Update Autorest C# - IOT

[pakrym]

Contributes to #13511

Major features

1. Collections are now always initialized and collection properties are readonly by default
2. Internal deserialization ctors are removed for input-only models
3. Improved nullability support - fewer extra null checks, correct nullable types generated. Might require adding missing annotations to the swagger spec.
4. Improved header support - descriptions and x-ms-client-name honored.
5. Single value, modelAsString enums are generated as types, they were string constants before.
6. Readonly properties are not serialized - affects recordings.

What you might need to do:

1. If you copied and overrode the serialization code you might want to update it to be in sync with new generator patterns.
2. Please follow up on updating the centralized swagger file if there were workarounds applied to autorest.md

[abhipsaMisra]

Was this class handcrafted, or generated by autorest?

[pakrym]

Handcrafted.

[abhipsaMisra]

As per # 1: So this is because these fields, being collections, are readonly by default, and so they need additional helper methods?
https://github.com/pakrym/azure-sdk-for-net/blob/pakrym/update-generator-IOT/sdk/iot/Azure.Iot.Hub.Service/src/Generated/Models/ExportImportDevice.cs

[pakrym]

Correct.

[abhipsaMisra]

I see, what was the driving force behind this change? Should collections not be settable?

[pakrym]

The following guideline:

https://docs.microsoft.com/en-us/dotnet/standard/design-guidelines/guidelines-for-collections#collection-properties-and-return-values

❌ DO NOT provide settable collection properties.

Users can replace the contents of the collection by clearing the collection first and then adding the new contents.

[vinagesh]

This class can probably be internal. Will check and let you know. If it is internal, we would not need the extensions right?

[pakrym]

I'm not sure I understand why not. We would still need to create instances of this class and the code-gen for properties doesn't change depending on the class being internal or not.

[vinagesh]

And I want to add here that this is still work in progress and we are yet to make some classes internal which we do not expose. Just curious, is there something you use to be able to detect these in the API surface?

[abhipsaMisra]

We'll go through the Model types, as we work on the APIs, and make necessary changes.