The future of Leaf and Tau

Leaf

Initially, if you do not know, the Leaf 4 launch comprises some main syntactical changes in comparison with the earlier model. Curly brackets had been changed with the brand new #finish prefix syntax.

This can be a main step ahead, but additionally a breaking change, meaning it’s a must to improve your presently present Leaf 3 codebase, in any other case your templates will not work. The opposite main change is expounded to template inheritance. The brand new prolong, export and import key phrases changed the earlier embed and set key phrases, once more.

So right me if I am flawed, however this enchancment is like taking a step backward, as a result of in Leaf 2, we had kind of the identical template inheritance API capabilities (import, export, prolong, and embed). I suppose that this modification will be complicated for some individuals who had been already accustomed to the 2nd or the 3rd version of Leaf. (I used to be shocked once I noticed these adjustments.) 😐

I do not wish to criticize this resolution, however these adjustments do not vital deserve a significant model quantity. It isn’t a giant enchancment from a developer (end-user) perspective. The one factor what modified with Leaf 4.0.0 is that we builders have to vary our codebase to make issues work once more, however we have gained nearly zero new options, that I would anticipate from a significant launch.

I used to be very unhappy about this and I can think about that this will make server facet Swift builders fairly upset. I’ve already missed various options from Leaf, that I would anticipate from a contemporary template engine. Simply check out mustache or handlebars, they’re in fact older, nevertheless it’s value to say that they’ve some far more superior options, that you simply nonetheless cannot do in Leaf. 😢

Now, in the midst of the 4.0.0 improvement an attention-grabbing factor occurred with Leaf…

Tau

There was a brand new department known as Tau (means rebirth) created and maintained by @tdotclare. I jumped the practice and began to make use of this experimental department as a substitute of the primary / dev.

We additionally began to speak rather a lot with tdotclare, since there have been some points, particularly at first, however lastly I’ve discovered somebody on Vapor’s discord who I may ask about Leaf. He helped me quite a bit and I am extraordinarily grateful, as a result of with out him, the template layer of Feather CMS would not be such a tremendous (modular, reusable, extensible) system. 🙏

Lengthy story quick, tdotclare carried out numerous great new features for Leaf Tau, the entire system began to appear like as an actual template engine, not simply one thing that you can use to switch key-based variables in a really lengthy output string. (Pardon me, however that is the case with Leaf.) 🙈

We had a imaginative and prescient about the way forward for Tau, the place you can differentiate sorts, create new language parts and particular extensions (capabilities, strategies, blocks, contexts) for the duty it’s essential clear up, in a protected and simple method. Tau already has all these goodies and much more.

You may outline variables and constants, and the brand new template hierarchy system appears to be extra logical and future proof than every other earlier variants of the template inheritance APIs. Lastly, after numerous hours of conversations, feedbacks, testing, and bug squashing, the Tau options had been merged to the primary department and launched underneath the 4.0.0-tau.1 tag.

If you wish to preserve utilizing Tau, you need to pin your Swift dependency variations to:
.bundle(url: "https://github.com/vapor/leaf", .precise("4.0.0-tau.1")),
.bundle(url: "https://github.com/vapor/leaf-kit", .precise("1.0.0-tau.1.1")),

Sadly, the Vapor core staff determined to revert these changes shortly after the Tau launch and not using a detailed rationalization. So far as I do know the primary motive was that the core staff needs to maintain Leaf as a “easy” template engine. Do not get me flawed, I am tremendous with that call, however then it was undoubtedly a mistake to formally launch Tau and shortly after take away it identical to that. 😕

The longer term

So this is what I used to be enthusiastic about this whole matter in the previous couple of months.

Leaf 4.x

I’ve all the time felt like these new Tau options are method too good to easily drop them, simply to go along with Leaf. Plus what does the time period “easy” means? Can I anticipate something new in Leaf or is it going to be solely bug fixes solely any more? Is the long run brilliant for Leaf or ought to I merely drop it? 💧

Effectively, sure. I am not going to make use of Leaf once more.

In case you are planning to construct a brand new mission and also you want a dependable, quick, dynamic template engine with a simply very primary (restricted) function set, then you need to think about using Leaf. 🍃

Area Particular Languages

These days everyone seems to be into DSL’s (SwiftUI), so why not use a DSL library, resembling HTMLKit or Plot as a substitute of Leaf? If the template engine will not permit me to do extra sooner or later then a DSL can be a method more sensible choice. It could possibly be extra protected and performant, however in fact we would sacrifice the dynamic nature (you all the time must recompile the complete server code after one thing adjustments), however nonetheless, based mostly on the circumstances, I can solely consider this resolution as a greater different.

If you happen to do not wish to dynamically replace templates and also you’re tremendous with the “static web site generator” strategy, then I would recommend to make use of a Area Particular Language based mostly template engine.

Tau

It’s a dynamic template engine with a really wealthy function set, that you should use to construct extra advanced templates. Since Tau is derived from Leaf it implies that the syntax may be very related, so the official Leaf documentation covers just about every thing that it’s a must to find out about it, plus I have already got some good tutorials on my web site about using the new features of Tau.

Primarily based on my expertise, I’ll stick to “Tau”.

You need to know, that the 4.0.0-tau.1 launch underneath the vapor/leaf repository may be very steady, so you should use that tag for now if you wish to give an opportunity to Tau.

It’s value to say that Tau will likely be re-released afterward in a separate repository underneath a model new identify. Sadly, I am unable to give a precise schedule for the transition course of simply but. Hopefully this manner we are able to keep away from additional confusions and builders can choose the precise software for the job.

The Vapor core staff and the authors of Leaf are doing a tremendous job. This submit just isn’t meant to hurt them in any method, however I simply wished to supply some actual rationalization for everybody who was asking me in regards to the present standing of Leaf and Tau. Thanks for understanding this. 🙏