Godot writes empty files when there is no space left on disk.

[CheesecakeCG]

Godot version: 3.2.4 beta 4 (It happens all the way back to 3.1 if I remember correctly, I forgot to report it then.)

OS/device including version:

Arch Linux (last updated 2021-1-18)
Intel i3-2100, AMD Radeon RX460, 5400rpm 250GB HDD with projects saved to a 50GB EXT4 partition.

Issue description:

When the drive containing the project runs out of disk space, when Godot attempts to save the a file, it overwrites the file with no contents. No error is displayed onscreen. Godot should not attempt write to the disk if there is no space left.

Steps to reproduce:
Fill up the drive with your Godot Project on it, then attempt to save.

Minimal reproduction project:

Only an "empty" project is needed, since project.godot gets wiped too.

[Calinou]

This is because the file is truncated when it is opened, not saved. I'm not sure if we can (or should) change this. Godot cannot predict how much data you're going to write to a file when you open it.

[smix8]

Since this has been marked as a discussion here are my cents.

I think at least the autoimporter in the editor could predict for enough diskspace before it tries to do anything.

Autoimport on larger imports triggers so many updates for editor and project files and if the diskspace is 100% full all of them fail and get corrupted creating a huge mess for the entire project that is far worse than the loss of a single file.

How do I know? Well from multiple surprise experiences where I had everything, from a small .import file up to the entire project settings, corrupted.

Why does it happen to me so regularly? I often have large 3D asset exports and updates from Blender that can range from a few 100mb to a few gb. They take from a few minutes to half an hour or more to process and I never know the final filesize and sometimes I forget to cleanup the harddrive. When Blender finishes in my absence Godot is already autoimporting the large .escn or .glb files after some time. Result is that Godot runs out of enough diskspace to write and save its own files before freezing and crashing. Everytime I come back to my desk and see the Godot editor frozen I know I forgot to cleanup my harddrive.

[CheesecakeCG]

Blender handles this by saving to a new file every time you save, then renaming the old file so the extension is "blend1" and then optionally deletes the file or renames more older versions. This way, Godot doesn't need to know how big the file is, and always fails safe if something goes wrong while saving. It would also work well for adding autosaving.

[Zireael07]

I am sure that a Blender-like behavior has been already requested, but I can't find the issue # ...

[CheesecakeCG]

I am sure that a Blender-like behavior has been already requested, but I can't find the issue # ...

Digging a bit deeper into this, the FileAccessUnix class has had this feature as long as Godot has been open-source, but for some reason it failed specifically when I ran out of disk space while Godot was saving.

Also, in hindsight this could have also been related to my system regularly running out of RAM and swap then...

[CorneliusChristian]

I also got this problem when saving, this should have a warning message when disk is full.

[Calinou]

Regarding editor warnings: We don't know the complete file size of most files until we finish saving or importing them, so we should probably have a "buffer" size to err on the side of safety. Also, saving or importing a file may result in additional files being written by the editor for internal usage, such as thumbnails or cache files.

It's very unlikely you'll be saving or importing a single file (+ thumbnails/cache) that is larger than 1 GB in size using the editor, so we could display a warning every time you save a file in the editor when there's less than 1 GB left on the disk the project is on. We can use similar logic to what #62418 did for Movie Maker mode, except use a lower size threshold.