include pep660 proof of concept

setup.cfg

@@ -109,6 +109,7 @@ distutils.commands =
 	develop = setuptools.command.develop:develop
 	dist_info = setuptools.command.dist_info:dist_info
 	easy_install = setuptools.command.easy_install:easy_install
+	editable_wheel = setuptools.command.editable_wheel:editable_wheel
 	egg_info = setuptools.command.egg_info:egg_info
 	install = setuptools.command.install:install
 	install_egg_info = setuptools.command.install_egg_info:install_egg_info

setuptools/build_meta.py

@@ -45,6 +45,8 @@
            'prepare_metadata_for_build_wheel',
            'build_wheel',
            'build_sdist',
+           'get_requires_for_build_editable',
+           'build_editable',
            '__legacy__',
            'SetupRequirementsError']
 
@@ -236,6 +238,23 @@ def build_sdist(self, sdist_directory, config_settings=None):
                                          config_settings)
 
 
+    # PEP660 hooks:
+    # build_editable
+    # get_requires_for_build_editable
+    # prepare_metadata_for_build_editable
+    def build_editable(
+        self, wheel_directory, scheme=None, config_settings=None
+    ):
+        # XXX can or should we hide our editable_wheel command normally?
+        return self._build_with_temp_dir(
+            ["editable_wheel"], ".whl", wheel_directory, config_settings
+        )
+
+
+    def get_requires_for_build_editable(self, config_settings=None):
+        return ['editables', 'wheel']
+
+
 class _BuildMetaLegacyBackend(_BuildMetaBackend):
     """Compatibility backend for setuptools
 
@@ -281,9 +300,11 @@ def run_setup(self, setup_script='setup.py'):
 
 get_requires_for_build_wheel = _BACKEND.get_requires_for_build_wheel
 get_requires_for_build_sdist = _BACKEND.get_requires_for_build_sdist
+get_requires_for_build_editable =  _BACKEND.get_requires_for_build_editable
 prepare_metadata_for_build_wheel = _BACKEND.prepare_metadata_for_build_wheel
 build_wheel = _BACKEND.build_wheel
 build_sdist = _BACKEND.build_sdist
+build_editable = _BACKEND.build_editable
 
 
 # The legacy backend

setuptools/command/editable_wheel.py

@@ -0,0 +1,157 @@
+"""
+Create a wheel that, when installed, will make the source package 'editable'
+(add it to the interpreter's path, including metadata) per PEP 660. Replaces
+'setup.py develop'. Based on the setuptools develop command.
+"""
+
+# TODO doesn't behave when called outside the hook
+
+import os
+import time
+from pathlib import Path
+
+from distutils.core import Command
+from distutils.errors import DistutilsError
+
+import pkg_resources
+
+SOURCE_EPOCH_ZIP = 499162860
+
+
+class editable_wheel(Command):
+    """Build 'editable' wheel for development"""
+
+    description = "create a PEP 660 'editable' wheel"
+
+    user_options = [
+        ("dist-dir=", "d", "directory to put final built distributions in"),
+    ]
+
+    boolean_options = []
+
+    def run(self):
+        self.build_editable_wheel()
+
+    def initialize_options(self):
+        self.dist_dir = None
+
+    def finalize_options(self):
+        # is this part of the 'develop' command needed?
+        ei = self.get_finalized_command("egg_info")
+        if ei.broken_egg_info:
+            template = "Please rename %r to %r before using 'develop'"
+            args = ei.egg_info, ei.broken_egg_info
+            raise DistutilsError(template % args)
+        self.args = [ei.egg_name]
+
+        # the .pth file should point to target
+        self.egg_base = ei.egg_base
+        self.target = pkg_resources.normalize_path(self.egg_base)
+        self.dist_info_dir = Path(
+            (ei.egg_info[: -len(".egg-info")] + ".dist-info").rpartition("/")[-1]
+        )
+
+    def build_editable_wheel(self):
+        if getattr(self.distribution, "use_2to3", False):
+            raise NotImplementedError("2to3 not supported")
+
+        di = self.get_finalized_command("dist_info")
+        di.egg_base = self.dist_dir
+        di.finalize_options()
+        self.run_command("dist_info")
+
+        # Build extensions in-place
+        self.reinitialize_command("build_ext", inplace=1)
+        self.run_command("build_ext")
+
+        # now build the wheel
+        # with the dist-info directory and .pth from 'editables' library
+        # ...
+
+        import zipfile
+        import editables    # could we use 'develop' command's .pth file
+
+        project = editables.EditableProject(
+            self.distribution.metadata.name, self.target
+        )
+        project.add_to_path(self.target)
+
+        dist_dir = Path(self.dist_dir)
+        dist_info_dir = self.dist_info_dir
+        fullname = self.distribution.metadata.get_fullname()
+        # superfluous 'ed' tag is only a hint to the user,
+        # and guarantees we can't overwrite the normal wheel
+        wheel_name = f"{fullname}-ed.py3-none-any.whl"
+        wheel_path = dist_dir / wheel_name
+
+        wheelmeta_builder(dist_dir / dist_info_dir / "WHEEL")
+
+        if wheel_path.exists():
+            wheel_path.unlink()
+
+        with zipfile.ZipFile(
+            wheel_path, "a", compression=zipfile.ZIP_DEFLATED
+        ) as archive:
+
+            # copy .pth file
+            for f, data in project.files():
+                archive.writestr(
+                    zipfile.ZipInfo(f, time.gmtime(SOURCE_EPOCH_ZIP)[:6]), data
+                )
+
+            # copy .dist-info directory
+            for f in sorted(os.listdir(dist_dir / dist_info_dir)):
+                with (dist_dir / dist_info_dir / f).open() as metadata:
+                    archive.writestr(
+                        zipfile.ZipInfo(
+                            str(dist_info_dir / f), time.gmtime(SOURCE_EPOCH_ZIP)[:6]
+                        ),
+                        metadata.read(),
+                    )
+
+            add_manifest(archive, dist_info_dir)
+
+
+import base64
+
+
+def urlsafe_b64encode(data):
+    """urlsafe_b64encode without padding"""
+    return base64.urlsafe_b64encode(data).rstrip(b"=")
+
+
+# standalone wheel helpers based on enscons
+def add_manifest(archive, dist_info_dir):
+    """
+    Add the wheel manifest.
+    """
+    import hashlib
+    import zipfile
+
+    lines = []
+    for f in archive.namelist():
+        data = archive.read(f)
+        size = len(data)
+        digest = hashlib.sha256(data).digest()
+        digest = "sha256=" + (urlsafe_b64encode(digest).decode("ascii"))
+        lines.append("%s,%s,%s" % (f.replace(",", ",,"), digest, size))
+
+    record_path = dist_info_dir / "RECORD"
+    lines.append(str(record_path) + ",,")
+    RECORD = "\n".join(lines)
+    archive.writestr(
+        zipfile.ZipInfo(str(record_path), time.gmtime(SOURCE_EPOCH_ZIP)[:6]), RECORD
+    )
+    archive.close()
+
+
+def wheelmeta_builder(target):
+    with open(target, "w+") as f:
+        f.write(
+            """Wheel-Version: 1.0
+Generator: setuptools_pep660 (0.1)
+Root-Is-Purelib: false
+Tag: py3-none-any
+Tag: ed-none-any
+"""
+        )