Updating a package now rebuilds what builds on it

Packages can share code. One package publishes source files; another says "build those into me too", and from then on the second package carries its own copy of that code. That is a real dependency, and it means the second package is out of date the moment the first one changes.

Until now, updating the first package rebuilt only itself. Everything built on top of it kept running the code it had been built with — and nothing said so. The two halves of the platform then disagreed about what the shared shapes were, which came out as a page that renders empty: no error banner, no failed install, nothing in the log to search for. The install even reported success, because as far as it could tell it had rebuilt everything it knew about. It had; the problem is that a package can only ever know about itself.

This is what took the Store down on 25 August. Every one of the Store's own pieces rebuilt cleanly and the page still went blank.

An update now rebuilds the whole set that depends on it, worked out across the entire mesh rather than inside the updated package: whichever packages build the changed files into themselves are rebuilt as well, dependencies first so nothing is rebuilt against something that is still moving. It applies to every kind of install — a full package, an incremental update, a single code package, and a plain content package, which previously triggered no rebuild at all even when the files it shipped were somebody's source code.

Two details worth knowing:

• Deleting a shared file counts as a change. A file the package no longer ships makes its consumers just as stale as an edited one, and they are rebuilt for it too.
• Nothing is rebuilt twice. The update still rebuilds its own pieces first, exactly as before, and the wider set skips whatever has already been handled — so an update does not get slower for packages that nothing depends on.

There was a second, quieter route to the same blank page, and it is closed in the same change: when a package's type definition arrived in a slightly different shape than expected, the installer concluded there was nothing to rebuild at all — and issued no rebuild, silently. That check no longer depends on the shape the content happened to arrive in.