From c801639e5127028a9ef4779fb17c9ae8193026b9 Mon Sep 17 00:00:00 2001
From: Tom de Geus <tom@geus.me>
Date: Thu, 3 Jun 2021 12:51:19 +0200
Subject: [PATCH 1/5] Adding possibility to 'cast' or copy to `xt::xarray` etc

---
 .azure-pipelines/unix-build.yml               |   8 ++
 docs/source/examples/copy_cast/CMakeLists.txt |  13 ++
 docs/source/examples/copy_cast/example.py     |   6 +
 docs/source/examples/copy_cast/main.cpp       |  25 ++++
 include/xtensor-python/pynative_casters.hpp   |   1 -
 .../xtensor_type_caster_base.hpp              | 121 +++++++++++++++---
 6 files changed, 157 insertions(+), 17 deletions(-)
 create mode 100644 docs/source/examples/copy_cast/CMakeLists.txt
 create mode 100644 docs/source/examples/copy_cast/example.py
 create mode 100644 docs/source/examples/copy_cast/main.cpp

diff --git a/.azure-pipelines/unix-build.yml b/.azure-pipelines/unix-build.yml
index d01651c3..0008e138 100644
--- a/.azure-pipelines/unix-build.yml
+++ b/.azure-pipelines/unix-build.yml
@@ -42,6 +42,14 @@ steps:
     displayName: Example - readme 1
     workingDirectory: $(Build.SourcesDirectory)/docs/source/examples/readme_example_1
 
+  - script: |
+      source activate xtensor-python
+      cmake . -DPYTHON_EXECUTABLE=`which python`
+      cmake --build .
+      python example.py
+    displayName: Example - Copy 'cast'
+    workingDirectory: $(Build.SourcesDirectory)/docs/source/examples/copy_cast
+
   - script: |
       source activate xtensor-python
       cmake . -DPYTHON_EXECUTABLE=`which python`
diff --git a/docs/source/examples/copy_cast/CMakeLists.txt b/docs/source/examples/copy_cast/CMakeLists.txt
new file mode 100644
index 00000000..e17611c1
--- /dev/null
+++ b/docs/source/examples/copy_cast/CMakeLists.txt
@@ -0,0 +1,13 @@
+cmake_minimum_required(VERSION 3.1..3.19)
+
+project(mymodule)
+
+find_package(pybind11 CONFIG REQUIRED)
+find_package(xtensor REQUIRED)
+find_package(xtensor-python REQUIRED)
+find_package(Python REQUIRED COMPONENTS NumPy)
+
+pybind11_add_module(mymodule main.cpp)
+target_link_libraries(mymodule PUBLIC pybind11::module xtensor-python Python::NumPy)
+
+target_compile_definitions(mymodule PRIVATE VERSION_INFO=0.1.0)
diff --git a/docs/source/examples/copy_cast/example.py b/docs/source/examples/copy_cast/example.py
new file mode 100644
index 00000000..d007e7c1
--- /dev/null
+++ b/docs/source/examples/copy_cast/example.py
@@ -0,0 +1,6 @@
+import mymodule
+import numpy as np
+
+c = np.array([[1, 2, 3], [4, 5, 6]])
+assert np.isclose(np.sum(np.sin(c)), mymodule.sum_of_sines(c))
+assert np.isclose(np.sum(np.cos(c)), mymodule.sum_of_cosines(c))
diff --git a/docs/source/examples/copy_cast/main.cpp b/docs/source/examples/copy_cast/main.cpp
new file mode 100644
index 00000000..cb3e65c8
--- /dev/null
+++ b/docs/source/examples/copy_cast/main.cpp
@@ -0,0 +1,25 @@
+#include <numeric>
+#include <xtensor.hpp>
+#include <pybind11/pybind11.h>
+#define FORCE_IMPORT_ARRAY
+#include <xtensor-python/pyarray.hpp>
+
+double sum_of_sines(xt::pyarray<double>& m)
+{
+    auto sines = xt::sin(m);  // sines does not actually hold values.
+    return std::accumulate(sines.begin(), sines.end(), 0.0);
+}
+
+double sum_of_cosines(const xt::xarray<double>& m)
+{
+    auto cosines = xt::cos(m);  // cosines does not actually hold values.
+    return std::accumulate(cosines.begin(), cosines.end(), 0.0);
+}
+
+PYBIND11_MODULE(mymodule, m)
+{
+    xt::import_numpy();
+    m.doc() = "Test module for xtensor python bindings";
+    m.def("sum_of_sines", sum_of_sines, "Sum the sines of the input values");
+    m.def("sum_of_cosines", sum_of_cosines, "Sum the cosines of the input values");
+}
diff --git a/include/xtensor-python/pynative_casters.hpp b/include/xtensor-python/pynative_casters.hpp
index f0f00652..caaad34b 100644
--- a/include/xtensor-python/pynative_casters.hpp
+++ b/include/xtensor-python/pynative_casters.hpp
@@ -12,7 +12,6 @@
 
