Bugfix 3752 - Artifacts disappearing when missing integrity file

[jamsinclair]

Summary

I encountered personally similar problems as described in #3752 after interrupting a yarn install.

After some debugging I isolated this to being that the integrity file is removed during the linking step (with good reasons).

However, if this file is never rewritten (e.g. user/system interrupted yarn) the next time yarn is invoked it no longer has context of package artifacts, as they are retrieved from the integrity file.

I played around with some solutions and would like to put forward an idea of forcing package installations if the integrity file is missing.

Test plan

I've added two test cases for add and install scripts that replicate the reproduction steps listed in #3752 (comment).

Without changes to the src code you can see these test cases fail (running Node v8.2.1):

With the src codes changes you can see on CI that all tests pass ✌️

Concerns

I'm not sure but, are there any scenarios where setting force in the PackageInstallScripts would cause the lockfile to be rewritten? Thinking of whether this change would affect flags like --frozen-lockfile 🤔

[arcanis]

Great work @jamsinclair, thanks! Have you checked if it works fine with the --ignore-scripts flag?

[BYK]

Do we really need these setters and getters?

[jamsinclair]

Good question.

The force property was formerly only set on construction of the PackageInstallScripts class:
https://github.com/yarnpkg/yarn/blob/master/src/cli/commands/install.js#L178

When the install bailout method runs, the PackageInstallScripts instance has already been created. Adding the setter, allowing overrides, seemed like a simpler solution rather than reinstantiating. Happy to hear another approach.

Edit: Oh, is it all good to override properties directly, this.scripts.force = true? In that case could definitely remove setter 😂

[arcanis]

I think a setter is fine, it's how we already do it (setArtifacts), and I have the feeling it makes the code a bit safer (because JS doesn't (yet) have private variables, setters are one of the only ways to clearly state that a variable might be updated from the outside).

[jamsinclair]

@arcanis, yup just tested changes now with --ignore-scripts 👍

Looks right. The package install scripts do not seem to take place and reports a warning:

warning Ignored scripts due to flag.

[arcanis]

Thanks @jamsinclair! A simple solution to an important issue 👌

[anhkind]

Will this fix be included in 0.27.x and 0.28.x versions soon enough?

[arcanis]

It's already available through the nightly builds. Otherwise, it will be in the next tagged release, which should be the 1.0.0 and should come in the next few weeks.