Allow flipping mapbox coordinates to/from db

The current Leaflet implementation expects coordinates in latitude-longitude order but GeoJSON and PostGIS works the other way around with lng first. These changes work around this behavior by passing the data to and from db through PostGIS’s `ST_FlipCoordinates` function if the setting `MAPBOX_FIX_POINT_COORDINATES` is something truthy. This is to not break the current behavior. Right now a warning is emitted when this setting hasn’t been enabled but I would recommend to remove this setting and make its behavior the default in the next major version.

flask_admin/contrib/geoa/fields.py

 import json
+import warnings
+
+import geoalchemy2
+from flask import current_app
+from shapely.geometry import shape
+from sqlalchemy import func
 from wtforms.fields import TextAreaField
-from shapely.geometry import shape, mapping
+
 from .widgets import LeafletWidget
-from sqlalchemy import func
-import geoalchemy2
-#from types import NoneType
-#from .. import db how do you get db.session in a Field?
 
 
 class JSONField(TextAreaField):
@@ -37,32 +39,69 @@ class JSONField(TextAreaField):
 
 class GeoJSONField(JSONField):
     widget = LeafletWidget()
-    
+
     def __init__(self, label=None, validators=None, geometry_type="GEOMETRY", srid='-1', session=None, **kwargs):
         super(GeoJSONField, self).__init__(label, validators, **kwargs)
         self.web_srid = 4326
         self.srid = srid
         if self.srid is -1:
-        	self.transform_srid = self.web_srid
+            self.transform_srid = self.web_srid
         else:
-        	self.transform_srid = self.srid
+            self.transform_srid = self.srid
         self.geometry_type = geometry_type.upper()
         self.session = session
-    
+
+    def _flip_coordinates(self, other_func):
+        if current_app.config.get('MAPBOX_FIX_COORDINATES_ORDER'):
+            return func.ST_FlipCoordinates(other_func)
+        else:
+            warnings.warn(
+                'Consider setting the Flask config option '
+                'MAPBOX_FIX_COORDINATES_ORDER as the current implementation '
+                'passes lng/lat coordinates in the wrong order to '
+                'Leaflet. Without this setting any coordinates saved will '
+                'have flipped coordinates in your database. '
+                'Please note that this will become the standard behavior in '
+                'the next major version of Flask-Admin.'
+            )
+            return other_func
+
     def _value(self):
         if self.raw_data:
             return self.raw_data[0]
         if type(self.data) is geoalchemy2.elements.WKBElement:
             if self.srid is -1:
-                self.data = self.session.scalar(func.ST_AsGeoJson(self.data))
+                self.data = self.session.scalar(
+                    func.ST_AsGeoJson(
+                        self._flip_coordinates(self.data)
+                    )
+                )
             else:
-                self.data = self.session.scalar(func.ST_AsGeoJson(func.ST_Transform(self.data, self.web_srid)))
+                self.data = self.session.scalar(
+                    func.ST_AsGeoJson(
+                        self._flip_coordinates(
+                            func.ST_Transform(self.data, self.web_srid)
+                        )
+                    )
+                )
         return super(GeoJSONField, self)._value()
-    
+
     def process_formdata(self, valuelist):
         super(GeoJSONField, self).process_formdata(valuelist)
         if str(self.data) is '':
             self.data = None
         if self.data is not None:
-            web_shape = self.session.scalar(func.ST_AsText(func.ST_Transform(func.ST_GeomFromText(shape(self.data).wkt, self.web_srid), self.transform_srid)))
-            self.data = 'SRID='+str(self.srid)+';'+str(web_shape)
+            web_shape = self.session.scalar(
+                func.ST_AsText(
+                    self._flip_coordinates(
+                        func.ST_Transform(
+                            func.ST_GeomFromText(
+                                shape(self.data).wkt,
+                                self.web_srid
+                            ),
+                            self.transform_srid
+                        )
+                    )
+                )
+            )
+            self.data = 'SRID=' + str(self.srid) + ';' + str(web_shape)

flask_admin/tests/geoa/test_basic.py

 from __future__ import unicode_literals
-from nose.tools import eq_, ok_
+import json
+import re
 
 from flask_admin.contrib.geoa import ModelView
+from flask_admin.contrib.geoa.fields import GeoJSONField
 from geoalchemy2 import Geometry
 from geoalchemy2.shape import to_shape
-from flask_admin.contrib.geoa.fields import GeoJSONField
+from nose.tools import eq_
 
 from . import setup
 
@@ -30,6 +32,8 @@ def test_model():
     app, db, admin = setup()
     GeoModel = create_models(db)
     db.create_all()
+    GeoModel.query.delete()
+    db.session.commit()
 
     view = ModelView(GeoModel, db.session)
     admin.add_view(view)
@@ -81,37 +85,84 @@ def test_model():
 
     rv = client.get('/admin/geomodel/')
     eq_(rv.status_code, 200)
-    point_opt_1 = '>{"type": "Point", "coordinates": [125.8, 10.0]}</textarea>'
-    point_opt_2 = '>{"coordinates": [125.8, 10.0], "type": "Point"}</textarea>'
-    point_opt_3 = '>{"type":"Point","coordinates":[125.8,10]}</textarea>'
+
     html = rv.data.decode('utf-8')
-    ok_(point_opt_1 in html or point_opt_2 in html or point_opt_3 in html, html)
+    pattern = r'(.|\n)+({.*"type": ?"Point".*})</textarea>(.|\n)+'
+    group = re.match(pattern, html).group(2)
+    p = json.loads(group)
+    eq_(p['coordinates'][0], 125.8)
+    eq_(p['coordinates'][1], 10.0)
 
     url = '/admin/geomodel/edit/?id=%s' % model.id
     rv = client.get(url)
     eq_(rv.status_code, 200)
 
