Make sure all warnings in pytest get turned into errors (#2838)

* Make sure all warnings in pytest get turned into errors

* Suppress DeprecationWarnings in test_int_convert and test_numpy_int_convert

* PyLong_AsLong only shouts "Deprecated!" on Python>=3.8

* Fix remaining warnings on PyPy and CPython 3.10-dev

Author: YannickJadoul

tests/pytest.ini

@@ -7,11 +7,11 @@ addopts =
     -rs
     # capture only Python print and C++ py::print, but not C output (low-level Python errors)
     --capture=sys
-    # enable all warnings
-    -Wa
 filterwarnings =
     # make warnings into errors but ignore certain third-party extension issues
     error
+    # somehow, some DeprecationWarnings do not get turned into errors
+    always::DeprecationWarning
     # importing scipy submodules on some version of Python
     ignore::ImportWarning
     # bogus numpy ABI warning (see numpy/#432)

tests/test_builtin_casters.py

@@ -299,7 +299,12 @@ def cant_convert(v):
     assert convert(7) == 7
     assert noconvert(7) == 7
     cant_convert(3.14159)
-    assert convert(Int()) == 42
+    # TODO: Avoid DeprecationWarning in `PyLong_AsLong` (and similar)
+    if (3, 8) <= env.PY < (3, 10):
+        with pytest.deprecated_call():
+            assert convert(Int()) == 42
+    else:
+        assert convert(Int()) == 42
     requires_conversion(Int())
     cant_convert(NotInt())
     cant_convert(Float())
@@ -329,7 +334,12 @@ def require_implicit(v):
     assert noconvert(np.intc(42)) == 42
 
     # The implicit conversion from np.float32 is undesirable but currently accepted.
-    assert convert(np.float32(3.14159)) == 3
+    # TODO: Avoid DeprecationWarning in `PyLong_AsLong` (and similar)
+    if (3, 8) <= env.PY < (3, 10):
+        with pytest.deprecated_call():
+            assert convert(np.float32(3.14159)) == 3
+    else:
+        assert convert(np.float32(3.14159)) == 3
     require_implicit(np.float32(3.14159))
 
 

tests/test_class.cpp

@@ -434,8 +434,7 @@ TEST_SUBMODULE(class_, m) {
     struct SamePointer {};
     static SamePointer samePointer;
     py::class_<SamePointer, std::unique_ptr<SamePointer, py::nodelete>>(m, "SamePointer")
-        .def(py::init([]() { return &samePointer; }))
-        .def("__del__", [](SamePointer&) { py::print("__del__ called"); });
+        .def(py::init([]() { return &samePointer; }));
 
     struct Empty {};
     py::class_<Empty>(m, "Empty")