Add support for XLIFF placeholders

This should allow to translate units containing placeholders such
as the one used by Angular i18n.

PoXliff will not support placehoders, because it probably doesn't
make sense to support XLIFF specific placeholders in a format that
actually embed PO placeholders.

Fixes WeblateOrg#490
Fixes WeblateOrg#1535

Signed-off-by: Adrien Crivelli <adrien.crivelli@gmail.com>

weblate/formats/ttkit.py

@@ -45,7 +45,9 @@
 
 from weblate.formats.base import TranslationUnit, TranslationFormat
 
-from weblate.trans.util import get_string, join_plural
+from weblate.trans.util import (
+    get_string, join_plural, xliff_string_to_rich, rich_to_xliff_string
+)
 
 from weblate.utils.errors import report_error
 
@@ -415,6 +417,29 @@ class XliffUnit(TTKitUnit):
         'new', 'needs-translation', 'needs-adaptation', 'needs-l10n'
     ))
 
+    @cached_property
+    def source(self):
+        """Return source string from a ttkit unit."""
+
+        if self.template is not None:
+            return rich_to_xliff_string(self.template.rich_target)
+        return rich_to_xliff_string(self.unit.rich_source)
+
+    @cached_property
+    def target(self):
+        """Return target string from a ttkit unit."""
+        if self.unit is None:
+            return ''
+
+        if self.unit.target is None:
+            return ''
+
+        return rich_to_xliff_string(self.unit.rich_target)
+
+    def set_target(self, target):
+        """Set translation unit target."""
+        self.unit.rich_target = xliff_string_to_rich(target)
+
     @cached_property
     def xliff_node(self):
         return self.unit.getlanguageNode(lang=None, index=1)
@@ -501,6 +526,19 @@ def mark_approved(self, value):
         if self.xliff_state:
             self.xliff_node.set('state', 'final' if value else 'translated')
 
+class PoXliffUnit(XliffUnit):
+
+    @cached_property
+    def source(self):
+        return TTKitUnit.source.__get__(self)
+
+    @cached_property
+    def target(self):
+        return TTKitUnit.target.__get__(self)
+
+    def set_target(self, target):
+        TTKitUnit.set_target(self, target)
+
 
 class MonolingualIDUnit(TTKitUnit):
     @cached_property
@@ -728,6 +766,7 @@ class PoXliffFormat(XliffFormat):
     format_id = 'poxliff'
     autoload = ('.poxliff',)
     loader = PoXliffFile
+    unit_class = PoXliffUnit
 
 
 class PropertiesBaseFormat(TTKitFormat):

weblate/trans/tests/test_xliff_placeholders.py

@@ -0,0 +1,47 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright © 2012 - 2018 Michal Čihař <michal@cihar.com>
+#
+# This file is part of Weblate <https://weblate.org/>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+#
+
+"""
+Tests for XLIFF rich string.
+"""
+
+from django.test import TestCase
+
+from weblate.trans.util import xliff_string_to_rich, rich_to_xliff_string
+from translate.storage.placeables.strelem import StringElem
+
+
+class XliffPlaceholdersTest(TestCase):
+
+    def test_bidirectional_xliff_string(self):
+        cases = [
+            'foo <x id="INTERPOLATION" equiv-text="{{ angularExpression }}"/> bar',
+            '',
+            'hello world',
+            'hello <p>world</p>'
+        ]
+
+        for string in cases:
+            rich = xliff_string_to_rich(string)
+            self.assertTrue(isinstance(rich, list))
+            self.assertTrue(isinstance(rich[0], StringElem))
+
+            final_string = rich_to_xliff_string(rich)
+            self.assertEqual(string, final_string)

weblate/trans/util.py

@@ -33,6 +33,8 @@
 from django.utils.encoding import force_text
 from django.utils.http import is_safe_url
 from django.utils.translation import ugettext as _, ugettext_lazy
+from translate.storage.placeables.lisa import parse_xliff, strelem_to_xml
+from lxml import etree
 
 try:
     import pyuca  # pylint: disable=import-error
@@ -284,3 +286,31 @@ def redirect_next(next_url, fallback):
             not next_url.startswith('/')):
         return redirect(fallback)
     return HttpResponseRedirect(next_url)
+
+
+def xliff_string_to_rich(string):
+    """XLIFF string to StringElement
+
+    Transform a string containing XLIFF placeholders as XML
+    into a rich content (StringElement)
+    """
+
+    return [parse_xliff(string)]
+
+
+def rich_to_xliff_string(string_elements):
+    """StringElement to XLIFF string
+
+    Transform rich content (StringElement) into
+    a string with placeholder kept as XML
+    """
+
+    result = ''
+    for string_element in string_elements:
+        xml = etree.Element(u'e')
+        strelem_to_xml(xml, string_element)
+        string_xml = etree.tostring(xml, encoding="unicode")
+        string_without_wrapping_element = string_xml[3:][:-4]
+        result += string_without_wrapping_element
+
+    return result