Discussion: Breaking changes for tag helper authors in RC1

[NTaylorMullen]

Due to the new TagHelper addition of Init used to setup your TagHelperContext and other related item bag info for executed children to consume we decided that the ability to execute children doesn't entirely make sense on the context object since it has no connection to the actual structure of the element.

The alternative would have been to make GetChildContentAsync throw when invoked within the Init method (yuck).

Before

public class CustomTagHelper : TagHelper
{
    public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
    {
        await context.GetChildContentAsync();
    }
}

After

public class CustomTagHelper : TagHelper
{
    public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
    {
        await output.GetChildContentAsync();
    }
}

[thoemmi]

Though I see the rationale behind the change, it seems strange to call output for the input. 😕

[dougbu]

seems strange to call output for the input. 😕

This delegate returns the output of the child elements. In MVC tag helpers that use this for example, the return value is often not used -- it's just called to ensure children have executed (and output whatever they're going to output).

[dougbu]

Broadening the subject to include additional changes. Please use this issue to discuss aspnet/Announcements#89 as well as aspnet/Announcements#90.