eleventyDataSchema is not working as expected or the example is very misleading

[1oglop1]

I am trying to learn from this repository but it took me some time to spot what was happening.
When I changed the front matter data in the fithpost.md to `draft: "no bool" but to my surprise nothing happened.

eleventy-base-blog/content/blog/fifthpost.md

Line 4 in 940e69d

const draft = true;

So I decided to console.log data for each page and the property eleventyDataSchema was undefined.

eleventy-base-blog/_data/eleventyDataSchema.js

Line 4 in 940e69d

export default function(data) {

then I logged data in the above file and found out it only runs once on this data structure and therefore can never trigger.

{
  eleventy: {
    version: '3.0.0',
    generator: 'Eleventy v3.0.0',
    env: {
      source: 'cli',
      runMode: 'build',
      config: '/Users/.../eleventy-base-blog/eleventy.config.js',
      root: '/Users/.../eleventy-base-blog'
    },
    directories: {
      input: './content/',
      inputFile: undefined,
      inputGlob: undefined,
      data: './_data/',
      includes: './_includes/',
      layouts: undefined,
      output: './_site/'
    }
  }
}

Then I went to dig deeper in the docs and found out that this page, it should be set for each page e.g.blog/blog.11tydata.js.
According to this page https://www.11ty.dev/docs/data-validate/
https://github.com/11ty/11ty-website/blob/508e420552742a7114eec1473802a6baa43e76d0/src/docs/data-validate.md?plain=1#L1

But none of that mattered because the enabled preprocessor disables the behaviour of the validator. (Explained in preprocessor docs page)

eleventy-base-blog/eleventy.config.js

Lines 10 to 16 in 940e69d

	export default async function(eleventyConfig) {
	// Drafts, see also _data/eleventyDataSchema.js
	eleventyConfig.addPreprocessor("drafts", "*", (data, content) => {
	if(data.draft && process.env.ELEVENTY_RUN_MODE === "build") {
	return false;
	}
	});

Summary of the problems

1. validator eleventyDataSchema.js runs on a wrong input file
2. preprocessor drafts disables the validator
3. using the approach from docs is not enough as long as the preprocessor is enabled

Possible fixes:

1. update the docstrings in files with more explanation
2. recommend https://github.com/uncenter/eleventy-plugin-validate ?