Use lex with custom lexicons

Have you seen the lex CLI tool? It can install lexicons, which are JSON documents, and also build the corresponding typescript.

Pass in the NSID of some lexicons. It will create a folder lexicons/ in the project root with the JSON definitions for the given NSIDs.

# install two lexicons
npx lex install app.bsky.feed.post app.bsky.feed.like

But — what if you are using custom lexicons? How to easily create typescript for them too? Put custom lexicons in a local directory, and copy them to the lexicons folder as part of an npm script.

The Custom Lexicon

This is defined locally. Is is copied by rsync to the lexicons/... folder.

The npx lex build command creates typescript based on lexicons/. It will create type definitions in the src/lexicons/ folder. src/lexicons is ignored by git.

// lexicons-custom/app/my-application/actor/profile.json
{
  "lexicon": 1,
  "id": "app.my-application.actor.profile",
  "defs": {
    "main": {
      "type": "record",
      "description": "A declaration of a basic account profile.",
      "key": "literal:self",
      "record": {
        "type": "object",
        "properties": {
          "displayName": {
            "type": "string",
            "maxGraphemes": 64,
            "maxLength": 640
          },
          "description": {
            "type": "string",
            "description": "Free-form profile description text.",
            "maxGraphemes": 256,
            "maxLength": 2560
          },
          "avatar": {
            "type": "blob",
            "description": "Small image to be displayed next to posts from account. AKA, 'profile picture'",
            "accept": ["image/png", "image/jpeg"],
            "maxSize": 1000000
          },
          "createdAt": { "type": "string", "format": "datetime" }
        }
      }
    }
  }
}

The Build Script

You can use the rsync command to copy your custom lexicons into the lexicons/ folder. That way you can re-install via npx lex install ..., and still keep your custom lexicons, because they are in a different source folder.

lexicons/ is the default folder name created by lex after you install. It is committed to git. It is used by lex build to create the corresponding typescript.

// package.json
{
    // ...
    "scripts": {
        "lex:install": "lex install app.bsky.feed.post app.bsky.feed.like && rsync -a ./lexicons-custom/app/my-application/ ./lexicons/app/my-application/",
        "lex:build": "rm -rf src/lexicons && lex build"
    }
    // ...
}