subxt metadata does not work when talking to older nodes

[atodorov]

I'm trying to download the metadata from a blockchain built with Substrate. I have a local node running and http://localhost:9933 is accessible:

$ curl -H "Content-Type: application/json" -d '{"id":"1", "jsonrpc":"2.0", "method": "state_getMetadata", "params":[]}' http://localhost:9933 
{"jsonrpc":"2.0","result":"0x6d6574610e5906000c1c73705f636f72651863727970746f2c4163636f756e7449643332000004000401205b75383b2033325d0000040000032000000008000800000503000c08306672616d655f73797374656d2c4163636f756e74496e666f0814496e64657801102c4163636f756e74446174610114001401146e6f6e6365100114496e646578000124636f6e73756d657273100120526566436f756e7400012470726f7669646572

... truncated ...

Trying subxt fails:

$ subxt metadata --format bytes 
Error: 
   0: Other error: The node can only return version 14 metadata using the legacy API but you've asked for something else

Location:
   /home/gluwa/.cargo/registry/src/index.crates.io-6f17d22bba15001f/subxt-cli-0.31.0/src/utils.rs:73

Backtrace omitted. Run with RUST_BACKTRACE=1 environment variable to display it.
Run with RUST_BACKTRACE=full to include source snippets.

[niklasad1]

hey @atodorov

Can you report which version of substrate that you are using?
I suspect the node is using older metadata than subxt supports

[atodorov]

The node is using https://github.com/paritytech/substrate/tree/polkadot-v0.9.41

[jsdw]

Ooh, sorry about that! Our fallback code was a bit wonky and didn't work in the default case of asking for "latest" metadata (see the fix in #1127)

As a workaround you can ask for an explicit metadata version, which should work, eg:

subxt metadata --version 14 --format bytes

(the node you're talking to won't have version 15 metadata yet)

[atodorov]

As a workaround you can ask for an explicit metadata version, which should work, eg:

Thanks, that worked in the sense that subxt didn't fail and was able to fetch metadata.

[jsdw]

Great! The next release will fix the CLI tool so that the fallback path should work properly without that workaround :)