Merge branch 'master' into sh_merge_master

.clang-tidy

@@ -3,6 +3,7 @@ FormatStyle: file
 Checks: '
 *bugprone*,
 cppcoreguidelines-init-variables,
+cppcoreguidelines-slicing,
 clang-analyzer-optin.cplusplus.VirtualCall,
 llvm-namespace-comment,
 misc-misplaced-const,

.github/CONTRIBUTING.md

@@ -68,8 +68,8 @@ nox -l
 # Run linters
 nox -s lint
 
-# Run tests
+# Run tests on Python 3.9
-nox -s tests
+nox -s tests-3.9
 
 # Build and preview docs
 nox -s docs -- serve

.github/workflows/ci.yml

@@ -862,32 +862,85 @@ jobs:
       run: cmake --build build -t check
 
   mingw:
+    name: "🐍 3 • windows-latest • ${{ matrix.sys }}"
     runs-on: windows-latest
     defaults:
       run:
         shell: msys2 {0}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - { sys: mingw64, env: x86_64 }
+          - { sys: mingw32, env: i686 }
     steps:
     - uses: msys2/setup-msys2@v2
       with:
+        msystem: ${{matrix.sys}}
         install: >-
-          mingw-w64-x86_64-gcc
+          git
-          mingw-w64-x86_64-python-pip
+          mingw-w64-${{matrix.env}}-gcc
-          mingw-w64-x86_64-cmake
+          mingw-w64-${{matrix.env}}-python-pip
-          mingw-w64-x86_64-make
+          mingw-w64-${{matrix.env}}-python-numpy
-          mingw-w64-x86_64-python-pytest
+          mingw-w64-${{matrix.env}}-python-scipy
-          mingw-w64-x86_64-eigen3
+          mingw-w64-${{matrix.env}}-cmake
-          mingw-w64-x86_64-boost
+          mingw-w64-${{matrix.env}}-make
-          mingw-w64-x86_64-catch
+          mingw-w64-${{matrix.env}}-python-pytest
+          mingw-w64-${{matrix.env}}-eigen3
+          mingw-w64-${{matrix.env}}-boost
+          mingw-w64-${{matrix.env}}-catch
 
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2
 
-    - name: Configure
+    - name: Configure C++11
       # LTO leads to many undefined reference like
       # `pybind11::detail::function_call::function_call(pybind11::detail::function_call&&)
-      run: cmake -G "MinGW Makefiles" -S . -B build
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=11 -S . -B build
 
-    - name: Build
+    - name: Build C++11
       run: cmake --build build -j 2
 
-    - name: Python tests
+    - name: Python tests C++11
-      run: cmake --build build --target pytest
+      run: cmake --build build --target pytest -j 2
+
+    - name: C++11 tests
+      run: cmake --build build --target cpptest -j 2
+
+    - name: Interface test C++11
+      run: cmake --build build --target test_cmake_build
+
+    - name: Clean directory
+      run: git clean -fdx
+
+    - name: Configure C++14
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=14 -S . -B build2
+
+    - name: Build C++14
+      run: cmake --build build2 -j 2
+
+    - name: Python tests C++14
+      run: cmake --build build2 --target pytest -j 2
+
+    - name: C++14 tests
+      run: cmake --build build2 --target cpptest -j 2
+
+    - name: Interface test C++14
+      run: cmake --build build2 --target test_cmake_build
+
+    - name: Clean directory
+      run: git clean -fdx
+
+    - name: Configure C++17
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=17 -S . -B build3
+
+    - name: Build C++17
+      run: cmake --build build3 -j 2
+
+    - name: Python tests C++17
+      run: cmake --build build3 --target pytest -j 2
+
+    - name: C++17 tests
+      run: cmake --build build3 --target cpptest -j 2
+
+    - name: Interface test C++17
+      run: cmake --build build3 --target test_cmake_build

.pre-commit-config.yaml

@@ -32,7 +32,7 @@ repos:
     exclude: ^noxfile.py$
 
 - repo: https://github.com/asottile/pyupgrade
-  rev: v2.23.3
+  rev: v2.24.0
   hooks:
   - id: pyupgrade
 

README.rst

@@ -138,9 +138,9 @@ About
 This project was created by `Wenzel
 Jakob <http://rgl.epfl.ch/people/wjakob>`_. Significant features and/or
 improvements to the code were contributed by Jonas Adler, Lori A. Burns,
-Sylvain Corlay, Eric Cousineau, Ralf Grosse-Kunstleve, Trent Houliston, Axel
+Sylvain Corlay, Eric Cousineau, Aaron Gokaslan, Ralf Grosse-Kunstleve, Trent Houliston, Axel
 Huebl, @hulucc, Yannick Jadoul, Sergey Lyskov Johan Mabille, Tomasz Miąsko,
-Dean Moldovan, Ben Pritchard, Jason Rhinelander, Boris Schäling,  Pim
+Dean Moldovan, Ben Pritchard, Jason Rhinelander, Boris Schäling, Pim
 Schellart, Henry Schreiner, Ivan Smirnov, Boris Staletic, and Patrick Stewart.
 
 We thank Google for a generous financial contribution to the continuous

docs/advanced/exceptions.rst

@@ -323,6 +323,34 @@ Alternately, to ignore the error, call `PyErr_Clear
 Any Python error must be thrown or cleared, or Python/pybind11 will be left in
 an invalid state.
 
