insta complains falsy assertion failure if the text snapshot starts with ---\n

[Myriad-Dreamin]

What happened?

I'm encountering Myriad-Dreamin/tinymist#868 in insta 1.41.1. In short, the issue reports that insta complains assertion failures on nixpkgs's build targets {x86_64,aarch64}-{linux,darwin}. After debug for a while, I suspect it is because some of my text snapshots start with ---\n, as shown in Myriad-Dreamin/tinymist#903. However, I'm not 100% confident on my judgement because I cannot trigger the failure on my local PC ({x86_64}-{windows,linux}). Could you help me?

Some build log containing such failures: https://build.alpinelinux.org/buildlogs/build-edge-x86_64/testing/tinymist/tinymist-0.12.2-r1.log

Reproduction steps

running cargo test might trigger the falsy assertion failure.

Insta Version

1.41.1

rustc Version

1.82

What did you expect?

I expect to pass all tests.

[max-sixty]

Yes, it's possible with that exact string that we'd see odd behavior, since we strip it.

Do you have a minimal reproduction?

[max-sixty]

I also don't see test failures in the log you linked to? I see some warnings about legacy snapshots — which is very much expected on inline snapshots starting with ---\n (insta's behavior used to be inconsistent between file & inline snapshots there).

I will prioritize if we can find a case of inconsistency / backward-compat issues!

[Myriad-Dreamin]

Hello, after investigation, I believe the assertion failures are caused by other reason. It is just causing falsy warnings. This should be the same conclusion as yours.

A minimum example of creating falsy warning might be creating a snapshot with content "---\ntest". Note: on windows, they might insert an \r implicitly.