Python: separate buildPythonPackage into two functions

1. mkDerivation which is used when the source is without setup.py and
not a wheel
2. buildPythonPackage which is used as before and calls mkDerivation

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

@@ -0,0 +1,87 @@
+/* Generic builder for Python packages that come without a setup.py. */
+
+{ lib
+, python
+, wrapPython
+, setuptools
+, unzip
+, ensureNewerSourcesHook
+}:
+
+{ name
+
+# by default prefix `name` e.g. "python3.3-${name}"
+, namePrefix ? python.libPrefix + "-"
+
+, buildInputs ? []
+
+# propagate build dependencies so in case we have A -> B -> C,
+# C can import package A propagated by B
+, propagatedBuildInputs ? []
+
+# DEPRECATED: use propagatedBuildInputs
+, pythonPath ? []
+
+# used to disable derivation, useful for specific python versions
+, disabled ? false
+
+# Raise an error if two packages are installed with the same name
+, catchConflicts ? true
+
+# Additional arguments to pass to the makeWrapper function, which wraps
+# generated binaries.
+, makeWrapperArgs ? []
+
+, meta ? {}
+
+, passthru ? {}
+
+, ... } @ attrs:
+
+
+# Keep extra attributes from `attrs`, e.g., `patchPhase', etc.
+if disabled
+then throw "${name} not supported for interpreter ${python.executable}"
+else
+
+python.stdenv.mkDerivation (builtins.removeAttrs attrs ["disabled"] // {
+
+  name = namePrefix + name;
+
+  inherit pythonPath;
+
+  buildInputs = [ wrapPython ] ++ buildInputs ++ pythonPath
+    ++ [ (ensureNewerSourcesHook { year = "1980"; }) ]
+    ++ (lib.optional (lib.hasSuffix "zip" attrs.src.name or "") unzip);
+
+  # propagate python/setuptools to active setup-hook in nix-shell
+  propagatedBuildInputs = propagatedBuildInputs ++ [ python setuptools ];
+
+  # Python packages don't have a checkPhase, only an installCheckPhase
+  doCheck = false;
+  doInstallCheck = attrs.doCheck or false;
+
+  postFixup = attrs.postFixup or ''
+    wrapPythonPrograms
+  '' + lib.optionalString catchConflicts ''
+    # check if we have two packages with the same name in closure and fail
+    # this shouldn't happen, something went wrong with dependencies specs
+    ${python.interpreter} ${./catch_conflicts.py}
+  '';
+
+  passthru = {
+    inherit python; # The python interpreter
+  } // passthru;
+
+  meta = with lib.maintainers; {
+    # default to python's platforms
+    platforms = python.meta.platforms;
+  } // meta // {
+    # add extra maintainer(s) to every package
+    maintainers = (meta.maintainers or []) ++ [ chaoflow domenkozar ];
+    # a marker for release utilities to discover python packages
+    isBuildPythonPackage = python.meta.platforms;
+  };
+})
+
+