Allow creation of empty files on GCS

[ttencate]

Passing data="" did not work because it evaluates to False.

Made the same change for filename as well, so that filename="" will now give a clearer error when trying to open the file.

[boring-cyborg]

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[kiran2706]

Looks good to me.

[potiuk]

Can you please add unit tests ?

[ttencate]

No, sorry. That'll turn a trivial five minute fix into a two hour ordeal figuring out your unit test structure, what and where to mock, how to run the tests, and dealing with spurious failures (I think CI already proved this above). I don't have time for that.

If you insist, I'd be happy to downgrade this PR into a bug report for someone else to pick up.

[kiran2706]

@ttencate - I can add those test cases.

[ttencate]

@kiran2706 Thank you!

[kiran2706]

@ttencate / @potiuk , I've added the necessary test cases and created a new PR, as I unfortunately had trouble updating the original one directly.
Here’s the new PR link

Kindly review and merge it when convenient, and please close both PRs afterward.

#51669

[ttencate]

Thank you @kiran2706 ! I'll go ahead and close this one, no need to keep it open until yours is merged.