feat: error handle generation on validation fail

[Duckaet]

implements follow-up #538

1.entrypoint expect() would cause panic, handled err better
2.PxStripper for Impl and Trait aswell
3.add ast nodes functions to re-emit with input
4.stripped almost at all entrypoints
5.also generated handle constants when validation fails... is it graceful?

add a fail test as suggested in issue.

[LukeMathWalker]

Thanks for picking this up!
I think we need to refine the approach a bit further: the user may have specified a custom id which will be used as the name of the generated handle type. If that's present, we should honor it.

[LukeMathWalker]

use pavex_macros::error_handler;

#[error_handler(id = "CUSTOM")]  
pub fn invalid_handler(_a: &str, _b: u64) -> pavex::Response {
    todo!()
}

fn test_handle_exists() {
    let _handle = CUSTOM;
}

fn main() {}

^ The above should not cause an error in test_handle_exists when compiled.

[Duckaet]

I'm not able to understand the better approach.. as custom id is already honored like this

in the error_handler.rs ->

Err(e) => {
let properties = Properties::new(metadata, 0);
let result = emit(impl_, item, properties);

and in emit function
let id = id.unwrap_or_else(|| default_id(impl_.as_ref(), &item));

and the test also does not cause an error in "fn test_handle_exists"

ig a better approach would be to re-emit striped functions? as now it only emits the error and handler
let combined_error = quote::quote! {
#error_tokens
#handle_def
};
return Err(combined_error.into());

should i implement this approach? @LukeMathWalker

[LukeMathWalker]

No need to handle foreign functions, it's a usecase that we won't officially support for a while, probably ever.

[LukeMathWalker]

Same as above, let's remove it.

[LukeMathWalker]

You're right, I was thinking of a slightly different scenario—parsing the entire metadata fails, but we can successfully parse a subset of it out (i.e. the id).
No need to handle everything at this stage though. Left a couple of small comments, then we're good to go.

[LukeMathWalker]

/ok-to-test sha=3f7f2b9

[LukeMathWalker]

Thanks!

[Duckaet]

Thanks!

I learnt alot, while reading the codebase... thanks to you ❤️