dynamic resolvers + theme code resolver

[therouv]

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Changes

Dynamic Resolvers

Previously, the environment variable resolver was the only available resolver. This was not very flexible if one might want to add additional resolvers (either to this module or project-specific resolvers).

The ImportProcessor now accepts an array with all resolvers that have been defined in di.xml.

Each resolver must implement a supports method which checks whether a value or a config path matches certain criteria. If yes, the resolver will be called.

If a value can not be resolved and should be skipped in the process, a UnresolveableValueException exception must be thrown by the resolver.

Environment Variable Resolver

The prompting for missing environment variables has been moved to the resolver and is no longer part of the ImportProcessor.

Theme Code Resolver (NEW)

When assigning a theme to a website/store, Magento internally saves the ID of the selected theme in the config database table (path design/theme/theme_id). Theme IDs might change but also hard-coding them in a config file is not recommended.

Previously, there was no way to configure this value using this module. Now, you can use a specific syntax for theme codes in the configuration files. This is done with the syntax %theme(path)% (after discussing with some people, I opted for a similar syntax like we already use for environment variables).

For example, this might be the content of your config file:

design/theme/theme_id:
  default:
    0: '%theme(frontend/Vendor/theme)%'

The placeholder requires the theme path that is defined as component name in the registration.php file of a Magento theme, e.g. frontend/Vendor/theme (never use just Vendor/theme!).

The module will check if this theme is available in Magento. If yes, the module will write the ID of the theme to the core_config_data table. If no theme with that path can be found, an UnresolveableValueException exception will be thrown.