pythonPackages.xgboost: fix build

The setup.py of `python-package` contains some path resolution magic to
find `libxgboost.so` which is needed for the python API.

Unfortunately the code is incompatible with Nix as it isn't compatible
with the store-based structure for each package and tries to express the
location of the shared object with relative paths.

The detection in `setup.py` and `xgboost/libpath.py` has been either
removed entirely or patched to link to the proper store path of the
`libxgboost` build input.

See https://hydra.nixos.org/build/77702715 for further reference.

pkgs/development/python-modules/xgboost/default.nix

@@ -3,30 +3,28 @@
 , nose
 , scipy
 , xgboost
+, substituteAll
 }:
 
 buildPythonPackage rec {
   pname = "xgboost";
   inherit (xgboost) version src meta;
 
+  patches = [
+    (substituteAll {
+      src = ./lib-path-for-python.patch;
+      libpath = "${xgboost}/lib";
+    })
+  ];
+
+  postPatch = "cd python-package";
+
   propagatedBuildInputs = [ scipy ];
+  buildInputs = [ xgboost ];
   checkInputs = [ nose ];
 
-  postPatch = let
-    libname = "libxgboost.${stdenv.hostPlatform.extensions.sharedLibrary}";
-
-  in ''
-    cd python-package
-
-    sed "s/CURRENT_DIR = os.path.dirname(__file__)/CURRENT_DIR = os.path.abspath(os.path.dirname(__file__))/g" -i setup.py
-    sed "/^LIB_PATH.*/a LIB_PATH = [os.path.relpath(LIB_PATH[0], CURRENT_DIR)]" -i setup.py
-    cat <<EOF >xgboost/libpath.py
-    def find_lib_path():
-      return ["${xgboost}/lib/${libname}"]
-    EOF
-  '';
-
-  postInstall = ''
-    rm -rf $out/xgboost
+  checkPhase = ''
+    ln -sf ../demo .
+    nosetests ../tests/python
   '';
 }

pkgs/development/python-modules/xgboost/lib-path-for-python.patch

@@ -0,0 +1,59 @@
+diff --git a/python-package/setup.py b/python-package/setup.py
+index e6c3386f..4ed0a8bd 100644
+--- a/python-package/setup.py
++++ b/python-package/setup.py
+@@ -16,8 +16,6 @@ libpath_py = os.path.join(CURRENT_DIR, 'xgboost/libpath.py')
+ libpath = {'__file__': libpath_py}
+ exec(compile(open(libpath_py, "rb").read(), libpath_py, 'exec'), libpath, libpath)
+ 
+-LIB_PATH = [os.path.relpath(libfile, CURRENT_DIR) for libfile in libpath['find_lib_path']()]
+-print("Install libxgboost from: %s" % LIB_PATH)
+ # Please use setup_pip.py for generating and deploying pip installation
+ # detailed instruction in setup_pip.py
+ setup(name='xgboost',
+@@ -35,7 +33,6 @@ setup(name='xgboost',
+       # this will use MANIFEST.in during install where we specify additional files,
+       # this is the golden line
+       include_package_data=True,
+-      data_files=[('xgboost', LIB_PATH)],
+       license='Apache-2.0',
+       classifiers=['License :: OSI Approved :: Apache Software License'],
+       url='https://github.com/dmlc/xgboost')
+diff --git a/python-package/xgboost/libpath.py b/python-package/xgboost/libpath.py
+index d87922c0..859a30fb 100644
+--- a/python-package/xgboost/libpath.py
++++ b/python-package/xgboost/libpath.py
+@@ -19,32 +19,4 @@ def find_lib_path():
+     lib_path: list(string)
+        List of all found library path to xgboost
+     """
+-    curr_path = os.path.dirname(os.path.abspath(os.path.expanduser(__file__)))
+-    # make pythonpack hack: copy this directory one level upper for setup.py
+-    dll_path = [curr_path, os.path.join(curr_path, '../../lib/'),
+-                os.path.join(curr_path, './lib/'),
+-                os.path.join(sys.prefix, 'xgboost')]
+-    if sys.platform == 'win32':
+-        if platform.architecture()[0] == '64bit':
+-            dll_path.append(os.path.join(curr_path, '../../windows/x64/Release/'))
+-            # hack for pip installation when copy all parent source directory here
+-            dll_path.append(os.path.join(curr_path, './windows/x64/Release/'))
+-        else:
+-            dll_path.append(os.path.join(curr_path, '../../windows/Release/'))
+-            # hack for pip installation when copy all parent source directory here
+-            dll_path.append(os.path.join(curr_path, './windows/Release/'))
+-        dll_path = [os.path.join(p, 'xgboost.dll') for p in dll_path]
+-    elif sys.platform.startswith('linux') or sys.platform.startswith('freebsd'):
+-        dll_path = [os.path.join(p, 'libxgboost.so') for p in dll_path]
+-    elif sys.platform == 'darwin':
+-        dll_path = [os.path.join(p, 'libxgboost.dylib') for p in dll_path]
+-
+-    lib_path = [p for p in dll_path if os.path.exists(p) and os.path.isfile(p)]
+-
+-    # From github issues, most of installation errors come from machines w/o compilers
+-    if not lib_path and not os.environ.get('XGBOOST_BUILD_DOC', False):
+-        raise XGBoostLibraryNotFound(
+-            'Cannot find XGBoost Library in the candidate path, ' +
+-            'did you install compilers and run build.sh in root path?\n'
+-            'List of candidates:\n' + ('\n'.join(dll_path)))
+-    return lib_path
++    return ["@libpath@/libxgboost.so"]