Install build requirements before calling setup.py

.gitignore

@@ -36,3 +36,4 @@ coverage.xml
 
 # Scratch Pad for experiments
 .scratch/
+.vscode

news/4799.bugfix

@@ -0,0 +1 @@
+Fix situation where build requirements are installed before calling setup.py.

src/pip/_internal/build_env.py

@@ -62,3 +62,17 @@ def __exit__(self, exc_type, exc_val, exc_tb):
             os.environ.pop('PYTHONPATH', None)
         else:
             os.environ['PYTHONPATH'] = self.save_pythonpath
+
+    def cleanup(self):
+        self._temp_dir.cleanup()
+
+
+class NoOpBuildEnvironment(BuildEnvironment):
+    def __enter__(self):
+        pass
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        pass
+
+    def cleanup(self):
+        pass

src/pip/_internal/operations/prepare.py

@@ -1,11 +1,15 @@
 """Prepares a distribution for installation
 """
 
+import itertools
 import logging
 import os
+import sys
+from copy import copy
 
 from pip._vendor import pkg_resources, requests
 
+from pip._internal.build_env import NoOpBuildEnvironment
 from pip._internal.compat import expanduser
 from pip._internal.download import (
     is_dir_url, is_file_url, is_vcs_url, unpack_url, url_to_path,
@@ -14,9 +18,14 @@
     DirectoryUrlHashUnsupported, HashUnpinned, InstallationError,
     PreviousBuildDirError, VcsHashUnsupported,
 )
+from pip._internal.index import FormatControl
+from pip._internal.req.req_install import InstallRequirement
 from pip._internal.utils.hashes import MissingHashes
 from pip._internal.utils.logging import indent_log
-from pip._internal.utils.misc import display_path, normalize_path
+from pip._internal.utils.misc import (
+    call_subprocess, display_path, normalize_path,
+)
+from pip._internal.utils.ui import open_spinner
 from pip._internal.vcs import vcs
 
 logger = logging.getLogger(__name__)
@@ -38,6 +47,23 @@ def make_abstract_dist(req):
         return IsSDist(req)
 
 
+def _install_build_reqs(finder, prefix, build_requirements):
+    finder = copy(finder)
+    finder.format_control = FormatControl(set(), set([":all:"]))
+    urls = [
+        finder.find_requirement(
+            InstallRequirement.from_line(r), upgrade=False).url
+        for r in build_requirements
+    ]
+    args = [
+        sys.executable, '-m', 'pip', 'install', '--ignore-installed',
+        '--prefix', prefix
+    ] + list(urls)
+
+    with open_spinner("Installing build dependencies") as spinner:
+        call_subprocess(args, show_stdout=False, spinner=spinner)
+
+
 class DistAbstraction(object):
     """Abstracts out the wheel vs non-wheel Resolver.resolve() logic.
 
@@ -64,7 +90,7 @@ def dist(self, finder):
         """Return a setuptools Dist object."""
         raise NotImplementedError(self.dist)
 
-    def prep_for_dist(self):
+    def prep_for_dist(self, finder):
         """Ensure that we can get a Dist for this requirement."""
         raise NotImplementedError(self.dist)
 
@@ -75,7 +101,7 @@ def dist(self, finder):
         return list(pkg_resources.find_distributions(
             self.req.source_dir))[0]
 
-    def prep_for_dist(self):
+    def prep_for_dist(self, finder):
         # FIXME:https://github.com/pypa/pip/issues/1112
         pass
 
@@ -91,17 +117,35 @@ def dist(self, finder):
             )
         return dist
 
-    def prep_for_dist(self):
-        self.req.run_egg_info()
-        self.req.assert_source_matches_version()
+    def prep_for_dist(self, finder):
+        # Before calling "setup.py egg_info", we need to set-up the build
+        # environment.
+
+        build_requirements, isolate = self.req.get_pep_518_info()
+
+        if 'setuptools' not in build_requirements:
+            logger.warning(
+                "This version of pip does not implement PEP 516, so "
+                "it cannot build a wheel without setuptools. You may need to "
+                "upgrade to a newer version of pip.")
+
+        if not isolate:
+            self.req.build_env = NoOpBuildEnvironment(no_clean=False)
+
+        with self.req.build_env as prefix:
+            if isolate:
+                _install_build_reqs(finder, prefix, build_requirements)
+
+            self.req.run_egg_info()
+            self.req.assert_source_matches_version()
 
 
 class Installed(DistAbstraction):
 
     def dist(self, finder):
         return self.req.satisfied_by
 
-    def prep_for_dist(self):
+    def prep_for_dist(self, finder):
         pass
 