+Chaining exceptions ('raise from')
+==================================
+
+In Python 3.3 a mechanism for indicating that exceptions were caused by other
+exceptions was introduced:
+
+.. code-block:: py
+
+    try:
+        print(1 / 0)
+    except Exception as exc:
+        raise RuntimeError("could not divide by zero") from exc
+
+To do a similar thing in pybind11, you can use the ``py::raise_from`` function. It
+sets the current python error indicator, so to continue propagating the exception
+you should ``throw py::error_already_set()`` (Python 3 only).
+
+.. code-block:: cpp
+
+    try {
+        py::eval("print(1 / 0"));
+    } catch (py::error_already_set &e) {
+        py::raise_from(e, PyExc_RuntimeError, "could not divide by zero");
+        throw py::error_already_set();
+    }
+
+.. versionadded:: 2.8
+
 .. _unraisable_exceptions:
 
 Handling unraisable exceptions

docs/advanced/pycpp/object.rst

@@ -20,6 +20,47 @@ Available types include :class:`handle`, :class:`object`, :class:`bool_`,
     Be sure to review the :ref:`pytypes_gotchas` before using this heavily in
     your C++ API.
 
+.. _instantiating_compound_types:
+
+Instantiating compound Python types from C++
+============================================
+
+Dictionaries can be initialized in the :class:`dict` constructor:
+
+.. code-block:: cpp
+
+    using namespace pybind11::literals; // to bring in the `_a` literal
+    py::dict d("spam"_a=py::none(), "eggs"_a=42);
+
+A tuple of python objects can be instantiated using :func:`py::make_tuple`:
+
+.. code-block:: cpp
+
+    py::tuple tup = py::make_tuple(42, py::none(), "spam");
+
+Each element is converted to a supported Python type.
+
+A `simple namespace`_ can be instantiated using
+:func:`py::make_simple_namespace`:
+
+.. code-block:: cpp
+
+    using namespace pybind11::literals; // to bring in the `_a` literal
+    py::object ns = py::make_simple_namespace("spam"_a=py::none(), "eggs"_a=42);
+
+Attributes on a namespace can be modified with the :func:`py::delattr`,
+:func:`py::getattr`, and :func:`py::setattr` functions. Simple namespaces can
+be useful as lightweight stand-ins for class instances.
+
+.. note::
+
+    ``make_simple_namespace`` is not available in Python 2.
+
+.. versionchanged:: 2.8
+    ``make_simple_namespace`` added.
+
+.. _simple namespace: https://docs.python.org/3/library/types.html#types.SimpleNamespace
+
 .. _casting_back_and_forth:
 
 Casting back and forth
@@ -30,7 +71,7 @@ types to Python, which can be done using :func:`py::cast`:
 
 .. code-block:: cpp
 
-    MyClass *cls = ..;
+    MyClass *cls = ...;
     py::object obj = py::cast(cls);
 
 The reverse direction uses the following syntax:

include/pybind11/cast.h

@@ -1045,6 +1045,16 @@ template <return_value_policy policy = return_value_policy::automatic_reference,
     return result;
 }
 
+#if PY_VERSION_HEX >= 0x03030000
+template <typename... Args,
+          typename = detail::enable_if_t<args_are_all_keyword_or_ds<Args...>()>>
+object make_simple_namespace(Args&&... args_) {
+    PyObject *ns = _PyNamespace_New(dict(std::forward<Args>(args_)...).ptr());
+    if (!ns) throw error_already_set();
+    return reinterpret_steal<object>(ns);
+}
+#endif
+
 /// \ingroup annotations
 /// Annotation for arguments
 struct arg {

include/pybind11/detail/common.h

@@ -315,6 +315,19 @@ extern "C" {
         }                                                                      \
     }
 
+#if PY_VERSION_HEX >= 0x03030000
+
+#define PYBIND11_CATCH_INIT_EXCEPTIONS \
+        catch (pybind11::error_already_set &e) {                                 \
+            pybind11::raise_from(e, PyExc_ImportError, "initialization failed"); \
+            return nullptr;                                                      \
+        } catch (const std::exception &e) {                                      \
+            PyErr_SetString(PyExc_ImportError, e.what());                        \
+            return nullptr;                                                      \
+        }                                                                        \
+
+#else
+
 #define PYBIND11_CATCH_INIT_EXCEPTIONS \
         catch (pybind11::error_already_set &e) {                               \
             PyErr_SetString(PyExc_ImportError, e.what());                      \
@@ -324,6 +337,8 @@ extern "C" {
             return nullptr;                                                    \
         }                                                                      \
 
+#endif
+
 /** \rst
     ***Deprecated in favor of PYBIND11_MODULE***
 

include/pybind11/embed.h

@@ -12,6 +12,9 @@
 #include "pybind11.h"
 #include "eval.h"
 
+#include <memory>
+#include <vector>
+
 #if defined(PYPY_VERSION)
 #  error Embedding the interpreter is not supported with PyPy
 #endif
@@ -83,29 +86,106 @@ struct embedded_module {
     }
 };
 
