robotframework / robotframework/SeleniumLibrary
Switch Window sporadically fails with TypeError
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Description
Observed with
Python 3.13.0
SeleniumLibrary 6.7.1
Scenario
I have the following scenario in a test which fails sporadically:
- Link in an (internal) application is clicked which opens a different URL in a new tab
Switch Windowis called with the expected URL as locator and10 sas a timeout
Expected behaviour
The new window is switched to. If the window is not immediately available/ready when this keyword is started, it should wait until the window can be switched to, within the given timeout limits.
Error
This works just fine most of the time, but occasionally I get the following error:
TypeError: cannot unpack non-iterable NoneType object
This error shows up pretty much instantly (within a few hundred ms), so the timeout is not taken into account.
However, in the associated screenshots, the expected page is always shown.
Analysis
I looked into the library's code and added some extra logging, which showed the error was coming from this line:
https://github.com/robotframework/SeleniumLibrary/blob/ce9d0ec510bd99c5a1b1cd114f767c7feeae1208/src/SeleniumLibrary/locators/windowmanager.py#L199
The call to self.driver.execute_script("return [ window.id, window.name ];") returns None, thus the assignment to the two variables fails with the above error.
Adding a 1 s sleep right before the call to execute_script makes the error no longer occur (even with many iterations of the test), so it does seem to be somehow timing related.
I guess there's a short timeframe where the window is there but not fully ready and this makes the function call fail? But I wasn't able to understand the exact nature of this presumed 'not ready' state so far.
Proposed solution
The TypeError could be added to the already present except, which successfully avoided failures due to this in my scenario.
Adding this would be trivial, but I'm not sure about the implications:
- does anything depend on the current behaviour that raises an error in this case (seems not, but I'm not super familiar with the library's codebase)?
- would it be appropriate to suppress this error in the library, given it is not fully understood what exactly the nature of the actual, underlying error is?
Do you have any guidance how to proceed here?
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start in src/SeleniumLibrary/locators/windowmanager.py at the line that unpacks the result of execute_script("return [ window.id, window.name ];"). Reproduce the Switch Window scenario with a delayed new tab and inspect the existing exception handling and timeout flow. Done means the intermittent TypeError is addressed without breaking window switching or the requested timeout behavior.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- testing-qa
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100