Handling cases where feature may not have any geometry at all

[phayes]

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• [✓] I added an entry to CHANGES.md if knowledge of this change could be valuable to users.

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I've run into a few instances where I'm loading data uploaded from users (for example CSV files) where GDAL isn't able to find any geometry. In instances where you might be working with user-provided data with no geometry, calls to Feature::geometry() simply panic.

This PR documents renders Feature::geometry non-panicking by returning an Option<&Geometry>

[lnicola]

It looks like GDAL returns nullptr for these. I think I'd prefer returning an Option<&Geometry> here. It feel like the "right thing" to do, instead of expecting the user to check beforehand.

[phayes]

@lnicola ,

I was wondering about returning an Option<&Geometry>. In 99.9% of cases, you're pretty much always working with data that has geometry, so I was feeling uncertain about forcing all users to unwrap and handle an Option instead of just documenting the panic and providing a has_geometry guard function.

I'd be happy to rework this into returning an Option if that's the consensus.

[lnicola]

Agreed, but in more than 99.9% of cases, writing to a file will succeed, yet Rust still makes us check for the outcome. It's just more idiomatic this way.

(and you don't strictly need to unwrap, pattern matching (e.g. let Some(geom) = feat.geometry() else { continue; }) is usually enough)

[phayes]

@metasim, @jdroenner , @ChristianBeilschmidt - do any of you have an opinion on panic vs Option?

If there's consensus, I'll rework this to return an Option

[metasim]

@phayes 1000% Option.

[phayes]

Thanks @metasim , @lnicola . I have now reworked this PR so that Feature::geometry returns an Option

[metasim]

bors r=lnicola

[bors]

Build succeeded:

• ci gdal-32
• ci gdal-32 (--all-features)
• ci gdal-33
• ci gdal-33 (--all-features)
• ci gdal-34
• ci gdal-34 (--all-features)
• ci gdal-35
• ci gdal-35 (--all-features)
• ci ubuntu-lts
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