[site:install] Distinguish between an empty db prefix and no db prefix

[jensschulze]

Distinguish between an empty db prefix and no db prefix

[site:install] Atm you have to use --no-interaction if you want to pass an empty db prefix. If you type --db-prefix="" the result is the same as if you had just simply omitted this option.

Problem/Motivation

If the value of an option is explicitly set it should not be asked for later. You can suppress this inconsistent behaviour with --no-interaction but one should not need
I am running into this issue whenever I'm trying to set up a "throw away" installation.

How to reproduce

Last checked on Drupal 8.6.1 with drupal/console 1.8.0

composer create-project drupal-composer/drupal-project:8.x-dev somedirectory --stability dev --no-interaction

cd somedirectory

vendor/bin/drupal si standard \
    --langcode="en" \
    --db-type="sqlite" \
    --db-file="sites/default/files/drupaldb.sqlite " \
    --db-prefix="" \
    --account-name=admin \
    --account-pass=admin \
    [email protected] \
    --site-name="This is just a test" \
    --site-mail="[email protected]"

Even though the --db-prefix is set, the command will ask for the prefix (the default value is an empty string).

Solution

If no --db-prefix is given, the option's default value is null. So in Site\InstallCommand::interact() we can easily distinguish between "no --db-prefix given" (ask) and "empty --db-prefix given" (no action).

[LOBsTerr]

@jensschulze Thanks I have merged it