buildPython*: store dist (wheel/sdist) in dist output

Store the intermediate artifacts. In time, we should build, install and
test in separate derivations as that reduces circular dependencies,
avoids rebuilds when fixing tests, and makes it possible to use the
wheels for creating say virtualenv's.

pkgs/development/interpreters/python/hooks/default.nix

@@ -115,6 +115,11 @@ in rec {
       };
     } ./python-namespaces-hook.sh) {};
 
+  pythonOutputDistHook = callPackage ({ }:
+    makeSetupHook {
+      name = "python-output-dist-hook";
+  } ./python-output-dist-hook.sh ) {};
+
   pythonRecompileBytecodeHook = callPackage ({ }:
     makeSetupHook {
       name = "python-recompile-bytecode-hook";

pkgs/development/interpreters/python/hooks/python-output-dist-hook.sh

@@ -0,0 +1,10 @@
+# Setup hook for storing dist folder (wheels/sdists) in a separate output
+echo "Sourcing python-catch-conflicts-hook.sh"
+
+pythonOutputDistPhase() {
+    echo "Executing pythonOutputDistPhase"
+    mv "dist" "$dist"
+    echo "Finished executing pythonOutputDistPhase"
+}
+
+preFixupPhases+=" pythonOutputDistPhase"

pkgs/development/interpreters/python/mk-python-derivation.nix

@@ -17,6 +17,7 @@
 , pythonCatchConflictsHook
 , pythonImportsCheckHook
 , pythonNamespacesHook
+, pythonOutputDistHook
 , pythonRemoveBinBytecodeHook
 , pythonRemoveTestsDirHook
 , setuptoolsBuildHook
@@ -49,6 +50,8 @@
 # Enabled to detect some (native)BuildInputs mistakes
 , strictDeps ? true
 
+, outputs ? [ "out" ]
+
 # used to disable derivation, useful for specific python versions
 , disabled ? false
 
@@ -106,11 +109,13 @@ else
 let
   inherit (python) stdenv;
 
+  withDistOutput = lib.elem format ["pyproject" "setuptools" "flit"];
+
   name_ = name;
 
   self = toPythonModule (stdenv.mkDerivation ((builtins.removeAttrs attrs [
     "disabled" "checkPhase" "checkInputs" "doCheck" "doInstallCheck" "dontWrapPythonPrograms" "catchConflicts" "format"
-    "disabledTestPaths"
+    "disabledTestPaths" "outputs"
   ]) // {
 
     name = namePrefix + name_;
@@ -144,6 +149,8 @@ let
     ] ++ lib.optionals (python.pythonAtLeast "3.3") [
       # Optionally enforce PEP420 for python3
       pythonNamespacesHook
+    ] ++ lib.optionals withDistOutput [
+      pythonOutputDistHook
     ] ++ nativeBuildInputs;
 
     buildInputs = buildInputs ++ pythonPath;
@@ -177,6 +184,8 @@ let
     # Python packages built through cross-compilation are always for the host platform.
     disallowedReferences = lib.optionals (python.stdenv.hostPlatform != python.stdenv.buildPlatform) [ python.pythonForBuild ];
 
+    outputs = outputs ++ lib.optional withDistOutput "dist";
+
     meta = {
       # default to python's platforms
       platforms = python.meta.platforms;

pkgs/top-level/python-packages.nix

@@ -119,6 +119,7 @@ in {
     pythonCatchConflictsHook
     pythonImportsCheckHook
     pythonNamespacesHook
+    pythonOutputDistHook
     pythonRecompileBytecodeHook
     pythonRelaxDepsHook
     pythonRemoveBinBytecodeHook