RPC call uses lowercase parameter name

[gregdhill]

See the example in interlay/interbtc#612

We have an RPC call which uses a CurrencyId argument, note the capitalized "Token" enum variant (see here). I can only assume polkadot-js uses the lowercase of this string which results in the "Invalid params" error as the correct capitalization works as expected. We do not have any issues with extrinsics or reading the chain state.

[jacogr]

As per the Substrate de-facto standard, all properties over RPC are camelCased, e.g.#[serde(rename_all = "camelCase")] is added everywhere RPCs are exposed.

As an example from Substrate (see the serde macro) -

/// Health struct returned by the RPC
#[derive(Debug, PartialEq, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct Health {
	/// Number of connected peers
	pub peers: usize,
	/// Is the node syncing
	pub is_syncing: bool,
	/// Should this node have any peers
	///
	/// Might be false for local chains or when running without discovery.
	pub should_have_peers: bool,
}

The same would apply to enums, e.g. an example from Substrate -

/// Possible transaction status events.
///
/// This events are being emitted by `TransactionPool` watchers,
/// which are also exposed over RPC.
/// ...
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
pub enum TransactionStatus<Hash, BlockHash> {
	/// Transaction is part of the future queue.
	Future,
	/// Transaction is part of the ready queue.
	Ready,
	/// The transaction has been broadcast to the given peers.
	Broadcast(Vec<String>),
	/// Transaction has been included in block with given hash.
	InBlock(BlockHash),
	/// The block this transaction was included in has been retracted.
	Retracted(BlockHash),
	/// Maximum number of finality watchers has been reached,
	/// old watchers are being removed.
	FinalityTimeout(BlockHash),
	/// Transaction has been finalized by a finality-gadget, e.g GRANDPA
	Finalized(BlockHash),
	/// Transaction has been replaced in the pool, by another transaction
	/// that provides the same tags. (e.g. same (sender, nonce)).
	Usurped(Hash),
	/// Transaction has been dropped from the pool because of the limit.
	Dropped,
	/// Transaction is no longer valid in the current state.
	Invalid,
}

This is what the API codes to and decodes from. (although in decoding it is more lenient, unlike Substrate which is very ridgit with the requirements). Trying to change this would mean all the base Substrate RPCs break. So the requirement would be to follow the Substrate standards and add the macro to your code if you want it to go over RPC.

TL:DR Add the required macros to the Rust code on everything exposed via RPC as per the Substrate de-facto standard (thus following the groundwork already laid by the Substrate team)

[gregdhill]

Thanks for the detailed answer @jacogr, much appreciated!

[polkadot-js-bot]

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