Fix rotation of log files.

[mortenboye]

Using AdvancedFileOutput on Linux (Debian) I noticed that the rotation of log files did not work as expected.
latest.log did get renamed to whatever the configuration defined, but the logger would keep writing to this file.
This would lead to log files far exceeding the size defined with maxFileSizeKB.

This PR fixes this.

[Bungeefan]

Hi, are you, by any chance, using different file systems for the latest.log and the archived/rotated logs?

https://api.flutter.dev/flutter/dart-io/File/rename.html

On some platforms, a rename operation cannot move a file between different file systems.

[mortenboye]

Hi, are you, by any chance, using different file systems for the latest.log and the archived/rotated logs?

https://api.flutter.dev/flutter/dart-io/File/rename.html

On some platforms, a rename operation cannot move a file between different file systems.

Good point.
I am not. The files reside in the same folder on the same drive.

[Bungeefan]

Then, how did you find your fix, just trial-and-error?

[mortenboye]

Then, how did you find your fix, just trial-and-error?

Kindof.
I could see the archived file kept increasing in size, and looking at the code it made sense to me that renaming the _file reference would rename the file on disk, but keep pointing to the same file from code.
So copying the contents of latest and then clearing it before keeping on writing to it, seemed like an easy, yet naive solution.

I'm sure there are better ways of doing it :-)

[Bungeefan]

Ah, ok. Did you test your fix, does it reliably fix your problem on Debian?

Yeah, I get why somebody would think that, even I had to check again:
In the default dart:io File implementation, the _path field is final and the rename method just returns a new File instance with the new path.
_path Field: https://github.com/dart-lang/sdk/blob/34fa3c1fb5da0751755061f35eebfd9c89dce09e/sdk/lib/io/file_impl.dart#L235
rename Method: https://github.com/dart-lang/sdk/blob/34fa3c1fb5da0751755061f35eebfd9c89dce09e/sdk/lib/io/file_impl.dart#L337

It is weird as it seems to be working just fine on Windows and Ubuntu (GitHub Actions).
So before accepting your fix, I would like to find out why it doesn't work for you and if more people are experiencing a similar behavior.

[mortenboye]

I did not look deeper into the actual implementation details. But the proposed "fix" does solve the issue on my own system.

Please do the proper due diligence before considering this.