.getMessage('short_greeting'), 'Hello!')
         self.assertRaises(KeyError, catalog.getMessage, 'foo')
 
-
     def testQueryMessage(self):
         catalog = self._catalog
         self.assertEqual(catalog.queryMessage('short_greeting'), 'Hello!')
         self.assertEqual(catalog.queryMessage('foo'), None)
         self.assertEqual(catalog.queryMessage('foo', 'bar'), 'bar')
 
-
     def testGetLanguage(self):
         catalog = self._catalog
         self.assertEqual(catalog.language, 'en')
 
-
     def testGetDomain(self):
         catalog = self._catalog
         self.assertEqual(catalog.domain, 'default')
 
-
     def testGetIdentifier(self):
         catalog = self._catalog
         self.assertEqual(catalog.getIdentifier(), self._getUniqueIndentifier())
diff --git a/src/zope/i18n/tests/test_plurals.py b/src/zope/i18n/tests/test_plurals.py
new file mode 100644
index 0000000..4f7813e
--- /dev/null
+++ b/src/zope/i18n/tests/test_plurals.py
@@ -0,0 +1,183 @@
+# -*- coding: utf-8 -*-
+##############################################################################
+#
+# Copyright (c) 2001, 2002 Zope Foundation and Contributors.
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+##############################################################################
+"""Test a gettext implementation of a Message Catalog.
+"""
+import os
+import unittest
+from zope.i18n import tests
+from zope.i18n.translationdomain import TranslationDomain
+from zope.i18n.gettextmessagecatalog import GettextMessageCatalog
+from zope.i18nmessageid import MessageFactory
+
+
+class TestPlurals(unittest.TestCase):
+
+    def _getMessageCatalog(self, locale, variant="default"):
+        path = os.path.dirname(tests.__file__)
+        self._path = os.path.join(path, '%s-%s.mo' % (locale, variant))
+        catalog = GettextMessageCatalog(locale, variant, self._path)
+        return catalog
+
+    def _getTranslationDomain(self, locale, variant="default"):
+        path = os.path.dirname(tests.__file__)
+        self._path = os.path.join(path, '%s-%s.mo' % (locale, variant))
+        catalog = GettextMessageCatalog(locale, variant, self._path)
+        domain = TranslationDomain('default')
+        domain.addCatalog(catalog)
+        return domain
+
+    def test_GermanPlurals(self):
+        """Germanic languages such as english and german share the plural
+        rule. We test the german here.
+        """
+        catalog = self._getMessageCatalog('de')
+        self.assertEqual(catalog.language, 'de')
+
+        self.assertEqual(catalog.getPluralMessage(
+                         'There is one file.', 'There are %d files.', 1),
+                         'Es gibt eine Datei.')
+        self.assertEqual(catalog.getPluralMessage(
+                         'There is one file.', 'There are %d files.', 3),
+                         'Es gibt 3 Dateien.')
+        self.assertEqual(catalog.getPluralMessage(
+                         'There is one file.', 'There are %d files.', 0),
+                         'Es gibt 0 Dateien.')
+
+        # Unknown id
+        self.assertRaises(KeyError, catalog.getPluralMessage,
+                          'There are %d files.', 'bar', 6)
+
+        # Query without default values
+        self.assertEqual(catalog.queryPluralMessage(
+                         'There is one file.', 'There are %d files.', 1),
+                         'Es gibt eine Datei.')
+        self.assertEqual(catalog.queryPluralMessage(
+                         'There is one file.', 'There are %d files.', 3),
+                         'Es gibt 3 Dateien.')
+
+        # Query with default values
+        self.assertEqual(catalog.queryPluralMessage(
+                         'There are %d files.', 'There is one file.', 1,
+                         'Es gibt 1 Datei.', 'Es gibt %d Dateien !', ),
+                         'Es gibt 1 Datei.')
+        self.assertEqual(catalog.queryPluralMessage(
+                         'There are %d files.', 'There is one file.', 3,
+                         'Es gibt 1 Datei.', 'Es gibt %d Dateien !', ),
+                         'Es gibt 3 Dateien !')
+
+    def test_PolishPlurals(self):
+        """Polish has a complex rule for plurals. It makes for a good
+        test subject.
+        """
+        catalog = self._getMessageCatalog('pl')
+        self.assertEqual(catalog.language, 'pl')
+
+        self.assertEqual(catalog.getPluralMessage(
+                         'There is one file.', 'There are %d files.', 0),
+                         u"Istnieją 0 plików.")
+        self.assertEqual(catalog.getPluralMessage(
