[FIX] product_extended: _get_variant_count

Due to the _set_product_template_field function, it is not possible
to set the standard price on a product template with more than one variant.

Due to the _compute_product_template_field function, it is not possible
to read the standard price on a product with more than one variant.

The field "standard_price" is in readonly to avoid some problems if the costing
method is in real time.

Closes: #11308

opw:671013

addons/product_extended/mrp_view.xml

@@ -7,7 +7,8 @@
             <field name="inherit_id" ref="mrp.mrp_bom_form_view"/>
             <field name="arch" type="xml">
                 <field name="product_id" position="after">
-                    <field name="standard_price"/>
+                    <field name="get_variant_count" invisible="1"/>
+                    <field name="standard_price" readonly="1" attrs="{'invisible': [('get_variant_count', '&gt;', 1)]}"/>
                     <newline/>
                 </field>
             </field>

addons/product_extended/product_extended.py

@@ -89,9 +89,16 @@ class product_template(osv.osv):
 
 class product_bom(osv.osv):
     _inherit = 'mrp.bom'
+
+    def _get_variant_count(self, cr, uid, ids, field_name, arg, context=None):
+        res = {}
+        for bom in self.browse(cr, uid, ids, context=context):
+            res[bom.id] = bom.product_tmpl_id.product_variant_count
+        return res
             
     _columns = {
-        'standard_price': fields.related('product_tmpl_id','standard_price',type="float",relation="product.product",string="Standard Price",store=False)
+        'standard_price': fields.related('product_tmpl_id','standard_price',type="float",relation="product.product",string="Standard Price",store=False),
+        'get_variant_count': fields.function(_get_variant_count, type='integer', string='Number of variant for the product'),
     }
 
 product_bom()