Empty

Available configuration keys: 

• negate: (optional) Whether the 'empty' condition should be negated. Defaults to FALSE. You can also negate the 'empty' plugin by using 'not:empty' as the plugin id.
• source: (optional) Property or array of properties on which to evaluate the condition. If not set, the condition will be evaluated on the source passed to the ::evaluate() method, typically the source of the process plugin that is using this condition.

Examples

1. Skip on empty with clear array handling

The core skip_on_empty process plugin can have trouble with arrays. (See #3254356: [meta] skip_on_empty problems with arrays). But unlike skip_on_empty, the skip_on_condition process plugin "handles multiples", which allows us to solve problems more exactly.

 Skip the row when the source is an empty array.

process:
  skip_on_empty_array:
    plugin: skip_on_condition
    condition: empty
    source: my_source_array
    method: row
    message: 'The source array was empty'

Or we can skip if any value in the source array is empty.

process:
  skip_if_any_array_element_is_empty:
    plugin: skip_on_condition
    condition:
      plugin: has_element
      condition: empty
    source: my_source_array
    method: row
    message: 'At least one element of the array was empty'

 2. Negate a boolean

That is, change TRUE to FALSE and FALSE to TRUE. This can be done with a static map, but my goodness is the following clearer.

process:
  field_boolean:
    plugin: evaluate_condition
    condition: not:empty
    source: my_source_boolean_with_the_wrong_sign