Cython 3.1+ fixes (#1452)

* MNT: Avoid borrowed Python reference error

In the Geod init there is an unsafe usage of inline if/else to cast
the values. This is only used for the repr, so just live with the
extra ".0" in the display rather than casting integers.

* MNT: Fix unsafe C derivates and str/bytes casting issues with Cython 3.1+

- Avoid Unsafe C derivative of temporary Python reference
  These are in the Geod repr and c_authority casting to a temp variable
- Explicitly cstrencode when bytes are expected instead of strings

* CI: Add Cython latest installation to a workflow

.github/workflows/test_proj_latest.yaml

@@ -1,4 +1,4 @@
-name: Test PROJ Latest
+name: Test PROJ and Cython Latest
 
 on:
   push:
@@ -41,7 +41,7 @@ jobs:
         shell: bash
         run: |
           python -V
-          python -m pip install cython
+          python -m pip install --upgrade --pre --only-binary :all: -i https://pypi.anaconda.org/scientific-python-nightly-wheels/simple cython
           python -m pip install -e .
           python -m pip install -r requirements-test.txt
           pyproj -v

pyproj/_crs.pyx

@@ -2352,13 +2352,13 @@ cdef class _CRS(Base):
         self._coordinate_operation = None
         self._type_name = None
 
-    def __init__(self, const char *proj_string):
+    def __init__(self, str proj_string):
         self.context = pyproj_context_create()
         self._context_manager = get_context_manager()
         # initialize projection
         self.projobj = proj_create(
             self.context,
-            proj_string,
+            cstrencode(proj_string),
         )
         if self.projobj == NULL:
             raise CRSError(f"Invalid projection: {proj_string}")

pyproj/_geod.pyx

@@ -90,10 +90,7 @@ cdef class Geod:
         geod_init(&self._geod_geodesic, <double> a, <double> f)
         self.a = a
         self.f = f
-        # convert 'a' only for initstring
-        a_str = int(a) if a.is_integer() else a
-        f_str = int(f) if f.is_integer() else f
-        self.initstring = f"+a={a_str} +f={f_str}"
+        self.initstring = f"+{a=} +{f=}"
         self.sphere = sphere
         self.b = b
         self.es = es

pyproj/_transformer.pyx

@@ -151,7 +151,8 @@ cdef class _TransformerGroup:
             double north_lat_degree
 
         if authority is not None:
-            c_authority = authority
+            tmp = cstrencode(authority)
+            c_authority = tmp
 
         try:
             operation_factory_context = proj_create_operation_factory_context(

pyproj/database.pyx

@@ -460,7 +460,7 @@ def get_database_metadata(str key not None):
     cdef const char* metadata = NULL
     metadata = proj_context_get_database_metadata(
         pyproj_context_create(),
-        cstrdecode(key),
+        cstrencode(key),
     )
     if metadata == NULL:
         return None

test/test_proj.py

@@ -232,7 +232,7 @@ def test_repr(self):
     def test_sphere(self):
         # ellipse is Venus 2000 (IAU2000:29900), which is a sphere
         g = Geod("+a=6051800 +b=6051800")
-        self.assertEqual(repr(g), "Geod('+a=6051800 +f=0')")
+        self.assertEqual(repr(g), "Geod('+a=6051800.0 +f=0.0')")
 
     # test __repr__ for Geod object
     def test_ellps_name_round_trip(self):