Support for .tt templates in .kproj files?

[kevinkuszyk]

Is there a plan to include support for .tt files in .kproj files in vnext?

I just tried adding T4MVC to an MVC6 project but the .tt files didn't get copied into the project.

When I manually copied the .tt into the project folder, it showed in in the solution explorer, but the option to run it was missing.

[Eilon]

No current plans to support it.

[kevinkuszyk]

Thanks for the quick reply.

Fyi. - I just posted this on the user voice page too:
https://aspnet.uservoice.com/forums/252111-asp-net-vnext/suggestions/6970908-support-t4-templates-in-kproj-in-visual-studio

[wwwlicious]

+1

Until MVC changes from using awful magic strings for routes, partials etc T4MVC has been invaluable for refactor friendly, view compile-time checking.

@Html.ActionLink("Home", "Index", "Home") == "urgh"
@Html.ActionLink("Home", MVC.Home.Index()) == "win"

[Eilon]

Indeed, you'll get no argument from anyone on the team that hard-coding repeated strings all over the place is rather... lame. OK actually it's super lame.

As part of this discussion I think it's important to share my thoughts as to why TT probably isn't going to be the long-term solution. First, it's pretty much a VS-only, design-time-only solution. People have done hacky workarounds to run TT files from the command-line but it's not a supported pattern. And in the world of ASP.NET 5, being a Windows-only VS-only solution just isn't going to cut it. I have to be able to use the feature when part of my team might be running Ubuntu and using vim to work on their part of the project. Secondly, editing support for TT files in VS is rather weak. There have been some reasonable 3rd party solutions, but nothing in-box.

So then what do we choose instead? I call my next witness, the Roslyn C# compiler. Roslyn lets you do neat things. Roslyn lets you do some pretty amazing things. One of those amazing things with the way ASP.NET 5 uses Roslyn is that it lets you at compile time (which is also potentially at run time (well, load time, really)) process the syntax trees, generate some code of your own, and then let the world keep turning.

This is how ASP.NET 5 does assembly neutral interfaces (ANIs). ANIs are implemented in ASP.NET 5 by having a scanner that looks for certain attributed types and deletes their syntax trees, and, instead, creates new tiny assemblies with just those types.

Now imagine a world where you could do the same functionality as you had with T4MVC, but potentially far more robust (you have Roslyn, after all), far faster (you already have all the syntax trees parsed), cross-platform (Windows, *nix, OS X, etc.), and can generate code hopefully more easily (well, with Roslyn that isn't always the case, but still).

So, I'd love to hear thoughts on a solution that heads in that direction. Anyone?

[kevinkuszyk]

I was thinking about this some more last week and came to the conclusion cross platform support might be the blocker and Roslyn the solution.

I opened this issue because I don't want to loose access to the strongly typed action name, view names etc. we get from T4MVC.

If there is better cross platform solution then I'd go for that.

Do you see a Roslyn based T4MVC replacement shipping as part of MVC 6 or in a future version, or is there still space for a community lead extension?

[Eilon]

The team doesn't have any immediate plans to build this out, so I think a community-organized solution is the best place to start. But, of course, the team would love to hear about any roadblocks or issues found while building such a solution because we would very much like to unblock any such issues.

[kevinkuszyk]

Thanks @Eilon. I'll try to build something, but I'm not sure where to start. I have two big questions to begin with, but I'm not sure where to post them:

1. Is there a project.json hook we can use to invoke our code generation? Or should we use the BeforeBuild target in the .krpoj file.
2. How to use Roslyn "reflection" to find all the controller classes in a project? I've looked through the samples in the Roslyn repro, but I can't see an example of loading a project and finding types in it.

[davidfowl]

You can follow the same pattern as the RazorView preprocessor https://github.com/aspnet/Mvc/blob/dev/samples/MvcSample.Web/Compiler/Preprocess/RazorPreCompilation.cs. In the target project, the file needs to go into compiler/preprocess/*.cs.

How to use Roslyn "reflection" to find all the controller classes in a project? I've looked through the samples in the Roslyn repro, but I can't see an example of loading a project and finding types in it.

You need to play with the API and learn how to use it. Not sure where you can find better examples but they do exist somewhere

[mcquiggd]

This really is not good enough.

There is huge investment in T4 throughout the .Net community, focusing directly on MVC applications from T4 scaffolding of custom project items, through utilities, to entire frameworks. There is an implementation of T4 for Mono; T4 is open source.

We have T4 templates for generating TypeScript, KnockOut Models, just about everything you could imagine that is related to web development.

While Visual Studio 2015 increases support for T4, the ASP.Net vNext team decided to quietly drop it completely. And to add insult to injury, the reasoning mentioned is because 'T4 would not work for my team members that use Ubuntu'. Comments such as 'Just rewrite it in Roslyn', 'maybe the community will come up with something' are far from helpful.

I am seriously concerned at the direction the ASP.Net team are taking. I could just about suffer the pain of being forced to write tortuous Gulp scripts to compile SASS and put it in a location, bundling and minification, that used to be simple and straightforward, but to find out that the ASP.Net team prefer to focus on the needs of the tiny Ubuntu / Sublime text on a Mac user base, rather than their core audience of Visual Studio users, is maybe the last straw.

Already .Net developers are looking at all these changes, and thinking 'why should I bother - if Microsoft doesn't even like its own ecosystem, I might as well become a Node developer, with WebStorm and AWS'.

P.S Regarding 'TT is design time only solution'; hmm... that would be why I can create runtime T4 templates - in anything but ASP.Net vNext.

[mcquiggd]

As a follow up, where is the best place to register opposition to this design decision? Can you recommend the relevant User Voice / blog / issue tracker for this, if you are not interested in listening to people?

[davidfowl]

We've been developing ASP.NET 5 so far by making so any solution we come up with is viable cross platform. It's a good principle and it helps us design things that can work well from the command line but that will also light up in visual studio.

We're looking at bringing back single file generators so things like T4 and resx will just work (within visual studio only of course). We'll likely have to find other solutions for problems like these when developing cross platform.

One of our devs even ported T4 to CoreCLR https://github.com/bricelam/TextTemplating.

Stay tuned.