client-default-value-type-mismatch

Id

@azure-tools/typespec-client-generator-core/client-default-value-type-mismatch

Severity: warning

This diagnostic is issued when the type of the value passed to @clientDefaultValue does not match the type of the property it is applied to. When @alternateType is present, the default value is validated against the alternate type instead.

Impact

• Area: Client default values. Catches mismatches where a string default is applied to a numeric property (or vice versa), which could produce incorrect defaults in generated SDKs.
• Not affected: Properties without @clientDefaultValue, properties where the value type matches, or properties where @alternateType makes the value type valid.

❌ Incorrect Usage

model RequestOptions {
  @Azure.ClientGenerator.Core.Legacy.clientDefaultValue("10")
  pageSize?: int32; // string default on numeric property

  @Azure.ClientGenerator.Core.Legacy.clientDefaultValue(123)
  sortOrder?: string; // numeric default on string property
}

Diagnostic Message

TCGC reports:

Client default value type "string" does not match property type "int32". The default value type should match the property type.

✅ How to Fix

Use a default value whose type matches the property type:

model RequestOptions {
  @Azure.ClientGenerator.Core.Legacy.clientDefaultValue(10)
  pageSize?: int32;

  @Azure.ClientGenerator.Core.Legacy.clientDefaultValue("asc")
  sortOrder?: string;
}

Or use @alternateType to change the client-facing type so it matches the default value:

@Azure.ClientGenerator.Core.Legacy.clientDefaultValue("10")
@Azure.ClientGenerator.Core.alternateType(string)
@query pageSize?: int32; // no warning — default matches alternate type

Suppression

If the mismatch is intentional, you can suppress this diagnostic. Note that the mismatched default value will still be applied to generated SDKs when suppressed.

#suppress "@azure-tools/typespec-client-generator-core/client-default-value-type-mismatch" "intentional mismatch"
@Azure.ClientGenerator.Core.Legacy.clientDefaultValue("10")
@query pageSize?: int32;