Problem with beforeBuild and fse.copySync (fs-extra), when rebuilding... endless loop of rebuilding.

[michelbaas]

Note: I'm not quite sure if this belongs to Issues or Discussions. But assuming the problem lies in my code I have posted it here. Also too much to post in Eleventy's Discord.

Objective
So I want to create a multi-site system on one single Eleventy system. All the data/posts (.md's or .json's) are in one place/folder. Each site is hosed in it's own folder, with a layout to filter out and load specific posts. Every site will have it's own title, logo and such.

Manually, permalinks or one off script
Anyhow, you could do this manually and create all the folders in the (input) src folders with files and frontmatter... or automatically as a one off. You could also just do it with the permalinks in the posts, to create the right folders; but then I'm still missing my layout and frontmatter inside these folders.

beforeBuild functions
I decided to try doing this within .eleventy.js and do this with every (re)build. And create them before Eleventy is doing all the site generation.

Endless loop of rebuilding
I got my testproject to work, but it's only working with the first build.
When I save an edit and Eleventy is doing a rebuild it will end up hanging in an endless loop of rebuilding.
And you get to see messages like: "[11ty] You saved while Eleventy was running, let’s run again. (28 remain)"
When hitting CTRL-C and check out the build log by scrolling up, you get to see all random numbers in the (** remain) tag.

Inside .eleventy.js:

const fse = require('fs-extra');
const arrayFromJSON = require('./_data/sites.json');
const arrayTitles = arrayFromJSON.titles;

  eleventyConfig.on("beforeBuild", () => {
  // Create site folders and copy layout and frontmatter data to the folders
    arrayTitles.forEach(element => 
      fse.copySync(`sitesource/index.njk`, `src/_sites/${element}/${element}.njk`, { recursive: true }));
    arrayTitles.forEach(element => 
      fse.copySync(`sitesource/fm.11tydata.js`, `src/_sites/${element}/${element}.11tydata.js`, { recursive: true }));
  });

The index.njk is loading a layout from _includes/layouts
And the frontmatter for the title is coming from ${folder}.11tydata.js:

// This is to fetch the foldername, and used in the frontmatter for the title
const folderName = __dirname.split("/").pop();
const siteTitle = folderName.charAt(0).toUpperCase() + folderName.slice(1);

module.exports = {
  eleventyComputed: {
    title: `This is the site title: ${siteTitle}, and assumed to be a template string!`,
  }
};

Array from sites.json:

{
    "titles": [
      "site1",
      "site2",
      "site3",
      "site4",
      "site5",
      "site6",  
      "site7",
      "site8"
    ]
}

So when doing the first build there's no problem but when rebuilding Eleventy keeps seeing a save. So somewhere there's some conflicting. Any ideas what the problem and solution could be?

I've already pretty much decided it would probably be better to make this a script that could be started with an npm run command. Only when needed, to copy everything necesarry to the (input) src folder.

[michelbaas]

So I have solved the problem by moving the copySync code from above into it's own file; titles.js.
This file is called with 'npm run titles'... or optional in combination with 'npm run start' or 'npm run build' scripts (in package.json).

I'm content with this solution.

But, the beforeBuild problem when rebuilding with the copySync code in .eleventy.js –– is this a bug in Eleventy or is this caused because I might be using it in an unintentional way?