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    Cadl ProviderHub Library

    This is a library provides additional functionality to aid in developing Azure ProviderHub service specifications.

    NOTE: This library is being deprecated in favor of the @azure-tools/cadl-azure-resource-manager library. Please consult the Migration Guide and the cadl-azure-resource-manager README for more details on how to use the new library.


    General Cadl information

    Service definition

    First thing is the global definition of the ProviderHub service. For that you can add the serviceTite, serviceVersion and armProviderNamespace decorator on your root namespace.

    @serviceTitle("<service name>")
    @serviceVersion("<service version>")
    namespace <mynamespace>;


    namespace Microsoft.MyService;

    Models/Arm Resources

    See Cadl Models docs for the basic on models.

    ProviderHub is composed of resources. Cadl ProviderHub library makes it much easier to define the structure and endpoints of such resources.

    1. Define a model representing the properties of the ARM resource.
    @doc("Properties of UserResource")
    model UserResourceProperties {
      @doc("The name of my resource")
      name: string;
      @doc("Details of my resource")
      details?: string;
    1. Define a model representing the parameter that corresponds to the resource name. Other resource identity parameters, like subscriptionId and resourceGroupName will automatically be added.
    model UserResourceNameParameter {
      @doc("UserResource resource name")
      userResourceName: string;
    1. Define the resource model as an Arm Tracked Resource
    @doc("A UserResource")
      path: "UserResources",
      parameterType: AccountNameParameter,
      collectionName: "UserResources",
    model UserResource is TrackedResource<UserResourceProperties>;

    This will now produce all the endpoints(get, post, put, patch and delete, listByResourceGroup, listBySubscription) for a resource called UserResources and the operations endpoint for the service:

    Method & Path Description
    GET /providers/Microsoft.MyService/operations List all operations for your service
    GET /subscriptions/{subscriptionId}/providers/Microsoft.MyService/userResources list all UserResource by subscription
    GET /subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.MyService/userResources list all UserResource by resource group
    GET /subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.MyService/userResources/{userResourceName} get item
    PUT /subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.MyService/userResources/{userResourceName} insert item
    PATCH /subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.MyService/userResources/{userResourceName} patch item
    DELETE /subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.MyService/userResources/{userResourceName} delete item


    Types of resources and common models for defining arm resources

    Name Description
    TrackedResource Defines a normal ARM resource, where TProperties is the model of the properties
    ProxyResource Defines a proxy Proxy resource, where TProperties is the model of the properties
    ExtensionResource Defines an extension ARM resource, where TProperties is the model of the properties


    For array type with object item , the x-ms-identifiers is used to the identifying properties, see x-ms-identifiers for detail. If the array type does not contain 'id' and no 'x-ms-identifiers' is specified explicitly, an "x-ms-identifiers" with empty array will be added for the array type by default. And there is a linter rule to check it and show below waring :

    Missing identifying properties of objects in the array item, please add @extension('x-ms-identifiers',...) to specify it.

    Sub resources

    Azure Management resources can be a sub resource of another. This can easily be defined by setting the parentResourceType property on the @armResource. The value is the parent resource type(Model with the @armResource decorator)

    For example to create a new AddressResource resource under the UserResource defined above.

    @doc("An AddressResource")
      path: "AddressResources",
      parameterType: AddressNameParameter,
      collectionName: "AddressResource",
      parentResourceType: UserResource,
    model AddressResource is TrackedResource<AddressResourceProperties>;

    Additional endpoints/operations

    Some resources will provide more than the basic CRUD operations and will need to define a custom endpoint. For that you can create a new namespace containing the operations and use the @armResourceOperations decorator referencing the resource those operations belong to.

    Example: To add a POST /notify operation on the UserResource.

    namespace Users {
      @doc("Send a notification to the user")
      op notifyUser(...CommonResourceParameters): ArmResponse<bool> | ErrorResponse;


    Custom operations in ARM still need to respect the correct response schema. Cadl-providerhub provide some models to help with reusablility and compliance.

    Model Code Description
    ArmResponse<T> 200 Base Arm 200 response.
    ArmCreatedResponse<T> 201 Resource created response
    ArmDeletedResponse 200 Resource deleted response
    ArmDeleteAcceptedResponse 202 Resource deletion in progress response
    ArmDeletedNoContentResponse 204 Resource deleted response
    Page<T> 200 Return a list of resource with ARM pagination
    ErrorResponse<T> x Error response


    Common parameters that can be used in operation

    Model In Description
    ApiVersionParameter query api-version parameter
    SubscriptionIdParameter path Subscription ID path parameter
    ResourceGroupNameParameter path Resource Group Name path parameter
    CommonResourceParameters path & query Group of Api version, Subscription ID and Resource group parameter
    ResourceUriParameter path Resource uri path parameter
    OperationIdParameter path Operation Id path parameter

    Migration Guide

    If you have been using this library to author Azure Resource Manager services, here is a short guide on how you can update your Cadl files to use the new @azure-tools/cadl-azure-resource-manager library.

    IMPORTANT: The @armResource-based service definition model will be deprecated in an upcoming release of this library so please migrate to the new library as soon as possible!

    In cadl-providerhub, ARM resource types are defined as model types which have an @armResource decorator applied:

    @doc("An AddressResource")
      path: "AddressResources",
      parameterType: AddressNameParameter,
      collectionName: "AddressResource",
      parentResourceType: UserResource,
    model AddressResource is TrackedResource<AddressResourceProperties> {}

    This would define an AddressResource tracked resource with all standard operations.

    In cadl-azure-resource-manager, the equivalent definition would be:

    @doc("An AddressResource")
    model AddressResource is TrackedResource<AddressResourceProperties> {
      name: string;
    interface AddressResource extends ResourceOperations<AddressResource> {

    Explaining the Changes

    Previously, the @armResource decorator would accept all necessary metadata for defining resource types and then generate the standard resource operations behind the scenes.

    In the new model, it is no longer necessary to mark a resource type with @armResource, but instead you must add a name property inside of your resource type which is marked with the @key and @segment decorators to replace the functionality of the parameterType nd path parameters to the old armResource decorator.

    Defining the resource type no longer automatically defines the standard lifecycle operations, either. You must now define an interface for your resource's operations which extends one or more of the Resource*<TResource> interfaces defined in cadl-azure-resource-manager. If you want all standard lifecycle operations, you only need to extend ResourceOperations<TResource, TProperties>. Otherwise, you can manually extend your interface from the standard resource operation interfaces:

    • ResourceRead<TResource>
    • ResourceCreate<TResource>
    • ResourceUpdate<TResource, TProperties>
    • ResourceDelete<TResource>
    • ResourceListBySubscription<TResource>
    • ResourceListByParent<TResource>

    For ProxyResource and ExtensionResource types, a different set of interfaces are necessary:

    • ProxyResourceOperations<TResource>

    • ExtensionResourceOperations<TResource, TProperties>: provides all standard extension resource operations

    • ExtensionResourceRead<TResource>

    • ExtensionResourceCreate<TResource>

    • ExtensionResourceUpdate<TResource, TProperties>

    • ExtensionResourceDelete<TResource>

    • ExtensionResourceList<TResource>

    Migrating Resource Operations



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