.NET: ExecutorIsh is confusingly named and hard to discover how to use

[stephentoub]

https://github.com/microsoft/agent-framework/blob/main/dotnet/src/Microsoft.Agents.Workflows/ExecutorIsh.cs

The name is hard to understand, with "Ish" as a suffix.

Also when looking at APIs that accept one, like WorkflowBuilder's constructor, it's hard to figure out how to get one. It relies on implicit cast operators to turn other things into this... and such implicit operators are also something we recommend folks avoid:
https://learn.microsoft.com/en-us/dotnet/standard/design-guidelines/operator-overloads#conversion-operators

The implicit operators also make it so that reference identity breaks, because code like:

AIAgent agent = ...;
ExecutorIsh e1 = agent;
ExecutorIsh e2 = agent;

ends up allocating new objects as part of those implicit casts.

[stephentoub]

I don't understand why Executorish is necessary at all. Why can't everything just be in terms of Executor? If we want convenience methods for creating Executors for really common cases, they can be static factories on the base Executor, or AsExecutor methods on the relevant types.

We should really get rid of it.

[stephentoub]

cc: @alliscode, @lokitoth

[lokitoth]

It was initially in place to allow creation of late-binding "slots" for executors. E.g. if you want to create a workflow template, then fill in "well-known-PARTs". Not sure if it is still relevant, or if can be entirely replaced by Configured<T> (or whatever it gets renamed to).

Fundamentally it only exists because it is impossible to create a type union of string and T in .NET.

[joslat]

love this, I support strongly using Executor as the name, if possible, for simplicity.

Also, this issues are related:

• .NET: Provide explicit API to convert AIAgent to Executor for workflow composition #1494
• .NET: API inconsistency with Python - ConfigureSubWorkflow vs WorkflowExecutor for workflow composition #1502

@stephentoub with this code suggested in Issue 1494 (but changing ExecutorIsh to Executor):

Executor physicistExecutor = physicist.AsExecutor(
    name: "PhysicistAgent_v1",           // Override display name for workflows
    description: "Physics domain expert"  // Add description for documentation
);

we could control if we create or not a new instance of an executor to wrap an agent, as otherwise how do we assign unique names that we want? (as you are doing in the agent Orchestrations) - using a GUID or the name plus a guid or, if an existing executor for this agent exists, reuse it.
But what if we want to have a new executor wrapping another instance of that agent? only way is to control the Executor creation... (please correct me if wrong, I may be).

Hope it helps.

[lokitoth]

We cannot simply use Executor because that would encourage people to pass AIAgent-hosting executors (and similar for RequestInfoExecutor) as instances, which will make their workflows instances single-usable. Having ExecutorIsh (now ExecutorRegistration) lets us force the factory behaviour in these known cases, while still allowing (in C#) a very lightweight API.