 #include "xtensor_type_caster_base.hpp"
 
-
 namespace pybind11
 {
     namespace detail
diff --git a/include/xtensor-python/xtensor_type_caster_base.hpp b/include/xtensor-python/xtensor_type_caster_base.hpp
index 3c8a015f..e587865e 100644
--- a/include/xtensor-python/xtensor_type_caster_base.hpp
+++ b/include/xtensor-python/xtensor_type_caster_base.hpp
@@ -23,6 +23,87 @@ namespace pybind11
 {
     namespace detail
     {
+        template <typename T, xt::layout_type L>
+        struct xtensor_get_buffer
+        {
+            template <typename H>
+            static auto get(H src)
+            {
+                return array_t<T, array::c_style | array::forcecast>::ensure(src);
+            }
+        };
+
+        template <typename T>
+        struct xtensor_get_buffer<T, xt::layout_type::column_major>
+        {
+            template <typename H>
+            static auto get(H src)
+            {
+                return array_t<T, array::f_style>::ensure(src);
+            }
+        };
+
+        template <class T>
+        struct xtensor_check_buffer
+        {
+        };
+
+        template <class T, xt::layout_type L>
+        struct xtensor_check_buffer<xt::xarray<T, L>>
+        {
+            template <typename H>
+            static auto get(H src)
+            {
+                auto buf = xtensor_get_buffer<T, L>::get(src);
+                return buf;
+            }
+        };
+
+        template <class T, std::size_t N, xt::layout_type L>
+        struct xtensor_check_buffer<xt::xtensor<T, N, L>>
+        {
+            template <typename H>
+            static auto get(H src)
+            {
+                auto buf = xtensor_get_buffer<T, L>::get(src);
+                if (buf.ndim() != N) {
+                    return false;
+                }
+                return buf;
+            }
+        };
+
+        template <class CT, class S, xt::layout_type L, class FST>
+        struct xtensor_check_buffer<xt::xstrided_view<CT, S, L, FST>>
+        {
+            template <typename H>
+            static auto get(H /*src*/)
+            {
+                return false;
+            }
+        };
+
+        template <class EC, xt::layout_type L, class SC, class Tag>
+        struct xtensor_check_buffer<xt::xarray_adaptor<EC, L, SC, Tag>>
+        {
+            template <typename H>
+            static auto get(H /*src*/)
+            {
+                return false;
+            }
+        };
+
+        template <class EC, std::size_t N, xt::layout_type L, class Tag>
+        struct xtensor_check_buffer<xt::xtensor_adaptor<EC, N, L, Tag>>
+        {
+            template <typename H>
+            static auto get(H /*src*/)
+            {
+                return false;
+            }
+        };
+
+
         // Casts a strided expression type to numpy array.If given a base,
         // the numpy array references the src data, otherwise it'll make a copy.
         // The writeable attributes lets you specify writeable flag for the array.
@@ -74,10 +155,6 @@ namespace pybind11
         template <class Type>
         struct xtensor_type_caster_base
         {
-            bool load(handle /*src*/, bool)
-            {
-                return false;
-            }
 
         private:
 
@@ -106,6 +183,30 @@ namespace pybind11
 
         public:
 
