Skip to content

arm-resource-patch

Full name
@azure-tools/typespec-azure-resource-manager/arm-resource-patch

Validate ARM PATCH operations. The request body of a PATCH must be a model with a subset of the resource properties. The PATCH body must not contain properties that do not exist on the resource. In addition, the rule validates that:

  • All properties in the PATCH request body are optional (PATCH supports partial updates) or read-only (not included in requests).
  • No PATCH request body property has a default value (a property absent from a PATCH request leaves the existing value unchanged; defaults are not applied).
  • Every PATCH request body property maps back to a resource property that is updateable or readOnly.
  • The content-type header (when explicitly specified) is application/merge-patch+json (or the implicit application/json).

❌ Incorrect

Section titled “❌ Incorrect”
model FooResource is TrackedResource<FooProperties> {
  ...ResourceNameParameter<FooResource>;
}


model MyBadPatch {
  name?: string;
  ...Foundations.ArmTagsProperty;
  blah?: string; // does not exist on FooResource
  required: string; // not optional
  withDefault?: string = "x"; // has a default value
}

✅ Correct

Section titled “✅ Correct”
model FooResource is TrackedResource<FooProperties> {
  ...ResourceNameParameter<FooResource>;
}


model FooPatch {
  name?: string;
  ...Foundations.ArmTagsProperty;
  properties?: FooProperties;
}