Allow users to add custom data extension for JSON files

[pdehaan]

Is your feature request related to a problem? Please describe.
I can add a custom data extension for .json5 files which allows me to load JSON files w/ comments (huzzah!)
But I wanted to shim that into .json files as well and was hoping I could just add a custom data extension for .json files as well, but no luck. Which is semi-understandable because Node, but unfortunate.

Describe the solution you'd like

const {inspect} = require("node:util");
const json5 = require("json5");

module.exports = eleventyConfig => {
  eleventyConfig.addDataExtension("json", contents => json5.parse(contents));
  eleventyConfig.addDataExtension("json5", contents => json5.parse(contents));

  eleventyConfig.addFilter("inspect", value => inspect(value));

  return {
    dir: {
      input: "src",
      output: "www",
    }
  };
};

> 11ty-json5-test@1.0.0 build
> eleventy

[11ty] > /private/tmp/11ty-json5-test/src/_data/def.json: Unexpected token n in JSON at position 4

`SyntaxError` was thrown:
[11ty]     SyntaxError: /private/tmp/11ty-json5-test/src/_data/def.json: Unexpected token n in JSON at position 4
        at parse (<anonymous>)
        at Object.Module._extensions..json (node:internal/modules/cjs/loader:1163:22)
        at Module.load (node:internal/modules/cjs/loader:975:32)
        at Function.Module._load (node:internal/modules/cjs/loader:822:12)
        at Module.require (node:internal/modules/cjs/loader:999:19)
        at require (node:internal/modules/cjs/helpers:102:18)
        at TemplateData.getDataValue (/private/tmp/11ty-json5-test/node_modules/@11ty/eleventy/src/TemplateData.js:477:25)
        at TemplateData.getAllGlobalData (/private/tmp/11ty-json5-test/node_modules/@11ty/eleventy/src/TemplateData.js:271:29)
        at async TemplateData.getData (/private/tmp/11ty-json5-test/node_modules/@11ty/eleventy/src/TemplateData.js:326:24)
The terminal process "/bin/zsh '-c', 'npm run build'" terminated with exit code: 1.

Describe alternatives you've considered
Not sure. Ideally I can override the JSON loader. I was hoping to come up w/ a workaround for #2299 where I could try building a safer JSON parser which would return empty objects on a parsing error to fail more silently.

Additional context
❤️

[pdehaan]

Where my src/_data/def.json looks like this:

{
  name: "Zaaaach"
  // A wild comment appears!
}

And the data loads a-ok if I rename it to def.json5 (see https://www.npmjs.com/package/json5)

[pdehaan]

Possible workaround via require-json5, which I believe shims the require.extensions mapping.

require("require-json5").replace();

module.exports = eleventyConfig => {
  return {
    dir: {
      input: "src",
      output: "www",
    }
  };
};

{
  // src/_data/sample.json
  name: "pdehaan"
}

---
# src/index.liquid
title: OK Computer!
---

<h1>{{ title }}</h1>
<pre>{{ sample.name }}</pre>

OUTPUT

<h1>OK Computer!</h1>
<pre>pdehaan</pre>

Of course, adding this to core is probably a bit too wild. But wasn't sure if there was a possibility of checking user defined data extensions before checking the default handlers for .js, .cjs, or .json (which I think is happening in src/TemplateData.js:459 in getDataValue() maybe).

[zachleat]

Yeah I don’t think we’ll want to use require.extensions for this but it does seem inevitable that we’ll refactor some of this require-based JSON loading out as we move to ECMAScript Modules.

#836 (required for first-class Deno support too)

[zachleat]

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View the enhancement backlog here. Don’t forget to upvote the top comment with 👍!