Jest: Jest seems to not be able to make up its mind between ' and \'

[aaronjensen]

We're constantly seeing jest switch its snapshot output between escaping apostrophes and not. I can't tell if it's related to certain peoples computers or what.

[cpojer]

Hmm.. this is very odd. Jest should always escape quotes. Would you mind letting me know which systems all your engineers are using?

[aaronjensen]

@cpojer we're all on macs. Why would it escape single quotes in a backquoted string? That seems unnecessary.

[cpojer]

Quotes always spell trouble. @kyldvs noticed the issues first. Does this happen in files where there are test failures or snapshot failures? I believe it is possible that this might happen when a test is thrown, yet we try to write the snapshot data back into the test file anyway.

[kyldvs]

Is everyone on latest version of jest? (check global jest and local one) If someone is ~month old it will mess up quotes

[aaronjensen]

@kyldvs what is "messed up"? escaping single quotes in backtick quoted strings? I'll ask people to check, there may be someone running jest watch w/ an old globally installed jest

[kyldvs]

The escapes are necessary to handle some edge cases. By mess up I just mean it will alternate adding/removing escapes. That's what an old version did. A single person could be on the old version and it would never be in a consistent state due to fun string escaping/parsing/serialization edge cases.

If everyone is on a recent version and it's alternating escapes still that would be a bug.

[aaronjensen]

@kyldvs I'm on 15.1.1 and it just stripped escapes on my last run.

[aaronjensen]

Also, I think the run that caused it did have errors.

[wdhorton]

Can confirm I'm also experiencing this issue on 15.1.1

[cpojer]

I haven't seen this since we rewrote snapshots in 16. Please try with Jest 17 and report back if this is still an issue.

[cpojer]

I think I finally found the issue. It's a combination between renaming and disabling tests.

[cpojer]

I did it! Here is the repro:

• Have three snapshots with quotes in a file, store them all.
• Delete one of the tests.
• Use test.only for the second one.
• Run with -u.
• This will remove the obsolete snapshot, write the one in test.only and use the existing value of the third snapshot because the test wasn't run; that third one will not use the proper escaping mechanism.

[aaronjensen]

wow, quite the repro. Nice work.

[cpojer]

Unfortunately since the way we encode/decode strings currently, I cannot think of a good way to fix this :( cc @dmitriiabramov had an idea.

[cpojer]

The problem is that we rely on pretty-format to escape quotes in strings, like "foo\'bar" but these go away when we require the file as JS. When we write a snapshot file, we use the data from pretty-format of the real value (passed to expect) so everything is escaped properly. When we write a snapshot file with data we read from a snapshot because we don't run the test that generates it, we don't have the data from pretty-format.

[vjeux]

This is also affecting @pieterv and myself if that's of any use :)

[cpojer]

@vjeux it's not, but thanks! Can you fix it? :)

[jlongster]

When we write a snapshot file with data we read from a snapshot because we don't run the test that generates it

When does this happen? I'm curious. That means if I remove all of my snapshots and re-generate them, it should never happen again right? How did unescaped snapshots get created in the first place when there wasn't a snapshot to read from?

Thanks for explaining!

[cpojer]

@jlongster when a snapshot file is written (either through -u or a new toMatchSnapshot call), we take all of the values passed to expect and call pretty-format on them and write a completely new snapshot file. When a test is disabled, we don't have the generated value so we use pretty-printed string from the snapshot file, which is what is causing the problem here. @vjeux is actually investigating a fix right now :) Seems like I might a bad call with regards to escaping.

[cpojer]

This will be fixed in Jest 19 thanks to @vjeux. It's a breaking change for snapshot and we'll try to message it appropriately.