How do I reference json schema emitted by wepack?

Question

I work on a Electron project that uses Webpack. I use json schemas, configured like this:

module.exports = {
  module: {
    rules: [
      {
        test: /\.schema.json$/,
        type: "asset/resource",
        generator: {
          filename: "schemas/[name].json",
        },
      }
    ]
  }
}

So, if I have somewhere in my sources file some-config.schema.json that looks like this:

{
  "$id": "/schemas/some-config",
  "$ref": "/schemas/other-config"
}

It is emitted as http://localhost:1212/dist/schemas/some-config.schema.json. Notice 1212 — this is port number that is configured dynamically by different tools that configure the build, so I can't even know that path when I write code or schemas.

However, the $ref above doesn't work:

Problems loading reference 'file:///schemas/other-config': Unable to load schema from '/schemas/other-config': Failed to fetch.

I would want for it to load http://localhost:1212/dist/schemas/other-config.schema.json. How do I set up this reference?

Answer 1

The value of $ref is a URI, and not a URL. This matters because the URI is not necessarily "network addressable", aka, not a real network address.

The value of $id is an identifier only.

When a JSON Schema parser gets a value in $id which is a relative URI, if it can't determine a base URI to resolve to an absolute URI, then it should make one up. So, pretend it makes one up, or uses https://example.com.

So, when you use an $id value of /schemas/other-config, we can pretend it's prefixed with https://example.com, and so resolves to https://example.com/schemas/other-config. The same is true for /schemas/some-config.

When a JSON Schema processes the schema you've provided, it should first be using the URI resolution process, matching up references with it's index of $id values to schemas.

Essentially, set up correctly, your schema files could be located anywhere, as long as they have the correct $id values, and you've loaded them in to the implementation you're using.