[Feature]: Throw error when staking is greater than balance

[enddynayn]

Description Currently, when a user attempts to stake an amount greater than their total account balance, the system stakes the entire balance minus a minimum amount required for unstaking. This behavior can confuse users who expect an error instead of staking the whole amount.

Acceptance Criteria

• [ ] When a user attempts to stake more than their available balance, an error is thrown, and no amount is staked.
  • Example: Balance: 10, Stake: 11. Nothing is staked, and an error is thrown.

~When a user attempts to stake an amount that is within the range of their balance minus the minimum required for unstaking, the system stakes the maximum allowable amount while leaving the minimum balance untouched. Example: Balance: 10, Minimum: 1, Stake: 9.5. The actual amount staked is 9, leaving the minimum balance of 1.~

[shannonwells]

There was an alternative to the 2nd checkbox suggested by @harry-evans, which I also prefer: an RPC call for asking what your maximum allowable stake is (which is free), and then requiring you to submit a value that will work. To me the Issue as written is just slightly less of a surprise than before, and can still leave you with no token left for transaction fees.

Of course, one can check an account balance but IMO it would be more helpful to app developers to provide an endpoint that lets you ask what you can stake instead of having them query (or worse, store it and risk it going out of date) what the minimum stake is, get an estimate of transaction fee and then query their balance and do the math client side. Instead it's just two calls. It simplifies the stake extrinsic logic, nobody is surprised by the result, and nobody has to field support calls why it doesn't stake the amount they asked for.

[wilwade]

Community Call Notes for 2024-10-17

• This is an experience feature
• How much we want to help the developer by reducing the work required to collect the information for the staking call

First Checkbox: Throwing an error

When a user attempts to stake more than their available balance, an error is thrown, and no amount is staked. Example: Balance: 10, Stake: 11. Nothing is staked, and an error is thrown.

• Reasonable to make the work clear
• Makes it hard when someone does want to stake the entire amount
• Does not resolve the issue of staking so much that one cannot unstake

Second Checkbox: Reserving an amount to force the ability to unstake

When a user attempts to stake an amount that is within the range of their balance minus the minimum required for unstaking, the system stakes the maximum allowable amount while leaving the minimum balance untouched. Example: Balance: 10, Minimum: 1, Stake: 9.5. The actual amount staked is 9, leaving the minimum balance of 1.

• What if one could unstake and use the locked funds to pay for unstaking?
  • Would require additional work with signed extensions to allow it to happen
  • Nice, but modifying a lot of work for a one-off setup
• How much do we require to be reserved to be able to unstake?
  • The amount could change over time
  • Users could still transfer away the unlocked tokens
• Do we need to do this at all?
  • Could it be handled on the client side instead?
  • aka, just do the First Checkbox: Throwing an error and don't do this part of it

Action

Only do the first First Checkbox: Throwing an error for now.

When a user attempts to stake more than their available balance, an error is thrown, and no amount is staked. Example: Balance: 10, Stake: 11. Nothing is staked, and an error is thrown.