core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php b/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php
index 2caddfe..68c2054 100644
--- a/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php
+++ b/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php
@@ -80,9 +80,15 @@ public function setValue($values, $notify = TRUE) {
     // Update any existing property objects.
     foreach ($this->properties as $name => $property) {
       $data_definition = $property->getDataDefinition();
+
+      // Some computed properties are computed only because they have custom
+      // storage (e.g. path aliases); setting a value on these is necessary. But
+      // read-only computed properties don't ever need writing to.
+      // @see path_entity_base_field_info()
       if ($data_definition->isReadOnly() && $data_definition->isComputed()) {
         continue;
       }
+
       $value = isset($values[$name]) ? $values[$name] : NULL;
       $property->setValue($value, FALSE);
       // Remove the value from $this->values to ensure it does not contain any