Phase 2 - generate metadata using PEP 517 hook

src/pip/_internal/commands/install.py

@@ -336,6 +336,24 @@ def run(self, options, args):
                             session=session, autobuilding=True
                         )
 
+                    # If we're using PEP 517, we cannot do a direct install
+                    # so we fail here.
+                    # TODO: Technically, if it's a setuptools-based project
+                    # we could fall back to setup.py install even if we've
+                    # been assuming PEP 517 to this point, but that would be
+                    # complicated to achieve, as none of the legacy setup has
+                    # been done. Better to get the user to specify
+                    # --no-use-pep517.
+                    failed_builds = [
+                        r for r in requirement_set.requirements.values()
+                        if r.use_pep517 and not r.is_wheel
+                    ]
+
+                    if failed_builds:
+                        raise InstallationError(
+                            "Could not build wheels for {}".format(
+                                failed_builds))
+
                     to_install = resolver.get_installation_order(
                         requirement_set
                     )

src/pip/_internal/operations/prepare.py

@@ -132,7 +132,7 @@ def _raise_conflicts(conflicting_with, conflicting_reqs):
                     " and ".join(map(repr, sorted(missing)))
                 )
 
-        self.req.run_egg_info()
+        self.req.prepare_metadata()
         self.req.assert_source_matches_version()
 
 

src/pip/_internal/req/req_install.py

@@ -107,6 +107,12 @@ def __init__(self, req, comes_from, source_dir=None, editable=False,
         self.isolated = isolated
         self.build_env = NoOpBuildEnvironment()
 
+        # For PEP 517, the directory where we request the project metadata
+        # gets stored. We need this to pass to build_wheel, so the backend
+        # can ensure that the wheel matches the metadata (see the PEP for
+        # details).
+        self.metadata_directory = None
+
         # The static build requirements (from pyproject.toml)
         self.pyproject_requires = None
 
@@ -311,6 +317,14 @@ def _correct_build_location(self):
         self.source_dir = os.path.normpath(os.path.abspath(new_location))
         self._egg_info_path = None
 
+        # Correct the metadata directory, if it exists
+        if self.metadata_directory:
+            old_meta = self.metadata_directory
+            rel = os.path.relpath(old_meta, start=old_location)
+            new_meta = os.path.join(new_location, rel)
+            new_meta = os.path.normpath(os.path.abspath(new_meta))
+            self.metadata_directory = new_meta
+
     def remove_temporary_source(self):
         """Remove the source files from this requirement, if they are marked
         for deletion"""
@@ -437,7 +451,12 @@ def load_pyproject_toml(self):
             self.pyproject_requires = requires
             self.pep517_backend = Pep517HookCaller(self.setup_py_dir, backend)
 
-    def run_egg_info(self):
+    def prepare_metadata(self):
+        """Ensure that project metadata is available.
+
+        Under PEP 517, call the backend hook to prepare the metadata.
+        Under legacy processing, call setup.py egg-info.
+        """
         assert self.source_dir
         if self.name:
             logger.debug(
@@ -451,26 +470,10 @@ def run_egg_info(self):
             )
 
         with indent_log():
-            script = SETUPTOOLS_SHIM % self.setup_py
-            base_cmd = [sys.executable, '-c', script]
-            if self.isolated:
-                base_cmd += ["--no-user-cfg"]
-            egg_info_cmd = base_cmd + ['egg_info']
-            # We can't put the .egg-info files at the root, because then the
-            # source code will be mistaken for an installed egg, causing
-            # problems
-            if self.editable:
-                egg_base_option = []
+            if self.use_pep517:
+                self.prepare_pep517_metadata()
             else:
-                egg_info_dir = os.path.join(self.setup_py_dir, 'pip-egg-info')
-                ensure_dir(egg_info_dir)
-                egg_base_option = ['--egg-base', 'pip-egg-info']
-            with self.build_env:
-                call_subprocess(
-                    egg_info_cmd + egg_base_option,
-                    cwd=self.setup_py_dir,
-                    show_stdout=False,
-                    command_desc='python setup.py egg_info')
+                self.run_egg_info()
 
         if not self.req:
             if isinstance(parse_version(self.metadata["Version"]), Version):
@@ -489,13 +492,56 @@ def run_egg_info(self):
             metadata_name = canonicalize_name(self.metadata["Name"])
             if canonicalize_name(self.req.name) != metadata_name:
                 logger.warning(
-                    'Running setup.py (path:%s) egg_info for package %s '
+                    'Generating metadata for package %s '
                     'produced metadata for project name %s. Fix your '
                     '#egg=%s fragments.',
-                    self.setup_py, self.name, metadata_name, self.name
+                    self.name, metadata_name, self.name
                 )
                 self.req = Requirement(metadata_name)
 
