Signal url couldnt be an expression

[rezabashiri]

At 'Signal' activity, elsa just get variable and compare it by the signal property, but it doesn't respect type signal, it could be java expression so I suggest an easy correction tp overcome this kind of lacking

protected override async Task<bool> OnCanExecuteAsync(WorkflowExecutionContext context, CancellationToken cancellationToken)
{
    var signal = await expressionEvaluator.EvaluateAsync(Signal, context, cancellationToken);
    var expression = new JavaScriptExpression<string>($"`{context.Workflow.Input.GetVariable<string>("Signal")}`");
    var signaled =await expressionEvaluator.EvaluateAsync<string>(expression,context, cancellationToken);
    return signaled == signal;
}

[craigfowler]

Hi @rezabashiri I'm sorry but I'm not really sure I understand your question, or maybe you trying to suggest a feature.
Could you give a little bit more information please?

(I edited your code sample - on Github you can use three back-ticks: ``` to mark a code-block)

[sfmskywalker]

I think I do understand actually. It looks like @rezabashiri wants to evaluate the signal provided as workflow input as well:

var expression = new JavaScriptExpression<string>($"``{context.Workflow.Input.GetVariable<string>("Signal")}``");

However, the suggested change will require the input to always be a valid JavaScript expression. Additionally, evaluating workflow input like this in a given activity seems too arbitrary for my sanity.

@rezabashiri Perhaps if you would share with us your use case, we can think of a better solution if we need one?

[rezabashiri]

@sfmskywalker yeah this is some kinda enhancement, I did a small hack to support both type of literal and javascript expressions

`
protected override async Task OnCanExecuteAsync(WorkflowExecutionContext context, CancellationToken cancellationToken)
{
var signal = await expressionEvaluator.EvaluateAsync(Signal, context, cancellationToken);
var signaled = await ExtractSignal(context, cancellationToken);
return signaled == signal;
}

    public async static Task<string> ExtractSignal(WorkflowExecutionContext context,    CancellationToken cancellationToken)
    {
        var received = context.Workflow.Input.GetVariable<string>("Signal");
        if (string.IsNullOrEmpty(received))
            return string.Empty;
        var syntax = received.Contains('$') switch
        {
            false => "Literal",
            true => "JavaScript"
        };
        var expression = syntax == "JavaScript" ? new JavaScriptExpression<string>($"`{received}`") : new WorkflowExpression<string>(syntax, received);
        var signaled = await context.EvaluateAsync<string>(expression, cancellationToken);
        return signaled;
    }`

[sfmskywalker]

With Elsa 2, it is now possible to define dynamically evaluated signal names. A sample of this can be found in this guide.