Writing custom kernels

The sources of the scala kernel have such an example demo kernel under this directory.

See the sources for its dependencies. Currently, these are only

the kernel module, "sh.almond" %% "kernel" % "0.13.2"
case-app, "com.github.alexarchambault" %% "case-app" % "2.0.0-M2"

Note that case-app can be replaced by the command-line parsing library of your choice.

The demo kernel mainly consists in EchoInterpreter, an implementation of almond.interpreter.Interpreter, and in EchoKernel, a small application that either installs the kernel, or actually runs it when it is launched by Jupyter.

When implementing a custom kernel, you may want to re-use almost as is EchoKernel, instantiating your own Interpreter instead of EchoInterpreter. You may optionally handle command-line arguments differently, or add extra command-line options to pass to your Interpreter implementation.

For the kernel installation to work out-of-the-box, the kernel should to be launched via coursier in one way or another. (It is possible nonetheless to rely on e.g. uber JARs, by tweaking the arg or command fields of InstallOptions). To test your kernel locally, publish it locally via a publishLocal from sbt. Note its organization, module name, and version. Then create a launcher for your kernel with

$ coursier bootstrap --embed-files=false \
    organization:module-name_2.1?:version \
    -o kernel

and install your kernel with

$ ./kernel --install

Your kernel should then be detected by Jupyter Notebook or nteract.