+    def prepare_pep517_metadata(self):
+        assert self.pep517_backend is not None
+
+        metadata_dir = os.path.join(
+            self.setup_py_dir,
+            'pip-wheel-metadata'
+        )
+        ensure_dir(metadata_dir)
+
+        with self.build_env:
+            # Note that Pep517HookCaller implements a fallback for
+            # prepare_metadata_for_build_wheel, so we don't have to
+            # consider the possibility that this hook doesn't exist.
+            backend = self.pep517_backend
+            distinfo_dir = backend.prepare_metadata_for_build_wheel(
+                metadata_dir
+            )
+
+        self.metadata_directory = os.path.join(metadata_dir, distinfo_dir)
+
+    def run_egg_info(self):
+        script = SETUPTOOLS_SHIM % self.setup_py
+        base_cmd = [sys.executable, '-c', script]
+        if self.isolated:
+            base_cmd += ["--no-user-cfg"]
+        egg_info_cmd = base_cmd + ['egg_info']
+        # We can't put the .egg-info files at the root, because then the
+        # source code will be mistaken for an installed egg, causing
+        # problems
+        if self.editable:
+            egg_base_option = []
+        else:
+            egg_info_dir = os.path.join(self.setup_py_dir, 'pip-egg-info')
+            ensure_dir(egg_info_dir)
+            egg_base_option = ['--egg-base', 'pip-egg-info']
+        with self.build_env:
+            call_subprocess(
+                egg_info_cmd + egg_base_option,
+                cwd=self.setup_py_dir,
+                show_stdout=False,
+                command_desc='python setup.py egg_info')
+
+
     @property
     def egg_info_path(self):
         if self._egg_info_path is None:
@@ -556,13 +602,23 @@ def metadata(self):
         return self._metadata
 
     def get_dist(self):
-        """Return a pkg_resources.Distribution built from self.egg_info_path"""
-        egg_info = self.egg_info_path.rstrip(os.path.sep)
-        base_dir = os.path.dirname(egg_info)
-        metadata = pkg_resources.PathMetadata(base_dir, egg_info)
-        dist_name = os.path.splitext(os.path.basename(egg_info))[0]
-        return pkg_resources.Distribution(
-            os.path.dirname(egg_info),
+        """Return a pkg_resources.Distribution for this requirement"""
+        if self.metadata_directory:
+            base_dir, distinfo = os.path.split(self.metadata_directory)
+            metadata = pkg_resources.PathMetadata(
+                base_dir, self.metadata_directory
+            )
+            dist_name = os.path.splitext(distinfo)[0]
+            typ = pkg_resources.DistInfoDistribution
+        else:
+            egg_info = self.egg_info_path.rstrip(os.path.sep)
+            base_dir = os.path.dirname(egg_info)
+            metadata = pkg_resources.PathMetadata(base_dir, egg_info)
+            dist_name = os.path.splitext(os.path.basename(egg_info))[0]
+            typ = pkg_resources.Distribution
+
+        return typ(
+            base_dir,
             project_name=dist_name,
             metadata=metadata,
         )
@@ -693,6 +749,7 @@ def _clean_zip_name(self, name, prefix):  # only used by archive.
 
     # TODO: Investigate if this should be kept in InstallRequirement
     #       Seems to be used only when VCS + downloads
+    # TODO: Consider PEP 517 implications
     def archive(self, build_dir):
         assert self.source_dir
         create_archive = True

src/pip/_internal/wheel.py

@@ -702,7 +702,7 @@ def _build_one_pep517(self, req, tempd, python_tag=None):
         spin_message = 'Running PEP 517 build_wheel for %s' % (req.name,)
         with open_spinner(spin_message) as spinner:
             logger.debug('Destination directory: %s', tempd)
-            # assert req.metadata_directory is not None
+            assert req.metadata_directory is not None
             try:
                 def runner(cmd, cwd=None, extra_environ=None):
                     call_subprocess(
@@ -715,8 +715,7 @@ def runner(cmd, cwd=None, extra_environ=None):
                 with req.pep517_backend.subprocess_runner(runner):
                     req.pep517_backend.build_wheel(
                         tempd,
-                        # metadata_directory=req.metadata_directory
-                        metadata_directory=None
+                        metadata_directory=req.metadata_directory
                     )
                 return True
             except Exception:

tests/unit/test_req.py

@@ -630,7 +630,7 @@ def test_mismatched_versions(caplog, tmpdir):
     shutil.copytree(original_source, source_dir)
     req = InstallRequirement(req=Requirement('simplewheel==2.0'),
                              comes_from=None, source_dir=source_dir)
-    req.run_egg_info()
+    req.prepare_metadata()
     req.assert_source_matches_version()
     assert caplog.records[-1].message == (
         'Requested simplewheel==2.0, '