Python 2 removal part 1: tests (C++ code is intentionally ~untouched) (#3688)

* `#error BYE_BYE_GOLDEN_SNAKE`

* Removing everything related to 2.7 from ci.yml

* Commenting-out Centos7

* Removing `PYTHON: 27` from .appveyor.yml

* "PY2" removal, mainly from tests. C++ code is not touched.

* Systematic removal of `u` prefix from `u"..."` and `u'...'` literals. Collateral cleanup of a couple minor other things.

* Cleaning up around case-insensitive hits for `[^a-z]py.*2` in tests/.

* Removing obsolete Python 2 mention in compiling.rst

* Proper `#error` for Python 2.

* Using PY_VERSION_HEX to guard `#error "PYTHON 2 IS NO LONGER SUPPORTED.`

* chore: bump pre-commit

* style: run pre-commit for pyupgrade 3+

* tests: use sys.version_info, not PY

* chore: more Python 2 removal

* Uncommenting Centos7 block (PR #3691 showed that it is working again).

* Update pre-commit hooks

* Fix pre-commit hook

* refactor: remove Python 2 from CMake

* refactor: remove Python 2 from setup code

* refactor: simplify, better static typing

* feat: fail with nice messages

* refactor: drop Python 2 C++ code

* docs: cleanup for Python 3

* revert: intree

revert: intree

* docs: minor touchup to py2 statement
Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>
Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>

tests/test_eigen.py

-# -*- coding: utf-8 -*-
 import pytest
 
 from pybind11_tests import ConstructorStats
@@ -201,7 +200,7 @@ def test_negative_stride_from_python(msg):
         double_threer(): incompatible function arguments. The following argument types are supported:
             1. (arg0: numpy.ndarray[numpy.float32[1, 3], flags.writeable]) -> None
 
-        Invoked with: """  # noqa: E501 line too long
+        Invoked with: """
         + repr(np.array([5.0, 4.0, 3.0], dtype="float32"))
     )
 
@@ -213,7 +212,7 @@ def test_negative_stride_from_python(msg):
         double_threec(): incompatible function arguments. The following argument types are supported:
             1. (arg0: numpy.ndarray[numpy.float32[3, 1], flags.writeable]) -> None
 
-        Invoked with: """  # noqa: E501 line too long
+        Invoked with: """
         + repr(np.array([7.0, 4.0, 1.0], dtype="float32"))
     )
 
@@ -724,13 +723,13 @@ def test_sparse_signature(doc):
         doc(m.sparse_copy_r)
         == """
         sparse_copy_r(arg0: scipy.sparse.csr_matrix[numpy.float32]) -> scipy.sparse.csr_matrix[numpy.float32]
-    """  # noqa: E501 line too long
+    """
     )
     assert (
         doc(m.sparse_copy_c)
         == """
         sparse_copy_c(arg0: scipy.sparse.csc_matrix[numpy.float32]) -> scipy.sparse.csc_matrix[numpy.float32]
-    """  # noqa: E501 line too long
+    """
     )
 
 

tests/test_embed/test_interpreter.cpp

@@ -126,7 +126,6 @@ TEST_CASE("Override cache") {
 TEST_CASE("Import error handling") {
     REQUIRE_NOTHROW(py::module_::import("widget_module"));
     REQUIRE_THROWS_WITH(py::module_::import("throw_exception"), "ImportError: C++ Error");
-#if PY_VERSION_HEX >= 0x03030000
     REQUIRE_THROWS_WITH(py::module_::import("throw_error_already_set"),
                         Catch::Contains("ImportError: initialization failed"));
 
@@ -142,10 +141,6 @@ TEST_CASE("Import error handling") {
              locals);
     REQUIRE(locals["is_keyerror"].cast<bool>() == true);
     REQUIRE(locals["message"].cast<std::string>() == "'missing'");
-#else
-    REQUIRE_THROWS_WITH(py::module_::import("throw_error_already_set"),
-                        Catch::Contains("ImportError: KeyError"));
-#endif
 }
 