+            PYBIND11_TYPE_CASTER(Type, _("numpy.ndarray[") + npy_format_descriptor<typename Type::value_type>::name + _("]"));
+
+            bool load(handle src, bool convert)
+            {
+                using T = typename Type::value_type;
+
+                if (!convert && !array_t<T>::check_(src)) {
+                    return false;
+                }
+
+                auto buf = xtensor_check_buffer<Type>::get(src);
+
+                if (!buf) {
+                    return false;
+                }
+
+                std::vector<size_t> shape(buf.ndim());
+                std::copy(buf.shape(), buf.shape() + buf.ndim(), shape.begin());
+                value = Type(shape);
+                std::copy(buf.data(), buf.data() + buf.size(), value.begin());
+
+                return true;
+            }
+
             // Normal returned non-reference, non-const value:
             static handle cast(Type&& src, return_value_policy /* policy */, handle parent)
             {
@@ -151,18 +252,6 @@ namespace pybind11
             {
                 return cast_impl(src, policy, parent);
             }
-
-#ifdef PYBIND11_DESCR // The macro is removed from pybind11 since 2.3
-            static PYBIND11_DESCR name()
-            {
-                return _("xt::xtensor");
-            }
-#else
-            static constexpr auto name = _("xt::xtensor");
-#endif
-
-            template <typename T>
-            using cast_op_type = cast_op_type<T>;
         };
     }
 }

From e21ecb0177268267df8aa16d4639d681ddc86dcd Mon Sep 17 00:00:00 2001
From: Tom de Geus <tom@geus.me>
Date: Sat, 5 Jun 2021 13:08:01 +0200
Subject: [PATCH 2/5] Adding example

---
 docs/source/examples.rst                      | 50 +++++++++++++++++++
 docs/source/examples/copy_cast/main.cpp       |  6 ++-
 .../xtensor_type_caster_base.hpp              | 24 ++++-----
 3 files changed, 63 insertions(+), 17 deletions(-)

diff --git a/docs/source/examples.rst b/docs/source/examples.rst
index 4788b8bf..cd7242a5 100644
--- a/docs/source/examples.rst
+++ b/docs/source/examples.rst
@@ -98,3 +98,53 @@ Then we can test the module:
     we should compile and run the example from the same folder.
     To install, please consult
     `this pybind11 / CMake example <https://github.com/pybind/cmake_example>`_.
+
+
+Fall-back cast
+==============
+
+The previous example showed you how to design your module to be flexible in accepting data.
+From C++ we used ``xt::xarray<double>``,
+whereas for the Python API we used ``xt::pyarray<double>`` to operate directly on the memory
+of a NumPy array from Python (without copying the data).
+
+Sometimes, you might not have the flexibility to design your module's methods
+with template parameters.
+This might occur when you want to ``override`` functions
+(though it is recommended to use CRTP to still use templates).
+In this case we can still bind the module in Python using *xtensor-python*,
+however, we have to copy the data from a (NumPy) array.
+This means that although the following signatures are quite different when used from C++,
+as follows:
+
+1.  *Constant reference*: read from the data, without copying it.
+
+    .. code-block:: cpp
+
+         void foo(const xt::xarray<double>& a);
+
+2.  *Reference*: read from and/or write to the data, without copying it.
+
+    .. code-block:: cpp
+
+         void foo(xt::xarray<double>& a);
+
+3.   *Copy*: copy the data.
+
+     .. code-block:: cpp
+
+         void foo(xt::xarray<double> a);
+
+The Python will all cases result in a copy to a temporary variable
+(though the last signature will lead to a copy to a temporary variable, and another copy to ``a``).
+On the one hand, this is more costly than when using ``xt::pyarray`` and ``xt::pyxtensor``,
+on the other hand, it means that all changes you make to a reference, are made to the temporary
+copy, and are thus lost.
+
+Still, it might be a convenient way to create Python bindings, using a minimal effort.
+Consider this example:
+
+:download:`main.cpp <examples/copy_cast/main.cpp>`
+
+.. literalinclude:: examples/copy_cast/main.cpp
+   :language: cpp
diff --git a/docs/source/examples/copy_cast/main.cpp b/docs/source/examples/copy_cast/main.cpp
index cb3e65c8..2e126098 100644
--- a/docs/source/examples/copy_cast/main.cpp
+++ b/docs/source/examples/copy_cast/main.cpp
@@ -4,12 +4,14 @@
 #define FORCE_IMPORT_ARRAY
 #include <xtensor-python/pyarray.hpp>
 
