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Issue Description

The default options for the @typescript-eslint/consistent-type-assertions rule are:

defaultOptions: [
  {
    assertionStyle: 'as',
    objectLiteralTypeAssertions: 'allow',
  },
],

If a user wishes to override just the objectLiteralTypeAssertions option to 'never', but retain the default assertionStyle option 'as', the expectation is that they could omit the assertionStyle option from their config, e.g.

"@typescript-eslint/consistent-type-assertions": [
  "error",
  {
    objectLiteralTypeAssertions: 'never',
  },
],

Default rule options should be deeply merged with any user-supplied config, so the expected merged result would be:

 {
    assertionStyle: 'as',
    objectLiteralTypeAssertions: 'never',
  },

However this results in the following error:

❯ eslint

Oops! Something went wrong! :(

ESLint: 9.16.0

Error: Key "rules": Key "@typescript-eslint/consistent-type-assertions":
        Value {"objectLiteralTypeAssertions":"never"} should NOT have additional properties.
                Unexpected property "objectLiteralTypeAssertions". Expected properties: "assertionStyle".
        Value {"objectLiteralTypeAssertions":"never"} should have required property 'assertionStyle'.
        Value {"objectLiteralTypeAssertions":"never"} should match exactly one schema in oneOf.

It would seem that the user-supplied config is completely replacing the default options instead of being merged?

Reproduction Repository Link

https://github.com/scottohara/ts-eslint-consistent-type-assertions

Repro Steps

1. clone the repo
2. npm install
3. eslint

Versions