SyntaxError: (IndexError) list index out of range

Start with the failing expression at line 80 of invoice.tex and trace Mako's path through template.py, lexer.py match_expression, parsetree.py PythonCode, and pyparser.py parse. Reproduce the intermittent failure with the reported Mako versions and determine whether caching affects it; done means the cause is isolated and the behavior is consistently explained.

Hello,

we are using mako as template engine for generating latex-reports in tryton.
After an update of the source system from python 3.3 to python 3.5 migration, we get the following error:

Traceback (most recent call last):
  File "/usr/local/lib/python3.7/dist-packages/trytond/worker.py", line 108, in run_task
    Queue(task_id).run()
  File "/usr/local/lib/python3.7/dist-packages/trytond/ir/queue.py", line 169, in run
    instances, *self.data['args'], **self.data['kwargs'])
  File "/usr/local/lib/python3.7/dist-packages/trytond/model/modelview.py", line 672, in wrapper
    return func(cls, records, *args, **kwargs)
  File "/usr/local/lib/python3.7/dist-packages/trytond/modules/sale/sale.py", line 885, in process
    sale.create_invoice()
  File "/usr/local/lib/python3.7/dist-packages/trytond/modules/ebb_sale/sale.py", line 287, in create_invoice
    Invoice.post([invoice])
  File "/usr/local/lib/python3.7/dist-packages/trytond/modules/sale/invoice.py", line 20, in wrapper
    func(cls, invoices)
  File "/usr/local/lib/python3.7/dist-packages/trytond/modules/sale/invoice.py", line 87, in post
    super(Invoice, cls).post(invoices)
  File "/usr/local/lib/python3.7/dist-packages/trytond/modules/purchase/invoice.py", line 21, in wrapper
    func(cls, invoices)
  File "/usr/local/lib/python3.7/dist-packages/trytond/modules/purchase/invoice.py", line 98, in post
    super(Invoice, cls).post(invoices)
  File "/usr/local/lib/python3.7/dist-packages/trytond/model/modelview.py", line 672, in wrapper
    return func(cls, records, *args, **kwargs)
  File "/usr/local/lib/python3.7/dist-packages/trytond/model/workflow.py", line 36, in wrapper
    result = func(cls, filtered, *args, **kwargs)
nvoice.py", line 1383, in post.7/dist-packages/trytond/modules/account_invoice/i--More--
    invoice.print_invoice()
  File "/usr/local/lib/python3.7/dist-packages/trytond/modules/account_invoice/invoice.py", line 1292, in print_invoice
    InvoiceReport.execute([self.id], {})
  File "/usr/local/lib/python3.7/dist-packages/trytond/modules/latex_reports/latex.py", line 282, in execute
    mytemplate = Template(filename=report_path.replace('.odt','.tex'), cache_enabled=False, input_encoding='utf-8', output_encoding='utf-8')
  File "/usr/local/lib/python3.7/dist-packages/mako/template.py", line 338, in __init__
    module = self._compile_from_file(path, filename)
  File "/usr/local/lib/python3.7/dist-packages/mako/template.py", line 416, in _compile_from_file
    filename)
  File "/usr/local/lib/python3.7/dist-packages/mako/template.py", line 705, in _compile_text
    generate_magic_comment=template.disable_unicode)
  File "/usr/local/lib/python3.7/dist-packages/mako/template.py", line 685, in _compile
    node = lexer.parse()
  File "/usr/local/lib/python3.7/dist-packages/mako/lexer.py", line 241, in parse
    if self.match_expression():
  File "/usr/local/lib/python3.7/dist-packages/mako/lexer.py", line 402, in match_expression
    lineno=line, pos=pos)
  File "/usr/local/lib/python3.7/dist-packages/mako/lexer.py", line 140, in append_node
    node = nodecls(*args, **kwargs)
  File "/usr/local/lib/python3.7/dist-packages/mako/parsetree.py", line 194, in __init__
    self.code = ast.PythonCode(text, **self.exception_kwargs)
  File "/usr/local/lib/python3.7/dist-packages/mako/ast.py", line 40, in __init__
    expr = pyparser.parse(code.lstrip(), "exec", **exception_kwargs)
  File "/usr/local/lib/python3.7/dist-packages/mako/pyparser.py", line 48, in parse
    ), **exception_kwargs)
mako.exceptions.SyntaxException: (IndexError) list index out of range ("sale.invoice_address.party_name.replace('&','\\&')") in file '/tmp/trytond-latex-aevzw0qf/invoice.tex' at line: 80 char: 1

What we are wondering about: This does not occurs with the first time. It took some generations, e.g. is it possible, that somehow a caching is used and we should remove it?

We did test this with mako 1.1.3 and 1.0.7.

Thank you and best regards,
Hendrik