+struct wide_char_arg_deleter {
+    void operator()(wchar_t *ptr) const {
+#if PY_VERSION_HEX >= 0x030500f0
+        // API docs: https://docs.python.org/3/c-api/sys.html#c.Py_DecodeLocale
+        PyMem_RawFree(ptr);
+#else
+        delete[] ptr;
+#endif
+    }
+};
+
+inline wchar_t *widen_chars(const char *safe_arg) {
+#if PY_VERSION_HEX >= 0x030500f0
+    wchar_t *widened_arg = Py_DecodeLocale(safe_arg, nullptr);
+#else
+    wchar_t *widened_arg = nullptr;
+#    if defined(HAVE_BROKEN_MBSTOWCS) && HAVE_BROKEN_MBSTOWCS
+    size_t count = strlen(safe_arg);
+#    else
+    size_t count = mbstowcs(nullptr, safe_arg, 0);
+#    endif
+    if (count != static_cast<size_t>(-1)) {
+        widened_arg = new wchar_t[count + 1];
+        mbstowcs(widened_arg, safe_arg, count + 1);
+    }
+#endif
+    return widened_arg;
+}
+
+/// Python 2.x/3.x-compatible version of `PySys_SetArgv`
+inline void set_interpreter_argv(int argc, const char *const *argv, bool add_program_dir_to_path) {
+    // Before it was special-cased in python 3.8, passing an empty or null argv
+    // caused a segfault, so we have to reimplement the special case ourselves.
+    bool special_case = (argv == nullptr || argc <= 0);
+
+    const char *const empty_argv[]{"\0"};
+    const char *const *safe_argv = special_case ? empty_argv : argv;
+    if (special_case)
+        argc = 1;
+
+    auto argv_size = static_cast<size_t>(argc);
+#if PY_MAJOR_VERSION >= 3
+    // SetArgv* on python 3 takes wchar_t, so we have to convert.
+    std::unique_ptr<wchar_t *[]> widened_argv(new wchar_t *[argv_size]);
+    std::vector<std::unique_ptr<wchar_t[], wide_char_arg_deleter>> widened_argv_entries;
+    widened_argv_entries.reserve(argv_size);
+    for (size_t ii = 0; ii < argv_size; ++ii) {
+        widened_argv_entries.emplace_back(widen_chars(safe_argv[ii]));
+        if (!widened_argv_entries.back()) {
+            // A null here indicates a character-encoding failure or the python
+            // interpreter out of memory. Give up.
+            return;
+        }
+        widened_argv[ii] = widened_argv_entries.back().get();
+    }
+
+    auto pysys_argv = widened_argv.get();
+#else
+    // python 2.x
+    std::vector<std::string> strings{safe_argv, safe_argv + argv_size};
+    std::vector<char *> char_strings{argv_size};
+    for (std::size_t i = 0; i < argv_size; ++i)
+        char_strings[i] = &strings[i][0];
+    char **pysys_argv = char_strings.data();
+#endif
+
+    PySys_SetArgvEx(argc, pysys_argv, static_cast<int>(add_program_dir_to_path));
+}
+
 PYBIND11_NAMESPACE_END(detail)
 
 /** \rst
     Initialize the Python interpreter. No other pybind11 or CPython API functions can be
     called before this is done; with the exception of `PYBIND11_EMBEDDED_MODULE`. The
-    optional parameter can be used to skip the registration of signal handlers (see the
+    optional `init_signal_handlers` parameter can be used to skip the registration of
-    `Python documentation`_ for details). Calling this function again after the interpreter
+    signal handlers (see the `Python documentation`_ for details). Calling this function
-    has already been initialized is a fatal error.
+    again after the interpreter has already been initialized is a fatal error.
 
     If initializing the Python interpreter fails, then the program is terminated.  (This
     is controlled by the CPython runtime and is an exception to pybind11's normal behavior
     of throwing exceptions on errors.)
 
+    The remaining optional parameters, `argc`, `argv`, and `add_program_dir_to_path` are
+    used to populate ``sys.argv`` and ``sys.path``.
+    See the |PySys_SetArgvEx documentation|_ for details.
+
     .. _Python documentation: https://docs.python.org/3/c-api/init.html#c.Py_InitializeEx
+    .. |PySys_SetArgvEx documentation| replace:: ``PySys_SetArgvEx`` documentation
+    .. _PySys_SetArgvEx documentation: https://docs.python.org/3/c-api/init.html#c.PySys_SetArgvEx
  \endrst */
-inline void initialize_interpreter(bool init_signal_handlers = true) {
+inline void initialize_interpreter(bool init_signal_handlers = true,
+                                   int argc = 0,
+                                   const char *const *argv = nullptr,
+                                   bool add_program_dir_to_path = true) {
     if (Py_IsInitialized() != 0)
         pybind11_fail("The interpreter is already running");
 
     Py_InitializeEx(init_signal_handlers ? 1 : 0);
 
-    // Make .py files in the working directory available by default
+    detail::set_interpreter_argv(argc, argv, add_program_dir_to_path);
-    module_::import("sys").attr("path").cast<list>().append(".");
 }
 
 /** \rst
@@ -167,6 +247,8 @@ inline void finalize_interpreter() {
     Scope guard version of `initialize_interpreter` and `finalize_interpreter`.
     This a move-only guard and only a single instance can exist.
 
