Should we support LINEARRING type? about wkt HOT 13 CLOSED

Feature-gated enum values are a bit weird. Take this example:

• program P uses crates C1 and C2
• crates C1 and C2 use wkt
• crate C2 enables the linearring feature
• crate C1 stops building because it's no longer exhaustively matching a wkt::Geometry value

C1 could prevent this by adding fallback match branches. Alternatively, wkt could mark Geometry as non_exhaustive to force dependent crates to use a fallback when matching against it. But neither solution seems ideal.

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We could also have a variant for it and a normalization method, but I'd go for silently converting them until a user asks for more support.

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Any further thoughts on this? I like the idea of silently reading LINEARRING and converting to LineString. Adding support for shapely and JTS extensions seems like a win for good interop.

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https://geos.osgeo.org/doxygen/classgeos_1_1io_1_1WKTWriter.html

GEOS also uses it apparently

A non-standard "LINEARRING" tag is used for LinearRings. The WKT spec does not define a special tag for LinearRings. The standard tag to use is "LINESTRING".

Not sure! My initial feeling is LINEARRING could be behind a feature flag? Though I'd love to hear how commonly it gets used, though not sure how to do that

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For comparison: openlayers seems to have considered this a while back (openlayers/openlayers#2679). IIUC, they did not support it! However, given JTS, geos and shapely output it, it would be good to support it behind a feature flag.

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Along the same lines as this issue: JTS, geos, shapely also seem to support nan, inf, etc. in WKT. They have an "is_valid" predicate that'll be false, but allow conversion to / from wkt with nans. Eg. POINT (nan 0.0) or POINT (10 inf)

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it would be good to support it behind a feature flag

That sounds like a smart approach to me.

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Should we support LINEARRING as another enum-case to the Geometry type here? Then, convert to LineString in the conversion to geo-types?

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Nice catch @lnicola ; I am also convinced against feature-gated addition to the enums. Should we then store the name of the tag in addition for this variant? We could also silently convert it to a linestring, but then parsing and writing back changes the wkt.

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To make sure I understand: by "silently convert", do you mean that any linestring which is closed will be serialized to WKT as LINEARRING?

Would that behavior be behind a feature flag?

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I meant reading LINEARRING as LineString, without a feature flag. It changes the WKT if you read and write back a file, but maybe it won't bother anyone.

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I support it!

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Fixed in #67

We might choose to do more in the future, but let's see what people's actual use cases are when they come up.

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