if custom utter message contains no value or integer value then rasa fails returning custom utter message

[keremcadirci]

Rasa version: 1.7.1

Rasa SDK version (if used & relevant):

Rasa X version (if used & relevant):

Python version: 3.6.10

Operating system (windows, osx, ...): all

Issue:

when using custom utter message and custom utter response contains an empty value or a integer value rasa does not respond.
Custom utter response example:

    utter_sifre:
        - custom:
              type: category
              categoryType: QuickReply
              title: menu
              menu:
                  - title: menu1
                    img: 
                  - title: menu2
                    img: 

the attribute img above has no value or when an attribure has integer value like img: 2 the same issue occures
the error is the fallowing:

Error (including full traceback):

Encountered an exception while running action 'utter_sifre'. Bot will continue, but the actions events are lost. Please check the logs of your action server for more information.
2020-03-20 07:37:14 DEBUG    rasa.core.processor  - expected string or bytes-like object
Traceback (most recent call last):
  File "/build/lib/python3.6/site-packages/rasa/core/processor.py", line 564, in _run_action
    events = await action.run(output_channel, nlg, tracker, self.domain)
  File "/usr/local/lib/python3.6/asyncio/coroutines.py", line 110, in __next__
    return self.gen.send(None)
  File "/build/lib/python3.6/site-packages/rasa/core/actions/action.py", line 253, in run
    message = await nlg.generate(self.template_name, tracker, output_channel.name())
  File "/usr/local/lib/python3.6/asyncio/coroutines.py", line 110, in __next__
    return self.gen.send(None)
  File "/build/lib/python3.6/site-packages/rasa/core/nlg/template.py", line 77, in generate
    template_name, filled_slots, output_channel, **kwargs
  File "/build/lib/python3.6/site-packages/rasa/core/nlg/template.py", line 93, in generate_from_slots
    return self._fill_template(r, filled_slots, **kwargs)
  File "/build/lib/python3.6/site-packages/rasa/core/nlg/template.py", line 119, in _fill_template
    template[key] = interpolate(template[key], template_vars)
  File "/build/lib/python3.6/site-packages/rasa/core/nlg/interpolator.py", line 51, in interpolate
    template[k] = [interpolate(i, values) for i in v]
  File "/build/lib/python3.6/site-packages/rasa/core/nlg/interpolator.py", line 51, in <listcomp>
    template[k] = [interpolate(i, values) for i in v]
  File "/build/lib/python3.6/site-packages/rasa/core/nlg/interpolator.py", line 53, in interpolate
    template[k] = interpolate_text(v, values)
  File "/build/lib/python3.6/site-packages/rasa/core/nlg/interpolator.py", line 17, in interpolate_text
    text = re.sub(r"{([^\n{}]+?)}", r"{0[\1]}", template)
  File "/usr/local/lib/python3.6/re.py", line 191, in sub
    return _compile(pattern, flags).sub(repl, string, count)
TypeError: expected string or bytes-like object
2020-03-20 07:37:14 DEBUG    rasa.core.processor  - Action 'utter_sifre' ended with events '[]'.

Command or request that led to error:

Content of configuration file (config.yml) (if relevant):

Content of domain file (domain.yml) (if relevant):

How we have solved the issue
we have modified the file rasa/rasa/core/nlg/interpolator.py :

def interpolate_text(template: Text, values: Dict[Text, Text]) -> Text:
    # transforming template tags from
    # "{tag_name}" to "{0[tag_name]}"
    # as described here:
    # https://stackoverflow.com/questions/7934620/python-dots-in-the-name-of-variable-in-a-format-string#comment9695339_7934969
    # black list character and make sure to not to allow
    # (a) newline in slot name
    # (b) { or } in slot name
    try:
        text = re.sub(r"{([^\n{}]+?)}", r"{0[\1]}", template) 
        text = text.format(values)
        if "0[" in text:
            # regex replaced tag but format did not replace
            # likely cause would be that tag name was enclosed
            # in double curly and format func simply escaped it.
            # we don't want to return {0[SLOTNAME]} thus
            # restoring original value with { being escaped.
            return template.format({})

we have changed:
text = re.sub(r"{([^\n{}]+?)}", r"{0[\1]}", template)
to
text = re.sub(r"{([^\n{}]+?)}", r"{0[\1]}", str(template))

[erohmensing]

Thanks for debugging @keremcadirci! Do you want to make a contribution to fix this bug?

[Archish27]

@erohmensing Have created PR for this. Please review -> #5875