 
@@ -259,14 +303,14 @@ def prepare_linked_requirement(self, req, session, finder,
                     (req, exc, req.link)
                 )
             abstract_dist = make_abstract_dist(req)
-            abstract_dist.prep_for_dist()
+            abstract_dist.prep_for_dist(finder)
             if self._download_should_save:
                 # Make a .zip of the source_dir we already created.
                 if req.link.scheme in vcs.all_schemes:
                     req.archive(self.download_dir)
         return abstract_dist
 
-    def prepare_editable_requirement(self, req, require_hashes):
+    def prepare_editable_requirement(self, req, require_hashes, finder):
         """Prepare an editable requirement
         """
         assert req.editable, "cannot prepare a non-editable req as editable"
@@ -284,7 +328,7 @@ def prepare_editable_requirement(self, req, require_hashes):
             req.update_editable(not self._download_should_save)
 
             abstract_dist = make_abstract_dist(req)
-            abstract_dist.prep_for_dist()
+            abstract_dist.prep_for_dist(finder)
 
             if self._download_should_save:
                 req.archive(self.download_dir)

src/pip/_internal/req/req_install.py

@@ -22,6 +22,7 @@
 from pip._vendor.pkg_resources import RequirementParseError, parse_requirements
 
 from pip._internal import wheel
+from pip._internal.build_env import BuildEnvironment
 from pip._internal.compat import native_str
 from pip._internal.download import (
     is_archive_file, is_url, path_to_url, url_to_path,
@@ -128,6 +129,7 @@ def __init__(self, req, comes_from, source_dir=None, editable=False,
         self.prepared = False
 
         self.isolated = isolated
+        self.build_env = BuildEnvironment(no_clean=True)
 
     @classmethod
     def from_editable(cls, editable_req, comes_from=None, isolated=False,
@@ -880,6 +882,7 @@ def remove_temporary_source(self):
             rmtree(self.source_dir)
         self.source_dir = None
         self._temp_build_dir.cleanup()
+        self.build_env.cleanup()
 
     def install_editable(self, install_options,
                          global_options=(), prefix=None):

src/pip/_internal/resolve.py

@@ -187,7 +187,9 @@ def _get_abstract_dist_for(self, req):
 
         if req.editable:
             return self.preparer.prepare_editable_requirement(
-                req, self.require_hashes
+                req,
+                self.require_hashes,
+                self.finder,
             )
 
         # satisfied_by is only evaluated by calling _check_skip_installed,
@@ -246,11 +248,12 @@ def _resolve_one(self, requirement_set, req_to_install):
             return []
 
         req_to_install.prepared = True
-        abstract_dist = self._get_abstract_dist_for(req_to_install)
 
         # register tmp src for cleanup in case something goes wrong
         requirement_set.reqs_to_cleanup.append(req_to_install)
 
+        abstract_dist = self._get_abstract_dist_for(req_to_install)
+
         # Parse and return dependencies
         dist = abstract_dist.dist(self.finder)
         try:

src/pip/_internal/wheel.py

@@ -617,37 +617,13 @@ def __init__(self, finder, preparer, wheel_cache,
         self.global_options = global_options or []
         self.no_clean = no_clean
 
-    def _install_build_reqs(self, reqs, prefix):
-        # Local import to avoid circular import (wheel <-> req_install)
-        from pip._internal.req.req_install import InstallRequirement
-        from pip._internal.index import FormatControl
-        # Ignore the --no-binary option when installing the build system, so
-        # we don't recurse trying to build a self-hosting build system.
-        finder = copy.copy(self.finder)
-        finder.format_control = FormatControl(set(), set([":all:"]))
-        urls = [finder.find_requirement(InstallRequirement.from_line(r),
-                                        upgrade=False).url
-                for r in reqs]
-
-        args = [sys.executable, '-m', 'pip', 'install', '--ignore-installed',
-                '--prefix', prefix] + list(urls)
-        with open_spinner("Installing build dependencies") as spinner:
-            call_subprocess(args, show_stdout=False, spinner=spinner)
-
     def _build_one(self, req, output_dir, python_tag=None):
         """Build one wheel.
 
         :return: The filename of the built wheel, or None if the build failed.
         """
-        build_reqs, isolate = req.get_pep_518_info()
-        if 'setuptools' not in build_reqs:
-            logger.warning(
-                "This version of pip does not implement PEP 516, so "
-                "it cannot build a wheel without setuptools. You may need to "
-                "upgrade to a newer version of pip.")
         # Install build deps into temporary directory (PEP 518)
-        with BuildEnvironment(self.no_clean) as prefix:
-            self._install_build_reqs(build_reqs, prefix)
+        with req.build_env:
             return self._build_one_inside_env(req, output_dir,
                                               python_tag=python_tag,
                                               isolate=True)

tests/data/src/pep518-3.0/setup.py

@@ -1,6 +1,8 @@
 #!/usr/bin/env python
 from setuptools import find_packages, setup
 
+import simple  # Test gh-4647 regression
+
 setup(name='pep518',
       version='3.0',
       packages=find_packages()