fix: prompt_template_resolved.output_variable is NoneType issue

[faaany]

Related Issues

• fixes bug: PromptNode.run() requires the optional argument prompt_template or output_variable  #4924

Proposed Changes:

• use try and except instead of using or

How did you test it?

• locally running the following code snippet, it won't crash.

from haystack.nodes.prompt import PromptNode, PromptModel
the_question = "What is the capital of Germany?"
node = PromptNode()
results, _ = node.run(query=the_question)

Notes for the reviewer

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added tests that demonstrate the correct behavior of the change
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.
• I documented my code
• I ran pre-commit hooks and fixed any issue

[coveralls]

Pull Request Test Coverage Report for Build 5086338918

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 27 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.0008%) to 39.621%

---

Files with Coverage Reduction	New Missed Lines	%
nodes/prompt/prompt_node.py	27	58.92%

Totals
Change from base Build 5081399763:	-0.0008%
Covered Lines:	8877
Relevant Lines:	22405

---

💛 - Coveralls

[faaany]

is there any concern with this fix? @silvanocerza

[silvanocerza]

@faaany I can't seem to reproduce the issue as specified in the linked issue, can you provide one please?

[faaany]

@faaany I can't seem to reproduce the issue as specified in the linked issue, can you provide one please?

the code snippet for reproduction is as follows:

from haystack.nodes.prompt import PromptNode, PromptModel

the_question = "What is the capital of Germany?"

node = PromptNode()
results, _ = node.run(query=the_question)

print(results)

And the error log is as follows:

Traceback (most recent call last):
  File "/localdisk/fanli/project/haystack/my_test.py", line 6, in <module>
    results, _ = node.run(query=the_question)
  File "/localdisk/fanli/project/haystack/haystack/nodes/prompt/prompt_node.py", line 375, in run
    output_variable = self.output_variable or prompt_template_resolved.output_variable or "results"
AttributeError: 'NoneType' object has no attribute 'output_variable'

prompt_template is an optional variable and is None by default. The problem is that we try to access output_variable from a None object. In our case what we really want with this line

output_variable = self.output_variable or prompt_template_resolved.output_variable or "results"

is that the output_variable has the value of results. try-except can get rid of this problem.

[faaany]

@silvanocerza any update? it has been a while...

[silvanocerza]

@faaany merged! Sorry but I was at a conference and didn't have time to handle some stuff. :)

[silvanocerza]

@652994331 please don't ask for support in unrelated PRs.

If you're unsure of what you're doing I suggest you read the official Haystack documentation and follow the tutorials.

If you want to report a bug open an issue here.

If instead you want to ask for some guidance or help I suggest you ask in GitHub discussions or in our community Discord.

Thanks. 🙏

[faaany]

@faaany merged! Sorry but I was at a conference and didn't have time to handle some stuff. :)

no problem! thanks so much for the approval!