Update from 8.x-1.x to 3.0.0

1, Replace the code with field validation 3.0.x, .

2, Do not clear the cache, goto '/admin/modules' directly, and enable field_validation_legacy first.

The original validation rule moved to field_validation_legacy sub-module.
If you clear the cache before enable  field_validation_legacy module, you will get  a fatal error, example:

Drupal\Component\Plugin\Exception\PluginException: Plugin (length_field_validation_rule) instance class "Drupal\field_validation\Plugin\FieldValidationRule\LengthFieldValidationRule" does not exist. 

The "words_field_validation_rule" plugin does not exist. Valid plugin IDs for Drupal\field_validation\FieldValidationRuleManager are: ......

If you get any of this errors, just run

drush en field_validation_legacy

 The original validation rule still works very well in 3.x.x.