Action exceptions should be recorded as a part of blockchain

[dahlia]

Due to the limitation of the current IAction API, validation logic tends to be duplicated (one in the Execute() method and other one in the game UI code). If exceptions raised by actions are recorded as a part of blockchain, such duplicated validation code in the game UI side can be replaced by reusing the result/error code of an action.

[dahlia]

@ipdae Any ideas?

[ipdae]

In my opinion, it would be nice to be able to retrieve the exception that occurs when executing the action in the game through an interface such as EvaluationOuputStates.Exception.

[longfin]

In my opinion, it would be nice to be able to retrieve the exception that occurs when executing the action in the game through an interface such as EvaluationOuputStates.Exception.

ActionEvaluation is public class but the game using Libplanet doesn't access it directly. Instead, the game does through IAction.Render().

so there are several options if we want to allow to access generated exception to users.

• give whole ActionEvaluation as .Render()'s argument instead of IActionContext and IAccountStateDelta.
• add exception to .Render()'s arguments.
• attach it to IAccountStateDelta or IActionContext.

The former is more natural to me. Is there any idea? @planetarium/libplanet @ipdae

[dahlia]

How about adding a new distinct method to IAction besides Render()/Unrender(), e.g., RenderError()/UnrenderError()? IAction would look like:

public interface IAction
{
    IAccountStateDelta Execute(IActionContext context);
    void Render(IActionContext context, IAccountStateDelta nextStates);
    void Unrender(IActionContext context, IAccountStateDelta nextStates);
    void RenderError(IActionContext context, Exception exception);    // 🆕
    void UnrenderError(IActionContext context, Exception exception);  // 🆕
    IValue PlainValue { get; }
    void LoadPlainValue(IValue plainValue);
}

[longfin]

How about adding a new distinct method to IAction besides Render()/Unrender(), e.g., RenderError()/UnrenderError()? IAction would look like:

public interface IAction
{
    IAccountStateDelta Execute(IActionContext context);
    void Render(IActionContext context, IAccountStateDelta nextStates);
    void Unrender(IActionContext context, IAccountStateDelta nextStates);
    void RenderError(IActionContext context, Exception exception);    // 🆕
    void UnrenderError(IActionContext context, Exception exception);  // 🆕
    IValue PlainValue { get; }
    void LoadPlainValue(IValue plainValue);
}

RenderError() / UnrenderError() seem good. I'll take them.

[longfin]

It seems resolved by #875