schemars_0_8 feature fails to compile when schemars/preserve_order is active

[campbellcole]

When schemars/preserve_order is enabled, the Map type alias used in e.g. ObjectValidation::properties switches from BTreeMap to IndexMap, and IndexMap::append does not exist, causing this line to fail compilation:

serde_with/serde_with/src/schemars_0_8.rs

Line 573 in 2274dd1

properties.append(&mut object.properties);

This feature is enabled by default by rocket_okapi which is how I encountered this:
https://github.com/GREsau/okapi/blob/cd59fb61c5c8db1ce1976cb782efd544d8f99c38/rocket-okapi/Cargo.toml#L33-L36

I don't know off the top of my head what method IndexMap has that is equivalent to BTreeMap::append but I'd imagine this feature can be checked or a notice in the documentation could point out this incompatibility.

Thanks

[jonasbb]

Thanks for reporting that. It is a bit unfortunate that the API differs here. I have a fix in #764 and tested it manually.