-double sum_of_sines(xt::pyarray<double>& m)
+template <class T>
+double sum_of_sines(T& m)
 {
     auto sines = xt::sin(m);  // sines does not actually hold values.
     return std::accumulate(sines.begin(), sines.end(), 0.0);
 }
 
+// In the Python API this a reference to a temporary variable
 double sum_of_cosines(const xt::xarray<double>& m)
 {
     auto cosines = xt::cos(m);  // cosines does not actually hold values.
@@ -20,6 +22,6 @@ PYBIND11_MODULE(mymodule, m)
 {
     xt::import_numpy();
     m.doc() = "Test module for xtensor python bindings";
-    m.def("sum_of_sines", sum_of_sines, "Sum the sines of the input values");
+    m.def("sum_of_sines", sum_of_sines<xt::pyarray<double>>, "Sum the sines of the input values");
     m.def("sum_of_cosines", sum_of_cosines, "Sum the cosines of the input values");
 }
diff --git a/include/xtensor-python/xtensor_type_caster_base.hpp b/include/xtensor-python/xtensor_type_caster_base.hpp
index e587865e..68218eea 100644
--- a/include/xtensor-python/xtensor_type_caster_base.hpp
+++ b/include/xtensor-python/xtensor_type_caster_base.hpp
@@ -26,8 +26,7 @@ namespace pybind11
         template <typename T, xt::layout_type L>
         struct xtensor_get_buffer
         {
-            template <typename H>
-            static auto get(H src)
+            static auto get(handle src)
             {
                 return array_t<T, array::c_style | array::forcecast>::ensure(src);
             }
@@ -36,8 +35,7 @@ namespace pybind11
         template <typename T>
         struct xtensor_get_buffer<T, xt::layout_type::column_major>
         {
-            template <typename H>
-            static auto get(H src)
+            static auto get(handle src)
             {
                 return array_t<T, array::f_style>::ensure(src);
             }
@@ -51,8 +49,7 @@ namespace pybind11
         template <class T, xt::layout_type L>
         struct xtensor_check_buffer<xt::xarray<T, L>>
         {
-            template <typename H>
-            static auto get(H src)
+            static auto get(handle src)
             {
                 auto buf = xtensor_get_buffer<T, L>::get(src);
                 return buf;
@@ -62,8 +59,7 @@ namespace pybind11
         template <class T, std::size_t N, xt::layout_type L>
         struct xtensor_check_buffer<xt::xtensor<T, N, L>>
         {
-            template <typename H>
-            static auto get(H src)
+            static auto get(handle src)
             {
                 auto buf = xtensor_get_buffer<T, L>::get(src);
                 if (buf.ndim() != N) {
@@ -76,8 +72,7 @@ namespace pybind11
         template <class CT, class S, xt::layout_type L, class FST>
         struct xtensor_check_buffer<xt::xstrided_view<CT, S, L, FST>>
         {
-            template <typename H>
-            static auto get(H /*src*/)
+            static auto get(handle /*src*/)
             {
                 return false;
             }
@@ -86,18 +81,17 @@ namespace pybind11
         template <class EC, xt::layout_type L, class SC, class Tag>
         struct xtensor_check_buffer<xt::xarray_adaptor<EC, L, SC, Tag>>
         {
-            template <typename H>
-            static auto get(H /*src*/)
+            static auto get(handle src)
             {
-                return false;
+                auto buf = xtensor_get_buffer<EC, L>::get(src);
+                return buf;
             }
         };
 
         template <class EC, std::size_t N, xt::layout_type L, class Tag>
         struct xtensor_check_buffer<xt::xtensor_adaptor<EC, N, L, Tag>>
         {
-            template <typename H>
-            static auto get(H /*src*/)
+            static auto get(handle /*src*/)
             {
                 return false;
             }

From 428ed03b5dbc2b9ab0a62ffbf9da5a4ed0705afe Mon Sep 17 00:00:00 2001
From: Tom de Geus <tom@geus.me>
Date: Sat, 5 Jun 2021 16:08:29 +0200
Subject: [PATCH 3/5] Adding tests & minor bugfix

