Enhancement: Enable placeholders for file prefixes

[estruyf]

Based on feedback from Discord, it would be useful to have the ability to use placeholders in the filePrefix template. That way, users can generate unique IDs for their files.

Documentation

• Add information on the file prefix that placeholders can be used
• Add information to the placeholder page
• Update the default value from the frontMatter.templates.prefix setting

[estruyf]

@wottpal it is now possible in the beta to use placeholders for defining your file prefixes. You are also able to use a custom placeholders with which you would be able to generate an index number during the file creation.

Example configuration:

{
   "frontMatter.content.pageFolders": [{
    "title": "articles",
    "path": "[[workspace]]/content/prefixes/",
    "filePrefix": "{{indexNr}}"
  }],
  "frontMatter.content.placeholders": [{
    "id": "indexNr",
    "script": "./scripts/indexNr.mjs",
    "command": "~/.nvm/versions/node/v18.17.1/bin/node"
  }]
}

The script:

import { PlaceholderScript } from "@frontmatter/extensibility";
import { readdir } from "fs/promises";

(async () => {
  // Filepath is the directory path where the file will be created
  const { filePath } = PlaceholderScript.getArguments();
  if (!filePath) {
    PlaceholderScript.done(`000`);
    return;
  }

  const files = await readdir(filePath);
  if (!files) {
    PlaceholderScript.done(`000`);
    return;
  }

  // Return the number of files + 1 with leading zeros
  PlaceholderScript.done((files.length + 1).toString().padStart(3, `0`));
})();

Notice that the @frontmatter/extensibility library is used. More information on how to install it can be found here: https://frontmatter.codes/docs/custom-actions#extensibility-library