+                         'There is one file.', 'There are %d files.', 1),
+                         u"Istnieje 1 plik.")
+        self.assertEqual(catalog.getPluralMessage(
+                         'There is one file.', 'There are %d files.', 3),
+                         u"Istnieją 3 pliki.")
+        self.assertEqual(catalog.getPluralMessage(
+                         'There is one file.', 'There are %d files.', 17),
+                         u"Istnieją 17 plików.")
+        self.assertEqual(catalog.getPluralMessage(
+                         'There is one file.', 'There are %d files.', 23),
+                         u"Istnieją 23 pliki.")
+        self.assertEqual(catalog.getPluralMessage(
+                         'There is one file.', 'There are %d files.', 28),
+                         u"Istnieją 28 plików.")
+
+    def test_floater(self):
+        """Test with the number being a float.
+        We can use %f or %s to make sure it works.
+        """
+        catalog = self._getMessageCatalog('en')
+        self.assertEqual(catalog.language, 'en')
+
+        # It's cast to integer because of the %d in the translation string.
+        self.assertEqual(catalog.getPluralMessage(
+                         'There is one file.', 'There are %d files.', 1.0),
+                         'There is one file.')
+        self.assertEqual(catalog.getPluralMessage(
+                         'There is one file.', 'There are %d files.', 3.5),
+                         'There are 3 files.')
+
+        # It's cast to a string because of the %s in the translation string.
+        self.assertEqual(catalog.getPluralMessage(
+            'The item is rated 1/5 star.',
+            'The item is rated %s/5 stars.', 3.5),
+                         'The item is rated 3.5/5 stars.')
+
+        # It's cast either to an int or a float because of the %s in
+        # the translation string.
+        self.assertEqual(catalog.getPluralMessage(
+            'There is %d chance.',
+            'There are %f chances.', 1.5),
+                         'There are 1.500000 chances.')
+        self.assertEqual(catalog.getPluralMessage(
+            'There is %d chance.',
+            'There are %f chances.', 3.5),
+                         'There are 3.500000 chances.')
+
+    def test_recursive_translation(self):
+        domain = self._getTranslationDomain('en')
+        factory = MessageFactory('default')
+        translate = domain.translate
+
+        # Singular
+        banana = factory('banana', msgid_plural='bananas', number=1)
+        phrase = factory('There is %d ${type}.',
+                         msgid_plural='There are %d ${type}.',
+                         number=1, mapping={'type': banana})
+        self.assertEqual(
+            translate(phrase, target_language="en"),
+            'There is 1 banana.')
+
+        # Plural
+        apple = factory('apple', msgid_plural='apples', number=10)
+        phrase = factory('There is %d ${type}.',
+                         msgid_plural='There are %d ${type}.',
+                         number=10, mapping={'type': apple})
+        self.assertEqual(
+            translate(phrase, target_language="en"),
+            'There are 10 apples.')
+
+        # Straight translation with translatable mapping
+        apple = factory('apple', msgid_plural='apples', number=75)
+        self.assertEqual(
+            translate(msgid='There is %d ${type}.',
+                      msgid_plural='There are %d ${type}.',
+                      mapping={'type': apple},
+                      target_language="en", number=75),
+            'There are 75 apples.')
+
+        # Add another catalog, to test the domain's catalogs iteration
+        # We add this catalog in first position, to resolve the translations
+        # there first.
+        alt_en = self._getMessageCatalog('en', variant="alt")
+        domain._data[alt_en.getIdentifier()] = alt_en
+        domain._catalogs[alt_en.language].insert(0, alt_en.getIdentifier())
+
+        apple = factory('apple', msgid_plural='apples', number=42)
+        self.assertEqual(
+            translate(msgid='There is %d ${type}.',
+                      msgid_plural='There are %d ${type}.',
+                      mapping={'type': apple},
+                      target_language="de", number=42),
+            'There are 42 oranges.')
diff --git a/src/zope/i18n/translationdomain.py b/src/zope/i18n/translationdomain.py
index 684fa9b..c7f064e 100644
--- a/src/zope/i18n/translationdomain.py
+++ b/src/zope/i18n/translationdomain.py
@@ -34,11 +34,13 @@ LANGUAGE_FALLBACKS = ['en']
 
