Request: specific alias to make build fail

[ymartin59]

I propose to create an alias which allows to make build fail without an explicit throw new exception after a if condition.
For instance Fail(bool conditionToFail, string exceptionMessage)
Cake may throw a specific exception in such case and report current task name and line location in cake build file.

[devlead]

This is a workaround, and not exactly what you're looking for, but still a tip of what you can do today.

What I've usually used in integration tests to fail fast is the Xunit.Assert package.
One thing it has in handy is that it has sensible errors when comparing expected vs actual values. And True / False has overloads that let you specify a user message.

An example script of that could look something like this:

xunit.cake

#addin "nuget:?package=xunit.assert&version=2.4.1"
using static Xunit.Assert;

var target = Argument("target", "Default");

Task("MaybeFail")
    .Does(()=> Equal("Default", target));

Task("MaybeFail2")
    .Does(()=> True(HasArgument("target"), "Target is expected to be specified."));


Task("Default")
    .IsDependentOn("MaybeFail")
    .IsDependentOn("MaybeFail2");

RunTarget(target);

Given Cake launched with dotnet cake xunit.cake

The expected result would be

    ========================================
    MaybeFail
    ========================================
    
    ========================================
    MaybeFail2
    ========================================
-   An error occurred when executing task 'MaybeFail2'.
-   Error: One or more errors occurred. (Target is expected to be specified.
-   Expected: True
-   Actual:   False)
-           Target is expected to be specified.
-           Assert.True() Failure
-   Expected: True
-   Actual:   False

Given Cake launched with dotnet cake .\xunit.cake --target=MaybeFail

The expected result would be

    ========================================
    MaybeFail
    ========================================
-   An error occurred when executing task 'MaybeFail'.
-   Error: One or more errors occurred. (Assert.Equal() Failure
-             ↓ (pos 0)
-   Expected: Default
-   Actual:   MaybeFail
-             ↑ (pos 0))
-           Assert.Equal() Failure
-             ↓ (pos 0)
-   Expected: Default
-   Actual:   MaybeFail
-             ↑ (pos 0)

Given cake launched with dotnet cake .\xunit.cake --target=MaybeFail2

    ========================================
    MaybeFail2
    ========================================
    
+   Task                          Duration
+   --------------------------------------------------
+   MaybeFail2                    00:00:00.0119659
+   --------------------------------------------------
+   Total:                        00:00:00.0119659