Install headers using both headers and package_data (#1995)

pybind11/__init__.py

diff --git a/pybind11/__init__.py b/pybind11/__init__.py
index c625e8c..4b1de3e 100644
--- a/pybind11/__init__.py
+++ b/pybind11/__init__.py
@@ -2,35 +2,11 @@
 
 
 def get_include(user=False):
-    from distutils.dist import Distribution
     import os
-    import sys
-
-    # Are we running in a virtual environment?
-    virtualenv = hasattr(sys, 'real_prefix') or \
-        sys.prefix != getattr(sys, "base_prefix", sys.prefix)
-
-    # Are we running in a conda environment?
-    conda = os.path.exists(os.path.join(sys.prefix, 'conda-meta'))
-
-    if virtualenv:
-        return os.path.join(sys.prefix, 'include', 'site',
-                            'python' + sys.version[:3])
-    elif conda:
-        if os.name == 'nt':
-            return os.path.join(sys.prefix, 'Library', 'include')
-        else:
-            return os.path.join(sys.prefix, 'include')
+    d = os.path.dirname(__file__)
+    if os.path.exists(os.path.join(d, "include")):
+        # Package is installed
+        return os.path.join(d, "include")
     else:
-        dist = Distribution({'name': 'pybind11'})
-        dist.parse_config_files()
-
-        dist_cobj = dist.get_command_obj('install', create=True)
-
-        # Search for packages in user's home directory?
-        if user:
-            dist_cobj.user = user
-            dist_cobj.prefix = ""
-        dist_cobj.finalize_options()
-
-        return os.path.dirname(dist_cobj.install_headers)
+        # Package is from a source directory
+        return os.path.join(os.path.dirname(d), "include")

pybind11/__main__.py

diff --git a/pybind11/__main__.py b/pybind11/__main__.py
index 9ef8378..89b263a 100644
--- a/pybind11/__main__.py
+++ b/pybind11/__main__.py
@@ -10,8 +10,7 @@
 def print_includes():
     dirs = [sysconfig.get_path('include'),
             sysconfig.get_path('platinclude'),
-            get_include(),
-            get_include(True)]
+            get_include()]
 
     # Make unique but preserve order
     unique_dirs = []

setup.py

diff --git a/setup.py b/setup.py
index f677f2a..473ea1e 100644
--- a/setup.py
+++ b/setup.py
@@ -4,40 +4,43 @@
 
 from setuptools import setup
 from distutils.command.install_headers import install_headers
+from distutils.command.build_py import build_py
 from pybind11 import __version__
 import os
 
+package_data = [
+    'include/pybind11/detail/class.h',
+    'include/pybind11/detail/common.h',
+    'include/pybind11/detail/descr.h',
+    'include/pybind11/detail/init.h',
+    'include/pybind11/detail/internals.h',
+    'include/pybind11/detail/typeid.h',
+    'include/pybind11/attr.h',
+    'include/pybind11/buffer_info.h',
+    'include/pybind11/cast.h',
+    'include/pybind11/chrono.h',
+    'include/pybind11/common.h',
+    'include/pybind11/complex.h',
+    'include/pybind11/eigen.h',
+    'include/pybind11/embed.h',
+    'include/pybind11/eval.h',
+    'include/pybind11/functional.h',
+    'include/pybind11/iostream.h',
+    'include/pybind11/numpy.h',
+    'include/pybind11/operators.h',
+    'include/pybind11/options.h',
+    'include/pybind11/pybind11.h',
+    'include/pybind11/pytypes.h',
+    'include/pybind11/stl.h',
+    'include/pybind11/stl_bind.h',
+]
+
 # Prevent installation of pybind11 headers by setting
 # PYBIND11_USE_CMAKE.
 if os.environ.get('PYBIND11_USE_CMAKE'):
     headers = []
 else:
-    headers = [
-        'include/pybind11/detail/class.h',
-        'include/pybind11/detail/common.h',
-        'include/pybind11/detail/descr.h',
-        'include/pybind11/detail/init.h',
-        'include/pybind11/detail/internals.h',
-        'include/pybind11/detail/typeid.h',
-        'include/pybind11/attr.h',
-        'include/pybind11/buffer_info.h',
-        'include/pybind11/cast.h',
-        'include/pybind11/chrono.h',
-        'include/pybind11/common.h',
-        'include/pybind11/complex.h',
-        'include/pybind11/eigen.h',
-        'include/pybind11/embed.h',
-        'include/pybind11/eval.h',
-        'include/pybind11/functional.h',
-        'include/pybind11/iostream.h',
-        'include/pybind11/numpy.h',
-        'include/pybind11/operators.h',
-        'include/pybind11/options.h',
-        'include/pybind11/pybind11.h',
-        'include/pybind11/pytypes.h',
-        'include/pybind11/stl.h',
-        'include/pybind11/stl_bind.h',
-    ]
+    headers = package_data
 
 
 class InstallHeaders(install_headers):
@@ -55,6 +58,16 @@
             self.outfiles.append(out)
 
 
+# Install the headers inside the package as well
+class BuildPy(build_py):
+    def build_package_data(self):
+        build_py.build_package_data(self)
+        for header in package_data:
+            target = os.path.join(self.build_lib, 'pybind11', header)
+            self.mkpath(os.path.dirname(target))
+            self.copy_file(header, target, preserve_mode=False)
+
+
 setup(
     name='pybind11',
     version=__version__,
@@ -66,7 +79,8 @@
     packages=['pybind11'],
     license='BSD',
     headers=headers,
-    cmdclass=dict(install_headers=InstallHeaders),
+    zip_safe=False,
+    cmdclass=dict(install_headers=InstallHeaders, build_py=BuildPy),
     classifiers=[
         'Development Status :: 5 - Production/Stable',
         'Intended Audience :: Developers',