Issue #2555089 by phenaproxima, mikeryan: d7_filter_format migration mishandles format IDs

core/modules/filter/migration_templates/d7_filter_format.yml

@@ -5,15 +5,7 @@ migration_tags:
 source:
   plugin: d7_filter_format
 process:
-  format:
-    -
-      plugin: machine_name
-      source: name
-    -
-      plugin: dedupe_entity
-      entity_type: filter_format
-      field: format
-      length: 32
+  format: format
   name: name
   cache: cache
   filters: filters

core/modules/filter/src/Tests/Migrate/d7/MigrateFilterFormatTest.php

@@ -28,6 +28,7 @@ class MigrateFilterFormatTest extends MigrateDrupal7TestBase {
    */
   protected function setUp() {
     parent::setUp();
+    $this->installConfig(static::$modules);
     $this->executeMigration('d7_filter_format');
   }
 
@@ -57,7 +58,11 @@ class MigrateFilterFormatTest extends MigrateDrupal7TestBase {
     $this->assertEntity('custom_text_format', 'Custom Text format', ['filter_autop', 'filter_html']);
     $this->assertEntity('filtered_html', 'Filtered HTML', ['filter_autop', 'filter_html', 'filter_htmlcorrector', 'filter_url']);
     $this->assertEntity('full_html', 'Full HTML', ['filter_autop', 'filter_htmlcorrector', 'filter_url']);
-    $this->assertEntity('plain_text', 'Plain text', ['filter_autop', 'filter_html_escape', 'filter_url']);
+    $this->assertEntity('plain_text', 'Plain text', ['filter_html_escape', 'filter_url', 'filter_autop']);
+    // This assertion covers issue #2555089. Drupal 7 formats are identified
+    // by machine names, so migrated formats should be merged into existing
+    // ones.
+    $this->assertNull(FilterFormat::load('plain_text1'));
 
     // Ensure that filter-specific settings were migrated.
     /** @var \Drupal\filter\FilterFormatInterface $format */