Fixed #29959 -- Cached GEOS version in WKBWriter class.

Regression in f185d929fa.

django/contrib/gis/geos/prototypes/io.py

@@ -213,6 +213,7 @@ class WKBWriter(IOBase):
     _constructor = wkb_writer_create
     ptr_type = WKB_WRITE_PTR
     destructor = wkb_writer_destroy
+    geos_version = geos_version_tuple()
 
     def __init__(self, dim=2):
         super().__init__()
@@ -235,7 +236,7 @@ class WKBWriter(IOBase):
         from django.contrib.gis.geos import Polygon
         geom = self._handle_empty_point(geom)
         wkb = wkb_writer_write(self.ptr, geom.ptr, byref(c_size_t()))
-        if geos_version_tuple() < (3, 6, 1) and isinstance(geom, Polygon) and geom.empty:
+        if self.geos_version < (3, 6, 1) and isinstance(geom, Polygon) and geom.empty:
             # Fix GEOS output for empty polygon.
             # See https://trac.osgeo.org/geos/ticket/680.
             wkb = wkb[:-8] + b'\0' * 4
@@ -246,7 +247,7 @@ class WKBWriter(IOBase):
         from django.contrib.gis.geos.polygon import Polygon
         geom = self._handle_empty_point(geom)
         wkb = wkb_writer_write_hex(self.ptr, geom.ptr, byref(c_size_t()))
-        if geos_version_tuple() < (3, 6, 1) and isinstance(geom, Polygon) and geom.empty:
+        if self.geos_version < (3, 6, 1) and isinstance(geom, Polygon) and geom.empty:
             wkb = wkb[:-16] + b'0' * 8
         return wkb
 

docs/releases/1.11.17.txt

@@ -9,4 +9,6 @@ Django 1.11.17 fixes several bugs in 1.11.16.
 Bugfixes
 ========
 
-* ...
+* Prevented repetitive calls to ``geos_version_tuple()`` in the ``WKBWriter``
+  class in an attempt to fix a random crash involving ``LooseVersion`` since
+  Django 1.11.14 (:ticket:`29959`).

docs/releases/2.0.10.txt

@@ -9,4 +9,6 @@ Django 2.0.10 fixes several bugs in 2.0.9.
 Bugfixes
 ========
 
-* ...
+* Prevented repetitive calls to ``geos_version_tuple()`` in the ``WKBWriter``
+  class in an attempt to fix a random crash involving ``LooseVersion`` since
+  Django 2.0.6 (:ticket:`29959`).

docs/releases/2.1.4.txt

@@ -12,3 +12,7 @@ Bugfixes
 * Corrected the default password list that ``CommonPasswordValidator`` uses by
   lowercasing all passwords to match the format expected by the validator
   (:ticket:`29952`).
+
+* Prevented repetitive calls to ``geos_version_tuple()`` in the ``WKBWriter``
+  class in an attempt to fix a random crash involving ``LooseVersion``
+  (:ticket:`29959`).