 TEST_CASE("There can be only one interpreter") {

tests/test_embed/test_interpreter.py

-# -*- coding: utf-8 -*-
 import sys
 
 from widget_module import Widget
@@ -6,7 +5,7 @@ from widget_module import Widget
 
 class DerivedWidget(Widget):
     def __init__(self, message):
-        super(DerivedWidget, self).__init__(message)
+        super().__init__(message)
 
     def the_answer(self):
         return 42

tests/test_embed/test_trampoline.py

-# -*- coding: utf-8 -*-
-
 import trampoline_module
 
 

tests/test_enum.py

-# -*- coding: utf-8 -*-
 import pytest
 
-import env
 from pybind11_tests import enums as m
 
 
@@ -241,10 +239,7 @@ def test_char_underlying_enum():  # Issue #1331/PR #1334:
     assert type(m.ScopedCharEnum.Positive.__int__()) is int
     assert int(m.ScopedChar16Enum.Zero) == 0
     assert hash(m.ScopedChar32Enum.Positive) == 1
-    if env.PY2:
-        assert m.ScopedCharEnum.Positive.__getstate__() == 1  # long
-    else:
-        assert type(m.ScopedCharEnum.Positive.__getstate__()) is int
+    assert type(m.ScopedCharEnum.Positive.__getstate__()) is int
     assert m.ScopedWCharEnum(1) == m.ScopedWCharEnum.Positive
     with pytest.raises(TypeError):
         # Even if the underlying type is char, only an int can be used to construct the enum:
@@ -255,10 +250,7 @@ def test_bool_underlying_enum():
     assert type(m.ScopedBoolEnum.TRUE.__int__()) is int
     assert int(m.ScopedBoolEnum.FALSE) == 0
     assert hash(m.ScopedBoolEnum.TRUE) == 1
-    if env.PY2:
-        assert m.ScopedBoolEnum.TRUE.__getstate__() == 1  # long
-    else:
-        assert type(m.ScopedBoolEnum.TRUE.__getstate__()) is int
+    assert type(m.ScopedBoolEnum.TRUE.__getstate__()) is int
     assert m.ScopedBoolEnum(1) == m.ScopedBoolEnum.TRUE
     # Enum could construct with a bool
     # (bool is a strict subclass of int, and False will be converted to 0)

tests/test_eval.py

-# -*- coding: utf-8 -*-
 import os
 
 import pytest
@@ -18,7 +17,7 @@ def test_evals(capture):
     assert m.test_eval_failure()
 
 
-@pytest.mark.xfail("env.PYPY and not env.PY2", raises=RuntimeError)
+@pytest.mark.xfail("env.PYPY", raises=RuntimeError)
 def test_eval_file():
     filename = os.path.join(os.path.dirname(__file__), "test_eval_call.py")
     assert m.test_eval_file(filename)

tests/test_eval_call.py

-# -*- coding: utf-8 -*-
 # This file is called from 'test_eval.py'
 
 if "call_test2" in locals():

tests/test_exceptions.cpp

@@ -276,8 +276,6 @@ TEST_SUBMODULE(exceptions, m) {
 
     m.def("throw_should_be_translated_to_key_error", []() { throw shared_exception(); });
 
-#if PY_VERSION_HEX >= 0x03030000
-
     m.def("raise_from", []() {
         PyErr_SetString(PyExc_ValueError, "inner");
         py::raise_from(PyExc_ValueError, "outer");
@@ -301,5 +299,4 @@ TEST_SUBMODULE(exceptions, m) {
             std::throw_with_nested(std::runtime_error("Outer Exception"));
         }
     });
-#endif
 }

tests/test_exceptions.py

-# -*- coding: utf-8 -*-
 import sys
 
 import pytest
@@ -24,7 +23,6 @@ def test_error_already_set(msg):
     assert msg(excinfo.value) == "foo"
 
 
-@pytest.mark.skipif("env.PY2")
 def test_raise_from(msg):
     with pytest.raises(ValueError) as excinfo:
         m.raise_from()
@@ -32,7 +30,6 @@ def test_raise_from(msg):
     assert msg(excinfo.value.__cause__) == "inner"
 
 
-@pytest.mark.skipif("env.PY2")
 def test_raise_from_already_set(msg):
     with pytest.raises(ValueError) as excinfo:
         m.raise_from_already_set()
@@ -102,7 +99,7 @@ def ignore_pytest_unraisable_warning(f):
 @ignore_pytest_unraisable_warning
 def test_python_alreadyset_in_destructor(monkeypatch, capsys):
     hooked = False
-    triggered = [False]  # mutable, so Python 2.7 closure can modify it
+    triggered = False
 
     if hasattr(sys, "unraisablehook"):  # Python 3.8+
         hooked = True
@@ -112,7 +109,8 @@ def test_python_alreadyset_in_destructor(monkeypatch, capsys):
         def hook(unraisable_hook_args):
             exc_type, exc_value, exc_tb, err_msg, obj = unraisable_hook_args
             if obj == "already_set demo":
-                triggered[0] = True
+                nonlocal triggered
+                triggered = True
             default_hook(unraisable_hook_args)
             return
 
@@ -121,11 +119,11 @@ def test_python_alreadyset_in_destructor(monkeypatch, capsys):
 
     assert m.python_alreadyset_in_destructor("already_set demo") is True
     if hooked:
-        assert triggered[0] is True
+        assert triggered is True
 
