build in place

docs/html/reference/pip_install.rst

@@ -728,8 +728,13 @@ You can install local projects by specifying the project path to pip::
 
 $ pip install path/to/SomeProject
 
-During regular installation, pip will copy the entire project directory to a temporary location and install from there.
-The exception is that pip will exclude .tox and .nox directories present in the top level of the project from being copied.
+Until version 20.0, pip did copy the entire project directory to a temporary
+location and installed from there. This approach was the cause of several
+performance and correctness issues. As of version 20.1 pip installs from the
+local project directory. Depending on the build backend used by the project,
+this may generate secondary build artifacts in the project directory, such as
+the ``.egg-info`` and ``build`` directories in the case of the setuptools
+backend.
 
 
 .. _`editable-installs`:

news/7555.removal

@@ -0,0 +1,9 @@
+Building of local directories is now done in place. Previously pip did copy the
+local directory tree to a temporary location before building. That approach had
+a number of drawbacks, among which performance issues, as well as various
+issues arising when the python project directory depends on its parent
+directory (such as the presence of a VCS directory). The user visible effect of
+this change is that secondary build artifacts, if any, may therefore be created
+in the local directory, whereas before they were created in a temporary copy of
+the directory and then deleted. This notably includes the ``build`` and
+``.egg-info`` directories in the case of the setuptools build backend.

src/pip/_internal/operations/prepare.py

@@ -27,12 +27,7 @@
 from pip._internal.utils.filesystem import copy2_fixed
 from pip._internal.utils.hashes import MissingHashes
 from pip._internal.utils.logging import indent_log
-from pip._internal.utils.misc import (
-    display_path,
-    hide_url,
-    path_to_display,
-    rmtree,
-)
+from pip._internal.utils.misc import display_path, hide_url, path_to_display
 from pip._internal.utils.temp_dir import TempDirectory
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 from pip._internal.utils.unpacking import unpack_file
@@ -239,11 +234,9 @@ def unpack_url(
         unpack_vcs_link(link, location)
         return None
 
-    # If it's a url to a local directory
+    # If it's a url to a local directory, we build in-place.
+    # There is nothing to be done here.
     if link.is_existing_dir():
-        if os.path.isdir(location):
-            rmtree(location)
-        _copy_source_tree(link.file_path, location)
         return None
 
     # file urls
@@ -415,21 +408,25 @@ def prepare_linked_requirement(
         with indent_log():
             # Since source_dir is only set for editable requirements.
             assert req.source_dir is None
-            req.ensure_has_source_dir(self.build_dir, autodelete_unpacked)
-            # If a checkout exists, it's unwise to keep going.  version
-            # inconsistencies are logged later, but do not fail the
-            # installation.
-            # FIXME: this won't upgrade when there's an existing
-            # package unpacked in `req.source_dir`
-            if os.path.exists(os.path.join(req.source_dir, 'setup.py')):
-                raise PreviousBuildDirError(
-                    "pip can't proceed with requirements '{}' due to a"
-                    " pre-existing build directory ({}). This is "
-                    "likely due to a previous installation that failed"
-                    ". pip is being responsible and not assuming it "
-                    "can delete this. Please delete it and try again."
-                    .format(req, req.source_dir)
-                )
+            if link.is_existing_dir():
+                # Build local directories in place.
+                req.source_dir = link.file_path
+            else:
+                req.ensure_has_source_dir(self.build_dir, autodelete_unpacked)
+                # If a checkout exists, it's unwise to keep going.  version
+                # inconsistencies are logged later, but do not fail the
+                # installation.
+                # FIXME: this won't upgrade when there's an existing
+                # package unpacked in `req.source_dir`
+                if os.path.exists(os.path.join(req.source_dir, 'setup.py')):
+                    raise PreviousBuildDirError(
+                        "pip can't proceed with requirements '{}' due to a"
+                        " pre-existing build directory ({}). This is "
+                        "likely due to a previous installation that failed"
+                        ". pip is being responsible and not assuming it "
+                        "can delete this. Please delete it and try again."
+                        .format(req, req.source_dir)
+                    )
 
             # Now that we have the real link, we can tell what kind of
             # requirements we have and raise some more informative errors

tests/unit/test_operations_prepare.py

@@ -214,40 +214,5 @@ def test_unpack_url_thats_a_dir(self, tmpdir, data):
         unpack_url(dist_url, self.build_dir,
                    downloader=self.no_downloader,
                    download_dir=self.download_dir)
-        assert os.path.isdir(os.path.join(self.build_dir, 'fspkg'))
-
-
-@pytest.mark.parametrize('exclude_dir', [
-    '.nox',
-    '.tox'
-])
-def test_unpack_url_excludes_expected_dirs(tmpdir, exclude_dir):
-    src_dir = tmpdir / 'src'
-    dst_dir = tmpdir / 'dst'
-    src_included_file = src_dir.joinpath('file.txt')
-    src_excluded_dir = src_dir.joinpath(exclude_dir)
-    src_excluded_file = src_dir.joinpath(exclude_dir, 'file.txt')
-    src_included_dir = src_dir.joinpath('subdir', exclude_dir)
-
-    # set up source directory
-    src_excluded_dir.mkdir(parents=True)
-    src_included_dir.mkdir(parents=True)
-    src_included_file.touch()
-    src_excluded_file.touch()
-
-    dst_included_file = dst_dir.joinpath('file.txt')
-    dst_excluded_dir = dst_dir.joinpath(exclude_dir)
-    dst_excluded_file = dst_dir.joinpath(exclude_dir, 'file.txt')
-    dst_included_dir = dst_dir.joinpath('subdir', exclude_dir)
-
-    src_link = Link(path_to_url(src_dir))
-    unpack_url(
-        src_link,
-        dst_dir,
-        Mock(side_effect=AssertionError),
-        download_dir=None
-    )
-    assert not os.path.isdir(dst_excluded_dir)
-    assert not os.path.isfile(dst_excluded_file)
-    assert os.path.isfile(dst_included_file)
-    assert os.path.isdir(dst_included_dir)
+        # test that nothing was copied to build_dir since we build in place
+        assert not os.path.exists(os.path.join(self.build_dir, 'fspkg'))