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union-null

Id
@azure-tools/typespec-client-generator-core/union-null

Severity: warning

This diagnostic is issued when TCGC converts a union whose only possible value is null. A union with no non-null alternatives cannot produce a useful SDK type.

Impact

Section titled “Impact”
  • Area: SDK union type conversion. Generation continues with a fallback union shape, but a null-only union cannot become a useful SDK type.
  • Not affected: Other nullable unions with non-null variants are unaffected.

Diagnostic Message

Section titled “Diagnostic Message”

TCGC reports:

Cannot have a union containing only null types.

✅ How to Fix

Section titled “✅ How to Fix”

Add at least one non-null variant to the union or remove the union from the generated client surface.

Suppression

Section titled “Suppression”

This diagnostic should not be suppressed. Fix the spec so the union has at least one non-null variant, or remove the union from the generated client surface.