Conflicts with black

Hi! Thanks for this useful tool!

When I save out new snapshots, they aren’t in the format recognized by Black, which involves running the formatter a second time. This is a little fiddly, and I don’t really care about having the format just so, so I would prefer to automatically ignore these files.

Some possible solutions:

1. Add

   # fmt: off
   

   to the block at the top of the snapshot file. I’ve tested this, it works, and it’s easy.
2. Let people decide whether they want this header. I’d turn it on by default – since it’s a good default – and let people turn it off if they really want their files formatted by Black.
3. If Black is available, before writing the file, attempt to run the output through Black. Let users disable this behavior in config. I like this option best because it’s a very nice developer experience (even though it would be a little inconvenient for my use case, which sadly is a lib that has Python 2 deps, so I can’t run tests and Black in the same env).
4. Try to modify the output to cohere to Black’s demands. I expect this is impractical.

With some guidance about which way to go, I’d be happy to contribute this.

[martijnthe]

How about adding a formatter hook to snapshottest and let people choose whatever formatter they like?

[skovhus]

Ideally, auto-generated files shouldn’t be formatted, so adding a # fmt: off line seems like a very simple solution to this problem compared to adding a formatting hook.

@syrusakbary would you accept a PR adding a # fmt: off line?