How to disable Nelmio UI in production?

@gp_sflover's comment got me on the right track, but there's more to it than just disabling NelmioApiDocBundle on prod in AppKernel.php. Configs & routes that refer to Nelmio will generate errors until you move them into dev-specific files. The following change in app/AppKernel.php was the first step:

public function registerBundles(){    $bundles = [        new Symfony\Bundle\FrameworkBundle\FrameworkBundle(),        ...        // new Nelmio\ApiDocBundle\NelmioApiDocBundle(), // <-- REMOVED FROM HERE        new Nelmio\CorsBundle\NelmioCorsBundle(),        new AppBundle\AppBundle(),    ];    if (in_array($this->getEnvironment(), ['dev', 'test'], true)) {        $bundles[] = new Nelmio\ApiDocBundle\NelmioApiDocBundle(); // <-- ADDED HERE        $bundles[] = new Symfony\Bundle\DebugBundle\DebugBundle();        ...

To eliminate the config errors, I had to move the following stuff out of app/config/config.yml and into config_dev.yml:

# nelmio Configurationnelmio_api_doc:    sandbox:        enabled: true    name: 'DLAP API Bridge'    swagger:        ...    cache:        enabled: false

Likewise, the following stuff came out of app/config/routing.yml and moved to routing_dev.yml:

NelmioApiDocBundle:    resource: "@NelmioApiDocBundle/Resources/config/routing.yml"    prefix:   /api/docnelmio_api_swagger:    resource: "@NelmioApiDocBundle/Resources/config/swagger_routing.yml"    resource: null    prefix: /api-docs

Now with symfony4 and flex you can install the bundle normally

composer require nelmio/api-doc-bundle

(So it won't be set as a require-dev depandency in your composer.json)

Now you change the setting in the project/config/bundles.php to:

Nelmio\ApiDocBundle\NelmioApiDocBundle::class => ['dev' => true]

So you don't get errors (eg from annotations), but it wont be loaded from Kernel.php

not loading the bundle in config/bundles.php throws an exception in Symfony 4.3 with NelmioApiDocBundle Version 3:

There is no extension able to load the configuration for "nelmio_api_doc" 

I ended up disabling the route for the api docs with a redirect in the environment, which needed to be disabled (prod):

#config/routes/prod/nelmio_api_doc.yamlapp.swagger:    path: /api/doc.json    methods: GET    defaults:        _controller: FrameworkBundle:Redirect:urlRedirect        path: /        permanent: trueapp.swagger_ui:    path: /api/doc    methods: GET    defaults:        _controller: FrameworkBundle:Redirect:urlRedirect        path: /        permanent: true