Fix initialization of ValidatedService.validatorFactory

[guillermocalvo]

Fixes grails/grails-core#13349

Initialization of ValidatedService.validatorFactory was accidentally bypassed in a recent PR:

ValidatorFactory getValidatorFactory() {
    if(validatorFactory == null) {
        // validator factory initialized here
    }
    return validatorFactory
}

As a result of that, data services cannot validate arguments anymore, throwing NPE.

[CLAassistant]

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[matrei]

@guillermocalvo Good catch! The field:

private ValidatorFactor validatorFactory

should probably be renamed to something else, like: factoryInstance or validatorFactoryInstance to prevent this in the future.

[matrei]

So this code actually compiles without @CompileDynamic:

    private ValidatorFactory validatorFactoryInstance

    // @CompileDynamic <-- Not needed
    private Map<Method, ExecutableValidator> executableValidatorMap = new LinkedHashMap<Method, ExecutableValidator>().withDefault {
        validatorFactory.getValidator().forExecutables()
    }

    /**
     * @return The validator factory for this service
     */
    ValidatorFactory getValidatorFactory() {
        if(validatorFactoryInstance == null) {

            Configuration configuration
            if(datastore != null) {
                configuration = JavaxValidatorRegistry.buildConfigurationFor(
                        datastore.mappingContext,
                        datastore.mappingContext.validatorRegistry.messageSource
                )
            }
            else {
                configuration = Validation.byDefaultProvider()
                                            .configure()
                configuration = configuration.ignoreXmlConfiguration()
            }
            if(parameterNameProvider != null) {
                configuration = configuration.parameterNameProvider(parameterNameProvider)
            }
            validatorFactoryInstance = configuration.buildValidatorFactory()
        }
        return validatorFactoryInstance
    }