     _, captured_stderr = capsys.readouterr()
-    # Error message is different in Python 2 and 3, check for words that appear in both
-    assert "ignored" in captured_stderr and "already_set demo" in captured_stderr
+    assert captured_stderr.startswith("Exception ignored in: 'already_set demo'")
+    assert captured_stderr.rstrip().endswith("KeyError: 'bar'")
 
 
 def test_exception_matches():
@@ -239,7 +237,6 @@ def test_nested_throws(capture):
     assert str(excinfo.value) == "this is a helper-defined translated exception"
 
 
-@pytest.mark.skipif("env.PY2")
 def test_throw_nested_exception():
     with pytest.raises(RuntimeError) as excinfo:
         m.throw_nested_exception()
@@ -249,7 +246,7 @@ def test_throw_nested_exception():
 
 # This can often happen if you wrap a pybind11 class in a Python wrapper
 def test_invalid_repr():
-    class MyRepr(object):
+    class MyRepr:
         def __repr__(self):
             raise AttributeError("Example error")
 

tests/test_factory_constructors.py

-# -*- coding: utf-8 -*-
 import re
 
 import pytest
 
-import env  # noqa: F401
 from pybind11_tests import ConstructorStats
 from pybind11_tests import factory_constructors as m
 from pybind11_tests.factory_constructors import tag
@@ -82,7 +80,7 @@ def test_init_factory_signature(msg):
             4. m.factory_constructors.TestFactory1(arg0: handle, arg1: int, arg2: handle)
 
         Invoked with: 'invalid', 'constructor', 'arguments'
-    """  # noqa: E501 line too long
+    """
     )
 
     assert (
@@ -465,12 +463,10 @@ def test_reallocation_g(capture, msg):
     )
 
 
-@pytest.mark.skipif("env.PY2")
 def test_invalid_self():
-    """Tests invocation of the pybind-registered base class with an invalid `self` argument.  You
-    can only actually do this on Python 3: Python 2 raises an exception itself if you try."""
+    """Tests invocation of the pybind-registered base class with an invalid `self` argument."""
 
-    class NotPybindDerived(object):
+    class NotPybindDerived:
         pass
 
     # Attempts to initialize with an invalid type passed as `self`:

tests/test_gil_scoped.py

-# -*- coding: utf-8 -*-
 import multiprocessing
 import threading
 

tests/test_iostream.py

-# -*- coding: utf-8 -*-
-import sys
-from contextlib import contextmanager
+from contextlib import redirect_stderr, redirect_stdout
+from io import StringIO
 
 from pybind11_tests import iostream as m
 
-try:
-    # Python 3
-    from io import StringIO
-except ImportError:
-    # Python 2
-    try:
-        from cStringIO import StringIO
-    except ImportError:
-        from StringIO import StringIO
-
-try:
-    # Python 3.4
-    from contextlib import redirect_stdout
-except ImportError:
-
-    @contextmanager
-    def redirect_stdout(target):
-        original = sys.stdout
-        sys.stdout = target
-        yield
-        sys.stdout = original
-
-
-try:
-    # Python 3.5
-    from contextlib import redirect_stderr
-except ImportError:
-
-    @contextmanager
-    def redirect_stderr(target):
-        original = sys.stderr
-        sys.stderr = target
-        yield
-        sys.stderr = original
-
 
 def test_captured(capsys):
     msg = "I've been redirected to Python, I hope!"

tests/test_kwargs_and_defaults.py

-# -*- coding: utf-8 -*-
 import pytest
 
-import env  # noqa: F401
 from pybind11_tests import kwargs_and_defaults as m
 
 
@@ -82,7 +80,7 @@ def test_mixed_args_and_kwargs(msg):
             1. (arg0: int, arg1: float, *args) -> tuple
 
         Invoked with: 1
-    """  # noqa: E501 line too long
+    """
     )
     with pytest.raises(TypeError) as excinfo:
         assert mpa()
@@ -93,7 +91,7 @@ def test_mixed_args_and_kwargs(msg):
             1. (arg0: int, arg1: float, *args) -> tuple
 
         Invoked with:
-    """  # noqa: E501 line too long
+    """
     )
 
     assert mpk(-2, 3.5, pi=3.14159, e=2.71828) == (
@@ -127,7 +125,7 @@ def test_mixed_args_and_kwargs(msg):
             1. (i: int = 1, j: float = 3.14159, *args, **kwargs) -> tuple
 