---
 .../xtensor_type_caster_base.hpp              | 39 ++++++++++++++-----
 test_python/main.cpp                          | 32 +++++++++++++++
 test_python/test_pyarray.py                   | 16 ++++++++
 3 files changed, 77 insertions(+), 10 deletions(-)

diff --git a/include/xtensor-python/xtensor_type_caster_base.hpp b/include/xtensor-python/xtensor_type_caster_base.hpp
index 68218eea..8db9e445 100644
--- a/include/xtensor-python/xtensor_type_caster_base.hpp
+++ b/include/xtensor-python/xtensor_type_caster_base.hpp
@@ -37,7 +37,7 @@ namespace pybind11
         {
             static auto get(handle src)
             {
-                return array_t<T, array::f_style>::ensure(src);
+                return array_t<T, array::f_style | array::forcecast>::ensure(src);
             }
         };
 
@@ -51,8 +51,7 @@ namespace pybind11
         {
             static auto get(handle src)
             {
-                auto buf = xtensor_get_buffer<T, L>::get(src);
-                return buf;
+                return xtensor_get_buffer<T, L>::get(src);
             }
         };
 
@@ -61,11 +60,7 @@ namespace pybind11
         {
             static auto get(handle src)
             {
-                auto buf = xtensor_get_buffer<T, L>::get(src);
-                if (buf.ndim() != N) {
-                    return false;
-                }
-                return buf;
+                return xtensor_get_buffer<T, L>::get(src);
             }
         };
 
@@ -98,6 +93,27 @@ namespace pybind11
         };
 
 
+        template <class T>
+        struct xtensor_verify
+        {
+            template <class B>
+            static bool get(const B& buf)
+            {
+                return true;
+            }
+        };
+
+        template <class T, std::size_t N, xt::layout_type L>
+        struct xtensor_verify<xt::xtensor<T, N, L>>
+        {
+            template <class B>
+            static bool get(const B& buf)
+            {
+                return buf.ndim() == N;
+            }
+        };
+
+
         // Casts a strided expression type to numpy array.If given a base,
         // the numpy array references the src data, otherwise it'll make a copy.
         // The writeable attributes lets you specify writeable flag for the array.
@@ -192,11 +208,14 @@ namespace pybind11
                 if (!buf) {
                     return false;
                 }
+                if (!xtensor_verify<Type>::get(buf)) {
+                    return false;
+                }
 
                 std::vector<size_t> shape(buf.ndim());
                 std::copy(buf.shape(), buf.shape() + buf.ndim(), shape.begin());
-                value = Type(shape);
-                std::copy(buf.data(), buf.data() + buf.size(), value.begin());
+                value = Type::from_shape(shape);
+                std::copy(buf.data(), buf.data() + buf.size(), value.data());
 
                 return true;
             }
diff --git a/test_python/main.cpp b/test_python/main.cpp
index 66f4e3ca..7e5963c1 100644
--- a/test_python/main.cpp
+++ b/test_python/main.cpp
@@ -33,6 +33,33 @@ xt::pyarray<double> example2(xt::pyarray<double>& m)
     return m + 2;
 }
 
+xt::xarray<int> example3_xarray(const xt::xarray<int>& m)
+{
+    return xt::transpose(m) + 2;
+}
+
+xt::xarray<int, xt::layout_type::column_major> example3_xarray_colmajor(
+    const xt::xarray<int, xt::layout_type::column_major>& m)
+{
+    return xt::transpose(m) + 2;
+}
+
+xt::xtensor<int, 3> example3_xtensor3(const xt::xtensor<int, 3>& m)
+{
+    return xt::transpose(m) + 2;
+}
+
+xt::xtensor<int, 2> example3_xtensor2(const xt::xtensor<int, 2>& m)
+{
+    return xt::transpose(m) + 2;
+}
+
+xt::xtensor<int, 2, xt::layout_type::column_major> example3_xtensor2_colmajor(
+    const xt::xtensor<int, 2, xt::layout_type::column_major>& m)
+{
+    return xt::transpose(m) + 2;
+}
+
 // Readme Examples
 
