Implemented TH splices for validated ByteString literals

[vdukhovni]

thLiteral    :: Quote m => String -> Code m ByteString
thHexLiteral :: Quote m => String -> Code m ByteString

The former rejects inputs with non-octet code points above 0xFF. The latter rejects odd-length inputs or inputs with characters other than non-hexadecimal digits.

[vdukhovni]

@Bodigrim I don't understand what's going on with CI. Any help appreciated.

[Bodigrim]

@vdukhovni no idea tbh. Maybe something changed under the hood, either in runner images or in the haskell action.

[vdukhovni]

I have very little experience tuning GitHub CI. Any chance someone can help?

[Bodigrim]

It seems it was an intermittent failure with https://github.com/haskell-actions/setup. I don't think you need to touch CI setup in this PR.

[vdukhovni]

Thanks, indeed most of the problems appear to have been transient. I reverted the CI changes, and the only failure so far is with OpenBSD, which reports:
⚠️ Not enough compute credits to prioritize tasks!

Otherwise, no issues. So I think I'm done, unless you'd prefer to name the two functions differently. The names thLiteral and thHexLiteral were a best effort choice at the time, but one can probably make a case for other choices if these don't appeal.

[vdukhovni]

Review request: @hsyl20 @Bodigrim @clyring

[hsyl20]

LGTM

I would prefer more explicit names: something like literalFromAscii (or literalFromChar8) and literalFromHex

[vdukhovni]

LGTM

I would prefer more explicit names: something like literalFromAscii (or literalFromChar8) and literalFromHex

Many thanks for the prompt review! I'm about to push a fixup for all the nits, and what remains then is to reach consensus on the splice names. Of the above I prefer literalFromChar8 over literalFromAscii and have no objections to literalFromHex. I take it you don't see any benefit from including a th prefix to make it clear these are splices rather than directly usable functions?

[hsyl20]

I take it you don't see any benefit from including a th prefix to make it clear these are splices rather than directly usable functions?

Yes the type and literal already convey that imo.

[vdukhovni]

@hsyl20, @Bodigrim Many thanks for the reviews, much appreciated. If at some point you find some more review cycles, I've revived, rebased and improved #569, so reviews there would also be great.