Fixed django#17736 -- Kept maximal floating-point accuracy in from_bbox

When constructing a polygon with Polygon.from_bbox, do not convert
parameters to strings at this stage (str defaults to 12 significant
digits).
Thanks tdihp@hotmail.com for the report and David Eklung for the patch.

AUTHORS

@@ -171,6 +171,7 @@ answer newbie questions, and generally made Django that much better:
     Clint Ecker
     Nick Efford <nick@efford.org>
     eibaan@gmail.com
+    David Eklund
     Julia Elman
     enlight
     Enrico <rico.bl@gmail.com>

django/contrib/gis/geos/polygon.py

@@ -55,8 +55,11 @@ def __len__(self):
     def from_bbox(cls, bbox):
         "Constructs a Polygon from a bounding box (4-tuple)."
         x0, y0, x1, y1 = bbox
-        return GEOSGeometry( 'POLYGON((%s %s, %s %s, %s %s, %s %s, %s %s))' %  (
-                x0, y0, x0, y1, x1, y1, x1, y0, x0, y0) )
+        for z in bbox:
+            if not isinstance(z, (int, long, float)):
+                return GEOSGeometry('POLYGON((%s %s, %s %s, %s %s, %s %s, %s %s))' %
+                                    (x0, y0, x0, y1, x1, y1, x1, y0, x0, y0))
+        return Polygon(((x0, y0), (x0, y1), (x1, y1), (x1, y0), (x0, y0)))
 
     ### These routines are needed for list-like operation w/ListMixin ###
     def _create_polygon(self, length, items):

django/contrib/gis/geos/tests/test_geos.py

@@ -384,6 +384,13 @@ def test_polygons_from_bbox(self):
         p = Polygon.from_bbox(bbox)
         self.assertEqual(bbox, p.extent)
 
+        # Testing numerical precision
+        x = 3.14159265358979323
+        bbox = (0, 0, 1, x)
+        p = Polygon.from_bbox(bbox)
+        y = p.extent[-1]
+        self.assertEqual(format(x, '.13f'), format(y, '.13f'))
+
     def test_polygons(self):
         "Testing Polygon objects."