sageWithDoc: make jupyter-sphinx available for docbuild

pkgs/applications/science/math/sage/default.nix

···
     logo64 = "${sage-src}/src/doc/common/themes/sage/static/sageicon.png";
   };
 
+  jupyter-kernel-specs = pkgs.jupyter-kernel.create {
+    definitions = pkgs.jupyter-kernel.default // {
+      sagemath = jupyter-kernel-definition;
+    };
+  };
+
   three = callPackage ./threejs-sage.nix { };
 
   # A bash script setting various environment variables to tell sage where
···
   # The documentation for sage, building it takes a lot of ram.
   sagedoc = callPackage ./sagedoc.nix {
     inherit sage-with-env;
-    inherit python3 maxima;
+    inherit python3 maxima jupyter-kernel-specs;
   };
 
   # sagelib with added wrappers and a dependency on sage-tests to make sure thet tests were run.
···
 in
 # A wrapper around sage that makes sure sage finds its docs (if they were build).
 callPackage ./sage.nix {
-  inherit sage-tests sage-with-env sagedoc jupyter-kernel-definition;
+  inherit sage-tests sage-with-env sagedoc jupyter-kernel-specs;
   inherit withDoc requireSageTests;
 }

pkgs/applications/science/math/sage/python-modules/sage-docbuild.nix

···
 , buildPythonPackage
 , sage-src
 , sphinx
+, jupyter-sphinx
 }:
 
 buildPythonPackage rec {
···
 
   propagatedBuildInputs = [
     sphinx
+    jupyter-sphinx
   ];
 
   preBuild = ''

pkgs/applications/science/math/sage/sage.nix

···
 , makeWrapper
 , sage-tests
 , sage-with-env
-, jupyter-kernel-definition
-, jupyter-kernel
+, jupyter-kernel-specs
 , sagedoc
 , withDoc
 , requireSageTests
···
 # A wrapper that makes sure sage finds its docs (if they were build) and the
 # jupyter kernel spec.
 
-let
-  # generate kernel spec + default kernels
-  kernel-specs = jupyter-kernel.create {
-    definitions = jupyter-kernel.default // {
-      sagemath = jupyter-kernel-definition;
-    };
-  };
-in
 stdenv.mkDerivation rec {
   version = src.version;
   pname = "sage";
···
       --set SAGE_DOC_SRC_OVERRIDE "${src}/src/doc" ${
         lib.optionalString withDoc "--set SAGE_DOC_OVERRIDE ${sagedoc}/share/doc/sage"
       } \
-      --prefix JUPYTER_PATH : "${kernel-specs}"
+      --prefix JUPYTER_PATH : "${jupyter-kernel-specs}"
   '';
 
   doInstallCheck = withDoc;
···
     quicktest = sage-tests.override { longTests = false; timeLimit = 600; }; # as many tests as possible in ~10m
     doc = sagedoc;
     lib = sage-with-env.env.lib;
-    kernelspec = jupyter-kernel-definition;
+    kernelspec = jupyter-kernel-specs.definition.sagemath;
   };
 
   meta = with lib; {

pkgs/applications/science/math/sage/sagedoc.nix

···
 { stdenv
 , sage-with-env
 , python3
+, jupyter-kernel-specs
 , maxima
 , tachyon
 , jmol
···
     OUTPUT="$OUTPUT_DIR/options.txt"
     ${sage-with-env}/bin/sage -advanced > "$OUTPUT"
 
-    ${sage-with-env}/bin/sage --docbuild \
+    # jupyter-sphinx calls the sagemath jupyter kernel during docbuild
+    export JUPYTER_PATH=${jupyter-kernel-specs}
+
+    # sage --docbuild unsets JUPYTER_PATH, so we call sage_docbuild directly
+    # https://trac.sagemath.org/ticket/33650#comment:32
+    ${sage-with-env}/bin/sage --python3 -m sage_docbuild \
       --mathjax \
       --no-pdf-links \
-      all html
+      all html < /dev/null
   '';
 
   installPhase = ''