Add ConcatenatedLazyText object

This object will allow splitting large translatable strings into more
pieces, so translators don't have to re-translate the entire text
when a small part changes.

https://fedorahosted.org/freeipa/ticket/3587

ipalib/text.py

@@ -136,6 +136,9 @@ class LazyText(object):
 
     This class is not used directly.  See the `Gettext` and `NGettext`
     subclasses.
+
+    Concatenating LazyText objects with the + operator gives
+    ConcatenatedLazyText objects.
     """
 
     __slots__ = ('domain', 'localedir', 'key', 'args')
@@ -176,6 +179,12 @@ class LazyText(object):
         """
         return not self.__eq__(other)
 
+    def __add__(self, other):
+        return ConcatenatedLazyText(self) + other
+
+    def __radd__(self, other):
+        return other + ConcatenatedLazyText(self)
+
 
 class Gettext(LazyText):
     """
@@ -390,6 +399,43 @@ class NGettext(LazyText):
         return ng(self.singular, self.plural, count)
 
 
+class ConcatenatedLazyText(object):
+    """Concatenation of multiple strings, or any objects convertible to unicode
+
+    Used to concatenate several LazyTexts together.
+    This allows large strings like help text to be split, so translators
+    do not have to re-translate the whole text when only a small part changes.
+
+    Additional strings may be added to the end with the + or += operators.
+    """
+    def __init__(self, *components):
+        self.components = list(components)
+
+    def __repr__(self):
+        return '%s(%r)' % (self.__class__.__name__, self.components)
+
+    def __unicode__(self):
+        return u''.join(unicode(c) for c in self.components)
+
+    def __json__(self):
+        return unicode(self)
+
+    def __mod__(self, kw):
+        return unicode(self) % kw
+
+    def __add__(self, other):
+        if isinstance(other, ConcatenatedLazyText):
+            return ConcatenatedLazyText(*self.components + other.components)
+        else:
+            return ConcatenatedLazyText(*self.components + [other])
+
+    def __radd__(self, other):
+        if isinstance(other, ConcatenatedLazyText):
+            return ConcatenatedLazyText(*other.components + self.components)
+        else:
+            return ConcatenatedLazyText(*[other] + self.components)
+
+
 class GettextFactory(object):
     """
     Factory for creating ``_()`` functions.

ipatests/test_ipalib/test_text.py

@@ -332,3 +332,49 @@ class test_NGettextFactory(object):
         assert ng.plural is plural
         assert ng.domain == 'foo'
         assert ng.localedir == 'bar'
+
+
+class test_ConcatenatedText(object):
+
+    klass = text.ConcatenatedLazyText
+
+    def test_init(self):
+        lst = ['a', 'b', 'c', 3]
+        inst = self.klass(*lst)
+        assert inst.components == lst
+        assert unicode(inst) == 'abc3'
+
+    def test_repr(self):
+        lazytext = text.Gettext('foo', 'bar', 'baz')
+        inst = self.klass(lazytext)
+        assert repr(inst) == "ConcatenatedLazyText([%r])" % lazytext
+
+    def test_unicode(self):
+        inst = self.klass('[', text.Gettext('green', 'foo', 'bar'), 1, ']')
+        assert unicode(inst) == u'[green1]'
+
+    def test_mod(self):
+        inst = self.klass('[', text.Gettext('%(color)s', 'foo', 'bar'), ']')
+        assert inst % dict(color='red', stuff='junk') == '[red]'
+
+    def test_add(self):
+        inst = (text.Gettext('pale ', 'foo', 'bar') +
+                text.Gettext('blue', 'foo', 'bar'))
+        assert unicode(inst) == 'pale blue'
+
+        inst = (text.Gettext('bright ', 'foo', 'bar') +
+                text.Gettext('pale ', 'foo', 'bar') +
+                text.Gettext('blue', 'foo', 'bar'))
+        assert unicode(inst) == 'bright pale blue'
+
+        inst = text.Gettext('yellow', 'foo', 'bar') + '!'
+        assert unicode(inst) == 'yellow!'
+
+        inst = '!' + text.Gettext('yellow', 'foo', 'bar')
+        assert unicode(inst) == '!yellow'
+
+        inst = '!' + ('!' + text.Gettext('yellow', 'foo', 'bar'))
+        assert unicode(inst) == '!!yellow'
+
+        inst = (text.Gettext('yellow', 'foo', 'bar') + '!') + '!'
+        assert unicode(inst) == 'yellow!!'

makeapi

@@ -31,7 +31,7 @@ import operator
 from ipalib import api
 from ipalib.parameters import Param
 from ipalib.output import Output
-from ipalib.text import Gettext, NGettext
+from ipalib.text import Gettext, NGettext, ConcatenatedLazyText
 from ipalib.capabilities import capabilities
 
 API_FILE='API.txt'
@@ -120,7 +120,7 @@ def validate_doc():
 
     def is_i18n(obj):
         'Helper utility to determine if object has been internationalized'
-        return isinstance(obj, (Gettext, NGettext))
+        return isinstance(obj, (Gettext, NGettext, ConcatenatedLazyText))
 
     # The return value
     rval = 0