         Invoked with: 1; kwargs: i=1
-    """  # noqa: E501 line too long
+    """
     )
     with pytest.raises(TypeError) as excinfo:
         assert mpakd(1, 2, j=1)
@@ -138,7 +136,7 @@ def test_mixed_args_and_kwargs(msg):
             1. (i: int = 1, j: float = 3.14159, *args, **kwargs) -> tuple
 
         Invoked with: 1, 2; kwargs: j=1
-    """  # noqa: E501 line too long
+    """
     )
 
     # Arguments after a py::args are automatically keyword-only (pybind 2.9+)
@@ -343,7 +341,6 @@ def test_signatures():
     )
 
 
-@pytest.mark.xfail("env.PYPY and env.PY2", reason="PyPy2 doesn't double count")
 def test_args_refcount():
     """Issue/PR #1216 - py::args elements get double-inc_ref()ed when combined with regular
     arguments"""

tests/test_local_bindings.py

-# -*- coding: utf-8 -*-
 import pytest
 
 import env  # noqa: F401
@@ -200,7 +199,7 @@ def test_stl_caster_vs_stl_bind(msg):
         1. (arg0: pybind11_cross_module_tests.VectorInt) -> int
 
     Invoked with: [1, 2, 3]
-    """  # noqa: E501 line too long
+    """
     )
 
 

tests/test_methods_and_attributes.py

-# -*- coding: utf-8 -*-
 import pytest
 
 import env  # noqa: F401
@@ -494,26 +493,17 @@ def test_overload_ordering():
     assert m.overload_order("string") == 1
     assert m.overload_order(0) == 4
 
-    # Different for Python 2 vs. 3
-    uni_name = type(u"").__name__
-
     assert "1. overload_order(arg0: int) -> int" in m.overload_order.__doc__
-    assert (
-        "2. overload_order(arg0: {}) -> int".format(uni_name)
-        in m.overload_order.__doc__
-    )
-    assert (
-        "3. overload_order(arg0: {}) -> int".format(uni_name)
-        in m.overload_order.__doc__
-    )
+    assert "2. overload_order(arg0: str) -> int" in m.overload_order.__doc__
+    assert "3. overload_order(arg0: str) -> int" in m.overload_order.__doc__
     assert "4. overload_order(arg0: int) -> int" in m.overload_order.__doc__
 
     with pytest.raises(TypeError) as err:
         m.overload_order(1.1)
 
     assert "1. (arg0: int) -> int" in str(err.value)
-    assert "2. (arg0: {}) -> int".format(uni_name) in str(err.value)
-    assert "3. (arg0: {}) -> int".format(uni_name) in str(err.value)
+    assert "2. (arg0: str) -> int" in str(err.value)
+    assert "3. (arg0: str) -> int" in str(err.value)
     assert "4. (arg0: int) -> int" in str(err.value)
 
 

tests/test_modules.py

-# -*- coding: utf-8 -*-
 from pybind11_tests import ConstructorStats
 from pybind11_tests import modules as m
 from pybind11_tests.modules import subsubmodule as ms

tests/test_multiple_inheritance.py

-# -*- coding: utf-8 -*-
 import pytest
 
 import env  # noqa: F401
@@ -13,8 +12,7 @@ def test_multiple_inheritance_cpp():
     assert mt.bar() == 4
 
 
-@pytest.mark.skipif("env.PYPY and env.PY2")
-@pytest.mark.xfail("env.PYPY and not env.PY2")
+@pytest.mark.xfail("env.PYPY")
 def test_multiple_inheritance_mix1():
     class Base1:
         def __init__(self, i):
@@ -53,15 +51,14 @@ def test_multiple_inheritance_mix2():
     assert mt.bar() == 4
 
 
-@pytest.mark.skipif("env.PYPY and env.PY2")
-@pytest.mark.xfail("env.PYPY and not env.PY2")
+@pytest.mark.xfail("env.PYPY")
 def test_multiple_inheritance_python():
     class MI1(m.Base1, m.Base2):
         def __init__(self, i, j):
             m.Base1.__init__(self, i)
             m.Base2.__init__(self, j)
 
-    class B1(object):
+    class B1:
         def v(self):
             return 1
 
@@ -96,7 +93,7 @@ def test_multiple_inheritance_python():
         def v(self):
             return 2
 
-    class B3(object):
+    class B3:
         def v(self):
             return 3
 

tests/test_numpy_array.py

-# -*- coding: utf-8 -*-
 import pytest
 
 import env  # noqa: F401

tests/test_numpy_dtypes.py

-# -*- coding: utf-8 -*-
 import re
 
 import pytest

tests/test_numpy_vectorize.py

-# -*- coding: utf-8 -*-
 import pytest
 
 from pybind11_tests import numpy_vectorize as m