[GraphQL] Explicit Mutation description is overwritten by the generated default

[fabianbloching]

Description

Setting description: on a GraphQL Mutation (or DeleteMutation) has no effect: the SDL always shows the generated "Creates a X." text. Query/QueryCollection are not affected — an explicit description on a query is preserved, so mutations behave inconsistently.

Minimal reproduction

#[ApiResource(graphQlOperations: [
    new Mutation(name: 'create', description: 'My custom description.'),
])]
class Book
{
}

Resulting SDL:

type Mutation {
  """Creates a Book."""
  createBook(input: createBookInput!): createBookPayload
}

Expected:

type Mutation {
  """My custom description."""
  createBook(input: createBookInput!): createBookPayload
}

Root cause

OperationDefaultsTrait::getOperationWithDefaults() overwrites the description of every mutation unconditionally:

https://github.com/api-platform/core/blob/4.3/src/Metadata/Resource/Factory/OperationDefaultsTrait.php#L205-L207

if ($operation instanceof Mutation) {
    $operation = $operation->withDescription(ucfirst("{$operation->getName()}s a {$resource->getShortName()}."));
}

There is no null-check, so a user-provided description is discarded.

Regression

The generated text was introduced in #3477 as a fallback only — "a custom value takes precedence; it does not overwrite existing descriptions". A later refactoring that moved this logic into OperationDefaultsTrait dropped the null-check.

This was reported before in #6035, which was closed as stale without a fix.

Versions

Reproduced with api-platform/metadata v4.2.15; the code is still present on 4.3 and main.

Expected behavior

An explicitly provided description is preserved; the generated "{name}s a {ShortName}." text is only a fallback when none is set.