[Bug]: Property is lost in projected versions

[archerzz]

Describe the bug

Let assume a service with 3 versions:

enum ApiVersions {
  @useDependency(global.Azure.Core.Versions.v1_0_Preview_2)
  v2022_06_01_preview: "2022-06-01-preview",

  v2022_09_01: "2022-09-01",
  v2022_12_01_preview: "2022-12-01-preview",
}

And a model has a property Type which is added in the first version, deleted in the 2nd version, and added back in the 3rd version:

model ExportedResource {
  id: string;
  resourceUri: string;

  @removed(ApiVersions.v2022_09_01)
  name: string;

  @removed(ApiVersions.v2022_09_01)
  @added(ApiVersions.v2022_12_01_preview)
  type: string;
}

If I specify api-version: "2022-06-01-preview", then Type should be generated. But currently the compiler will return ExportedResource without Type property.

Reproduction

Check this playground: https://azure.github.io/typespec-azure/playground?c=aW1wb3J0ICJAdHlwZXNwZWMvcmVzdCI7DQrJGmF6dXJlLXRvb2xzL8gmLcYVY29yZd8sZWMtY2xpZW50LWdlbmVyYXRvcsk3DQp1c2luZyBUeXBlU3BlYy5IdHRwO9EWUmVzdNIWVmVyc2lvbmluZ8kcQcR%2BLkNvcmXTEy5Gb3VuZGF0aW9uc9QfVHJhaXTEGg0KQHNlcnZpY2Uoew0KICB0aXRsZTogIspxIiwNCn0pDQpAdsYTZWQoQXBpxyBzKQ0KbmFtZXNwYWNl9ACvLk9sZOYA0g0KZW51bSDLPCDFckB1c2VEZXBlbmRlbmN5KGdsb2JhbC7rAKzILy52MV8wX1ByZXZpZXdfMinEPXYyMDIyXzA2XzAxX3DGGjogIsQVLTA2LTAxLccV5ADFyzA5XzAxySg5LTAxxCDIHjEy004xMs9OfcRRQHJlc291cmNlKCLICnMiKQ0KbW9kZWwgUscT5wDodmlzaWJpbGl0ecQuYWTEKSAgaWQ6IHN0cuYB2sUoa2V52zDkAW7PMuQCfMsT5QCa5gCCRXjkAqtlZO4Ais1zICDoALpVcmnPWUByZW1vdu4B8S7rAUP4AJHfOMY4QGFkZNUj7QGAxSv%2FAOF0UGFyYW3oAk9xdWVy5QFBcHJvamVjdEZpbGXHYj%2FLRf8Ag%2FAAg9FXZWTEWUZvcm1hdNFY%2FwEAz1LHLlHEEOUAy99Q11D%2FAM31AM1tYXhMaW5lcz86IGludDMy7gFeTGlzdOoAlucBYS4uLlNlbGVjyxpldGVy%2FwFT%2FQCGQGRvYygiRmlsdGVyIHRoZeQCk3VsdCBsaXN0IOYEvMQWZ2l2ZW4gZXhwcmVzxFsu5gMSZsU4%2FwE0%2FwCL6QCLZXhwYW5kzE3lARBpbnRlcmbkBOToA0tPcOQF4MRWxjd0ZW5kc%2BwFY9IpPE5vUmVwZWF0YWJsZVJlcXVlc3RzICbEQMQBTm9Db25kacQrYWzVH%2BUGW8caSWQ%2BIHvnBIVvdXRlKCIv5wWh5AW0KewAs%2BoFjk9w5wMlcG9sbMUQ5wCcKPIAri5HZXTRFlN0YXR1czzIGCzxBGI%2B5QFQZcUWIGlz8wEvLkxvbmdSdW7kAJDIHkFjxBvRV%2BYCd9Nl5wHk5QIg1mXIE%2BQCw8tY7gLS5AK4c%2BUHCzzOGXM%2ByGP%2FAkfvAkdzaGFyZWRS5AGQxBBjcmVhdGX%2FAKJDxSVPclJlcGxhY2XpAK3pAIL%2FA1L%2FAIB0ZesBcP8BkusBkvwAln0%3D&e=%40azure-tools%2Ftypespec-autorest&options=%7B%7D

Checklist

• Follow our Code of Conduct
• Check that there isn't already an issue that request the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion.
• The provided reproduction is a minimal reproducible example of the bug.

[timotheeguerin]

Minimal repo

The problem seems to be we don't assume anymore that there it was added in v1 if it was removed after.
I am not sure this is really a bug in the projection as much as it should maybe validate this scenario to tell you you might need to be explicit here otherwise its a bit ambigous

[tjprescott]

Hm... this is made trickier by the fact that whether we treat the parent containing no version information as "this thing was always available" depends on a lot of assumptions:

// Here we DO NOT want to assume val was available in v1
model Foo {
  @added(Versions.v2);
  val: string;
}

// But here we are saying do assume that val was available in v1
model Bar {
  @removed(Versions.v2);
  val: string;
}

The more special case assumptions we build in, the harder it will be to maintain the code. It may be better to simply be explicit here.

[timotheeguerin]

being explicit was also my idea, if you have a @removed and @added ask for user to be explicit on when was the first added