Skip on Condition

Skips processing when the input value matches a condition.

Available configuration keys:

• method: What to do if the condition is met. Possible values:
  1. row: Skips the entire row when an empty value is encountered.
  2. process: Prevents further processing of the input property when the value is empty.
• condition: The condition plugin to evaluate on the source. Can be either:
  1. The id of the condition. This is possible if the condition does not require any configuration, such as the 'empty' condition.
  2. An array with a 'plugin' key that is the id of the condition. Any additional properties will be used as configuration when creating an instance of the condition.
• message: (optional) A message to be logged in the {migrate_message_*} table for this row. Messages are only logged for the 'row' method. If not set, nothing is logged in the message table.

• message_context: (optional) One or more source or destination properties to be used in the message. If message_context is set, the message will be passed as the first argument to sprintf, with the values of the properties specified in message_context passed as the subsequent arguments to sprintf.

Examples

1. Recreate core's skip_on_empty

...but with fine control over how to handle an array. Skip on Condition is set to "handle multiples" which means that the process plugin gets the whole current value of the process pipeline at once.

1.a) 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

If we instead want to evaluate the condition on each element of the array individually, we use the "helper" condition has_element as follows.

1.b) Skip the row if any item 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

2. Skip old content

Using the older_than condition, we can skip a row if the content is older than we would like. We can also log a message that contains context.

process:
  skip_old_content:
    plugin: skip_on_condition
    source: my_source_date
    condition:
      plugin: older_than
      format: 'j M Y' #the format of the source date
      value: '-1 month'
    method: row
    message: 'This content is from %s and is soooooo last month.'
    message_context:
      - my_source_date

The value of the my_source_date property will replace the %s when the message is logged.

3. Skip on NOT empty

Sometimes we want to skip a row/process if a certain source value is NOT empty. Here are two versions of the syntax that skip on not empty.

process:
  skip_on_not_empty:
    plugin: skip_on_condition
    condition:
      plugin: empty
      negate: true
    source: my_source_value
    method: row

process:
  skip_on_not_empty:
    plugin: skip_on_condition
    condition: not:empty
    source: my_source_value
    method: row

4. Skip process if not set

The core Migrate module provides a skip_row_if_not_set process plugin. However, there is no dedicated plugin to skip a process rather than the row if the source if not set.

process:
  skip_process_if_not_set:
    plugin: skip_on_condition
    condition: not:isset
    source: my_source_value
    method: process

Equivalently, the is_null condition could be used in place of not:isset.

5. Skip content cloned by date_repeat_entity

The contributed D7 module date_repeat_entity allows for recurring events by cloning content automatically. When migrating that content to D9, you may want to ignore the cloned content and only migrate the original node. 

process:
  _skip_clones:
    plugin: skip_on_condition
    method: row
    condition:
      plugin: not:equals
      property: uuid # Notice this is a source property, not a constant value.
    source: date_repeat_entity_master_uuid/0/value

This is interesting in that we compare two source values, which cannot be done by skip_on_value from migrate_plus.