+    See `initialize_interpreter` for a discussion of its constructor arguments.
+
     .. code-block:: cpp
 
         #include <pybind11/embed.h>
@@ -178,8 +260,11 @@ inline void finalize_interpreter() {
  \endrst */
 class scoped_interpreter {
 public:
-    scoped_interpreter(bool init_signal_handlers = true) {
+    scoped_interpreter(bool init_signal_handlers = true,
-        initialize_interpreter(init_signal_handlers);
+                       int argc = 0,
+                       const char *const *argv = nullptr,
+                       bool add_program_dir_to_path = true) {
+        initialize_interpreter(init_signal_handlers, argc, argv, add_program_dir_to_path);
     }
 
     scoped_interpreter(const scoped_interpreter &) = delete;

include/pybind11/numpy.h

@@ -198,6 +198,9 @@ struct npy_api {
     // Unused. Not removed because that affects ABI of the class.
     int (*PyArray_SetBaseObject_)(PyObject *, PyObject *);
     PyObject* (*PyArray_Resize_)(PyObject*, PyArray_Dims*, int, int);
+    PyObject* (*PyArray_Newshape_)(PyObject*, PyArray_Dims*, int);
+    PyObject* (*PyArray_View_)(PyObject*, PyObject*, PyObject*);
+
 private:
     enum functions {
         API_PyArray_GetNDArrayCFeatureVersion = 211,
@@ -212,10 +215,12 @@ private:
         API_PyArray_NewCopy = 85,
         API_PyArray_NewFromDescr = 94,
         API_PyArray_DescrNewFromType = 96,
+        API_PyArray_Newshape = 135,
+        API_PyArray_Squeeze = 136,
+        API_PyArray_View = 137,
         API_PyArray_DescrConverter = 174,
         API_PyArray_EquivTypes = 182,
         API_PyArray_GetArrayParamsFromObject = 278,
-        API_PyArray_Squeeze = 136,
         API_PyArray_SetBaseObject = 282
     };
 
@@ -243,11 +248,14 @@ private:
         DECL_NPY_API(PyArray_NewCopy);
         DECL_NPY_API(PyArray_NewFromDescr);
         DECL_NPY_API(PyArray_DescrNewFromType);
+        DECL_NPY_API(PyArray_Newshape);
+        DECL_NPY_API(PyArray_Squeeze);
+        DECL_NPY_API(PyArray_View);
         DECL_NPY_API(PyArray_DescrConverter);
         DECL_NPY_API(PyArray_EquivTypes);
         DECL_NPY_API(PyArray_GetArrayParamsFromObject);
-        DECL_NPY_API(PyArray_Squeeze);
         DECL_NPY_API(PyArray_SetBaseObject);
+
 #undef DECL_NPY_API
         return api;
     }
@@ -785,6 +793,33 @@ public:
         if (isinstance<array>(new_array)) { *this = std::move(new_array); }
     }
 
+    /// Optional `order` parameter omitted, to be added as needed.
+    array reshape(ShapeContainer new_shape) {
+        detail::npy_api::PyArray_Dims d
+            = {reinterpret_cast<Py_intptr_t *>(new_shape->data()), int(new_shape->size())};
+        auto new_array
+            = reinterpret_steal<array>(detail::npy_api::get().PyArray_Newshape_(m_ptr, &d, 0));
+        if (!new_array) {
+            throw error_already_set();
+        }
+        return new_array;
+    }
+
+    /// Create a view of an array in a different data type.
+    /// This function may fundamentally reinterpret the data in the array.
+    /// It is the responsibility of the caller to ensure that this is safe.
+    /// Only supports the `dtype` argument, the `type` argument is omitted,
+    /// to be added as needed.
+    array view(const std::string &dtype) {
+        auto &api = detail::npy_api::get();
+        auto new_view = reinterpret_steal<array>(api.PyArray_View_(
+            m_ptr, dtype::from_args(pybind11::str(dtype)).release().ptr(), nullptr));
+        if (!new_view) {
+            throw error_already_set();
+        }
+        return new_view;
+    }
+
     /// Ensure that the argument is a NumPy array
     /// In case of an error, nullptr is returned and the Python error is cleared.
     static array ensure(handle h, int ExtraFlags = 0) {

include/pybind11/pybind11.h

@@ -1778,7 +1778,7 @@ inline str enum_name(handle arg) {
 }
 
 struct enum_base {
-    enum_base(handle base, handle parent) : m_base(base), m_parent(parent) { }
+    enum_base(const handle &base, const handle &parent) : m_base(base), m_parent(parent) { }
 
     PYBIND11_NOINLINE void init(bool is_arithmetic, bool is_convertible) {
         m_base.attr("__entries") = dict();
@@ -1928,6 +1928,19 @@ struct enum_base {
     handle m_parent;
 };
 
+template <bool is_signed, size_t length> struct equivalent_integer {};
+template <> struct equivalent_integer<true,  1> { using type = int8_t;   };
+template <> struct equivalent_integer<false, 1> { using type = uint8_t;  };
+template <> struct equivalent_integer<true,  2> { using type = int16_t;  };
+template <> struct equivalent_integer<false, 2> { using type = uint16_t; };
+template <> struct equivalent_integer<true,  4> { using type = int32_t;  };
+template <> struct equivalent_integer<false, 4> { using type = uint32_t; };
+template <> struct equivalent_integer<true,  8> { using type = int64_t;  };
+template <> struct equivalent_integer<false, 8> { using type = uint64_t; };
+
+template <typename IntLike>
+using equivalent_integer_t = typename equivalent_integer<std::is_signed<IntLike>::value, sizeof(IntLike)>::type;
+
 PYBIND11_NAMESPACE_END(detail)
 
