For tera templates, use indent crate

[berkus]

interoptopus/crates/core/src/backend/writer.rs

Line 87 in 2ab80e7

#[macro_export]

https://lib.rs/crates/indent

[enbyted]

I have used genco in the past and it was really useful, particularly in my use case where I needed to either generate a single, concatenated C++ file or traditional split files.

Right now, it kind of requires rust nightly (otherwise the generated code will look different between nightly & stable, especially relevant for Python I assume). However, with rust 1.88 releasing soon they should work on stable.

I'm not sure if you'd want to commit to requiring latest rustc for the ergonomics, though.

[berkus]

Probably not, but i have a prototype which uses tera templates instead of manually written line-by-line code and to make those full templates indentable i will need something like indent.

[berkus]

Implemented in template-wip branch.

[ralfbiedert]

Can't remember if I commented on this in a chat or an issue, but to write down some thoughts, in brief:

• Generally, I agree the current indent! system is weird and I'd be open to replacing it with something nicer
• The main issue (and ugliness of indent) however is that lots of generation logic happens 'ad hoc', at various places, such as collecting parameter names and emitting code that forwards parameter calls; or async transforms.
• The issue with that is that these are probably hard to templatize, and / or would ideally have some sort of model first of what's to be expressed (like, some 'MIR' that knows about parameters and understands how various parameter types, such as strings, are supposed to be converted), and then emits code according to these transforms.

With that said, I fear that tera, the 'indent' crate, or something similar, would only really improve a very limited codegen subset (such as the mostly invariant 'builtins'), at the cost of the added complexity now having to understand that template system, and adding a new set of dependencies.

I'm happy to be proven wrong here, but I think the threshold should be replacing something like C# function overloads, and see if whatever template system used would still make sense for these.

[berkus]

At least it clears up some of the codegen templates (even the simplest ones you can now edit mostly natively, without fighting through counting number of indents - after generating I found a couple places where indents were incorrect in the generated code, so I guess it already paid off). It does not preclude using indent!() macros for the most hairy bits of codegen, although I think it will be possible to clean up and turn into nicer tera template blocks over time.