Analyzer package

We could invest some time to tackle some common issues users might face (or antipatterns) with our own analyzer. If we have a look into the issue tracker, we see this example a few times:

The render handle is not yet assigned.

Users might define a razor file with bunit like this:

@code
{
    [Fact]
    public void Test()
    {
        using var ctx = new BunitContext();

        Action<MouseEventArgs> onClickHandler = _ => { Assert.True(true); };

        var cut = ctx.Render(@<EventCallbackParams
                                  OnClick="onClickHandler" />);
        cut.Find("button").Click();
    }
}

This fails with

"System.InvalidOperationException : The render handle is not yet assigned."

Because the razor component isn't part of the RenderTree of the Blazor Renderer. So everytime we have a callback or variable (also two-way bindings) in razor syntax it might fail.

Therefore the fix is to do

@inherits BunitContext
@code
{
    [Fact]
    public async Task Test()
    {
        var wasInvoked = false;

        Action<MouseEventArgs> onClick = _ => { wasInvoked = true; };

        var cut = Render(@<EventCallbackParams OnClick="onClick" />);
        var button = cut.Find("button");
        await button.ClickAsync(new MouseEventArgs());

        cut.WaitForAssertion(() => Assert.True(wasInvoked));
    }
}

Here we can easily help the user that if he uses a .razor file and has some variables passed from the test bi-directional (or events) to the cut, the user should use @inherits BunitContext.

Another one might be (in any variation):

IHtmlAnchorElement elem = (IHtmlAnchorElement)cut.Find("cssSelector");

// Could be
var elem = cut.Find<IHtmlAnchorElement>("cssSelector");

We probably could find more examples.

Risks

• The biggest risk I see is our time. Maintaining that might be an additional burden.

Additional

• We need to add also some documentation in our docs/ directory so people know what the Analyzer is and does.
• We might want to promote this in the README.md (link to the nuget package - once it is available)