 /// Binds C++ enumerations and enumeration classes to Python
@@ -1938,13 +1951,17 @@ public:
     using Base::attr;
     using Base::def_property_readonly;
     using Base::def_property_readonly_static;
-    using Scalar = typename std::underlying_type<Type>::type;
+    using Underlying = typename std::underlying_type<Type>::type;
+    // Scalar is the integer representation of underlying type
+    using Scalar = detail::conditional_t<detail::any_of<
+        detail::is_std_char_type<Underlying>, std::is_same<Underlying, bool>
+    >::value, detail::equivalent_integer_t<Underlying>, Underlying>;
 
     template <typename... Extra>
     enum_(const handle &scope, const char *name, const Extra&... extra)
       : class_<Type>(scope, name, extra...), m_base(*this, scope) {
         constexpr bool is_arithmetic = detail::any_of<std::is_same<arithmetic, Extra>...>::value;
-        constexpr bool is_convertible = std::is_convertible<Type, Scalar>::value;
+        constexpr bool is_convertible = std::is_convertible<Type, Underlying>::value;
         m_base.init(is_arithmetic, is_convertible);
 
         def(init([](Scalar i) { return static_cast<Type>(i); }), arg("value"));

include/pybind11/pytypes.h

@@ -382,6 +382,47 @@ private:
 #  pragma warning(pop)
 #endif
 
+#if PY_VERSION_HEX >= 0x03030000
+
+/// Replaces the current Python error indicator with the chosen error, performing a
+/// 'raise from' to indicate that the chosen error was caused by the original error.
+inline void raise_from(PyObject *type, const char *message) {
+    // Based on _PyErr_FormatVFromCause:
+    // https://github.com/python/cpython/blob/467ab194fc6189d9f7310c89937c51abeac56839/Python/errors.c#L405
+    // See https://github.com/pybind/pybind11/pull/2112 for details.
+    PyObject *exc = nullptr, *val = nullptr, *val2 = nullptr, *tb = nullptr;
+
+    assert(PyErr_Occurred());
+    PyErr_Fetch(&exc, &val, &tb);
+    PyErr_NormalizeException(&exc, &val, &tb);
+    if (tb != nullptr) {
+        PyException_SetTraceback(val, tb);
+        Py_DECREF(tb);
+    }
+    Py_DECREF(exc);
+    assert(!PyErr_Occurred());
+
+    PyErr_SetString(type, message);
+
+    PyErr_Fetch(&exc, &val2, &tb);
+    PyErr_NormalizeException(&exc, &val2, &tb);
+    Py_INCREF(val);
+    PyException_SetCause(val2, val);
+    PyException_SetContext(val2, val);
+    PyErr_Restore(exc, val2, tb);
+}
+
+/// Sets the current Python error indicator with the chosen error, performing a 'raise from'
+/// from the error contained in error_already_set to indicate that the chosen error was
+/// caused by the original error. After this function is called error_already_set will
+/// no longer contain an error.
+inline void raise_from(error_already_set& err, PyObject *type, const char *message) {
+    err.restore();
+    raise_from(type, message);
+}
+
+#endif
+
 /** \defgroup python_builtins _
     Unless stated otherwise, the following C++ functions behave the same
     as their Python counterparts.

noxfile.py

@@ -2,6 +2,8 @@ import nox
 
 nox.options.sessions = ["lint", "tests", "tests_packaging"]
 
+PYTHON_VERISONS = ["2.7", "3.5", "3.6", "3.7", "3.8", "3.9", "3.10"]
+
 
 @nox.session(reuse_venv=True)
 def lint(session: nox.Session) -> None:
@@ -12,7 +14,7 @@ def lint(session: nox.Session) -> None:
     session.run("pre-commit", "run", "-a")
 
 
-@nox.session
+@nox.session(python=PYTHON_VERISONS)
 def tests(session: nox.Session) -> None:
     """
     Run the tests (requires a compiler).

tests/requirements.txt

@@ -2,11 +2,11 @@
 numpy==1.16.6; python_version<"3.6" and sys_platform!="win32"
 numpy==1.18.0; platform_python_implementation=="PyPy" and sys_platform=="darwin" and python_version>="3.6"
 numpy==1.19.3; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version=="3.6"
-numpy==1.20.0; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version>="3.7" and python_version<"3.10"
+numpy==1.21.2; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version>="3.7" and python_version<"3.10"
+numpy==1.21.2; platform_python_implementation!="PyPy" and sys_platform=="linux" and python_version=="3.10"
 pytest==4.6.9; python_version<"3.5"
 pytest==6.1.2; python_version=="3.5"
-pytest==6.2.1; python_version>="3.6" and python_version<="3.8"
+pytest==6.2.4; python_version>="3.6"
-pytest @ git+https://github.com/pytest-dev/pytest@5d8392cb68fe0b3d6aba3a351d76fc9f02297980; python_version>="3.9"
 pytest-timeout
 scipy==1.2.3; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version<"3.6"
 scipy==1.5.4; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version>="3.6" and python_version<"3.10"

tests/test_embed/test_interpreter.cpp

@@ -23,6 +23,7 @@ public:
 
     std::string the_message() const { return message; }
     virtual int the_answer() const = 0;
+    virtual std::string argv0() const = 0;
 
 private:
     std::string message;
@@ -32,6 +33,7 @@ class PyWidget final : public Widget {
     using Widget::Widget;
 
     int the_answer() const override { PYBIND11_OVERRIDE_PURE(int, Widget, the_answer); }
+    std::string argv0() const override { PYBIND11_OVERRIDE_PURE(std::string, Widget, argv0); }
 };
 
