Issue #3262149: New non-translatable field on translatable paragraph throws error

tests/src/Functional/WidgetStable/ParagraphsTranslationTest.php

@@ -840,6 +840,58 @@ class ParagraphsTranslationTest extends ParagraphsTestBase {
     $this->assertParagraphsLangcode($node2->id(), 'de');
   }
 
+  /**
+   * Test adding a new non-translatable field to translatable paragraph.
+   */
+  public function testNewNonTranslatableField() {
+
+    // Hide untranslatable fields from the "text_image" paragraph form.
+    $edit = [
+      'settings[paragraph][text_image][settings][content_translation][untranslatable_fields_hide]' => TRUE,
+    ];
+    $this->drupalGet('admin/config/regional/content-language');
+    $this->submitForm($edit, 'Save configuration');
+
+    // Use the stable widget.
+    $form_display = EntityFormDisplay::load('paragraph.nested_paragraph.default')
+      ->setComponent('field_paragraphs_demo', [
+        'type' => 'paragraphs',
+      ]);
+    $form_display->save();
+
+    // Create paragraphed_content_demo node.
+    $this->drupalGet('node/add/paragraphed_content_demo');
+    $this->submitForm([], 'Add text_image');
+    $edit = [
+      'title[0][value]' => 'example_publish_unpublish',
+      'field_paragraphs_demo[0][subform][field_text_demo][0][value]' => 'Example published and unpublished',
+    ];
+    $this->submitForm($edit, 'Save');
+    $node = $this->drupalGetNodeByTitle('example_publish_unpublish');
+
+    // Add an untranslatable field to the 'text' paragraph.
+    static::fieldUIAddNewField('admin/structure/paragraphs_type/text_image', 'boolean', 'Boolean', 'boolean', [
+      'cardinality' => "number",
+      'cardinality_number' => "1",
+    ], [
+      'translatable' => "0",
+    ]);
+
+    $this->drupalGet('node/' . $node->id());
+    // Add french translation.
+    $this->clickLink('Translate');
+    $this->clickLink('Add', 1);
+
+    $edit = array(
+      'title[0][value]' => 'Title in french',
+      'field_paragraphs_demo[0][subform][field_text_demo][0][value]' => 'Text in french',
+      'revision' => TRUE,
+      'revision_log[0][value]' => 'french 1',
+    );
+    $this->submitForm($edit, 'Save (this translation)');
+    $this->assertSession()->pageTextNotContains('Non-translatable fields can only be changed when updating the original language.');
+  }
+
   /**
    * Passes if the paragraphs buttons are present.
    *