Tempfile closing and unlinking

[Alagaesia93]

Is your feature request related to a problem? Please describe.

I was today years old when I found out that Tempfile are supposed to be unlinked and closed for the GC to free the memory. I had a huge spike in memory and took me hours of investigations

Describe the solution you'd like

whenever using a Tempfile, raise a Rubocop error if it's not unlinked and closed - something similar to what happens when calling Kernel.open

Describe alternatives you've considered

I have not considered any, tbh

Additional context

I'm more than happy to help with a PR, but I don't know where to start and I don't have enough time in the next few weeks

[fatkodima]

Change line here

rubocop/lib/rubocop/cop/style/auto_resource_cleanup.rb

Line 22 in f981a1a

TARGET_METHODS = { File: :open }.freeze

, add a test case in the relevant file, generate a changelog entry and thats it.

Note, that rubocop does only static analysis of the code (no target code execution), and the AutoResourceCleanup cop is pretty useless, because it can generate a lot of false positives, thats why it is disable by default. It detects only #open methods. It is possible, that in the source some file is created in one place and closed in another. This cop won't identify this.

[Alagaesia93]

Thank @fatkodima, that was exactly my concern. I'm not super experienced in Rubocop, so I have no idea how to check that a Tempfile is created and never closed. It could be in the same metod, or another method, or somewhere else. Is that possible with Rubocop?

[fatkodima]

Is that possible with Rubocop?

No, because rubocop is a static code analyzer and does not run the user's code. The best it can do, as seen in the mentioned cop, is checking that File.open with block is used.

[fatkodima]

Actually you can check that the file is closed in the same method, but this is a perfect case for calling open with a block.

[koic]

I opened #12330 and also refactored it to tweak some redundant logic.