 double readme_example1(xt::pyarray<double>& m)
@@ -249,6 +276,11 @@ PYBIND11_MODULE(xtensor_python_test, m)
 
     m.def("example1", example1);
     m.def("example2", example2);
+    m.def("example3_xarray", example3_xarray);
+    m.def("example3_xarray_colmajor", example3_xarray_colmajor);
+    m.def("example3_xtensor3", example3_xtensor3);
+    m.def("example3_xtensor2", example3_xtensor2);
+    m.def("example3_xtensor2_colmajor", example3_xtensor2_colmajor);
 
     m.def("complex_overload", no_complex_overload);
     m.def("complex_overload", complex_overload);
diff --git a/test_python/test_pyarray.py b/test_python/test_pyarray.py
index 71e9dd33..8760c974 100644
--- a/test_python/test_pyarray.py
+++ b/test_python/test_pyarray.py
@@ -36,6 +36,22 @@ def test_example2(self):
         y = xt.example2(x)
         np.testing.assert_allclose(y, res, 1e-12)
 
+    def test_example3(self):
+        x = np.arange(2 * 3).reshape(2, 3)
+        xc = np.asfortranarray(x)
+        y = np.arange(2 * 3 * 4).reshape(2, 3, 4)
+        v = y[1:, 1:, 0]
+        z = np.arange(2 * 3 * 4 * 5).reshape(2, 3, 4, 5)
+        np.testing.assert_array_equal(xt.example3_xarray(x), x.T + 2)
+        np.testing.assert_array_equal(xt.example3_xarray_colmajor(xc), xc.T + 2)
+        np.testing.assert_array_equal(xt.example3_xtensor3(y), y.T + 2)
+        np.testing.assert_array_equal(xt.example3_xtensor2(x), x.T + 2)
+        np.testing.assert_array_equal(xt.example3_xtensor2(y[1:, 1:, 0]), v.T + 2)
+        np.testing.assert_array_equal(xt.example3_xtensor2_colmajor(xc), xc.T + 2)
+
+        with self.assertRaises(TypeError):
+            xt.example3_xtensor3(x)
+
     def test_vectorize(self):
         x1 = np.array([[0, 1], [2, 3]])
         x2 = np.array([0, 1])

From acc30eddda5089dbd7873897c479dbd72c116d46 Mon Sep 17 00:00:00 2001
From: Tom de Geus <tom@geus.me>
Date: Thu, 10 Jun 2021 11:51:03 +0200
Subject: [PATCH 4/5] Nitpicking

---
 .../xtensor_type_caster_base.hpp              | 55 ++++++++++---------
 1 file changed, 29 insertions(+), 26 deletions(-)

diff --git a/include/xtensor-python/xtensor_type_caster_base.hpp b/include/xtensor-python/xtensor_type_caster_base.hpp
index 8db9e445..672bd644 100644
--- a/include/xtensor-python/xtensor_type_caster_base.hpp
+++ b/include/xtensor-python/xtensor_type_caster_base.hpp
@@ -24,69 +24,69 @@ namespace pybind11
     namespace detail
     {
         template <typename T, xt::layout_type L>
-        struct xtensor_get_buffer
+        struct pybind_array_getter_impl
         {
-            static auto get(handle src)
+            static auto run(handle src)
             {
                 return array_t<T, array::c_style | array::forcecast>::ensure(src);
             }
         };
 
         template <typename T>
-        struct xtensor_get_buffer<T, xt::layout_type::column_major>
+        struct pybind_array_getter_impl<T, xt::layout_type::column_major>
         {
-            static auto get(handle src)
+            static auto run(handle src)
             {
                 return array_t<T, array::f_style | array::forcecast>::ensure(src);
             }
         };
 
         template <class T>
-        struct xtensor_check_buffer
+        struct pybind_array_getter
         {
         };
 
         template <class T, xt::layout_type L>
-        struct xtensor_check_buffer<xt::xarray<T, L>>
+        struct pybind_array_getter<xt::xarray<T, L>>
         {
-            static auto get(handle src)
+            static auto run(handle src)
             {
-                return xtensor_get_buffer<T, L>::get(src);
+                return pybind_array_getter_impl<T, L>::run(src);
             }
         };
 
