A package's names, and watching a linked checkout

How a name written through a package is told apart from the app's own, and how jadpo dev and jadpo test --watch follow a package you have linked to a checkout you are working on.

• Where a package's name must be unique. In its package only. Two declarations of one package can't share a name (semantic.duplicate_declaration), but none clashes with the app's, of any kind and wherever it is declared (a domain, shared/, public or not), nor with another package's: Postcodes.uk.tidy beside the app's action tidy, or Postcodes.UkPostcode beside the app's UkPostcode and ZipCodes.UkPostcode, are three things. Their file names never fold together either, since each package is its own folder. A package's library may be named as an app's library or domain is, since it is always written through its package.
• Which one a name means. In the app, a bare name is always the app's and Postcodes.<name> always the package's, so returning Postcodes.UkPostcode where the app's UkPostcode is declared is type.mismatch. Inside a package, a bare name is the package's own. Failures keep their package too: fails Postcodes.InvalidPostcode and the app's fails InvalidPostcode are told apart in tests and at runtime.
• What a watch watches. The files every load reads: for a linked package, its checkout's sources and data, each at its path in the package's folder (packages/postcodes/v2/libraries/uk.jadpo), and not the installed copy, which stays as it was. The watcher reads the lock at every look, so jadpo package link or unlink while jadpo dev or jadpo test --watch runs moves the watch, and test --watch reads the whole folder again from where it now lives. A save in the checkout gets the watcher's guard for a file emptied mid-save. jadpo dev loads the project afresh on each save, so it needs nothing more.
• Where its problems show. At the checkout's paths in jadpo test, test --watch and jadpo dev, as jadpo check shows them, since that is where they are fixed; the rule line still names the save at the package's path, as the project reads it.