Re: [MirageOS-devel] Handling Lwt exceptions

[Thomas Leonard <talex5@xxxxxxxxx>]

On 5 May 2016 at 12:01, Joel Hughes <rudenoise@xxxxxxxxx> wrote:
> Morning all,
>
> I was hoping to get some pointers to good/simple examples of error-handling
> in Lwt.
>
> After yesterday's call I started looking at getting latest "tag" rather than
> "release" using ocaml-github - Github's API's concept of a release is
> distinct from git tagging, which explains some repos showing no releases.
>
> The approach is fine for repos that have tags but
> Github.Repo.get_tags_and_times raises an Lwt exception for repos without any
> tags.
>
> https://github.com/rudenoise/mirage-dashboard/blob/tags/src/get_releases.ml#L66
>
> I'd like to get my head around how I could catch this exception and swallow
> it (as needed during the cycle through each repo) - returning a default
> value/message.
>
> Does anyone have a link to a very simple example or tutorial, I'm having
> trouble finding one?

I'll let someone else answer about whether the API should be changed,
but given that it does raise, you can handle it like this:

 Lwt.catch
  (fun () -> call_that_might_raise ...)
  (function
   | Error_you_want_to_catch -> handle error here
   | ex -> Lwt.fail ex  (* Pass others on *)
  )

> Thanks
>
> Joel
>
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>



-- 
Dr Thomas Leonard        http://roscidus.com/blog/
GPG: DA98 25AE CAD0 8975 7CDA  BD8E 0713 3F96 CA74 D8BA

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