pythonPackages.pip: make reproducible (#102222)

The previous attempt wasn't covering all of the bases. It relied on
invoking that pip-install-hook, and didn't apply to pip itself.

The core issue is that the generated .pyc files embed some of the
temporary paths, which are randomly generated. See
https://r13y.com/diff/bf8c3ca3148ebff9ecf41f294cc60b9f209c006d49699e356969ff32d736f1c6-8806a7cca91fdd300e48736bfcd57c4d0b54c1cc2fd61609f35143170862b59c.html

In this new attempt, the approach is to patch the TempFile
implementation directly, so that it creates stable temporary
directories. We also assume that if SOURCE_DATE_EPOCH is set, we are in
a scenario where reproducible builds are desirable and enter that
branch.

See also https://github.com/pypa/pip/issues/7808

pkgs/development/interpreters/python/hooks/pip-install-hook.sh

@@ -12,7 +12,7 @@ pipInstallPhase() {
 
     pushd dist || return 1
     mkdir tmpbuild
-    NIX_PIP_INSTALL_TMPDIR=tmpbuild @pythonInterpreter@ -m pip install ./*.whl --no-index --prefix="$out" --no-cache $pipInstallFlags
+    @pythonInterpreter@ -m pip install ./*.whl --no-index --prefix="$out" --no-cache $pipInstallFlags
     rm -rf tmpbuild
     popd || return 1
 

pkgs/development/python-modules/bootstrapped-pip/default.nix

@@ -23,6 +23,11 @@ stdenv.mkDerivation rec {
   ];
 
   postPatch = ''
+    # Apply the pip reproducible patch
+    pushd "${pip.src.name}"
+      patch -p1 < ${../pip/reproducible.patch}
+    popd
+
     mkdir -p $out/bin
   '';
 

pkgs/development/python-modules/pip/default.nix

@@ -26,7 +26,7 @@ buildPythonPackage rec {
   };
 
   # Remove when solved https://github.com/NixOS/nixpkgs/issues/81441
-  # Also update pkgs/development/interpreters/python/hooks/pip-install-hook.sh accordingly
+  # See also https://github.com/pypa/pip/issues/7808
   patches = [ ./reproducible.patch ];
 
   nativeBuildInputs = [ bootstrapped-pip ];

pkgs/development/python-modules/pip/reproducible.patch

@@ -1,13 +1,25 @@
-diff --git a/src/pip/_internal/operations/install/wheel.py b/src/pip/_internal/operations/install/wheel.py
+diff --git a/src/pip/_internal/utils/temp_dir.py b/src/pip/_internal/utils/temp_dir.py
-index e7315ee4..4e36b03d 100644
+index 201ba6d98..f1569fecd 100644
---- a/src/pip/_internal/operations/install/wheel.py
+--- a/src/pip/_internal/utils/temp_dir.py
-+++ b/src/pip/_internal/operations/install/wheel.py
++++ b/src/pip/_internal/utils/temp_dir.py
-@@ -615,6 +615,8 @@ def install_wheel(
+@@ -3,6 +3,7 @@ from __future__ import absolute_import
-     direct_url=None,  # type: Optional[DirectUrl]
+ import errno
- ):
+ import itertools
-     # type: (...) -> None
+ import logging
-+    _temp_dir_for_testing = (
++import os
-+        _temp_dir_for_testing or os.environ.get("NIX_PIP_INSTALL_TMPDIR"))
+ import os.path
-     with TempDirectory(
+ import tempfile
-         path=_temp_dir_for_testing, kind="unpacked-wheel"
+ from contextlib import contextmanager
-     ) as unpacked_dir, ZipFile(wheel_path, allowZip64=True) as z:
+@@ -181,6 +182,11 @@ class TempDirectory(object):
+         # symlinked to another directory.  This tends to confuse build
+         # scripts, so we canonicalize the path by traversing potential
+         # symlinks here.
++        if "SOURCE_DATE_EPOCH" in os.environ:
++            path = os.path.join(tempfile.gettempdir(), "pip-{}-immobile".format(kind))
++            os.mkdir(path)
++            return path
++
+         path = os.path.realpath(
+             tempfile.mkdtemp(prefix="pip-{}-".format(kind))
+         )
+