wip: PEP 660 backend support

currently the contents for the {name}.pth file is hardcoded for the
psf/black project (because of course :P)

setuptools/build_meta.py

@@ -34,10 +34,16 @@
 import contextlib
 import tempfile
 import warnings
+import zipfile
+import base64
+import textwrap
+import hashlib
+import csv
 
 import setuptools
 import distutils
 
+import pkg_resources
 from pkg_resources import parse_requirements
 
 __all__ = ['get_requires_for_build_sdist',
@@ -126,6 +132,27 @@ def suppress_known_deprecation():
         yield
 
 
+def _urlsafe_b64encode(data):
+    """urlsafe_b64encode without padding"""
+    return base64.urlsafe_b64encode(data).rstrip(b"=")
+
+
+def _add_wheel_record(archive, dist_info):
+    """
+    Add the wheel RECORD manifest.
+    """
+    buffer = io.StringIO()
+    writer = csv.writer(buffer, delimiter=',', quotechar='"', lineterminator='\n')
+    for f in archive.namelist():
+        data = archive.read(f)
+        size = len(data)
+        digest = hashlib.sha256(data).digest()
+        digest = "sha256=" + (_urlsafe_b64encode(digest).decode("ascii"))
+        writer.writerow((f, digest, size))
+    record_path = os.path.join(dist_info, "RECORD")
+    archive.writestr(zipfile.ZipInfo(record_path), buffer.read())
+
+
 class _BuildMetaBackend(object):
 
     def _fix_config(self, config_settings):
@@ -146,6 +173,29 @@ def _get_build_requires(self, config_settings, requirements):
 
         return requirements
 
+    def _build_dist_info_metadata(self, result_directory):
+        sys.argv = sys.argv[:1] + [
+            'dist_info', '--egg-base', result_directory]
+        with no_install_setup_requires():
+            self.run_setup()
+
+        dist_info_directory = result_directory
+        while True:
+            dist_infos = [f for f in os.listdir(dist_info_directory)
+                          if f.endswith('.dist-info')]
+
+            if (
+                len(dist_infos) == 0 and
+                len(_get_immediate_subdirectories(dist_info_directory)) == 1
+            ):
+
+                dist_info_directory = os.path.join(
+                    dist_info_directory, os.listdir(dist_info_directory)[0])
+                continue
+
+            assert len(dist_infos) == 1
+            return dist_infos[0], dist_info_directory
+
     def run_setup(self, setup_script='setup.py'):
         # Note that we can reuse our build directory between calls
         # Correctness comes first, then optimization later
@@ -166,39 +216,23 @@ def get_requires_for_build_sdist(self, config_settings=None):
         config_settings = self._fix_config(config_settings)
         return self._get_build_requires(config_settings, requirements=[])
 
+    def get_requires_for_build_editable(self, config_settings=None):
+        config_settings = self._fix_config(config_settings)
+        return self._get_build_requires(config_settings, requirements=[])
+
     def prepare_metadata_for_build_wheel(self, metadata_directory,
                                          config_settings=None):
-        sys.argv = sys.argv[:1] + [
-            'dist_info', '--egg-base', metadata_directory]
-        with no_install_setup_requires():
-            self.run_setup()
-
-        dist_info_directory = metadata_directory
-        while True:
-            dist_infos = [f for f in os.listdir(dist_info_directory)
-                          if f.endswith('.dist-info')]
-
-            if (
-                len(dist_infos) == 0 and
-                len(_get_immediate_subdirectories(dist_info_directory)) == 1
-            ):
-
-                dist_info_directory = os.path.join(
-                    dist_info_directory, os.listdir(dist_info_directory)[0])
-                continue
-
-            assert len(dist_infos) == 1
-            break
-
+        dist_info, dist_info_directory = \
+            self._build_dist_info_metadata(metadata_directory)
         # PEP 517 requires that the .dist-info directory be placed in the
         # metadata_directory. To comply, we MUST copy the directory to the root
         if dist_info_directory != metadata_directory:
             shutil.move(
-                os.path.join(dist_info_directory, dist_infos[0]),
+                os.path.join(dist_info_directory, dist_info),
                 metadata_directory)
             shutil.rmtree(dist_info_directory, ignore_errors=True)
 
-        return dist_infos[0]
+        return dist_info
 
     def _build_with_temp_dir(self, setup_command, result_extension,
                              result_directory, config_settings):
@@ -235,6 +269,55 @@ def build_sdist(self, sdist_directory, config_settings=None):
                                          '.tar.gz', sdist_directory,
                                          config_settings)
 
+    def build_editable(self, wheel_directory, config_settings=None,
+                       metadata_directory=None):
+        config_settings = self._fix_config(config_settings)
+        # TODO: using wheel_directory like this is probably a bad idea, fix it
+        dist_info, dist_info_directory = self._build_dist_info_metadata(wheel_directory)
+        dist_info_path = os.path.join(dist_info_directory, dist_info)
+
+        sys.argv = [
+            *sys.argv[:1], 'build_ext', '--inplace',
+            *config_settings['--global-option']
+        ]
+        with no_install_setup_requires():
+            self.run_setup()
+        # TODO: this is super sketchy, it's worth a cleanup
+        provider = pkg_resources.PathMetadata(dist_info_path, dist_info_path)
+        dist = pkg_resources.DistInfoDistribution.from_filename(
+            dist_info_path, metadata=provider
+        )
+        wheel_name = f"{dist.project_name}-{dist.version}-ed.py3-none-any.whl"
+        wheel_path = os.path.join(wheel_directory, wheel_name)
+
+        with zipfile.ZipFile(
+            wheel_path, "a", compression=zipfile.ZIP_DEFLATED
+        ) as archive:
+            # TODO: don't hardcode this obviously *somehow*
+            data = "/home/ichard26/programming/oss/black/src"
+            archive.writestr(zipfile.ZipInfo(f'{dist.project_name}.pth'), data)
+
+            for file in sorted(os.listdir(dist_info_path)):
+                file = os.path.join(dist_info_path, file)
+                with open(file, "r", encoding="utf-8") as metadata:
+                    zip_filename = os.path.relpath(file, dist_info_directory)
+                    archive.writestr(
+                        zipfile.ZipInfo(zip_filename), metadata.read()
+                    )
+
+            archive.writestr(
+                zipfile.ZipInfo(os.path.join(dist_info, "WHEEL")),
+                textwrap.dedent(f"""\
+                    Wheel-Version: 1.0
+                    Generator: setuptools ({setuptools.__version__})
+                    Root-Is-Purelib: false
+                    Tag: ed.py3-none-any
+                """)
+            )
+            _add_wheel_record(archive, dist_info)
+
+        return os.path.basename(wheel_path)
+
 
 class _BuildMetaLegacyBackend(_BuildMetaBackend):
     """Compatibility backend for setuptools
@@ -281,9 +364,12 @@ 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
+prepare_metadata_for_build_editable = _BACKEND.prepare_metadata_for_build_wheel
 build_wheel = _BACKEND.build_wheel
 build_sdist = _BACKEND.build_sdist
+build_editable = _BACKEND.build_editable
 
 
 # The legacy backend