Add an overwrite argument to the Writer to add the possibility to allow for overwriting existing file.

[mscheltienne]

Hi! I would like to propose a small additional feature: the possibility to overwrite an existing file. This would be handy as I am adding the overwrite argument to MNE export function in this PR: mne-tools/mne-python#9975

For now, the PR will delete existing files if overwrite is set to True, which is not really a clean way of doing it. The possibility to set overwrite upstream would be appreciated.

You can find the minimal changes I think are necessary to add this feature. I am not familiar with mffpy and I might have overlooked something. Please let me know!

[jusjusjus]

Hi @mscheltienne, your suggestion makes sense to me. Thanks. However, I'm worried that as a result of your implementation some, e.g., Event files wouldn't be overwritten, but just remained astray from the old MFF. I propose to cleanly unlink the whole MFF dir if it already exists. What do you think?

[mscheltienne]

@jusjusjus Glad to hear that you like it.

As I expected, I don't know enough about mffpy to cleanly implement it. You know better than me how to properly overwrite the writer output; so you are definitely right.
I will check tomorrow more in detail to figure out what is created by the writer and what should be removed, and I'll update the proposal accordingly.

[mscheltienne]

What do you mean by unlink? I just had a quick second look at the writer code, and your remark is sound.
How about:

If filename already exists and overwrite is True: list the files in mffdir; overwrite the one to overwrite and delete the one that were not overwritten?

[jusjusjus]

@ephathaway, let's discuss how this API should look like.

[ephathaway]

@mscheltienne, @jusjusjus, so sorry I am just now responding to this.

If filename already exists and overwrite is True: list the files in mffdir; overwrite the one to overwrite and delete the one that were not overwritten?

This sounds like a good solution. We could add a cleanup step to Writer.write which deletes any files in the output directory that are not in Writer.files.

[mscheltienne]

Hey, this PR was kind of forgotten. I really don't know much about mffpy, and I haven't tested the changes I made; but based on the code and on the conversation here, this last commit should address your concerns.

Could you spend the time to finalize this one?

[ephathaway]

Hi @mscheltienne, thanks for your contribution. With the requested changes, it should work as expected.

[mscheltienne]

@ephathaway Done

[ephathaway]

So we need to account for the overwrite .mfz edge case. Currently, attempting to overwrite a .mfz file errors out because the 'mffdir' is removed (filename + .mff), but the zipped MFF is not removed (filename + .mfz). We will need to add some logic to remove both filename.mff and filename.mfz.

[mscheltienne]

Done. As there is no writer test to .mfz, I based my edit on your comment:

(filename + .mff) [...] (filename + .mfz)

[ephathaway]

@mscheltienne, thanks for your contribution! We will cut a new release with this feature.