Support scalar-only union values in generated connector property maps (Python) #104

Problem

The generated connector SDK needs to preserve a scalar-only application-property map contract. A JSON Schema value can allow strings, numbers and Booleans while excluding nested objects and arrays. Treating schema type as only a single string does not represent that contract; an object-only generated value model rejects valid scalar callers, while unrestricted values erase the declared constraint.

This issue tracks SDK/generator support, separately from corrections needed in a connector's published source schema. A generated SDK must not guess scalar support from an empty object definition.

Minimal Schema

{
  "type": "object",
  "properties": {
    "Properties": {
      "type": "object",
      "additionalProperties": {
        "type": ["string", "number", "boolean"]
      }
    }
  }
}

This is a JSON Schema example, not a claim that every Swagger 2.0 importer accepts array-valued type. Equivalent union constructs must be handled according to the supported schema dialect. If the import path cannot preserve a construct, provide an actionable diagnostic rather than silently dropping it or publishing an incorrect generated contract.

Valid property maps include {"eventType":"sample"}, {"attempt":1,"ratio":1.5}, {"enabled":true}, and a mixture of those values. {"eventType":{"value":"sample"}} and {"eventType":["sample"]} are outside this scalar-only contract. JSON Schema number includes integers. Nullability is a separate contract decision, not assumed here.

Expected Result

Emit a dictionary whose value annotation preserves the allowed scalar alternatives, for example dict[str, str | int | float | bool], with the repository-supported spelling. Do not emit ObjectEntity-valued maps or silently widen an explicit scalar-only union to Any.

Acceptance Criteria

• Generate from a pinned scalar-union schema and verify the emitted API/model, not just generator source text.
• Type-level positive cases accept each scalar type and mixed maps; negative cases reject object/array entries where the language supports static checking.
• Serialization preserves JSON strings, numbers and Booleans without coercing every value to text.
• Exercise supported equivalent union forms and unsupported-dialect diagnostics; do not silently discard union constraints.
• Preserve genuinely object-valued maps, including referenced structured model schemas. Do not globally reinterpret object-only schemas as scalar unions.
• Keep generated operation inventories and distinct wire-property names unchanged.
• Test nullable and non-nullable contracts separately. Designer enforcement is not required for this SDK work.

Public Context

The Event Hubs scalar-property typing symptom was reported in this public Python SDK review discussion. The reproducer above is synthetic and independent of any deployment, subscription, account or non-public repository.

Specification: JSON Schema Draft-4 type validation.

Prepared with GitHub Copilot.

Cross-Language Tracking

• .NET issue
• TypeScript issue