 PYBIND11_EMBEDDED_MODULE(widget_module, m) {
@@ -74,8 +76,24 @@ 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"));
+
+    auto locals = py::dict("is_keyerror"_a=false, "message"_a="not set");
+    py::exec(R"(
+        try:
+            import throw_error_already_set
+        except ImportError as e:
+            is_keyerror = type(e.__cause__) == KeyError
+            message = str(e.__cause__)
+    )", py::globals(), 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") {
@@ -283,3 +301,25 @@ TEST_CASE("Reload module from file") {
     result = module_.attr("test")().cast<int>();
     REQUIRE(result == 2);
 }
+
+TEST_CASE("sys.argv gets initialized properly") {
+    py::finalize_interpreter();
+    {
+        py::scoped_interpreter default_scope;
+        auto module = py::module::import("test_interpreter");
+        auto py_widget = module.attr("DerivedWidget")("The question");
+        const auto &cpp_widget = py_widget.cast<const Widget &>();
+        REQUIRE(cpp_widget.argv0().empty());
+    }
+
+    {
+        char *argv[] = {strdup("a.out")};
+        py::scoped_interpreter argv_scope(true, 1, argv);
+        free(argv[0]);
+        auto module = py::module::import("test_interpreter");
+        auto py_widget = module.attr("DerivedWidget")("The question");
+        const auto &cpp_widget = py_widget.cast<const Widget &>();
+        REQUIRE(cpp_widget.argv0() == "a.out");
+    }
+    py::initialize_interpreter();
+}

tests/test_embed/test_interpreter.py

@@ -1,4 +1,6 @@
 # -*- coding: utf-8 -*-
+import sys
+
 from widget_module import Widget
 
 
@@ -8,3 +10,6 @@ class DerivedWidget(Widget):
 
     def the_answer(self):
         return 42
+
+    def argv0(self):
+        return sys.argv[0]

tests/test_enum.cpp

@@ -84,4 +84,65 @@ TEST_SUBMODULE(enums, m) {
             .value("ONE", SimpleEnum::THREE)
             .export_values();
     });
+
+    // test_enum_scalar
+    enum UnscopedUCharEnum : unsigned char {};
+    enum class ScopedShortEnum : short {};
+    enum class ScopedLongEnum : long {};
+    enum UnscopedUInt64Enum : std::uint64_t {};
+    static_assert(py::detail::all_of<
+        std::is_same<py::enum_<UnscopedUCharEnum>::Scalar, unsigned char>,
+        std::is_same<py::enum_<ScopedShortEnum>::Scalar, short>,
+        std::is_same<py::enum_<ScopedLongEnum>::Scalar, long>,
+        std::is_same<py::enum_<UnscopedUInt64Enum>::Scalar, std::uint64_t>
+    >::value, "Error during the deduction of enum's scalar type with normal integer underlying");
+
+    // test_enum_scalar_with_char_underlying
+    enum class ScopedCharEnum   : char     { Zero, Positive };
+    enum class ScopedWCharEnum  : wchar_t  { Zero, Positive };
+    enum class ScopedChar32Enum : char32_t { Zero, Positive };
+    enum class ScopedChar16Enum : char16_t { Zero, Positive };
+
+    // test the scalar of char type enums according to chapter 'Character types'
+    // from https://en.cppreference.com/w/cpp/language/types
+    static_assert(py::detail::any_of<
+        std::is_same<py::enum_<ScopedCharEnum>::Scalar, signed char>, // e.g. gcc on x86
+        std::is_same<py::enum_<ScopedCharEnum>::Scalar, unsigned char>  // e.g. arm linux
+    >::value, "char should be cast to either signed char or unsigned char");
+    static_assert(
+        sizeof(py::enum_<ScopedWCharEnum>::Scalar) == 2 ||
+        sizeof(py::enum_<ScopedWCharEnum>::Scalar) == 4
+    , "wchar_t should be either 16 bits (Windows) or 32 (everywhere else)");
+    static_assert(py::detail::all_of<
+        std::is_same<py::enum_<ScopedChar32Enum>::Scalar, std::uint_least32_t>,
+        std::is_same<py::enum_<ScopedChar16Enum>::Scalar, std::uint_least16_t>
+    >::value, "char32_t, char16_t (and char8_t)'s size, signedness, and alignment is determined");
+#if defined(PYBIND11_HAS_U8STRING)
+    enum class ScopedChar8Enum : char8_t { Zero, Positive };
+    static_assert(std::is_same<py::enum_<ScopedChar8Enum>::Scalar, unsigned char>::value);
+#endif
+
+    // test_char_underlying_enum
+    py::enum_<ScopedCharEnum>(m, "ScopedCharEnum")
+        .value("Zero", ScopedCharEnum::Zero)
+        .value("Positive", ScopedCharEnum::Positive);
+    py::enum_<ScopedWCharEnum>(m, "ScopedWCharEnum")
+        .value("Zero", ScopedWCharEnum::Zero)
+        .value("Positive", ScopedWCharEnum::Positive);
+    py::enum_<ScopedChar32Enum>(m, "ScopedChar32Enum")
+        .value("Zero", ScopedChar32Enum::Zero)
+        .value("Positive", ScopedChar32Enum::Positive);
+    py::enum_<ScopedChar16Enum>(m, "ScopedChar16Enum")
+        .value("Zero", ScopedChar16Enum::Zero)
+        .value("Positive", ScopedChar16Enum::Positive);
+
+    // test_bool_underlying_enum
+    enum class ScopedBoolEnum : bool { FALSE, TRUE };
+
+    // bool is unsigned (std::is_signed returns false) and 1-byte long, so represented with u8
+    static_assert(std::is_same<py::enum_<ScopedBoolEnum>::Scalar, std::uint8_t>::value, "");
+
+    py::enum_<ScopedBoolEnum>(m, "ScopedBoolEnum")
+        .value("FALSE", ScopedBoolEnum::FALSE)
+        .value("TRUE", ScopedBoolEnum::TRUE);
 }

