Add documents count smart buttons for document type

document_type/models/document_type.py

@@ -9,6 +9,11 @@ class DocumentType(models.Model):
     ir_model_id = fields.Many2one('ir.model', string='Object')
     document_ids = fields.One2many(
         'ir.attachment', 'document_type_id', string='Documents')
+    documents_count = fields.Integer(compute='_compute_documents_count')
+
+    def _compute_documents_count(self):
+        for record in self:
+            record.documents_count = len(record.document_ids)
 
 
 class IrAttachment(models.Model):

document_type/views/document_type.xml

@@ -13,6 +13,11 @@
     <field name="arch" type="xml">
       <form>
         <sheet>
+          <div class="oe_button_box" name="button_box">
+			      <button name="documents" class="oe_stat_button" icon="fa-book">
+              <field name="documents_count" string="Documents" widget="statinfo"/>
+			      </button>
+          </div>
           <group>
             <field name="name"/>
             <field name="ir_model_id"/>