From 1e03faf76e25553734e10464e63802a6e1891e5c Mon Sep 17 00:00:00 2001
From: Dario Marcelino <dario@appscot.com>
Date: Tue, 12 Dec 2017 20:19:17 +0000
Subject: [PATCH 1/2] #143: adds failing tests for StreamField fallback

---
 wagtail_modeltranslation/tests/settings.py |  2 +-
 wagtail_modeltranslation/tests/tests.py    | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/wagtail_modeltranslation/tests/settings.py b/wagtail_modeltranslation/tests/settings.py
index 4d5caa7..0c50767 100755
--- a/wagtail_modeltranslation/tests/settings.py
+++ b/wagtail_modeltranslation/tests/settings.py
@@ -18,6 +18,6 @@ USE_TZ = False
 MIDDLEWARE_CLASSES = ()
 
 MODELTRANSLATION_AUTO_POPULATE = False
-MODELTRANSLATION_FALLBACK_LANGUAGES = ()
+MODELTRANSLATION_FALLBACK_LANGUAGES = {'default': (MODELTRANSLATION_DEFAULT_LANGUAGE,)}
 
 ROOT_URLCONF = 'wagtail_modeltranslation.tests.urls'
diff --git a/wagtail_modeltranslation/tests/tests.py b/wagtail_modeltranslation/tests/tests.py
index e037770..4beb17d 100755
--- a/wagtail_modeltranslation/tests/tests.py
+++ b/wagtail_modeltranslation/tests/tests.py
@@ -348,3 +348,16 @@ class WagtailModeltranslationTest(WagtailModeltranslationTestBase):
         except AttributeError:
             # python 2.7
             self.assertItemsEqual(expected_fields, model_search_fields)
+
+    def test_streamfield_fallback(self):
+        body_text = '[{"value": "Some text", "type": "text"}]'
+        page = models.StreamFieldPanelPage(title='Streamfield Fallback', slug='streamfield_fallback',
+                                           depth=1, path='0005', body=body_text)
+        page.save()
+
+        self.assertEqual(str(page.body), '<div class="block-text">Some text</div>')
+
+        trans_real.activate('en')
+
+        self.assertEqual(str(page.body), '<div class="block-text">Some text</div>',
+                         'page.body did not fallback to original language.')

From 1f36b55f0c5e95945b4ae4136035d53681cfe147 Mon Sep 17 00:00:00 2001
From: Dario Marcelino <dario@appscot.com>
Date: Tue, 12 Dec 2017 20:21:07 +0000
Subject: [PATCH 2/2] #143: Fixes StreamField fallback behaviour

---
 .../patch_wagtailadmin.py                     | 20 +++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/wagtail_modeltranslation/patch_wagtailadmin.py b/wagtail_modeltranslation/patch_wagtailadmin.py
index fbb6eb7..c6d5377 100644
--- a/wagtail_modeltranslation/patch_wagtailadmin.py
+++ b/wagtail_modeltranslation/patch_wagtailadmin.py
@@ -17,6 +17,7 @@ from wagtail.contrib.wagtailroutablepage.models import RoutablePageMixin
 from wagtail.wagtailadmin.edit_handlers import FieldPanel, \
     MultiFieldPanel, FieldRowPanel, InlinePanel, StreamFieldPanel, RichTextFieldPanel
 from wagtail.wagtailcore.models import Page, Site
+from wagtail.wagtailcore.fields import StreamField, StreamValue
 from wagtail.wagtailcore.url_routing import RouteResult
 from wagtail.wagtailimages.edit_handlers import ImageChooserPanel
 from wagtail.wagtailsearch.index import SearchField
@@ -88,6 +89,13 @@ class WagtailTranslator(object):
                     translated_field.field_name = build_localized_fieldname(field.field_name, language)
                     model.search_fields = list(model.search_fields) + [translated_field]
 
+        # OVERRIDE FIELDS
+        model_fields = model._meta.get_fields()
+        for field in model_fields:
+            if isinstance(field, StreamField) and field.name in translation_registered_fields:
+                descriptor = getattr(model, field.name)
+                _patch_stream_field_meaningful_value(descriptor)
+
         # OVERRIDE PAGE METHODS
 
         model.move = _new_move
@@ -402,6 +410,18 @@ def _patch_clean(model):
 
     model.clean = clean
 
+def _patch_stream_field_meaningful_value(field):
+    old_meaningful_value = field.meaningful_value
+
+    def meaningful_value(self, val, undefined):
+        """
+            Check if val is considered non-empty.
+        """
+        if isinstance(val, StreamValue):
+            return len(val.stream_data) != 0
+        return old_meaningful_value(self, val, undefined)
+
+    field.meaningful_value = meaningful_value.__get__(field)
 
 def patch_wagtail_models():
     # After all models being registered the Page or BaseSetting subclasses and snippets are patched