Missing `type` field results in silent schema generation failure

[eric-carlsson]

What happened?

When generating types for an XRD with a schema containing a field missing the type property, it generates stub types containing no fields, but doesn't print any warning or error.

Instead, it should print a warning or error, ideally pointing to the invalid line/type.

How can we reproduce it?

1. Initialize a new Crossplane project.

2. Add an XRD that contains a field missing the type field:

   apiVersion: apiextensions.crossplane.io/v2
   kind: CompositeResourceDefinition
   metadata:
     name: foobar.example.com
   spec:
     group: example.com
     names:
       kind: Foobar
       plural: foobar
     scope: Namespaced
     versions:
       - name: v1alpha1
         referenceable: true
         served: true
         schema:
           openAPIV3Schema:
             type: object
             properties:
               spec:
                 properties:
                   foobar:
                     description: Notice this field's missing the "type" field
   

3. Generate types: crossplane project build

4. Look at the resulting types, such as schemas/python/models/com/example/foobar/v1alpha1.py. Notice they are just stubs—they don't even include the spec field which is correctly defined in the schema:

   # generated by datamodel-codegen:
   #   filename:  workdir/example_com_v1alpha1_foobar.yaml
   
   from __future__ import annotations
   
   from pydantic import BaseModel
   
   from ....io.k8s.apimachinery.pkg.apis.meta import v1
   
   
   class Foobar(BaseModel):
       pass
   
   
   class FoobarList(BaseModel):
       apiVersion: str | None = None
       """
       APIVersion defines the versioned schema of this representation of an object. Servers should convert recognized schemas to the latest internal value, and may reject unrecognized values. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#resources
       """
       items: list[Foobar]
       """
       List of foobar. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md
       """
       kind: str | None = None
       """
       Kind is a string value representing the REST resource this object represents. Servers may infer this from the endpoint the client submits requests to. Cannot be updated. In CamelCase. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#types-kinds
       """
       metadata: v1.ListMeta | None = None
       """
       Standard list metadata. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#types-kinds
       """

What environment did it happen in?

• Crossplane CLI version: v2.4.1
• Platform (e.g., linux/amd64): darwin/arm64
• Crossplane version (if applicable): N/A