Derive macro: single field for multiple snippets

[Schniz]

Allowing dynamic list of spans to provide highlights you can be good for using miette to wrap tools like TypeScript (tsc).

Looking at the source code, maybe Vec<SourceSpan> might not cut it, but introducing a new LabelledSourceSpan and allowing everything that is Into<Vec<LabelledSourceSpan>> could also make sense.

What do you think?

[zkat]

You can actually provide as many snippets as you want if you use the Diagnostic protocol directly, which is probably a good idea if you're wrapping a tool that spits out many snippets: https://docs.rs/miette/2.0.0/miette/trait.Diagnostic.html#method.snippets

Is this what you're looking for?

[Schniz]

Ha! Indeed! This issue can be closed if you don't think the drive micro should support this use case (but I'd be happy to know and learn why!)

Anyway, thanks for your work! It works great :)

[zkat]

I mean, I guess the derive macro could support this! I'll leave this issue open in case someone wants to contribute it, but I have no drive to do this myself. Maybe you can nerd snipe @cormacrelf into wanting to do it? ;)

I'm thinking maybe something like a #[all-snippets] foo: Vec<impl Into<DiagnosticSnippet>> or something of the sort?

[cormacrelf]

Ah yes, @, the nerd sniper's targeting reticle. Good shot.

First off, I am pretty sure the lifetime on DiagnosticSnippet<'a> makes Into a bit awkward, maybe even a for<'a> kind of deal. You don't want to foray too far into that if you can avoid it ;) At least with macros you don't usually need to write down a trait's name to use it. Generally the Diagnostic trait itself with &self receivers is better suited to the task of implementing one of its methods than Into with a self receiver. Telling people to impl<'a> Into< box dyn gore > for &'a MySnippet (?) is not exactly the pinnacle of usability.

With that in mind, this is maybe a use case for my pet #41. If you can implement the Diagnostic::snippets function on a struct SnippetList(Vec<_>); then you could reuse it on other diagnostic types via the macro, no extra traits required. I figured there'd be a need for some composability of the snippets, but I would have thought it would be when building tons of similarly shaped diagnostics. As you have observed, for wrapping another compiler's output, you probably want to implement Diagnostic manually with all the methods in one spot on one type. So not quite a solution to the "solution in search of a problem" problem yet. Not specifically this, anyway, but there is definitely crossover and 41 would help anyone who wanted what was requested here.

Another option is adding an OwnedSnippet type to store in vectors, almost identical to DiagnosticSnippet except the source, which would be owned; then this all becomes very easy. It loses flexibility and I don't know who would miss that but the most plausible idea would be localisation of error messages, hints and such. Miette seems to be uniquely positioned for accessibility right now so I would want to keep that kind of thing open. I hope one day more compilers can have multilingual UIs.

[cormacrelf]

Also just noticed 2.0, nice work! You SEMVER BUMP miette? You interpret her MUST and MAY NOT as described in the RFC 2119?

[wizard-28]

Was this attribute ever added to derive macro? I can't find it in the docs.

[zkat]

An attribute was not added, no.