Currently component parameters must not take Null values, otherwise a component isn't called at all, so any property-setter component wouldn't work when a property is NULL.
Example: you create a component to calculate and set price for a commerce product so you pass commerce price property to that component. The problem comes when price is not set yet, since you can't pass NULL values to component.
The patch provided resolves this issue by adding "Required" column to the parameters table on the component settings form (see the screenshot NOTE: initially the option was logically inverted and was called "Allow Null". Now it is called "Required"). It is a checkbox with default value set to true (checked).
Needs work
2.0
Rules Core
A documentation change is requested elsewhere. For Drupal core (and possibly other projects), once the change has been committed, this status should be recorded in a change record node.
Changes an existing API or subsystem. Not backportable to earlier major versions, unless absolutely required to fix a critical bug.
Enhances an existing API or introduces a new subsystem. Depending on the size and impact, possibly backportable to earlier major versions.
The change is currently missing an automated test that fails when run with the original code, and succeeds when the bug has been fixed.
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