Add Scheme model and use for wheel installation

src/pip/_internal/locations.py

@@ -16,6 +16,7 @@
 from distutils.command.install import SCHEME_KEYS  # type: ignore
 from distutils.command.install import install as distutils_install_command
 
+from pip._internal.models.scheme import Scheme
 from pip._internal.utils import appdirs
 from pip._internal.utils.compat import WINDOWS
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING, cast
@@ -153,3 +154,41 @@ def distutils_scheme(
             )
 
     return scheme
+
+
+def get_scheme(
+    dist_name,  # type: str
+    user=False,  # type: bool
+    home=None,  # type: Optional[str]
+    root=None,  # type: Optional[str]
+    isolated=False,  # type: bool
+    prefix=None,  # type: Optional[str]
+):
+    # type: (...) -> Scheme
+    """
+    Get the "scheme" corresponding to the input parameters. The distutils
+    documentation provides the context for the available schemes:
+    https://docs.python.org/3/install/index.html#alternate-installation
+
+    :param dist_name: the name of the package to retrieve the scheme for, used
+        in the headers scheme path
+    :param user: indicates to use the "user" scheme
+    :param home: indicates to use the "home" scheme and provides the base
+        directory for the same
+    :param root: root under which other directories are re-based
+    :param isolated: equivalent to --no-user-cfg, i.e. do not consider
+        ~/.pydistutils.cfg (posix) or ~/pydistutils.cfg (non-posix) for
+        scheme paths
+    :param prefix: indicates to use the "prefix" scheme and provides the
+        base directory for the same
+    """
+    scheme = distutils_scheme(
+        dist_name, user, home, root, isolated, prefix
+    )
+    return Scheme(
+        platlib=scheme["platlib"],
+        purelib=scheme["purelib"],
+        headers=scheme["headers"],
+        scripts=scheme["scripts"],
+        data=scheme["data"],
+    )

src/pip/_internal/models/scheme.py

@@ -0,0 +1,25 @@
+"""
+For types associated with installation schemes.
+
+For a general overview of available schemes and their context, see
+https://docs.python.org/3/install/index.html#alternate-installation.
+"""
+
+
+class Scheme(object):
+    """A Scheme holds paths which are used as the base directories for
+    artifacts associated with a Python package.
+    """
+    def __init__(
+        self,
+        platlib,  # type: str
+        purelib,  # type: str
+        headers,  # type: str
+        scripts,  # type: str
+        data,  # type: str
+    ):
+        self.platlib = platlib
+        self.purelib = purelib
+        self.headers = headers
+        self.scripts = scripts
+        self.data = data

src/pip/_internal/req/req_install.py

@@ -8,7 +8,6 @@
 import os
 import shutil
 import sys
-import sysconfig
 import zipfile
 from distutils.util import change_root
 
@@ -22,7 +21,7 @@
 from pip._internal import pep425tags, wheel
 from pip._internal.build_env import NoOpBuildEnvironment
 from pip._internal.exceptions import InstallationError
-from pip._internal.locations import distutils_scheme
+from pip._internal.locations import get_scheme
 from pip._internal.models.link import Link
 from pip._internal.operations.build.metadata import generate_metadata
 from pip._internal.operations.build.metadata_legacy import \
@@ -65,11 +64,12 @@
 
 if MYPY_CHECK_RUNNING:
     from typing import (
-        Any, Dict, Iterable, List, Mapping, Optional, Sequence, Union,
+        Any, Dict, Iterable, List, Optional, Sequence, Union,
     )
     from pip._internal.build_env import BuildEnvironment
     from pip._internal.cache import WheelCache
     from pip._internal.index.package_finder import PackageFinder
+    from pip._internal.models.scheme import Scheme
     from pip._vendor.pkg_resources import Distribution
     from pip._vendor.packaging.specifiers import SpecifierSet
     from pip._vendor.packaging.markers import Marker
@@ -540,7 +540,7 @@ def is_wheel(self):
     def move_wheel_files(
         self,
         wheeldir,  # type: str
-        scheme,  # type: Mapping[str, str]
+        scheme,  # type: Scheme
         warn_script_location=True,  # type: bool
         pycompile=True  # type: bool
     ):
@@ -852,6 +852,15 @@ def install(
         pycompile=True  # type: bool
     ):
         # type: (...) -> None
+        scheme = get_scheme(
+            self.name,
+            user=use_user_site,
+            home=home,
+            root=root,
+            isolated=self.isolated,
+            prefix=prefix,
+        )
+
         global_options = global_options if global_options is not None else []
         if self.editable:
             self.install_editable(
@@ -862,14 +871,11 @@ def install(
                 use_user_site=use_user_site,
             )
             return
+
         if self.is_wheel:
             version = wheel.wheel_version(self.source_dir)
             wheel.check_compatibility(version, self.name)
 
-            scheme = distutils_scheme(
-                self.name, user=use_user_site, home=home, root=root,
-                isolated=self.isolated, prefix=prefix,
-            )
             self.move_wheel_files(
                 self.source_dir,
                 scheme=scheme,
@@ -889,12 +895,7 @@ def install(
         install_options = list(install_options) + \
             self.options.get('install_options', [])
 
