DynamoDB: empty update expression now returns a ValidationException

[felixscherz]

Hi, this is intended to fix an issue with dynamodb where an emtpy update expression given to update_item raises an unexpected exception: #7988

[felixscherz]

I see some tests are failing, I'll have another look:)

[bblommers]

Hi @felixscherz, thanks for opening a PR for this!

The update_expression can be None when calling update_item in models, which would be absolutely valid. I would suggest to add this validation in responses.py instead, where the request first comes in:

moto/moto/dynamodb/responses.py

Line 892 in 856ded1

update_expression = self.body.get("UpdateExpression", "").strip()

If the user-provided value is an empty string here, we should throw an exception - everything else can stay the same.

[felixscherz]

Ok great, thanks for the help! I will have a look at the responses.py

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.37%. Comparing base (856ded1) to head (a7c2d93).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7989   +/-   ##
=======================================
  Coverage   94.37%   94.37%           
=======================================
  Files        1125     1125           
  Lines       96369    96374    +5     
=======================================
+ Hits        90948    90953    +5     
  Misses       5421     5421           

Flag	Coverage Δ
servertests	28.93% <0.00%> (-0.01%)	⬇️
unittests	94.34% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[bblommers]

Great - thank you for adding this to Moto @felixscherz!

[github-actions]

This is now part of moto >= 5.0.13.dev55