 text_type = str if bytes is not str else unicode
 
+
 @zope.interface.implementer(ITranslationDomain)
 class TranslationDomain(object):
 
     def __init__(self, domain, fallbacks=None):
-        self.domain = domain.decode("utf-8") if isinstance(domain, bytes) else domain
+        self.domain = (
+            domain.decode("utf-8") if isinstance(domain, bytes) else domain)
         # _catalogs maps (language, domain) to IMessageCatalog instances
         self._catalogs = {}
         # _data maps IMessageCatalog.getIdentifier() to IMessageCatalog
@@ -63,7 +65,8 @@ class TranslationDomain(object):
         self._fallbacks = fallbacks
 
     def translate(self, msgid, mapping=None, context=None,
-                  target_language=None, default=None):
+                  target_language=None, default=None,
+                  msgid_plural=None, default_plural=None, number=None):
         """See zope.i18n.interfaces.ITranslationDomain"""
         # if the msgid is empty, let's save a lot of calculations and return
         # an empty string.
@@ -78,37 +81,43 @@ class TranslationDomain(object):
             target_language = negotiator.getLanguage(langs, context)
 
         return self._recursive_translate(
-            msgid, mapping, target_language, default, context)
+            msgid, mapping, target_language, default, context,
+            msgid_plural, default_plural, number)
 
     def _recursive_translate(self, msgid, mapping, target_language, default,
-                             context, seen=None):
+                             context,  msgid_plural, default_plural, number,
+                             seen=None):
         """Recursively translate msg."""
         # MessageID attributes override arguments
         if isinstance(msgid, Message):
             if msgid.domain != self.domain:
-                return translate(msgid, msgid.domain, mapping, context,
-                                 target_language, default)
+                return translate(
+                    msgid, msgid.domain, mapping, context, target_language,
+                    default, msgid_plural, default_plural, number)
             default = msgid.default
             mapping = msgid.mapping
+            msgid_plural = msgid.msgid_plural
+            default_plural = msgid.default_plural
+            number = msgid.number
 
         # Recursively translate mappings, if they are translatable
         if (mapping is not None
             and Message in (type(m) for m in mapping.values())):
             if seen is None:
                 seen = set()
-            seen.add(msgid)
+            seen.add((msgid, msgid_plural))
             mapping = mapping.copy()
             for key, value in mapping.items():
                 if isinstance(value, Message):
                     # TODO Why isn't there an IMessage interface?
                     # https://bugs.launchpad.net/zope3/+bug/220122
-                    if value in seen:
+                    if (value, value.msgid_plural) in seen:
                         raise ValueError(
                             "Circular reference in mappings detected: %s" %
                             value)
                     mapping[key] = self._recursive_translate(
-                        value, mapping, target_language,
-                        default, context, seen)
+                        value, mapping, target_language, default, context,
+                        msgid_plural, default_plural, number, seen)
 
         if default is None:
             default = text_type(msgid)
@@ -128,12 +137,23 @@ class TranslationDomain(object):
                 # single catalog. More importantly, it is extremely helpful
                 # when testing and the test language is used, because it
                 # allows the test language to get the default.
-                text = self._data[catalog_names[0]].queryMessage(
-                    msgid, default)
+                if msgid_plural is not None:
+                    # This is a plural
+                    text = self._data[catalog_names[0]].queryPluralMessage(
+                        msgid, msgid_plural, number, default, default_plural)
+                else:
+                    text = self._data[catalog_names[0]].queryMessage(
+                        msgid, default)
             else:
                 for name in catalog_names:
                     catalog = self._data[name]
-                    s = catalog.queryMessage(msgid)
+                    if msgid_plural is not None:
+                        # This is a plural
+                        s = catalog.queryPluralMessage(
+                            msgid, msgid_plural, number,
+                            default, default_plural)
+                    else:
+                        s = catalog.queryMessage(msgid)
                     if s is not None:
                         text = s
                         break
diff --git a/src/zope/i18n/zcml.py b/src/zope/i18n/zcml.py
index 39a4a29..4df9ccb 100644
--- a/src/zope/i18n/zcml.py
+++ b/src/zope/i18n/zcml.py
@@ -100,7 +100,7 @@ def registerTranslations(_context, directory, domain='*'):
                 loaded = True
                 domain_file = os.path.basename(domain_path)
                 name = domain_file[:-3]
-                if not name in domains:
+                if name not in domains:
                     domains[name] = {}
                 domains[name][language] = domain_path
     if loaded: