[FIX] Various fixes:

- Error with the sequence number.
- Visible texts that should be in uppercases.
- order_id should only be visible if group_stock_request_order
  option is enabled.
- adds more tests
- adds consistency between models company-wise

stock_request_purchase/models/purchase_order_line.py

@@ -1,7 +1,8 @@
 # Copyright 2017 Eficent Business and IT Consulting Services, S.L.
 # License LGPL-3.0 or later (https://www.gnu.org/licenses/lgpl.html).
 
-from odoo import api, fields, models
+from odoo import api, fields, models, _
+from odoo.exceptions import ValidationError
 
 
 class PurchaseOrderLine(models.Model):
@@ -21,3 +22,12 @@ class PurchaseOrderLine(models.Model):
                     'requested_product_uom_qty': request.product_qty,
                 }) for request in self.stock_request_ids]
         return res
+
+    @api.constrains('stock_request_ids')
+    def _check_purchase_company_constrains(self):
+        if any(any(req.company_id != pol.company_id for
+                   req in pol.stock_request_ids) for pol in self):
+                raise ValidationError(
+                    _('You cannot link a purchase order line '
+                      'to a stock request that belongs to '
+                      'another company.'))

stock_request_purchase/models/stock_request.py

@@ -1,7 +1,8 @@
 # Copyright 2017 Eficent Business and IT Consulting Services, S.L.
 # License LGPL-3.0 or later (https://www.gnu.org/licenses/lgpl.html).
 
-from odoo import api, fields, models
+from odoo import api, fields, models, _
+from odoo.exceptions import ValidationError
 
 
 class StockRequest(models.Model):
@@ -23,6 +24,14 @@ class StockRequest(models.Model):
             request.purchase_ids = request.purchase_line_ids.mapped('order_id')
             request.purchase_count = len(request.purchase_ids)
 
+    @api.constrains('purchase_line_ids', 'company_id')
+    def _check_purchase_company_constrains(self):
+        if any(any(line.company_id != req.company_id for
+                   line in req.purchase_line_ids) for req in self):
+            raise ValidationError(
+                _('You have linked to a purchase order line '
+                  'that belongs to another company.'))
+
     @api.multi
     def action_view_purchase(self):
         action = self.env.ref(

stock_request_purchase/tests/test_stock_request_purchase.py

@@ -105,6 +105,8 @@ class TestStockRequestPurchase(common.TransactionCase):
         self.assertEqual(order.stock_request_ids.qty_in_progress, 0.0)
 
         purchase = order.sudo().purchase_ids[0]
+        self.assertEqual(purchase.company_id,
+                         order.stock_request_ids[0].company_id)
         purchase.button_confirm()
         picking = purchase.picking_ids[0]
         picking.action_confirm()