fix: better PyPy support

Author: henryiii

include/pybind11/eval.h

@@ -19,11 +19,11 @@ PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 inline void ensure_builtins_in_globals(object &global) {
-    #if PY_VERSION_HEX < 0x03080000
+    #if defined(PYPY_VERSION) || PY_VERSION_HEX < 0x03080000
         // Running exec and eval on Python 2 and 3 adds `builtins` module under
         // `__builtins__` key to globals if not yet present.
         // Python 3.8 made PyRun_String behave similarly. Let's also do that for
-        // older versions, for consistency.
+        // older versions, for consistency. This was missing from PyPy3.8 7.3.7.
         if (!global.contains("__builtins__"))
             global["__builtins__"] = module_::import(PYBIND11_BUILTINS_MODULE);
     #else

tests/test_buffers.py

@@ -59,6 +59,7 @@ def test_to_python():
     assert cstats.alive() == 1
     del mat
     pytest.gc_collect()
+    pytest.gc_collect()  # Needed for PyPy
     assert cstats.alive() == 1
     del mat2  # holds a mat reference
     pytest.gc_collect()

tests/test_builtin_casters.py

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