tests/test_enum.py

@@ -218,10 +218,16 @@ def test_binary_operators():
 def test_enum_to_int():
     m.test_enum_to_int(m.Flags.Read)
     m.test_enum_to_int(m.ClassWithUnscopedEnum.EMode.EFirstMode)
+    m.test_enum_to_int(m.ScopedCharEnum.Positive)
+    m.test_enum_to_int(m.ScopedBoolEnum.TRUE)
     m.test_enum_to_uint(m.Flags.Read)
     m.test_enum_to_uint(m.ClassWithUnscopedEnum.EMode.EFirstMode)
+    m.test_enum_to_uint(m.ScopedCharEnum.Positive)
+    m.test_enum_to_uint(m.ScopedBoolEnum.TRUE)
     m.test_enum_to_long_long(m.Flags.Read)
     m.test_enum_to_long_long(m.ClassWithUnscopedEnum.EMode.EFirstMode)
+    m.test_enum_to_long_long(m.ScopedCharEnum.Positive)
+    m.test_enum_to_long_long(m.ScopedBoolEnum.TRUE)
 
 
 def test_duplicate_enum_name():
@@ -230,6 +236,28 @@ def test_duplicate_enum_name():
     assert str(excinfo.value) == 'SimpleEnum: element "ONE" already exists!'
 
 
+def test_char_underlying_enum():  # Issue #1331/PR #1334:
+    assert type(m.ScopedCharEnum.Positive.__int__()) is int
+    assert int(m.ScopedChar16Enum.Zero) == 0  # int() call should successfully return
+    assert hash(m.ScopedChar32Enum.Positive) == 1
+    assert m.ScopedCharEnum.Positive.__getstate__() == 1  # return type is long in py2.x
+    assert m.ScopedWCharEnum(1) == m.ScopedWCharEnum.Positive
+    with pytest.raises(TypeError):
+        # Enum should construct with a int, even with char underlying type
+        m.ScopedWCharEnum("0")
+
+
+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
+    assert m.ScopedBoolEnum.TRUE.__getstate__() == 1
+    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)
+    assert m.ScopedBoolEnum(False) == m.ScopedBoolEnum.FALSE
+
+
 def test_docstring_signatures():
     for enum_type in [m.ScopedEnum, m.UnscopedEnum]:
         for attr in enum_type.__dict__.values():

tests/test_exceptions.cpp

@@ -262,4 +262,24 @@ TEST_SUBMODULE(exceptions, m) {
     m.def("simple_bool_passthrough", [](bool x) {return x;});
 
     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");
+        throw py::error_already_set();
+    });
+
+    m.def("raise_from_already_set", []() {
+        try {
+            PyErr_SetString(PyExc_ValueError, "inner");
+            throw py::error_already_set();
+        } catch (py::error_already_set& e) {
+            py::raise_from(e, PyExc_ValueError, "outer");
+            throw py::error_already_set();
+        }
+    });
+
+#endif
 }

tests/test_exceptions.py

@@ -24,6 +24,22 @@ 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()
+    assert msg(excinfo.value) == "outer"
+    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()
+    assert msg(excinfo.value) == "outer"
+    assert msg(excinfo.value.__cause__) == "inner"
+
+
 def test_cross_module_exceptions(msg):
     with pytest.raises(RuntimeError) as excinfo:
         cm.raise_runtime_error()

tests/test_numpy_array.cpp

@@ -405,6 +405,16 @@ TEST_SUBMODULE(numpy_array, sm) {
         return a;
     });
 
+    sm.def("array_view",
+           [](py::array_t<uint8_t> a, const std::string &dtype) { return a.view(dtype); });
+
+    sm.def("reshape_initializer_list", [](py::array_t<int> a, size_t N, size_t M, size_t O) {
+        return a.reshape({N, M, O});
+    });
+    sm.def("reshape_tuple", [](py::array_t<int> a, const std::vector<int> &new_shape) {
+        return a.reshape(new_shape);
+    });
+
     sm.def("index_using_ellipsis",
            [](const py::array &a) { return a[py::make_tuple(0, py::ellipsis(), 0)]; });
 

tests/test_numpy_array.py

@@ -411,7 +411,7 @@ def test_array_unchecked_fixed_dims(msg):
     assert m.proxy_auxiliaries2_const_ref(z1)
 
 
-def test_array_unchecked_dyn_dims(msg):
+def test_array_unchecked_dyn_dims():
     z1 = np.array([[1, 2], [3, 4]], dtype="float64")
     m.proxy_add2_dyn(z1, 10)
     assert np.all(z1 == [[11, 12], [13, 14]])
@@ -444,7 +444,7 @@ def test_initializer_list():
     assert m.array_initializer_list4().shape == (1, 2, 3, 4)
 
 
-def test_array_resize(msg):
+def test_array_resize():
     a = np.array([1, 2, 3, 4, 5, 6, 7, 8, 9], dtype="float64")
     m.array_reshape2(a)
     assert a.size == 9
@@ -470,12 +470,52 @@ def test_array_resize(msg):
 
 
 @pytest.mark.xfail("env.PYPY")
-def test_array_create_and_resize(msg):
+def test_array_create_and_resize():
     a = m.create_and_resize(2)
     assert a.size == 4
     assert np.all(a == 42.0)
 
