Hallo

I added a custom field to the project and I'd need to access it from within the invoice.

Which is the syntax to use in the t-field?

By using o.invoice_line[0].account_analytic_id.property_name I can print the value of property_name from the analytic account related to that invoice line, but I am not able to reach the related project, I tried things like:

o.invoice_line[0].account_analytic_id.project_id.property_name 

I tried another approach, without luck:
<span t-esc="self.pool.get('project.project').search([('analytic_account_id', '=', o.invoice_line[0].account_analytic_id.id)]).x_customfield" />

It fails with the error "'NoneType' object has no attribute 'pool'" since the QWeb renderer does not understand the "self" of "self.pool"