hook_migration_plugins_alter does not alter permanently

#2711099: Categorize migrations according to their type demonstrates that hook_migration_plugins_alter() works in a pure core context - if there's an issue with it applying to migrate_plus configuration entities, that's a migrate_plus issue (which I would expect would be addressed by #2752335: Properly integrate configuration-entity-based migrations with the core plugin manager).

migrate_plus_migration_plugins_alter() alters successfully, so there's not a broad issue with the alter hook. Unless/until there is a concrete example of this failing, closing.

i got this error.
i'm using drush ms command.

versions:

drupal/core 8.6.7
drupal/migrate_plus 4.1.0
drupal/migrate_source_csv 2.2.0
drupal/migrate_tools 4.1.0

web/modules/custom/brands/artifacts/brands.csv

id,name
1,Yamaha
2,BMW

web/modules/custom/brands/config/install/migrate_plus.migration.brands_csv.yml

langcode: en
status: true
dependencies:
  enforced:
    module:
      - brands
id: brands_csv
migration_tags:
  - CSV
migration_group: null
label: 'CSV file migration of brands'
source:
  plugin: csv
  path: /artifacts/brands.csv
  header_row_count: 1
  keys:
    - id
  column_names:
    -
      id: 'Identify'
    -
      name: 'Brand Name'
process:
  tid:
    - plugin: get
      source: id
    - plugin: make_unique_entity_field
      entity_type: taxonomy_term
      field: tid
  vid:
    plugin: default_value
    default_value: brands
  name: name
destination:
  plugin: 'entity:taxonomy_term'
migration_dependencies:
  required: {  }
optional: {  }

And in web/modules/custom/brands/brands.module

/**
 * Implements hook_migration_plugins_alter().
 */
function brands_migration_plugins_alter(&$definitions) {
  $definitions['brands_csv']['source']['path'] = drupal_get_path('module', 'brands') . $definitions['brands_csv']['source']['path'];
}

when i run drush ms, then show this error:

 [error]  Could not retrieve source count from brands_csv: File path (/artifacts/brands.csv) does not exist. 
 ------------------- -------------- -------- ------- ---------- ------------- --------------- 
  Group               Migration ID   Status   Total   Imported   Unprocessed   Last Imported  
 ------------------- -------------- -------- ------- ---------- ------------- --------------- 
  Default (default)   brands_csv     Idle     N/A     0          N/A                          
 ------------------- -------------- -------- ------- ---------- ------------- --------------- 

Did you clear cache?

Yes, I had try to clear the cache by using drupal cr and drush cr command, but it doesn't work.
Actually I also had try to reinstall my custom module several times.

function brands_migration_plugins_alter(&$definitions) {
  foreach ($definitions as $key => $migration) {
    if ($migration['id'] === 'brands_csv') {
      $migration['source']['path'] = 'asdfasdf'.drupal_get_path('module', 'brands') . $migration['source']['path'];
    }
  }
}

I try to do this, but still doesn't work.

Sorry, I have found my wrong after 9 months later.
The code should be:

function brands_migration_plugins_alter(&$definitions) {
  foreach ($definitions as $key => $migration) {
    if ($migration['id'] === 'brands_csv') {
      $migration['source']['path'] = 'asdfasdf'.drupal_get_path('module', 'brands') . $migration['source']['path'];
      $definitions['brands_csv'] = $migration;
    }
  }
}