Search for discriminator children through multiple levels of allOf nesting

[krishanjmistry]

Attempts to fix #1458 - see the issue for more details.

I've tested this by modifying the codegen/examples/resources_mgmt.rs to point to:
azure-rest-api-specs/specification/recoveryservicesbackup/resource-manager/Microsoft.RecoveryServices/stable/2023-04-01/bms.json

This now produces the enum like so:

#[doc = "Type of the backup item."]
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
#[serde(tag = "protectableItemType")]
pub enum WorkloadProtectableItemUnion {
    AzureFileShare(AzureFileShareProtectableItem),
    #[serde(rename = "Microsoft.ClassicCompute/virtualMachines")]
    MicrosoftClassicComputeVirtualMachines(AzureIaaSClassicComputeVmProtectableItem),
    #[serde(rename = "Microsoft.Compute/virtualMachines")]
    MicrosoftComputeVirtualMachines(AzureIaaSComputeVmProtectableItem),
    AzureVmWorkloadProtectableItem(AzureVmWorkloadProtectableItem),
    #[serde(rename = "SAPAseSystem")]
    SapAseSystem(AzureVmWorkloadSapAseSystemProtectableItem),
    #[serde(rename = "SAPHanaDBInstance")]
    SapHanaDbInstance(AzureVmWorkloadSapHanaDbInstance),
    #[serde(rename = "SAPHanaDatabase")]
    SapHanaDatabase(AzureVmWorkloadSapHanaDatabaseProtectableItem),
    #[serde(rename = "HanaHSRContainer")]
    HanaHsrContainer(AzureVmWorkloadSapHanaHsrProtectableItem),
    #[serde(rename = "SAPHanaSystem")]
    SapHanaSystem(AzureVmWorkloadSapHanaSystemProtectableItem),
    #[serde(rename = "SQLAvailabilityGroupContainer")]
    SqlAvailabilityGroupContainer(AzureVmWorkloadSqlAvailabilityGroupProtectableItem),
    #[serde(rename = "SQLDataBase")]
    SqlDataBase(AzureVmWorkloadSqlDatabaseProtectableItem),
    #[serde(rename = "SQLInstance")]
    SqlInstance(AzureVmWorkloadSqlInstanceProtectableItem),
    #[serde(rename = "IaaSVMProtectableItem")]
    IaaSvmProtectableItem(IaaSvmProtectableItem),
}

I'm unsure how to test this more generally across all the API's - happy to be steered on this

[krishanjmistry]

I'm starting to think it should be a breadth-first search rather than depth-first (what I've currently implemented). That way, we'd stop at the level where we find another "discriminator"...

[cataggar]

Thanks @krishanjmistry! I ran the code generation. Here is how I ran it:

~/ms/azure-rest-api-specs> git checkout 7c906b15744aaf7b782dfb82ccefcbef05cbf20b
~/ms/azure-sdk-for-rust/services/autorust> cargo run -p azure-autorust --release

It fixed 7 control plane and 3 data place services.

Once a unit test is added, this should be good to merge.

[cataggar]

Thanks again! For extra credit, a unit test that used to fail deserialization, but now works would be nice. json from a specification example could probably be copied.

[krishanjmistry]

I've added a test in the mgmt/recoveryservicesbackup crate which does just this. Based off of the example in REST API specs which handily used one of the previous problem cases

[cataggar]

Perfect. Thanks!