Remove boilerplates and fix bugs

[ryo33]

Requires: jsinger67/parol_runtime#2

I removed the boilerplates by using re-exports from parol_runtime.
Also, I fixed two bugs:

• parol generates a comment like /* */ */ for token '*/', and this causes a compile error.
• #![allow(unused_imports)] generated by parol causes a compile error when using import!() macro. [Rust] error: an inner attribute is not permitted in this context - #4968 regression google/flatbuffers#6261

[jsinger67]

Looks good 👍

[jsinger67]

Thanks a lot for your great work 🥇

[jsinger67]

I have problems with generated crates via parol new subcommands that relate to the removal of dependencies in user crates.
error[E0433]: failed to resolve: could not find derive_builder in the list of imported crates

• parol_runtime is updated to version 0.9.0
• parol's changes are on main branch

Please have a look at this.

To reproduce this, please issue the command
parol new -b -p .\my-grammar
then
cd .\my-grammar\
and
cargo build

[ryo33]

Thanks for merging!

Please have a look at this.

I'll try to fix that as soon as possible.

[ryo33]

Fixed in #24

[jsinger67]

@ryo33, I experienced a problem with features of crates that are re-exported for reuse from parol_runtime crate.
I used to enable the feature fancy of miette to get useful error reports in crates generated by parol new like this:

Error: parol_runtime::parser::unprocessed_input

× Failed parsing file ./test.txt
╰─▶ Unprocessed input is left after parsing has finished
╭─[./test.txt:5:1]
5 │
6 │ # End
· ───┬──
· ╰── Last processed token
╰────
help: Unprocessed input is left after parsing has finished

But currently I get this:

Error: Diagnostic { message: "Failed parsing file ./test.txt", code: "parol_runtime::parser::unprocessed_input", help: "Unprocessed input is left after parsing has finished", labels: "[LabeledSpan { label: Some("Last processed token"), span: SourceSpan { offset: SourceOffset(86), length: SourceOffset(5) } }]" }
NOTE: If you're looking for the fancy error reports, install miette with the fancy feature, or write your own and hook it up with miette::set_hook().

The feature fancy is not enabled in parol_runtime itself, because it is not needed there, which explains the changed behavior.

I think that it isn't possible to use a re-exported crate and thereby changing the used feature set.

Do you have any idea how to deal with that?

I could simply add the line

miette = { version = "5.2.0", features = ["fancy"] }

to the crate's Cargo.toml but this seems awkward.

[ryo33]

I have an idea of one way that might work. I will try it tomorrow.

[ryo33]

I tried it and found it difficult at present.

rust-lang/cargo#674

[ryo33]

This is a separate discussion, but it seems a bit awkward that the generated code returns miette::Report. Since the generated parser is more of a library than an application, it looks more natural to return a dedicated error enum, as said in https://docs.rs/miette/latest/miette/#-in-libraries:

Then, return this error type from all your fallible public APIs. It’s a best practice to wrap any “external” error types in your error enum instead of using something like Report in a library.

Sometime soon, I was going to open an issue titled "Structural Errors". IMO It's sufficient to return the information necessary to produce a fancy error message as most parser combinator libraries do.

[jsinger67]

You are right.
miette gave me the opportunity to get quickly to a result. For instance, I used support from miette like miette::protocol::SourceSpan to covey the error position to the caller.

This can surely be redesigned to emphasize the role of parol_runtime and also the generated parsers as libraries.
I think it should be possible to use e.g., thiserror or anyhow as a substitution and miette, if desired, as error wrapper in applications using those parsers.
This choice should be given to the user.