-        header_dir = None  # type: Optional[str]
-        if running_under_virtualenv():
-            py_ver_str = 'python' + sysconfig.get_python_version()
-            header_dir = os.path.join(
-                sys.prefix, 'include', 'site', py_ver_str, self.name
-            )
+        header_dir = scheme.headers
 
         with TempDirectory(kind="record") as temp_dir:
             record_filename = os.path.join(temp_dir.path, 'install-record.txt')

src/pip/_internal/wheel.py

@@ -36,9 +36,11 @@
 
 if MYPY_CHECK_RUNNING:
     from typing import (
-        Dict, List, Optional, Sequence, Mapping, Tuple, IO, Text, Any,
+        Dict, List, Optional, Sequence, Tuple, IO, Text, Any,
         Iterable, Callable, Set,
     )
+
+    from pip._internal.models.scheme import Scheme
     from pip._internal.pep425tags import Pep425Tag
 
     InstalledCSVRow = Tuple[str, ...]
@@ -289,7 +291,7 @@ def make(self, specification, options=None):
 def install_unpacked_wheel(
     name,  # type: str
     wheeldir,  # type: str
-    scheme,  # type: Mapping[str, str]
+    scheme,  # type: Scheme
     req_description,  # type: str
     pycompile=True,  # type: bool
     warn_script_location=True  # type: bool
@@ -311,9 +313,9 @@ def install_unpacked_wheel(
     #       installation.
 
     if root_is_purelib(name, wheeldir):
-        lib_dir = scheme['purelib']
+        lib_dir = scheme.purelib
     else:
-        lib_dir = scheme['platlib']
+        lib_dir = scheme.platlib
 
     info_dir = []  # type: List[str]
     data_dirs = []
@@ -458,10 +460,10 @@ def is_entrypoint_wrapper(name):
                 fixer = fix_script
                 filter = is_entrypoint_wrapper
             source = os.path.join(wheeldir, datadir, subdir)
-            dest = scheme[subdir]
+            dest = getattr(scheme, subdir)
             clobber(source, dest, False, fixer=fixer, filter=filter)
 
-    maker = PipScriptMaker(None, scheme['scripts'])
+    maker = PipScriptMaker(None, scheme.scripts)
 
     # Ensure old scripts are overwritten.
     # See https://github.com/pypa/pip/issues/1800

tests/unit/test_wheel.py

@@ -11,8 +11,9 @@
 from pip._internal import pep425tags, wheel
 from pip._internal.commands.wheel import WheelCommand
 from pip._internal.exceptions import InvalidWheelFilename, UnsupportedWheel
-from pip._internal.locations import distutils_scheme
+from pip._internal.locations import get_scheme
 from pip._internal.models.link import Link
+from pip._internal.models.scheme import Scheme
 from pip._internal.req.req_install import InstallRequirement
 from pip._internal.utils.compat import WINDOWS
 from pip._internal.utils.misc import hash_file
@@ -482,29 +483,31 @@ def prep(self, data, tmpdir):
         self.src = os.path.join(tmpdir, 'src')
         self.dest = os.path.join(tmpdir, 'dest')
         unpack_file(self.wheelpath, self.src)
-        self.scheme = {
-            'scripts': os.path.join(self.dest, 'bin'),
-            'purelib': os.path.join(self.dest, 'lib'),
-            'data': os.path.join(self.dest, 'data'),
-        }
+        self.scheme = Scheme(
+            purelib=os.path.join(self.dest, 'lib'),
+            platlib=os.path.join(self.dest, 'lib'),
+            headers=os.path.join(self.dest, 'headers'),
+            scripts=os.path.join(self.dest, 'bin'),
+            data=os.path.join(self.dest, 'data'),
+        )
         self.src_dist_info = os.path.join(
             self.src, 'sample-1.2.0.dist-info')
         self.dest_dist_info = os.path.join(
-            self.scheme['purelib'], 'sample-1.2.0.dist-info')
+            self.scheme.purelib, 'sample-1.2.0.dist-info')
 
     def assert_installed(self):
         # lib
         assert os.path.isdir(
-            os.path.join(self.scheme['purelib'], 'sample'))
+            os.path.join(self.scheme.purelib, 'sample'))
         # dist-info
         metadata = os.path.join(self.dest_dist_info, 'METADATA')
         assert os.path.isfile(metadata)
         # data files
-        data_file = os.path.join(self.scheme['data'], 'my_data', 'data_file')
+        data_file = os.path.join(self.scheme.data, 'my_data', 'data_file')
         assert os.path.isfile(data_file)
         # package data
         pkg_data = os.path.join(
-            self.scheme['purelib'], 'sample', 'package_data.dat')
+            self.scheme.purelib, 'sample', 'package_data.dat')
         assert os.path.isfile(pkg_data)
 
     def test_std_install(self, data, tmpdir):
@@ -520,7 +523,7 @@ def test_std_install(self, data, tmpdir):
     def test_install_prefix(self, data, tmpdir):
         prefix = os.path.join(os.path.sep, 'some', 'path')
         self.prep(data, tmpdir)
-        scheme = distutils_scheme(
+        scheme = get_scheme(
             self.name,
             user=False,
             home=None,