Hi @madbence ,

Two quick things:

1. There is no definition for #item only for #items (missing an s)
2. The other.json reference does not look valid.

This tool should support any fully-internal references. 😄 Let me know if that still does not work.

@robertmassaioli I took the example from the spec, so I think it's valid (sure, the other.json reference is external, which isn't supported, and that is fine)

The #item reference in #/items/items/$ref is a valid reference (to #/definitions/single), as described in the spec:

   When an implementation encounters the <#/definitions/single> schema,
   it resolves the "$id" URI reference against the current base URI to
   form <http://example.net/root.json#item>.

   When an implementation then looks inside the <#/items> schema, it
   encounters the <#item> reference, and resolves this to
   <http://example.net/root.json#item>, which it has seen defined in
   this same document and can therefore use automatically.

   When an implementation encounters the reference to "other.json", it
   resolves this to <http://example.net/other.json>, which is not
   defined in this document.  If a schema with that identifier has
   otherwise been supplied to the implementation, it can also be used
   automatically.

A more complex example that I was trying to examine: https://raw.githubusercontent.com/usnistgov/OSCAL/main/json/schema/oscal_assessment-results_schema.json

The following change kinda resolved the issue (yes, it's an ugly hack, and doesn't care about the base URI, or nested definitions):

--- a/src/lookup/index.ts
+++ b/src/lookup/index.ts
@@ -62,7 +62,10 @@ export class InternalLookup implements Lookup {
       return undefined;
     }
 
-    const result = pointerGet(this.schema, ref.slice(1));
+    if (ref === '#') return this.getSchema(this.schema);
+
+    const result = ref.includes('/') ? pointerGet(this.schema, ref.slice(1)) : Object.values((this.schema as any).definitions).find(a => a['$id'] == ref) as any;
 
     if (result === undefined) {
       return undefined;

Okay, I've had a sit down and read through the schema. Essentially, the "$id": "#<identifier>" format overrides standard JSON Pointer logic and becomes the first lookup for within the file.

That's fairly annoying but not impossible to replicate, we would just need to generate a map when we first load the schema for usage in follow-up references.