Illegal op_code error with recursive blobs

[bdemann]

Running this code

import { IDL } from '@dfinity/candid';

const RecursiveBlob = IDL.Rec();
RecursiveBlob.fill(IDL.Vec(IDL.Nat8));

const UsesRecursiveBlob = IDL.Rec();
UsesRecursiveBlob.fill(
    IDL.Record({
        myBlob: RecursiveBlob
    })
);

const RecursiveRecord = IDL.Rec();
RecursiveRecord.fill(
    IDL.Record({
        field1: IDL.Vec(IDL.Nat8),
        field2: IDL.Vec(IDL.Nat8)
    })
);

const RecReturn = IDL.Rec();
RecReturn.fill(
    IDL.Opt(
        IDL.Record({
            rec_rec: RecursiveRecord,
            rec_blob: UsesRecursiveBlob
        })
    )
);

const toEncode = [];

const encoded = IDL.encode([RecReturn], [toEncode]);
console.log(encoded);
const decoded = IDL.decode([RecReturn], encoded);
console.log(decoded);

gives the following error

Uint8Array(46) [
   68,  73,  68,  76,   5, 110,   4, 108,   2, 183,
  156, 186, 132,   8,   2, 184, 156, 186, 132,   8,
    2, 108,   1, 233, 221, 211, 226,   6,   4, 108,
    2, 161, 191, 159, 179,   2,   1, 236, 251, 182,
  207,   6,   3,   1,   0,   0
]
node_modules/@dfinity/candid/src/idl.ts:1734
          throw new Error('Illegal op_code: ' + ty);
                ^


Error: Illegal op_code: 1
    at readTypeTable (node_modules/@dfinity/candid/src/idl.ts:1734:17)
    at Object.decode (node_modules/@dfinity/candid/src/idl.ts:1745:32)
    at <anonymous> (test.ts:35:21)
    at ModuleJob.run (node:internal/modules/esm/module_job:271:25)
    at async onImport.tracePromise.__proto__ (node:internal/modules/esm/loader:578:26)
    at async asyncRunEntryPointWithESMLoader (node:internal/modules/run_main:116:5)

Node.js v22.14.0

[bdemann]

I'm guessing I could break it out to just IDL.encode and IDL.decode with a little bit of work just like in #1518

[bdemann]

This is still a problem in stable

import { IDL, query } from 'azle';

const RecursiveBlob = IDL.Rec();
RecursiveBlob.fill(IDL.Vec(IDL.Nat8));
type RecursiveBlob = Uint8Array;

const UsesRecursiveBlob = IDL.Rec();
UsesRecursiveBlob.fill(
    IDL.Record({
        myBlob: RecursiveBlob
    })
);
type UsesRecursiveBlob = {
    myBlob: RecursiveBlob;
};

const RecursiveRecord = IDL.Rec();
RecursiveRecord.fill(
    IDL.Record({
        field1: IDL.Vec(IDL.Nat8),
        field2: IDL.Vec(IDL.Nat8)
    })
);
type RecursiveRecord = {
    field1: Uint8Array;
    field2: Uint8Array;
};

const RecReturn = IDL.Rec();
RecReturn.fill(
    IDL.Opt(
        IDL.Record({
            rec_rec: RecursiveRecord,
            rec_blob: UsesRecursiveBlob
        })
    )
);
type RecReturn =
    | [
          {
              rec_rec: RecursiveRecord;
              rec_blob: UsesRecursiveBlob;
          }
      ]
    | [];

export default class {
    @query([], RecReturn)
    recBlobTest(): RecReturn {
        return [];
    }
}

it('makes a query call that returns a recursive blob', async () => {
    const result = await canister.recBlobTest();

    expect(result).toBe([]);
});

fails with

Illegal op_code: 1

[bdemann]

This was the description but since the functional syntax isn't the main thing anymore I want to move it down here and put the simplified only-using-dfinity-candid code into the description

Original Description

While we were doing property tests I ran into this strange issue with recursion. I got it down to a relatively small example that still breaks, at this point changing any little thing causes the error to go away.

The error is a little different in the cli than in the agent. If you run into the issue with the agent the error is

Error: Illegal op_code: 1

The error from the cli is:

Error deserializing blob 0x4449444c056e046c02b79cba840802b89cba8408026c01e9ddd3e206046c02a1bf9fb30201ecfbb6cf0603010000
Error: Failed to deserialize idl blob: Invalid data.
Caused by: Failed to deserialize idl blob: Invalid data.
 Cannot parse header 4449444c056e046c02b79cba840802b89cba8408026c01e9ddd3e206046c02a1bf9fb30201ecfbb6cf0603010000
   binary parser error: 1 is not a valid future type at byte offset 43

The hex 0x4449... changed as the example changed and the offset 43 also changed. but the rest of the error stayed the same regardless of how I changed the example.

The example that I got down to is:

import { Canister, query, Recursive, Opt, blob, Record, None } from 'azle';

const recursive_blob = Recursive(() => blob);
const uses_recursive_blob = Recursive(() =>
    Record({
        myBlob: recursive_blob
    })
);
const recursive_record = Recursive(() =>
    Record({
        field1: blob,
        field2: blob
    })
);
const rec_return = Recursive(() =>
    Opt(
        Record({
            rec_rec: recursive_record,
            rec_blob: uses_recursive_blob
        })
    )
);

export default Canister({
    rec_blob_test: query([], rec_return, () => None)
});

[lastmjs]

This is still a problem as of @dfinity.candid 3.1.0`