python3Packages.ipykernel: add missing deps and split off tests

The package now requires debugpy and the tests require ipyparallel.

The latter causes an infinite recursion, which is why I split out the
tests into `passthru.tests.pytest`. There is not dedicated tests output,
because the tests require relative imports.

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

@@ -1,15 +1,14 @@
 { lib
 , stdenv
 , buildPythonPackage
+, callPackage
 , fetchPypi
-, flaky
+, debugpy
 , ipython
 , jupyter_client
-, traitlets
 , tornado
+, traitlets
 , pythonOlder
-, pytestCheckHook
-, nose
 }:
 
 buildPythonPackage rec {
@@ -21,36 +20,20 @@ buildPythonPackage rec {
     sha256 = "4439459f171d77f35b7f7e72dace5d7c2dd10a5c9e2c22b173ad9048fbfe7656";
   };
 
-  propagatedBuildInputs = [ ipython jupyter_client traitlets tornado ];
+  propagatedBuildInputs = [
+    debugpy
+    ipython
+    jupyter_client
+    tornado
+    traitlets
+  ];
 
-  checkInputs = [ pytestCheckHook nose flaky ];
+  # check in passthru.tests.pytest to escape infinite recursion with ipyparallel
-  dontUseSetuptoolsCheck = true;
+  doCheck = false;
-  preCheck = ''
-    export HOME=$(mktemp -d)
-  '';
-  disabledTests = lib.optionals stdenv.isDarwin ([
-    # see https://github.com/NixOS/nixpkgs/issues/76197
-    "test_subprocess_print"
-    "test_subprocess_error"
-    "test_ipython_start_kernel_no_userns"
 
-    # https://github.com/ipython/ipykernel/issues/506
+  passthru.tests = {
-    "test_unc_paths"
+    pytest = callPackage ./tests.nix { };
-  ] ++ lib.optionals (pythonOlder "3.8") [
+  };
-    # flaky test https://github.com/ipython/ipykernel/issues/485
-    "test_shutdown"
-
-    # test regression https://github.com/ipython/ipykernel/issues/486
-    "test_sys_path_profile_dir"
-    "test_save_history"
-    "test_help_output"
-    "test_write_kernel_spec"
-    "test_ipython_start_kernel_userns"
-    "ZMQDisplayPublisherTests"
-  ]);
-
-  # Some of the tests use localhost networking.
-  __darwinAllowLocalNetworking = true;
 
   meta = {
     description = "IPython Kernel for Jupyter";

pkgs/development/python-modules/ipykernel/tests.nix

@@ -0,0 +1,57 @@
+{ lib
+, stdenv
+, buildPythonPackage
+, pythonOlder
+, flaky
+, ipykernel
+, ipyparallel
+, nose
+, pytestCheckHook
+
+}:
+
+buildPythonPackage rec {
+  pname = "ipykernel-tests";
+  inherit (ipykernel) version;
+
+  src = ipykernel.src;
+
+  dontBuild = true;
+  dontInstall = true;
+
+  checkInputs = [
+    flaky
+    ipykernel
+    ipyparallel
+    nose
+    pytestCheckHook
+  ];
+
+  preCheck = ''
+    export HOME=$(mktemp -d)
+  '';
+
+  disabledTests = lib.optionals stdenv.isDarwin ([
+    # see https://github.com/NixOS/nixpkgs/issues/76197
+    "test_subprocess_print"
+    "test_subprocess_error"
+    "test_ipython_start_kernel_no_userns"
+
+    # https://github.com/ipython/ipykernel/issues/506
+    "test_unc_paths"
+  ] ++ lib.optionals (pythonOlder "3.8") [
+    # flaky test https://github.com/ipython/ipykernel/issues/485
+    "test_shutdown"
+
+    # test regression https://github.com/ipython/ipykernel/issues/486
+    "test_sys_path_profile_dir"
+    "test_save_history"
+    "test_help_output"
+    "test_write_kernel_spec"
+    "test_ipython_start_kernel_userns"
+    "ZMQDisplayPublisherTests"
+  ]);
+
+  # Some of the tests use localhost networking.
+  __darwinAllowLocalNetworking = true;
+}