fix(plugin-pack): reload manifest after prepack script

[kherock]

What's the problem this PR addresses?

Resolves #3145 - see issue for rationale.

How did you fix it?

This unconditionally reloads the active workspace's manifest during prepareForPack after the prepack lifecycle script exits.

Checklist

• I have read the Contributing Guide.

• I have set the packages that need to be released for my changes to be effective.

• I will check that all automated PR checks pass before the PR gets reviewed.

[arcanis]

That won't work. We special-case package.json precisely because we want to use the manifest from memory, because beforeWorkspacePacking is meant to allow in-memory package mutations (which we use to implement publishConfig).

Generally, prepack is intended to be idempotent, so mutating the package.json isn't a practice we'd recommend. Instead, you should use beforeWorkspacePacking (which is more verbose). It's a bit unclear by your issue what you mean by "I want to Yarn to still perform the processing it normally does", so I'm not sure why it wouldn't work.

[kherock]

Just to be clear, this isn't at odds with what beforeWorkspacePacking does. I also wouldn't advise mutating package.json, but I think disallowing it altogether is unfair especially since this flow works just fine with npm (and I believe Yarn classic). I'm viewing this as an escape hatch when publishConfig isn't enough.

It's a bit unclear by your issue what you mean by "I want to Yarn to still perform the processing it normally does"

I want Yarn and its plugins to still run their beforeWorkspacePacking after the updated package.json is loaded. There's the built-in one that validates and replaces workspace: protocols, but I also don't want to interfere with any other hooks. If I were to write my own beforeWorkspacePacking, I'd need a way to ensure that my hook runs first.

[kherock]

Any further thoughts on this? I really can't see how supporting this would disrupt anything. I've been using this patch in my CI/CD pipeline for the past few weeks, and I actually already do use publishConfig in addition to some prepack scripts that do further preprocessing work.

[kherock]

@arcanis @merceyz Just bumping this one last time for a second opinion. I'm not really sure how else to really solve this short of patching the Yarn CLI with every release 😕. Intuitively, I'd expect that yarn run prepack && yarn pack would generate the same archive as a single run of yarn pack.

[arcanis]

Yep, that looks good to me - I've updated the versions since I think it qualifies as a bugfix more than a breaking change.