         template <class T, std::size_t N, xt::layout_type L>
-        struct xtensor_check_buffer<xt::xtensor<T, N, L>>
+        struct pybind_array_getter<xt::xtensor<T, N, L>>
         {
-            static auto get(handle src)
+            static auto run(handle src)
             {
-                return xtensor_get_buffer<T, L>::get(src);
+                return pybind_array_getter_impl<T, L>::run(src);
             }
         };
 
         template <class CT, class S, xt::layout_type L, class FST>
-        struct xtensor_check_buffer<xt::xstrided_view<CT, S, L, FST>>
+        struct pybind_array_getter<xt::xstrided_view<CT, S, L, FST>>
         {
-            static auto get(handle /*src*/)
+            static auto run(handle /*src*/)
             {
                 return false;
             }
         };
 
         template <class EC, xt::layout_type L, class SC, class Tag>
-        struct xtensor_check_buffer<xt::xarray_adaptor<EC, L, SC, Tag>>
+        struct pybind_array_getter<xt::xarray_adaptor<EC, L, SC, Tag>>
         {
-            static auto get(handle src)
+            static auto run(handle src)
             {
-                auto buf = xtensor_get_buffer<EC, L>::get(src);
+                auto buf = pybind_array_getter_impl<EC, L>::run(src);
                 return buf;
             }
         };
 
         template <class EC, std::size_t N, xt::layout_type L, class Tag>
-        struct xtensor_check_buffer<xt::xtensor_adaptor<EC, N, L, Tag>>
+        struct pybind_array_getter<xt::xtensor_adaptor<EC, N, L, Tag>>
         {
-            static auto get(handle /*src*/)
+            static auto run(handle /*src*/)
             {
                 return false;
             }
@@ -94,20 +94,20 @@ namespace pybind11
 
 
         template <class T>
-        struct xtensor_verify
+        struct pybind_array_dim_checker
         {
             template <class B>
-            static bool get(const B& buf)
+            static bool run(const B& buf)
             {
                 return true;
             }
         };
 
         template <class T, std::size_t N, xt::layout_type L>
-        struct xtensor_verify<xt::xtensor<T, N, L>>
+        struct pybind_array_dim_checker<xt::xtensor<T, N, L>>
         {
             template <class B>
-            static bool get(const B& buf)
+            static bool run(const B& buf)
             {
                 return buf.ndim() == N;
             }
@@ -199,16 +199,19 @@ namespace pybind11
             {
                 using T = typename Type::value_type;
 
-                if (!convert && !array_t<T>::check_(src)) {
+                if (!convert && !array_t<T>::check_(src))
+                {
                     return false;
                 }
 
-                auto buf = xtensor_check_buffer<Type>::get(src);
+                auto buf = pybind_array_getter<Type>::run(src);
 
-                if (!buf) {
+                if (!buf)
+                {
                     return false;
                 }
-                if (!xtensor_verify<Type>::get(buf)) {
+                if (!pybind_array_dim_checker<Type>::run(buf))
+                {
                     return false;
                 }
 

From af91def5d4bb9b7966f134adb581c59f6c66af87 Mon Sep 17 00:00:00 2001
From: Tom de Geus <tom@geus.me>
Date: Thu, 10 Jun 2021 11:52:58 +0200
Subject: [PATCH 5/5] Fixing CI

---
 .azure-pipelines/unix-build.yml | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/.azure-pipelines/unix-build.yml b/.azure-pipelines/unix-build.yml
index 0fcf6924..97cb4052 100644
--- a/.azure-pipelines/unix-build.yml
+++ b/.azure-pipelines/unix-build.yml
@@ -52,13 +52,16 @@ steps:
       cmake --build .
       cp ../example.py .
       python example.py
+      cd ..
     displayName: Example - Copy 'cast'
     workingDirectory: $(Build.SourcesDirectory)/docs/source/examples/copy_cast
 
   - script: |
       source activate xtensor-python
-      cmake . -DPYTHON_EXECUTABLE=`which python`
+      cmake -Bbuild -DPython_EXECUTABLE=`which python`
+      cd build
       cmake --build .
+      cp ../example.py .
       python example.py
       cd ..
     displayName: Example - SFINAE