Restore compatibility with expected minimum Cython version

.github/workflows/main.yml

@@ -59,19 +59,27 @@ jobs:
           select-by-folder: /home/runner/work/cantera/cantera/test/matlab_experimental
 
   ubuntu-multiple-pythons:
-    name: ${{ matrix.os }} with Python ${{ matrix.python-version }}, Numpy ${{ matrix.numpy || 'latest' }}
+    name: ${{ matrix.os }} with Python ${{ matrix.python-version }}, Numpy ${{ matrix.numpy || 'latest' }}, Cython ${{ matrix.cython || 'latest' }}
     runs-on: ${{ matrix.os }}
     timeout-minutes: 60
     strategy:
       matrix:
         python-version: ['3.8', '3.10', '3.11', '3.12']
         os: ['ubuntu-20.04', 'ubuntu-22.04']
         numpy: ['']
+        cython: ['']
         include:
           # Keep some test cases with NumPy 1.x until we drop support
         - python-version: '3.12'
           os: 'ubuntu-24.04'
           numpy: "'<2.0'"
+          # Keep some test cases with older Cython versions
+        - python-version: '3.10'
+          os: 'ubuntu-24.04'
+          cython: "==0.29.31" # minimum supported version
+        - python-version: '3.11'
+          os: 'ubuntu-24.04'
+          cython: "==3.0.8" # System version for Ubuntu 24.04
 
       fail-fast: false
     steps:
@@ -95,8 +103,8 @@ jobs:
     - name: Install Python dependencies
       run: |
         python3 -m pip install ruamel.yaml scons==3.1.2 numpy${{ matrix.numpy }} \
-          cython pandas pytest pytest-github-actions-annotate-failures pytest-xdist \
-          pint graphviz
+          cython${{ matrix.cython }} pandas pytest \
+          pytest-github-actions-annotate-failures pytest-xdist pint graphviz
     - name: Build Cantera
       run: |
         python3 `which scons` build env_vars=all -j4 debug=n --debug=time \

interfaces/cython/cantera/func1.pxd

@@ -59,6 +59,6 @@ cdef class Func1:
     cdef object exception
     cpdef void _set_callback(self, object) except *
     @staticmethod
-    cdef shared_ptr[CxxFunc1] _make_cxx_func1(string, tuple)
+    cdef shared_ptr[CxxFunc1] _make_cxx_func1(string, tuple) except *
     @staticmethod
     cdef Func1 _make_func1(shared_ptr[CxxFunc1])

interfaces/cython/cantera/func1.pyx

@@ -152,7 +152,7 @@
         return pystr(self.func.type())
 
     @staticmethod
-    cdef shared_ptr[CxxFunc1] _make_cxx_func1(string cxx_string, tuple args):
+    cdef shared_ptr[CxxFunc1] _make_cxx_func1(string cxx_string, tuple args) except *:
         """Create C++ functor from type specifier and arguments."""
         cdef shared_ptr[CxxFunc1] func
         cdef Func1 f0
@@ -244,7 +244,15 @@
         if not isinstance(other, Func1):
             other = Func1(other)
         cdef Func1 f1 = other
-        return Func1._make_func1(CxxNewSumFunction(self._func, f1._func))
+
+        # @todo: When dropping support for Cython < 3.0.0, 'f0' can be removed and
+        # 'self._func' can be used directly in the C++ call
+        cdef Func1 f0
+        if isinstance(self, Func1):
+            f0 = self
+        else:
+            f0 = Func1(self)
+        return Func1._make_func1(CxxNewSumFunction(f0._func, f1._func))
 
     def __radd__(self, other):
         if not isinstance(other, Func1):
@@ -256,7 +264,15 @@
         if not isinstance(other, Func1):
             other = Func1(other)
         cdef Func1 f1 = other
-        return Func1._make_func1(CxxNewDiffFunction(self._func, f1._func))
+
+        # @todo: When dropping support for Cython < 3.0.0, 'f0' can be removed and
+        # 'self._func' can be used directly in the C++ call
+        cdef Func1 f0
+        if isinstance(self, Func1):
+            f0 = self
+        else:
+            f0 = Func1(self)
+        return Func1._make_func1(CxxNewDiffFunction(f0._func, f1._func))
 
     def __rsub__(self, other):
         if not isinstance(other, Func1):
@@ -268,7 +284,14 @@
         if not isinstance(other, Func1):
             other = Func1(other)
         cdef Func1 f1 = other
-        return Func1._make_func1(CxxNewProdFunction(self._func, f1._func))
+        # @todo: When dropping support for Cython < 3.0.0, 'f0' can be removed and
+        # 'self._func' can be used directly in the C++ call
+        cdef Func1 f0
+        if isinstance(self, Func1):
+            f0 = self
+        else:
+            f0 = Func1(self)
+        return Func1._make_func1(CxxNewProdFunction(f0._func, f1._func))
 
     def __rmul__(self, other):
         if not isinstance(other, Func1):
@@ -280,7 +303,14 @@
         if not isinstance(other, Func1):
             other = Func1(other)
         cdef Func1 f1 = other
-        return Func1._make_func1(CxxNewRatioFunction(self._func, f1._func))
+        # @todo: When dropping support for Cython < 3.0.0, 'f0' can be removed and
+        # 'self._func' can be used directly in the C++ call
+        cdef Func1 f0
+        if isinstance(self, Func1):
+            f0 = self
+        else:
+            f0 = Func1(self)
+        return Func1._make_func1(CxxNewRatioFunction(f0._func, f1._func))
 
     def __rtruediv__(self, other):
         if not isinstance(other, Func1):