Jupyter extension for Jupytext

An extension for Jupyter would make the configuration of paired notebooks easier. Rather than asking to edit the jupytext_formats metadata, we should offer the user an interface where the user can select the desired notebook extensions (among ipynb, py, jl, R, md, Rmd; the order matters), and the format for each extension (default, light, percent, sphinx…).

The documentation on how to distribute a notebook extension is here. Extensions have to be written in Javascript, which I have almost never practiced before - help is welcome!

Useful references are:

• 4 ways to extend jupyter notebook by @parente
• the gist extension by @minrk

[fwouts]

@mwouts Sorry for the delay! It looks like JSONValue is a custom type defined by @phosphor/coreutils here: https://github.com/phosphorjs/phosphor/blob/cdb412e9dfb9a987b99143e4be79d477e5136832/packages/coreutils/src/json.ts#L21

What this is saying is basically: “this could be anything” (it’s effectively untyped). In this specific case, I think the jupytext field is likely to be an object with a specific structure (including the formats field you expect).

You could do the following:

// Using an unsafe cast (tell TypeScript you know what type this is).
const jupytextConfig = notebook_tracker.currentWidget.context.model.metadata.get("jupytext") as JupytextConfig;

interface JupytextConfig {
  formats: string[];
}

Or if you want to catch any unexpected values, a more verbose approach:

const jupytextConfig = notebook_tracker.currentWidget.context.model.metadata.get("jupytext");
if (jupytextConfig === null || typeof jupytextConfig !== "object") {
  throw new Error("Invalid Jupytext config");
}
if (!("formats" in jupytextConfig)) {
  throw new Error("Invalid Jupytext config (no formats field)");
}
const formats = jupytextConfig["formats"]
if (!(formats instanceof Array)) {
  throw new Error("Invalid Jupytext config (formats is not an array)");
}
// At this point TypeScript knows that `formats` is a JsonArray. You may still want to check that
// every value is a string.
for (const format of formats) {
  if (typeof format !== "string") {
    throw new Error("Format isn't a string");
  }
  // Now TypeScript knows that `format` is a string.
}

[mwouts]

Hi everyone, I’m happy to let you know that

• the jupyter notebook extension works well
• and the jupyter lab extension started working.

Both require the latest rc (now 1.0.0-rc3):

pip install jupytext --pre --upgrade

Feedback is welcome.

Also, before I let the 1.0.0 version go I’ll try to bind the extensions with the python package, as nbdime or plotly seem to do.