Write custom deserializer function for Option<Cow<str>>

[sffc]

Workaround for serde-rs/serde#2016

@Manishearth: opinions on where this should go?

[codecov-commenter]

Codecov Report

Merging #821 (1ad8852) into main (2b7ca3b) will increase coverage by 0.09%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #821      +/-   ##
==========================================
+ Coverage   75.34%   75.44%   +0.09%     
==========================================
  Files         197      193       -4     
  Lines       12563    12499      -64     
==========================================
- Hits         9466     9430      -36     
+ Misses       3097     3069      -28     

Impacted Files	Coverage Δ
provider/testdata/src/test_data_provider.rs
provider/testdata/src/paths.rs
provider/testdata/src/lib.rs
provider/testdata/src/metadata.rs
experimental/provider_ppucd/src/parse_ppucd.rs	93.13% <0.00%> (+0.13%)	⬆️

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[coveralls]

Pull Request Test Coverage Report for Build 1e77bd4636ba5acea5377d8af8f385012fd077ad-PR-821

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.008%) to 75.516%

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Totals
Change from base Build 2b7ca3bd55486daafbcf579d05243773e006ec89:	0.008%
Covered Lines:	9558
Relevant Lines:	12657

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💛 - Coveralls

[Manishearth]

No opinion on where this should go. Probably worth making it a public export of provider/core? Other data structs will need this, yes?

[Manishearth]

chore: Probably should have a comment saying why we have this

[sffc]

I can stick it in the icu_provider module, but I'm just a little hesitant to start making icu_provider a bag of random utilities. But maybe there just isn't a better place to use it, and most call sites that need this will be depending on icu_provider.

[Manishearth]

Yeah I don't have a good answer for you, I don't have strong opinions on where it should go so use your best judgement imo.

[sffc]

2021-06-24:

• @nordzilla - I kind-of- like the idea of adding it as a separate utility.
• @Manishearth - But then it has to be published on crates.io.
• @nordzilla - Yeah, good point. So I think we should put this in icu_provider and hopefully we can delete it when the upstream bug gets fixed.
• @sffc - I filed a follow-up issue: Upstream workaround for Option<Cow> in Serde #825

[Manishearth]

I think upstreaming this is going to be unlikely and for now we should just stick this in provider_core.

[sffc]

I think upstreaming this is going to be unlikely and for now we should just stick this in provider_core.

Acknowledged, but I made a PR for upstreaming this anyway:

serde-rs/serde#2072

It should be noted that this only affects serde_derive, not serde itself.

[sffc]

So we may not end up needing this in the short-term because PluralRules is going to be migrated off of Option<Cow>. However, we may need it in the future. I will file a follow-up issue to discuss further.

[robertbastian]

I need this in #1550, so let's merge? We could put it alongside deduplicating_array in a serde_utils crate.

[sffc]

Superseded by #1556.