stake: Delegating an amount below the minimum returns a misleading error message

[brooksprumo]

Problem

When the following features are enabled, delegating a stake amount below the minimum will return with an error saying "Error: split amount is more than is staked", which is misleading since the error was caused during delegate and not split.

Features:

• Feature Gate: Raise stake minimum delegation to 1.0 sol #24357
• Feature Gate: Allow undelegated stakes to be below the minimum delegation #24669

Code in question:

solana/sdk/program/src/stake/instruction.rs

Lines 35 to 36 in c49efae

	#[error("split amount is more than is staked")]
	InsufficientStake,

Originally encountered in #25336

Proposed Solution

Reword the error message.
Add a new error behind a feature-gate.

[brooksprumo]

cc: @joncinque

[joncinque]

Bah, sorry about that, we need to actually add a new error and return that finally, based on another feature flag probably

[brooksprumo]

Bummer. It is insufficient to just reword the error message?

[joncinque]

I think it could cause issues, since during rollout some nodes would produce the old error message, and others produce the new one. It depends on how those error messages are used by the runtime, but I'm cautious due to this note:

solana/sdk/program/src/instruction.rs

Lines 220 to 230 in 84f1e5c

	/// Failed to serialize or deserialize account data
	///
	/// Warning: This error should never be emitted by the runtime.
	///
	/// This error includes strings from the underlying 3rd party Borsh crate
	/// which can be dangerous because the error strings could change across
	/// Borsh versions. Only programs can use this error because they are
	/// consistent across Solana software versions.
	///
	#[error("Failed to serialize or deserialize account data: {0}")]
	BorshIoError(String),

Maybe @jackcmay can tell us for sure what we should do since he put in #17864

[jackcmay]

Yeah, changing the String value without a feature flag is a bad idea because the return value is part of the bank hash