Resource model changes the order of properties

[pshao25]

Think about this case:

"experiment": {
  "type": "object",
  "description": "Model that represents a Experiment resource.",
  "allOf": [
    {
      "$ref": "../../../../../../common-types/resource-management/v2/types.json#/definitions/TrackedResource"
    }
  ],
  "properties": {
    "systemData": {
      "description": "The system metadata of the experiment resource.",
      "$ref": "../../../../../../common-types/resource-management/v2/types.json#/definitions/systemData",
      "readOnly": true
    },
    "identity": {
      "description": "The identity of the experiment resource.",
      "$ref": "./common.json#/definitions/resourceIdentity"
    },
    "properties": {
      "description": "The properties of the experiment resource.",
      "x-ms-client-flatten": true,
      "$ref": "#/definitions/experimentProperties"
    }
  },
  "required": [
    "properties"
  ]
}

identity is in front of properties.

Transform it into TypeSpec:

model Experiment
  is Azure.ResourceManager.TrackedResource<ExperimentProperties, false> {
  ...ResourceNameParameter<
    Resource = Experiment,
    KeyName = "experimentName",
    SegmentName = "experiments",
    NamePattern = "^[^<>%&:?#/\\\\]+$"
  >;
  ...Azure.ResourceManager.ManagedServiceIdentityProperty;
}

identity goes after properties.

Change the order of properties is breaking change in .net SDK.

Though we might somehow do customization to mitigate,

1. It looks so common. We don't want to do so many customizations.
2. If there is a new property added in XXXProperties (in this case, customer does add a new property to ExperimentProperties), it would be a disaster to mitigate.
3. Further, if identity is type of string, experimentProperties contains xxx: string. the order changes from (string identity, string xxx) to (string xxx, string identity). There is no solution to customize.

[markcowl]

If the order of properties is a critical issue, then the template is not required for this scenario:

model Experiment extends Core.TrackedResource {
  ...ResourceNameParameter<
    Resource = Experiment,
    KeyName = "experimentName",
    SegmentName = "experiments",
    NamePattern = "^[^<>%&:?#/\\\\]+$"
  >;
 
  ...Azure.ResourceManager.ManagedServiceIdentityProperty;
  properties?: ExperimentProperties;
}

Using a template is not required.

[brrusino]

@markcowl After making this change, I am getting the following error:
No @armResource registration found for type Experiment

Also, which Core library is this TrackedResource model in? I was able to find it in Azure.ResourceManager.Foundations but not Azure.Core.

[pshao25]

More specifically for this case, you should do

/**
 * Model that represents a Experiment resource.
 */
@Azure.ResourceManager.Private.armResourceInternal(ExperimentProperties)
@includeInapplicableMetadataInPayload(false)
model Experiment extends Foundations.TrackedResource {
  ...ResourceNameParameter<
    Resource = Experiment,
    KeyName = "experimentName",
    SegmentName = "experiments",
    NamePattern = "^[^<>%&:?#/\\\\]+$"
  >;
  ...Azure.ResourceManager.ManagedServiceIdentityProperty;

  @doc("The resource-specific properties for this resource.")
  @Azure.ResourceManager.Private.conditionalClientFlatten
  @Azure.ResourceManager.Private.armResourcePropertiesOptionality(false)
  properties?: ExperimentProperties;
}

Then suppress all the warnings because of the private decorators.