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Moldable Emacs: how to explore JSON via Elisp

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You may need to explore JSON data: a mold can help you with that! You can view what you need with a bit of Elisp.

The problem

Sometimes I have some JSON I want to explore. Often I read its contents in the browser view or in an Emacs buffer. Every so often I fell into jq. As we learned before, we would be better off by having a view to extract only the contents we need. That would make our reading faster and nicer.

For example, what should I do to see all the official descriptions of Ghibli's movies?

And there is a solution

Naturally I have a mold for that! The presentation is rather raw for now, so I will show you also what GlamorousToolkit can do to let you compare where we could get to.

First let me show the data with the Ghibli API. The Ghibli studio made available information about their movies via an open API. For example, if you want to get the films they produced so far, we will have just to run the request that follows.

curl -X GET -H "Content-Type: application/json" https://ghibliapi.herokuapp.com/films

This returns a list that looks like:

    "id": "2baf70d1-42bb-4437-b551-e5fed5a87abe",
    "title": "Castle in the Sky",
    "original_title": "天空の城ラピュタ",
    "original_title_romanised": "Tenkū no shiro Rapyuta",
    "description": "The orphan Sheeta inherited a mysterious crystal that links her to the mythical sky-kingdom of Laputa. With the help of resourceful Pazu and a rollicking band of sky pirates, she makes her way to the ruins of the once-great civilization. Sheeta and Pazu must outwit the evil Muska, who plans to use Laputa's science to make himself ruler of the world.",
    "director": "Hayao Miyazaki",
    "producer": "Isao Takahata",
    "release_date": "1986",
    "running_time": "124",
    "rt_score": "95",
    "people": [
    "species": [
    "locations": [
    "vehicles": [
    "url": "https://ghibliapi.herokuapp.com/films/2baf70d1-42bb-4437-b551-e5fed5a87abe"

Our aim is to get all the movie =description=s to give them a look.

Let me show how this works with my moldable-emacs.

First, we download the JSON and load json-mode in that buffer.

Now we transform the JSON in a flattened tree of elements parsed with tree-sitter JSON gramma.

Now if we were interested only in an entry description (because we are exploring), we could do the following.

Note that in the tree view I can always jump back to the original JSON buffer with the me/open-at-point command.

Anyway, that was not our goal! Instead from the original JSON, let's get all the descriptions with a Playground. This mold has available the flattened tree of the previous buffer in a variable called self.

We just needed a couple of filters to get all pairs. Of those we got only the ones containing descriptions.

I used the following code for reference.

 (plist-get it :text)
 (--filter (s-starts-with-p "\"description" (plist-get it :text)) (me/by-type 'pair self)))

Note that this kind of code is meant to throw away. If you keep repeating it, you can store it in a function. If you bet this is something others would find useful, be generous and open a PR to my repo (or share in a fork). For example, me/by-type is just a shortcut for filtering the flattened tree by the :type field: I used it so many times I found that shortcut useful.

Anyway you saw that in a few steps we could get to what we needed.

Now that I think of it, I could easily add a Playground mold that does not use Lisp. For example, a Playground In Python or Playground In JS. Well, I did not need that yet, so let me know if you wish one.

This is what I needed so far for my workflow in moldable-emacs. Let me show you how Glamorous people make developers explore JSON.

I did not become familiar enough with Pharo to show you how to collect only descriptions fields. Still it is much more beautiful and accessible than what I got in moldable-emacs.

The Pharo code I used for convenience.

json := ZnClient new get: 'https://ghibliapi.herokuapp.com/films'
dictionary := STON fromString: json.

You can see that there is much more humane ways to present the information!


Again this is just a way to use moldable-emacs to your needs. With this you can explore data with programming in Lisp from within your editor. If you want to try the code is available at https://github.com/ag91/moldable-emacs. If you have troubles running this, please ping me! At the moment I have a story for letting the user discover the dependencies they need for a mold, but I kept postponing it (because I got the dependencies already installed XD).

Hope this made curious and you will have fun with this extension.

Happy exploring!