[Bug?]: yarn npm login remove trailing slash

[rpo-fr]

Self-service

• I'd be willing to implement a fix

Describe the bug

Yarn npm login remove trailing slash during authentication, and store registry url without

To reproduce

Create a project with a local .yarnrc.yml like

npmRegistries:
  "https://<myrepo>/repository/npm-all/":
    npmAlwaysAuth: true

npmRegistryServer: "https://<myrepo>/repository/npm-all/"

yarnPath: .yarn/releases/yarn-4.15.0.cjs

Run yarn npm login
output:

➤ YN0000: Logging in to https://<myrepo>/repository/npm-all

√ Username: · <user>
√ Password: · ******************

➤ YN0000: Successfully logged in

You can see that trailing slash is removed on the url

If I look into ~/.yarnrc.yml, the trailing slash is not present:

npmRegistries:
  "https://<myrepo>/repository/npm-all":
    npmAuthToken: NpmToken.<token>

When i run 'yarn install --check-cache', I have messages 'Invalid authentication (as an anonymous user)'

If I had a trailing slash on registry into ~/.yarnrc.yml

npmRegistries:
  "https://<myrepo>/repository/npm-all/":
    npmAuthToken: NpmToken.<token>

and rerun 'yarn install --check-cache', I don't have error and packages are installed

yarn install --check-cache        
➤ YN0000: · Yarn 4.15.0
➤ YN0000: ┌ Resolution step
➤ YN0000: └ Completed
➤ YN0000: ┌ Post-resolution validation
➤ YN0086: │ Some peer dependencies are incorrectly met by dependencies; run yarn explain peer-requirements for details.
➤ YN0000: └ Completed
➤ YN0000: ┌ Fetch step
➤ YN0000: └ Completed in 2s 994ms
➤ YN0000: ┌ Link step
➤ YN0000: └ Completed in 1s 148ms
➤ YN0000: · Done with warnings in 4s 203ms

Environment

System:
    OS: Windows 11 10.0.26200
    CPU: (12) x64 12th Gen Intel(R) Core(TM) i7-1265U
  Binaries:
    Node: 22.17.1 - C:\Users\ROMAIN~1\AppData\Local\Temp\xfs-1d2b1fb8\node.CMD
    Yarn: 4.15.0 - C:\Users\ROMAIN~1\AppData\Local\Temp\xfs-1d2b1fb8\yarn.CMD
    npm: 10.9.2 - C:\nvm4w\nodejs\npm.CMD

Additional context

No response

[StantonMatt]

I can reproduce the auth failure shape on current master, but it looks like the trailing slash is the trigger rather than the whole root cause.

With a project rc like:

npmRegistries:
  "https://example.org/repository/npm-all/":
    npmAlwaysAuth: true
npmRegistryServer: "https://example.org/repository/npm-all/"

and a home rc like the one yarn npm login writes:

npmRegistries:
  "https://example.org/repository/npm-all":
    npmAuthToken: token-without-slash

yarn config get --json npmRegistries resolves to:

{"https://example.org/repository/npm-all":{"npmAlwaysAuth":true,"npmAuthIdent":null,"npmAuthToken":null}}

So the token is lost before the request is made. A config-auth npm request for that registry then fails with No authentication configured for request, which matches the later anonymous-user behavior.

One wrinkle: in my scratch repro, adding the trailing slash to the home key didn't change this on current master; npmRegistries normalizes both spellings to the same key. That makes this look more like the project registry entry shadowing the home registry entry, rather than just login preserving or removing the slash.