From 15b3d9d2773b6ff919b324d756e23f0f8bf9fc3f Mon Sep 17 00:00:00 2001
From: Jon <jonringer@users.noreply.github.com>
Date: Sat, 16 May 2020 00:34:11 -0700
Subject: [PATCH] python3Packages.venvShellHook: add postVenvCreation (#87850)

* python3Packages.venvShellHook: add postVenvCreation

* python: docs: add postVenvCreation explaination
---
 doc/languages-frameworks/python.section.md           | 12 ++++++++++--
 .../interpreters/python/hooks/venv-shell-hook.sh     |  6 ++++--
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/doc/languages-frameworks/python.section.md b/doc/languages-frameworks/python.section.md
index 35ea480e6b94..838426afa04f 100644
--- a/doc/languages-frameworks/python.section.md
+++ b/doc/languages-frameworks/python.section.md
@@ -1023,7 +1023,8 @@ are used in `buildPythonPackage`.
 - `setuptoolsBuildHook` to build a wheel using `setuptools`.
 - `setuptoolsCheckHook` to run tests with `python setup.py test`.
 - `venvShellHook` to source a Python 3 `venv` at the `venvDir` location. A
-  `venv` is created if it does not yet exist.
+  `venv` is created if it does not yet exist. `postVenvCreation` can be used to
+  to run commands only after venv is first created.
 - `wheelUnpackHook` to move a wheel to the correct folder so it can be installed
   with the `pipInstallHook`.
 
@@ -1291,10 +1292,17 @@ in pkgs.mkShell rec {
     zlib
   ];
 
+  # Run this command, only after creating the virtual environment
+  postVenvCreation = ''
+    unset SOURCE_DATE_EPOCH
+    pip install -r requirements.txt
+  '';
+
   # Now we can execute any commands within the virtual environment.
   # This is optional and can be left out to run pip manually.
   postShellHook = ''
-    pip install -r requirements.txt
+    # allow pip to install wheels
+    unset SOURCE_DATE_EPOCH
   '';
 
 }
diff --git a/pkgs/development/interpreters/python/hooks/venv-shell-hook.sh b/pkgs/development/interpreters/python/hooks/venv-shell-hook.sh
index 3185b1f9fae9..1fcc0bbd4b13 100644
--- a/pkgs/development/interpreters/python/hooks/venv-shell-hook.sh
+++ b/pkgs/development/interpreters/python/hooks/venv-shell-hook.sh
@@ -4,12 +4,14 @@ venvShellHook() {
 
     if [ -d "${venvDir}" ]; then
       echo "Skipping venv creation, '${venvDir}' already exists"
+      source "${venvDir}/bin/activate"
     else
       echo "Creating new venv environment in path: '${venvDir}'"
       @pythonInterpreter@ -m venv "${venvDir}"
-    fi
 
-    source "${venvDir}/bin/activate"
+      source "${venvDir}/bin/activate"
+      runHook postVenvCreation
+    fi
 
     runHook postShellHook
     echo "Finished executing venvShellHook"