BusinessTemplate: don't uninstall module containing documents

uninstalling a ModuleTemplateItem containing document is usually not
what people want, so the default option should be to keep.

bt5/erp5_core_test/TestTemplateItem/portal_components/test.erp5.testBusinessTemplate.py

@@ -7211,6 +7211,53 @@ class TestBusinessTemplate(BusinessTemplateMixin):
     self.assertEqual(module_content_uid, self.portal.geek_module['1'].uid)
     self.assertEqual('kept', self.portal.geek_module['1'].title)
 
+  def test_update_business_template_with_module_removed(self):
+    """Updating business template with a module removed keeps the module if it contains documents
+    """
+    self.portal.newContent(
+      portal_type='Person Module',
+      id='kept_module',
+    ).newContent(
+      portal_type='Person',
+      id='keep',
+    )
+    self.portal.newContent(portal_type='Person Module', id='removed_module')
+    self.tic()
+
+    # install a bt containing two modules
+    bt = self.portal.portal_templates.newContent(
+      portal_type='Business Template',
+      title=self.id(),
+      template_module_id_list=['kept_module', 'removed_module'])
+    bt.build()
+    self.tic()
+    bt.install()
+    self.tic()
+
+    # in next version, both modules are removed
+    bt = self.portal.portal_templates.newContent(
+      portal_type='Business Template',
+      title=self.id(),
+    )
+    bt.build()
+    self.tic()
+
+    export_dir = tempfile.mkdtemp()
+    try:
+      bt.export(path=export_dir, local=True)
+      self.tic()
+      new_bt = self.portal.portal_templates.download(
+          url='file://%s' % export_dir)
+    finally:
+      shutil.rmtree(export_dir)
+
+    self.assertEqual(
+      new_bt.preinstall(),
+      {
+        'removed_module': ('Removed', 'Module'),
+        'kept_module': ('Removed but should be kept', 'Module'),
+      })
+
   def test_BusinessTemplateWithTest(self):
     sequence_list = SequenceList()
     sequence_string = '\

product/ERP5/Document/BusinessTemplate.py

@@ -3775,6 +3775,20 @@ class ModuleTemplateItem(BaseTemplateItem):
       xml_data = self.generateXml(path=key)
       bta.addObject(xml_data, name=key, path=path)
 
+  def preinstall(self, context, installed_item, **kw):
+    """Keep modules when they are not empty.
+    """
+    _modified_object_dict = super(ModuleTemplateItem, self).preinstall(context, installed_item, **kw)
+    portal = context.getPortalObject()
+    modified_object_dict = {}
+    for module_id, (action, item_class) in _modified_object_dict.items():
+      if action == 'Removed':
+        module = portal._getOb(module_id, None)
+        if module is not None and len(module.objectValues()):
+          action = 'Removed but should be kept'
+      modified_object_dict[module_id] = (action, item_class)
+    return modified_object_dict
+
   def install(self, context, trashbin, **kw):
     portal = context.getPortalObject()
     update_dict = kw.get('object_to_update')