From eba1f794184f6bc08558a6506ed62eada008f37e Mon Sep 17 00:00:00 2001
From: Frederik Rietdijk <fridh@fridh.nl>
Date: Mon, 13 Jan 2020 21:45:24 +0100
Subject: pythonPackages.venvShellHook: init

This is a hook that loads a virtualenv from the specified `venvDir`
location. If the virtualenv does not exist, it is created.
---
 doc/languages-frameworks/python.section.md         |  1 +
 .../interpreters/python/hooks/default.nix          | 12 ++++++++++
 .../interpreters/python/hooks/venv-shell-hook.sh   | 26 ++++++++++++++++++++++
 pkgs/top-level/python-packages.nix                 |  2 +-
 4 files changed, 40 insertions(+), 1 deletion(-)
 create mode 100644 pkgs/development/interpreters/python/hooks/venv-shell-hook.sh

diff --git a/doc/languages-frameworks/python.section.md b/doc/languages-frameworks/python.section.md
index 199e678bc29..bbcf82f7ed6 100644
--- a/doc/languages-frameworks/python.section.md
+++ b/doc/languages-frameworks/python.section.md
@@ -833,6 +833,7 @@ used in `buildPythonPackage`.
 - `pythonRemoveBinBytecode` to remove bytecode from the `/bin` folder.
 - `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.
 - `wheelUnpackHook` to move a wheel to the correct folder so it can be installed with the `pipInstallHook`.
 
 ### Development mode
diff --git a/pkgs/development/interpreters/python/hooks/default.nix b/pkgs/development/interpreters/python/hooks/default.nix
index f05b3b1eec6..159637ae9d5 100644
--- a/pkgs/development/interpreters/python/hooks/default.nix
+++ b/pkgs/development/interpreters/python/hooks/default.nix
@@ -2,6 +2,9 @@
 { python
 , callPackage
 , makeSetupHook
+, disabledIf
+, isPy3k
+, ensureNewerSourcesForZipFilesHook
 }:
 
 let
@@ -109,6 +112,15 @@ in rec {
       };
     } ./setuptools-check-hook.sh) {};
 
+  venvShellHook = disabledIf (!isPy3k) (callPackage ({ }:
+    makeSetupHook {
+      name = "venv-shell-hook";
+      deps = [ ensureNewerSourcesForZipFilesHook ];
+      substitutions = {
+        inherit pythonInterpreter;
+    };
+  } ./venv-shell-hook.sh) {});
+
   wheelUnpackHook = callPackage ({ wheel }:
     makeSetupHook {
       name = "wheel-unpack-hook.sh";
diff --git a/pkgs/development/interpreters/python/hooks/venv-shell-hook.sh b/pkgs/development/interpreters/python/hooks/venv-shell-hook.sh
new file mode 100644
index 00000000000..3185b1f9fae
--- /dev/null
+++ b/pkgs/development/interpreters/python/hooks/venv-shell-hook.sh
@@ -0,0 +1,26 @@
+venvShellHook() {
+    echo "Executing venvHook"
+    runHook preShellHook
+
+    if [ -d "${venvDir}" ]; then
+      echo "Skipping venv creation, '${venvDir}' already exists"
+    else
+      echo "Creating new venv environment in path: '${venvDir}'"
+      @pythonInterpreter@ -m venv "${venvDir}"
+    fi
+
+    source "${venvDir}/bin/activate"
+
+    runHook postShellHook
+    echo "Finished executing venvShellHook"
+}
+
+if [ -z "${dontUseVenvShellHook:-}" ] && [ -z "${shellHook-}" ]; then
+    echo "Using venvShellHook"
+    if [ -z "${venvDir-}" ]; then
+        echo "Error: \`venvDir\` should be set when using \`venvShellHook\`."
+        exit 1
+    else
+        shellHook=venvShellHook
+    fi
+fi
diff --git a/pkgs/top-level/python-packages.nix b/pkgs/top-level/python-packages.nix
index 5b148263388..a3ba61e27d5 100644
--- a/pkgs/top-level/python-packages.nix
+++ b/pkgs/top-level/python-packages.nix
@@ -108,7 +108,7 @@ in {
   inherit buildSetupcfg;
 
   inherit (callPackage ../development/interpreters/python/hooks { })
-    eggUnpackHook eggBuildHook eggInstallHook flitBuildHook pipBuildHook pipInstallHook pytestCheckHook pythonCatchConflictsHook pythonImportsCheckHook pythonRemoveBinBytecodeHook setuptoolsBuildHook setuptoolsCheckHook wheelUnpackHook;
+    eggUnpackHook eggBuildHook eggInstallHook flitBuildHook pipBuildHook pipInstallHook pytestCheckHook pythonCatchConflictsHook pythonImportsCheckHook pythonRemoveBinBytecodeHook setuptoolsBuildHook setuptoolsCheckHook venvShellHook wheelUnpackHook;
 
   # helpers
 
-- 
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