Implement procedural macro for getting the required balance for a transaction

[rrtti]

Setup is stash account (proxy) <-- multisig wallet <-- user account

1. I sign with my account to call approve on this multisig, that has a stash account with funds as proxy.
2. all accounts have a few dots each that are transferrable, which I initially thought was sufficient for the call.

When trying to confirm the tx, the call returns "Insufficient balance" - more transparency might be needed around what kind of balance they need to interact with an extrinsics.

[bkchr]

After paritytech/substrate#5678 is finished, we should add support for a new attribute macro.
This attribute macro should be similar to the weight and should expose information about deposits, locks etc to the outside. This could be combined with the transaction payment pr to find out how much balance a user requires for a certain transaction, instead of doing trial and error as described above.

So we will require the following:

• Some type that expresses how much and for what a transaction requires tokens (reserve, spent, etc)
• Add a new attribute macro (name tbd)
• If the attribute macro is not given, we would only fallback to show the amount of tokens being payed for the transaction itself.
• Provide a RPC that probably replaces the transaction payment RPC to make these information accessible.

[kianenigma]

Provide a RPC that probably replaces the transaction payment RPC to make these information accessible.

Can't the content of this new attribute macro be a new filed in the metadata?

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@rrtti with just your description and and the title I can barely understand the issue, can you elaborate bit more? and is it similar to this? paritytech/substrate#7240

[bkchr]

@kianenigma For that reason I have added a comment that explains on what should be done :P

[bkchr]

Regarding paritytech/substrate#7240, this is something different AFAIK. This new macro should be able to express stuff like deposits. So, you can query how much actual tokens you need (deposit + fees). Currently we can only query the fees and we need to know that a certain function requires a fixed amount for deposits.