[1.6.x] Fixed #20998 -- Allow custom (de)serialization for GIS widgets

Thanks Mathieu Leplatre for the report and the initial patch.
Backport of 102f26c92 from master.

4 files changed, 53 insertions, 23 deletions

diff --git a/django/contrib/gis/forms/widgets.py b/django/contrib/gis/forms/widgets.py
index d50c7c005a..0102ab6745 100644
--- a/django/contrib/gis/forms/widgets.py
+++ b/django/contrib/gis/forms/widgets.py
@@ -22,51 +22,54 @@ class BaseGeometryWidget(Widget):
     map_srid = 4326
     map_width = 600
     map_height = 400
-    display_wkt = False
+    display_raw = False
 
     supports_3d = False
     template_name = ''  # set on subclasses
 
     def __init__(self, attrs=None):
         self.attrs = {}
-        for key in ('geom_type', 'map_srid', 'map_width', 'map_height', 'display_wkt'):
+        for key in ('geom_type', 'map_srid', 'map_width', 'map_height', 'display_raw'):
             self.attrs[key] = getattr(self, key)
         if attrs:
             self.attrs.update(attrs)
 
+    def serialize(self, value):
+        return value.wkt if value else ''
+
+    def deserialize(self, value):
+        try:
+            return GEOSGeometry(value)
+        except (GEOSException, ValueError) as err:
+            logger.error(
+                "Error creating geometry from value '%s' (%s)" % (
+                value, err)
+            )
+        return None
+
     def render(self, name, value, attrs=None):
         # If a string reaches here (via a validation error on another
         # field) then just reconstruct the Geometry.
         if isinstance(value, six.string_types):
-            try:
-                value = GEOSGeometry(value)
-            except (GEOSException, ValueError) as err:
-                logger.error(
-                    "Error creating geometry from value '%s' (%s)" % (
-                    value, err)
-                )
-                value = None
+            value = self.deserialize(value)
 
-        wkt = ''
         if value:
             # Check that srid of value and map match
             if value.srid != self.map_srid:
                 try:
                     ogr = value.ogr
                     ogr.transform(self.map_srid)
-                    wkt = ogr.wkt
+                    value = ogr
                 except gdal.OGRException as err:
                     logger.error(
                         "Error transforming geometry from srid '%s' to srid '%s' (%s)" % (
                         value.srid, self.map_srid, err)
                     )
-            else:
-                wkt = value.wkt
 
         context = self.build_attrs(attrs,
             name=name,
             module='geodjango_%s' % name.replace('-','_'),  # JS-safe
-            wkt=wkt,
+            serialized=self.serialize(value),
             geom_type=gdal.OGRGeomType(self.attrs['geom_type']),
             STATIC_URL=settings.STATIC_URL,
             LANGUAGE_BIDI=translation.get_language_bidi(),
diff --git a/django/contrib/gis/templates/gis/openlayers.html b/django/contrib/gis/templates/gis/openlayers.html
index 281c0badd6..4884f48106 100644
--- a/django/contrib/gis/templates/gis/openlayers.html
+++ b/django/contrib/gis/templates/gis/openlayers.html
@@ -2,7 +2,7 @@
     #{{ id }}_map { width: {{ map_width }}px; height: {{ map_height }}px; }
     #{{ id }}_map .aligned label { float: inherit; }
     #{{ id }}_div_map { position: relative; vertical-align: top; float: {{ LANGUAGE_BIDI|yesno:"right,left" }}; }
-    {% if not display_wkt %}#{{ id }} { display: none; }{% endif %}
+    {% if not display_raw %}#{{ id }} { display: none; }{% endif %}
     .olControlEditingToolbar .olControlModifyFeatureItemActive {
         background-image: url("{{ STATIC_URL }}admin/img/gis/move_vertex_on.png");
         background-repeat: no-repeat;
@@ -16,8 +16,8 @@
 <div id="{{ id }}_div_map">
     <div id="{{ id }}_map"></div>
     <span class="clear_features"><a href="javascript:{{ module }}.clearFeatures()">Delete all Features</a></span>
-    {% if display_wkt %}<p> WKT debugging window:</p>{% endif %}
-    <textarea id="{{ id }}" class="vWKTField required" cols="150" rows="10" name="{{ name }}">{{ wkt }}</textarea>
+    {% if display_raw %}<p>Debugging window (serialized value):</p>{% endif %}
+    <textarea id="{{ id }}" class="vSerializedField required" cols="150" rows="10" name="{{ name }}">{{ serialized }}</textarea>
     <script type="text/javascript">
         {% block map_options %}var map_options = {};{% endblock %}
         {% block options %}var options = {
diff --git a/django/contrib/gis/tests/test_geoforms.py b/django/contrib/gis/tests/test_geoforms.py
index 402d9b944b..47d66d6919 100644
--- a/django/contrib/gis/tests/test_geoforms.py
+++ b/django/contrib/gis/tests/test_geoforms.py
@@ -3,9 +3,9 @@ from django.contrib.gis.gdal import HAS_GDAL
 from django.contrib.gis.tests.utils import HAS_SPATIALREFSYS
 from django.test import SimpleTestCase
 from django.utils import six
+from django.utils.html import escape
 from django.utils.unittest import skipUnless
 
