WIP prototype pep517-style editable

src/pip/_internal/operations/install/wheel.py

@@ -314,10 +314,53 @@ def install_unpacked_wheel(
     # TODO: Look into moving this into a dedicated class for representing an
     #       installation.
 
-    source = wheeldir.rstrip(os.path.sep) + os.path.sep
-
     info_dir, metadata = parse_wheel(wheel_zip, name)
 
+    return install_unpacked_parsed_wheel(
+        name,
+        wheeldir,
+        info_dir,
+        metadata,
+        scheme,
+        req_description,
+        pycompile=pycompile,
+        warn_script_location=warn_script_location,
+        direct_url=direct_url
+    )
+
+
+def install_unpacked_parsed_wheel(
+    name,  # type: str
+    wheeldir,  # type: str
+    info_dir,  # type: str
+    metadata,  # type: Message
+    scheme,  # type: Scheme
+    req_description,  # type: str
+    pycompile=True,  # type: bool
+    warn_script_location=True,  # type: bool
+    direct_url=None,  # type: Optional[DirectUrl]
+):
+    # type: (...) -> None
+    """Install a wheel.
+
+    :param name: Name of the project to install
+    :param wheeldir: Base directory of the unpacked wheel
+    :param info_dir: Wheel's .dist-info directory
+    :param metadata: Wheel's parsed WHEEL-file
+    :param scheme: Distutils scheme dictating the install directories
+    :param req_description: String used in place of the requirement, for
+        logging
+    :param pycompile: Whether to byte-compile installed Python files
+    :param warn_script_location: Whether to check that scripts are installed
+        into a directory on PATH
+    :raises UnsupportedWheel:
+        * when the directory holds an unpacked wheel with incompatible
+          Wheel-Version
+        * when the .dist-info dir does not match the wheel
+    """
+
+    source = wheeldir.rstrip(os.path.sep) + os.path.sep
+
     if wheel_root_is_purelib(metadata):
         lib_dir = scheme.purelib
     else:

src/pip/_internal/req/req_install.py

@@ -27,7 +27,7 @@
     install_editable as install_editable_legacy
 from pip._internal.operations.install.legacy import LegacyInstallFailure
 from pip._internal.operations.install.legacy import install as install_legacy
-from pip._internal.operations.install.wheel import install_wheel
+from pip._internal.operations.install.wheel import install_wheel, install_unpacked_parsed_wheel
 from pip._internal.pyproject import load_pyproject_toml, make_pyproject_path
 from pip._internal.req.req_uninstall import UninstallPathSet
 from pip._internal.utils.deprecation import deprecated
@@ -777,18 +777,47 @@ def install(
 
         global_options = global_options if global_options is not None else []
         if self.editable:
-            install_editable_legacy(
-                install_options,
-                global_options,
-                prefix=prefix,
-                home=home,
-                use_user_site=use_user_site,
-                name=self.name,
-                setup_py_path=self.setup_py_path,
-                isolated=self.isolated,
-                build_env=self.build_env,
-                unpacked_source_directory=self.unpacked_source_directory,
-            )
+            if self.metadata_directory and self.metadata_directory.endswith('.dist-info'):
+
+                editable_path = self.pep517_backend.build_editable()
+
+                # create empty RECORD
+                with open(os.path.join(self.metadata_directory, 'RECORD'), 'w+'):
+                    pass
+
+                wheeldir = os.path.dirname(self.metadata_directory)
+
+                # put .pth file in wheeldir
+                with open(os.path.join(wheeldir, self.name + '.pth'), 'w+') as pthfile:
+                    pthfile.write(editable_path['src_root'] + '\n')
+
+                install_unpacked_parsed_wheel(
+                    self.name,
+                    wheeldir,
+                    self.metadata_directory,
+                    {
+                        "Root-Is-Purelib" : "false", # shouldn't matter
+                    },
+                    scheme=scheme,
+                    req_description=str(self.req),
+                    pycompile=pycompile,
+                    warn_script_location=warn_script_location,
+                    direct_url=None,
+                )
+
+            else:
+                install_editable_legacy(
+                    install_options,
+                    global_options,
+                    prefix=prefix,
+                    home=home,
+                    use_user_site=use_user_site,
+                    name=self.name,
+                    setup_py_path=self.setup_py_path,
+                    isolated=self.isolated,
+                    build_env=self.build_env,
+                    unpacked_source_directory=self.unpacked_source_directory,
+                )
             self.install_succeeded = True
             return
 

src/pip/_vendor/pep517/_in_process.py

@@ -238,12 +238,22 @@ def build_sdist(sdist_directory, config_settings):
         raise GotUnsupportedOperation(traceback.format_exc())
 
 
+def build_editable():
+    """Invoke the optional build_editable hook."""
+    backend = _build_backend()
+    try:
+        return backend.build_editable()
+    except getattr(backend, 'UnsupportedOperation', _DummyException):
+        raise GotUnsupportedOperation(traceback.format_exc())
+
+
 HOOK_NAMES = {
     'get_requires_for_build_wheel',
     'prepare_metadata_for_build_wheel',
     'build_wheel',
     'get_requires_for_build_sdist',
     'build_sdist',
+    'build_editable',
 }
 
 

src/pip/_vendor/pep517/wrappers.py

@@ -1,7 +1,7 @@
 import threading
 from contextlib import contextmanager
 import os
-from os.path import dirname, abspath, join as pjoin
+from os.path import dirname, abspath, normpath, join as pjoin
 import shutil
 from subprocess import check_call, check_output, STDOUT
 import sys
@@ -225,6 +225,19 @@ def build_sdist(self, sdist_directory, config_settings=None):
             'config_settings': config_settings,
         })
 
+
+    def build_editable(self):
+        """Build this project for editable. Usually in-place.
+
+        Returns a dict with the source directory (point .pth here)
+
+        This calls the 'build_editable' backend hook in a subprocess.
+        """
+        editable = self._call_hook('build_editable', {})
+        editable['src_root'] = normpath(pjoin(self.source_dir, editable['src_root']))
+        return editable
+
+
     def _call_hook(self, hook_name, kwargs):
         # On Python 2, pytoml returns Unicode values (which is correct) but the
         # environment passed to check_call needs to contain string values. We