Fix Android tests (#23)

* Android tests working

* Clarifications

Author: mhsmith

tests/env.py

@@ -6,6 +6,7 @@
 
 import pytest
 
+ANDROID = sys.platform.startswith("android")
 LINUX = sys.platform.startswith("linux")
 MACOS = sys.platform.startswith("darwin")
 WIN = sys.platform.startswith("win32") or sys.platform.startswith("cygwin")

tests/pyproject.toml

@@ -33,6 +33,4 @@ pyodide.test-groups = ["numpy", "scipy"]
 ios.test-groups = ["numpy"]
 ios.xbuild-tools = ["cmake", "ninja"]
 ios.environment.PIP_EXTRA_INDEX_URL = "https://pypi.anaconda.org/beeware/simple"
-android.test-groups = ["numpy"]
-android.xbuild-tools = ["cmake", "ninja"]
-android.environment.PIP_EXTRA_INDEX_URL = "https://chaquo.com/pypi-13.1"
+android.environment.ANDROID_API_LEVEL = "24"  # Needed to include libc++ in the wheel.

tests/test_exceptions.py

@@ -76,7 +76,7 @@ def test_cross_module_exceptions(msg):
 
 # TODO: FIXME
 @pytest.mark.xfail(
-    "env.MACOS and env.PYPY",
+    "(env.MACOS and env.PYPY) or env.ANDROID",
     raises=RuntimeError,
     reason="See Issue #2847, PR #2999, PR #4324",
     strict=not env.PYPY,  # PR 5569

tools/pybind11NewTools.cmake

@@ -243,6 +243,17 @@ if(TARGET ${_Python}::Python)
 endif()
 
 if(TARGET ${_Python}::Module)
+  # On Android, older versions of CMake don't know that modules need to link against
+  # libpython, so Python::Module will be an INTERFACE target with no associated library
+  # files.
+  get_target_property(module_target_type ${_Python}::Module TYPE)
+  if(ANDROID AND module_target_type STREQUAL INTERFACE_LIBRARY)
+    set_property(
+      TARGET ${_Python}::Module
+      APPEND
+      PROPERTY INTERFACE_LINK_LIBRARIES "${${_Python}_LIBRARIES}")
+  endif()
+
   set_property(
     TARGET pybind11::module
     APPEND

tools/pybind11Tools.cmake

@@ -119,7 +119,8 @@ target_link_libraries(
   pybind11::module
   INTERFACE
     pybind11::python_link_helper
-    "$<$<OR:$<PLATFORM_ID:Windows>,$<PLATFORM_ID:Cygwin>>:pybind11::_ClassicPythonLibraries>")
+    "$<$<OR:$<PLATFORM_ID:Windows>,$<PLATFORM_ID:Cygwin>,$<PLATFORM_ID:Android>>:pybind11::_ClassicPythonLibraries>"
+)
 
 target_link_libraries(pybind11::embed INTERFACE pybind11::pybind11
                                                 pybind11::_ClassicPythonLibraries)