-    #rv = client.post(url, data={
-    #    "name": "edited",
-    #    "point": '{"type": "Point", "coordinates": [99.9, 10.5]}',
-    #    "line": '',  # set to NULL in the database
-    #})
-    #eq_(rv.status_code, 302)
+    # rv = client.post(url, data={
+    #     "name": "edited",
+    #     "point": '{"type": "Point", "coordinates": [99.9, 10.5]}',
+    #     "line": '',  # set to NULL in the database
+    # })
+    # eq_(rv.status_code, 302)
     #
-    #model = db.session.query(GeoModel).first()
-    #eq_(model.name, "edited")
-    #eq_(to_shape(model.point).geom_type, "Point")
-    #eq_(list(to_shape(model.point).coords), [(99.9, 10.5)])
-    #eq_(to_shape(model.line), None)
-    #eq_(to_shape(model.polygon).geom_type, "Polygon")
-    #eq_(list(to_shape(model.polygon).exterior.coords),
-    #    [(100.0, 0.0), (101.0, 0.0), (101.0, 1.0), (100.0, 1.0), (100.0, 0.0)])
-    #eq_(to_shape(model.multi).geom_type, "MultiPoint")
-    #eq_(len(to_shape(model.multi).geoms), 2)
-    #eq_(list(to_shape(model.multi).geoms[0].coords), [(100.0, 0.0)])
-    #eq_(list(to_shape(model.multi).geoms[1].coords), [(101.0, 1.0)])
+    # model = db.session.query(GeoModel).first()
+    # eq_(model.name, "edited")
+    # eq_(to_shape(model.point).geom_type, "Point")
+    # eq_(list(to_shape(model.point).coords), [(99.9, 10.5)])
+    # eq_(to_shape(model.line), None)
+    # eq_(to_shape(model.polygon).geom_type, "Polygon")
+    # eq_(list(to_shape(model.polygon).exterior.coords),
+    #     [(100.0, 0.0), (101.0, 0.0), (101.0, 1.0), (100.0, 1.0), (100.0, 0.0)])
+    # eq_(to_shape(model.multi).geom_type, "MultiPoint")
+    # eq_(len(to_shape(model.multi).geoms), 2)
+    # eq_(list(to_shape(model.multi).geoms[0].coords), [(100.0, 0.0)])
+    # eq_(list(to_shape(model.multi).geoms[1].coords), [(101.0, 1.0)])
 
     url = '/admin/geomodel/delete/?id=%s' % model.id
     rv = client.post(url)
     eq_(rv.status_code, 302)
     eq_(db.session.query(GeoModel).count(), 0)
+
+
+def test_mapbox_fix_point_coordinates():
+    app, db, admin = setup()
+    app.config['MAPBOX_FIX_COORDINATES_ORDER'] = True
+    GeoModel = create_models(db)
+    db.create_all()
+    GeoModel.query.delete()
+    db.session.commit()
+
+    view = ModelView(GeoModel, db.session)
+    admin.add_view(view)
+
+    # Make some test clients
+    client = app.test_client()
+
+    rv = client.post('/admin/geomodel/new/', data={
+        "name": "test1",
+        "point": '{"type": "Point", "coordinates": [125.8, 10.0]}',
+        "line": '{"type": "LineString", "coordinates": [[50.2345, 94.2], [50.21, 94.87]]}',
+        "polygon": '{"type": "Polygon", "coordinates": [[[100.0, 0.0], [101.0, 0.0], [101.0, 1.0], [100.0, 1.0], [100.0, 0.0]]]}',
+        "multi": '{"type": "MultiPoint", "coordinates": [[100.0, 0.0], [101.0, 1.0]]}',
+    })
+
+    model = db.session.query(GeoModel).first()
+    # Notice how the coordinates are reversed here, i.e. longitude first which
+    # is the way it's stored in PostGIS columns.
+    eq_(list(to_shape(model.point).coords), [(10.0, 125.8)])
+    eq_(list(to_shape(model.line).coords), [(94.2, 50.2345), (94.87, 50.21)])
+    eq_(list(to_shape(model.polygon).exterior.coords),
+        [(0.0, 100.0), (0.0, 101.0), (1.0, 101.0), (1.0, 100.0), (0.0, 100.0)])
+    eq_(list(to_shape(model.multi).geoms[0].coords), [(0.0, 100.0)])
+    eq_(list(to_shape(model.multi).geoms[1].coords), [(1.0, 101.0)])
+
+    rv = client.get('/admin/geomodel/')
+    eq_(rv.status_code, 200)
+
+    html = rv.data.decode('utf-8')
+    pattern = r'(.|\n)+({.*"type": ?"Point".*})</textarea>(.|\n)+'
+    group = re.match(pattern, html).group(2)
+    p = json.loads(group)
+
+    # Reversed order again, so that it's parsed correctly by leaflet
+    eq_(p['coordinates'][0], 10.0)
+    eq_(p['coordinates'][1], 125.8)