support/testing: add test for python-pybind

The way that python-pybind can be used is fairly complicated, so a
runtime test for it is convenient. In addition, this test validates that
the headers actually work at runtime.

Signed-off-by: Guillaume W. Bres <guillaume.bressaix@gmail.com>
[Arnout:
 - Retain python3 only.
 - python-pybind is a target package, not host.
 - Select python-pybind instead of depend.
 - Simplify python-pybind-example package.
 - Check in python-pybind-example build if pybind11.get_include()
   produces output.
 - Don't use python3 -m pybind11 --includes: it includes the main python
   includes, which are for the host, not for the target.
 - Use TestPythonPackageBase instead of open-coding something imported
   with host python.
]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

DEVELOPERS

@@ -1124,6 +1124,9 @@ F:	package/liquid-dsp/
 F:	package/pixiewps/
 F:	package/python-pybind/
 F:	package/reaver/
+F:	support/testing/tests/package/br2-external/python-pybind
+F:	support/testing/tests/package/sample_python_pybind.py
+F:	support/testing/tests/package/test_python_pybind.py
 
 N:	Guo Ren <ren_guo@c-sky.com>
 F:	arch/Config.in.csky

support/testing/tests/package/br2-external/python-pybind/Config.in

@@ -0,0 +1 @@
+source "$BR2_EXTERNAL_PYTHON_PYBIND_PATH/package/python-pybind-example/Config.in"

support/testing/tests/package/br2-external/python-pybind/external.desc

@@ -0,0 +1 @@
+name: PYTHON_PYBIND

support/testing/tests/package/br2-external/python-pybind/external.mk

@@ -0,0 +1 @@
+include $(sort $(wildcard $(BR2_EXTERNAL_PYTHON_PYBIND_PATH)/package/*/*.mk))

support/testing/tests/package/br2-external/python-pybind/package/python-pybind-example/Config.in

@@ -0,0 +1,6 @@
+config BR2_PACKAGE_PYTHON_PYBIND_EXAMPLE
+	bool "python-pybind-example"
+	depends on BR2_PACKAGE_PYTHON3
+	select BR2_PACKAGE_PYTHON_PYBIND
+	help
+	  This test creates a cpp macro later used on target in python

support/testing/tests/package/br2-external/python-pybind/package/python-pybind-example/example.cpp

@@ -0,0 +1,16 @@
+#include <pybind11/pybind11.h>
+namespace py = pybind11;
+
+int add (int i, int j) {
+    return i + j;
+}
+
+PYBIND11_MODULE (example, m) {
+    // optional module description
+    m.doc() = "pybind11 example plugin";
+    // test a module method
+    m.def("add", &add, "example::add adds two integer numbers");
+    // test a module attribute
+    py::object hello = py::cast("Hello World");
+    m.attr("says") = hello;
+}

support/testing/tests/package/br2-external/python-pybind/package/python-pybind-example/python-pybind-example.mk

@@ -0,0 +1,41 @@
+################################################################################
+#
+# python-pybind-example
+#
+################################################################################
+
+# this builds a C++ macro "add(a,b)"
+# that we expose to host-python with a custom install
+# and that the python test script will later use
+PYTHON_PYBIND_EXAMPLE_DEPENDENCIES = python-pybind
+
+PYTHON_PYBIND_EXAMPLE_PYBIND_INCLUDE = \
+	$(shell $(HOST_DIR)/usr/bin/python3 -c 'import pybind11; print(pybind11.get_include())')
+
+PYTHON_PYBIND_EXAMPLE_CXX_FLAGS = \
+	$(TARGET_CXXFLAGS) \
+	-Wall -shared -std=c++11 -fPIC \
+	-I$(PYTHON_PYBIND_EXAMPLE_PYBIND_INCLUDE) \
+	$(shell $(STAGING_DIR)/usr/bin/python3-config --includes --libs --ldflags)
+
+# .so to be installed must have exact suffix
+# otherwise import() in python will not work
+HOST_LIB_BINARY_SUFFIX = \
+	$(shell $(STAGING_DIR)/usr/bin/python3-config --extension-suffix)
+
+define PYTHON_PYBIND_EXAMPLE_BUILD_CMDS
+	if [ -z "$(PYTHON_PYBIND_EXAMPLE_PYBIND_INCLUDE)" ]; then \
+		echo "pybind11.get_include() returned empty"; \
+		exit 1; \
+	fi
+	$(TARGET_CXX) $(PYTHON_PYBIND_EXAMPLE_CXX_FLAGS) \
+		$(PYTHON_PYBIND_EXAMPLE_PKGDIR)/example.cpp \
+		-o $(@D)/example$(HOST_LIB_BINARY_SUFFIX)
+endef
+
+define PYTHON_PYBIND_EXAMPLE_INSTALL_TARGET_CMDS
+	$(INSTALL) -D -m 755 $(@D)/example$(HOST_LIB_BINARY_SUFFIX) \
+		$(TARGET_DIR)/usr/lib/python$(PYTHON3_VERSION_MAJOR)/site-packages/example$(HOST_LIB_BINARY_SUFFIX)
+endef
+
+$(eval $(generic-package))

support/testing/tests/package/sample_python_pybind.py

@@ -0,0 +1,4 @@
+#!/usr/bin/env python
+import example
+print(example.add(1, 2))
+print(example.says)

support/testing/tests/package/test_python_pybind.py

@@ -0,0 +1,15 @@
+import os
+import infra
+import subprocess
+from tests.package.test_python import TestPythonPackageBase
+
+class TestPythonPybind (TestPythonPackageBase):
+    __test__ = True
+    config = TestPythonPackageBase.config + \
+        """
+        BR2_PACKAGE_PYTHON3=y
+        BR2_PACKAGE_PYTHON_PYBIND_EXAMPLE=y
+        """
+    sample_scripts = ["tests/package/sample_python_pybind.py"]
+    # ship examples macro & installs it to host
+    br2_external = [infra.filepath("tests/package/br2-external/python-pybind")]