-
 if HAS_SPATIALREFSYS:
     from django.contrib.gis import forms
     from django.contrib.gis.geos import GEOSGeometry
@@ -241,3 +241,30 @@ class SpecializedFieldTest(SimpleTestCase):
 
         for invalid in [geom for key, geom in self.geometries.items() if key!='geometrycollection']:
             self.assertFalse(GeometryForm(data={'g': invalid.wkt}).is_valid())
+
+@skipUnless(HAS_GDAL and HAS_SPATIALREFSYS,
+    "CustomGeometryWidgetTest needs gdal support and a spatial database")
+class CustomGeometryWidgetTest(SimpleTestCase):
+    class CustomGeometryWidget(forms.BaseGeometryWidget):
+        template_name = 'gis/openlayers.html'
+        deserialize_called = 0
+        def serialize(self, value):
+            return value.json if value else ''
+
+        def deserialize(self, value):
+            self.deserialize_called += 1
+            return GEOSGeometry(value)
+
+    def test_custom_serialization_widget(self):
+        class PointForm(forms.Form):
+            p = forms.PointField(widget=self.CustomGeometryWidget)
+
+        point = GEOSGeometry("SRID=4326;POINT(9.052734375 42.451171875)")
+        form = PointForm(data={'p': point})
+        self.assertIn(escape(point.json), form.as_p())
+
+        self.CustomGeometryWidget.called = 0
+        widget = form.fields['p'].widget
+        # Force deserialize use due to a string value
+        self.assertIn(escape(point.json), widget.render('p', point.json))
+        self.assertEqual(widget.deserialize_called, 1)
diff --git a/docs/ref/contrib/gis/forms-api.txt b/docs/ref/contrib/gis/forms-api.txt
index d0c671958f..7fe04f6dec 100644
--- a/docs/ref/contrib/gis/forms-api.txt
+++ b/docs/ref/contrib/gis/forms-api.txt
@@ -114,11 +114,11 @@ from other Django widget attributes.
 
     SRID code used by the map (default is 4326).
 
-.. attribute:: BaseGeometryWidget.display_wkt
+.. attribute:: BaseGeometryWidget.display_raw
 
-    Boolean value specifying if a textarea input showing the WKT representation
-    of the current geometry is visible, mainly for debugging purposes (default
-    is ``False``).
+    Boolean value specifying if a textarea input showing the serialized
+    representation of the current geometry is visible, mainly for debugging
+    purposes (default is ``False``).
 
 .. attribute:: BaseGeometryWidget.supports_3d