 
+def test_array_view():
+    a = np.ones(100 * 4).astype("uint8")
+    a_float_view = m.array_view(a, "float32")
+    assert a_float_view.shape == (100 * 1,)  # 1 / 4 bytes = 8 / 32
+
+    a_int16_view = m.array_view(a, "int16")  # 1 / 2 bytes = 16 / 32
+    assert a_int16_view.shape == (100 * 2,)
+
+
+def test_array_view_invalid():
+    a = np.ones(100 * 4).astype("uint8")
+    with pytest.raises(TypeError):
+        m.array_view(a, "deadly_dtype")
+
+
+def test_reshape_initializer_list():
+    a = np.arange(2 * 7 * 3) + 1
+    x = m.reshape_initializer_list(a, 2, 7, 3)
+    assert x.shape == (2, 7, 3)
+    assert list(x[1][4]) == [34, 35, 36]
+    with pytest.raises(ValueError) as excinfo:
+        m.reshape_initializer_list(a, 1, 7, 3)
+    assert str(excinfo.value) == "cannot reshape array of size 42 into shape (1,7,3)"
+
+
+def test_reshape_tuple():
+    a = np.arange(3 * 7 * 2) + 1
+    x = m.reshape_tuple(a, (3, 7, 2))
+    assert x.shape == (3, 7, 2)
+    assert list(x[1][4]) == [23, 24]
+    y = m.reshape_tuple(x, (x.size,))
+    assert y.shape == (42,)
+    with pytest.raises(ValueError) as excinfo:
+        m.reshape_tuple(a, (3, 7, 1))
+    assert str(excinfo.value) == "cannot reshape array of size 42 into shape (3,7,1)"
+    with pytest.raises(ValueError) as excinfo:
+        m.reshape_tuple(a, ())
+    assert str(excinfo.value) == "cannot reshape array of size 42 into shape ()"
+
+
 def test_index_using_ellipsis():
     a = m.index_using_ellipsis(np.zeros((5, 6, 7)))
     assert a.shape == (6,)

tests/test_numpy_dtypes.py

@@ -63,14 +63,20 @@ def partial_ld_offset():
 def partial_dtype_fmt():
     ld = np.dtype("longdouble")
     partial_ld_off = partial_ld_offset()
-    return dt_fmt().format(ld.itemsize, partial_ld_off, partial_ld_off + ld.itemsize)
+    partial_size = partial_ld_off + ld.itemsize
+    partial_end_padding = partial_size % np.dtype("uint64").alignment
+    return dt_fmt().format(
+        ld.itemsize, partial_ld_off, partial_size + partial_end_padding
+    )
 
 
 def partial_nested_fmt():
     ld = np.dtype("longdouble")
     partial_nested_off = 8 + 8 * (ld.alignment > 8)
     partial_ld_off = partial_ld_offset()
-    partial_nested_size = partial_nested_off * 2 + partial_ld_off + ld.itemsize
+    partial_size = partial_ld_off + ld.itemsize
+    partial_end_padding = partial_size % np.dtype("uint64").alignment
+    partial_nested_size = partial_nested_off * 2 + partial_size + partial_end_padding
     return "{{'names':['a'], 'formats':[{}], 'offsets':[{}], 'itemsize':{}}}".format(
         partial_dtype_fmt(), partial_nested_off, partial_nested_size
     )
@@ -91,10 +97,12 @@ def test_format_descriptors():
     ldbl_fmt = ("4x" if ld.alignment > 4 else "") + ld.char
     ss_fmt = "^T{?:bool_:3xI:uint_:f:float_:" + ldbl_fmt + ":ldbl_:}"
     dbl = np.dtype("double")
+    end_padding = ld.itemsize % np.dtype("uint64").alignment
     partial_fmt = (
         "^T{?:bool_:3xI:uint_:f:float_:"
         + str(4 * (dbl.alignment > 4) + dbl.itemsize + 8 * (ld.alignment > 8))
-        + "xg:ldbl_:}"
+        + "xg:ldbl_:"
+        + (str(end_padding) + "x}" if end_padding > 0 else "}")
     )
     nested_extra = str(max(8, ld.alignment))
     assert m.print_format_descriptors() == [

tests/test_pytypes.cpp

@@ -70,6 +70,19 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("dict_contains",
           [](const py::dict &dict, const char *val) { return dict.contains(val); });
 
+    // test_tuple
+    m.def("get_tuple", []() { return py::make_tuple(42, py::none(), "spam"); });
+
+#if PY_VERSION_HEX >= 0x03030000
+    // test_simple_namespace
+    m.def("get_simple_namespace", []() {
+        auto ns = py::make_simple_namespace("attr"_a=42, "x"_a="foo", "wrong"_a=1);
+        py::delattr(ns, "wrong");
+        py::setattr(ns, "right", py::int_(2));
+        return ns;
+    });
+#endif
+
     // test_str
     m.def("str_from_string", []() { return py::str(std::string("baz")); });
     m.def("str_from_bytes", []() { return py::str(py::bytes("boo", 3)); });

tests/test_pytypes.py

@@ -99,6 +99,19 @@ def test_dict(capture, doc):
     assert m.dict_keyword_constructor() == {"x": 1, "y": 2, "z": 3}
 
 
+def test_tuple():
+    assert m.get_tuple() == (42, None, "spam")
+
+
+@pytest.mark.skipif("env.PY2")
+def test_simple_namespace():
+    ns = m.get_simple_namespace()
+    assert ns.attr == 42
+    assert ns.x == "foo"
+    assert ns.right == 2
+    assert not hasattr(ns, "wrong")
+
+
 def test_str(doc):
     assert m.str_from_string().encode().decode() == "baz"
     assert m.str_from_bytes().encode().decode() == "boo"