A package deploy's branchedDatabases is ignored at load, so the application runs on its base databases #3071

Problem

branchedDatabases on a root-config entry that also has package never takes effect. The application loads with no branches, and reads and writes the base databases it asked to fork. Every package and by_ref deploy writes such an entry. Together with deploy_component accepts branchedDatabases on a payload deploy and silently ignores it, this means no deploy request can give an application a fork on 5.3.0 or 5.3.1.

Nothing reports it. The deploy succeeds, no fork directory is created, and nothing is logged.

Cause

• Branches are prepared only when loadComponent is called without an applicationScope (components/componentLoader.ts:865 at v5.3.0).
• The root component's loop loads a package: entry with that entry's applicationScope and no branchedDatabases (:1000-1016).
• Only the components-root directory loop passes rootConfigBranchedDatabases(appName) (:312, :363). An application with a package entry is evidently loaded by the root loop, since no fork directory appears.

The same code is at v5.3.1 and on main. The branched-database integration tests declare the key on an entry with no package (integrationTests/components/branched-database.test.ts:36), so this path is untested.

Reproduce (5.3.0)

An application with schema.graphql declaring type Item @table @export (default database data), packed with npm pack. Scratch install with http.securePort set and tls.unixDomainSockets: true.

1. Deploy a base copy and write a row:

   harper deploy_component project=my-app package=/path/app-1.0.0.tgz restart=true
   curl -X PUT http://localhost:9926/Item/base-1 -d '{"name":"base"}' ...

2. Deploy a second copy with a fork. isolated and host are there only to reach this copy apart from the base copy:

   harper deploy_component project=pkg-2 package=/path/app-1.0.0.tgz \
     isolated=true branchedDatabases='["data"]' host=pkg-2.example.test restart=true

   The root-config entry now has package, host, branchedDatabases: [data] and isolated: true.
3. Write through the copy's own socket:

   curl --unix-socket '<rootPath>/sockets/app-pkg%2D2-<securePort>.sock' \
     -X PUT http://pkg-2.example.test/Item/pkg2-only -d '{"name":"pkg-2"}' ...

4. GET /Item/ on the shared port returns pkg2-only: the write landed in the base. <rootPath>/database/`branches` has no pkg-2 directory.

The result is the same after a full harper stop / harper start, and with a local-path package (a symlink) instead of a tarball.

Contrast: payload-deploy the same application as pay-1, add host, isolated and branchedDatabases: [data] to its root-config entry by hand, and restart. The fork is created at <rootPath>/database/`branches`/pay-1/data, and writes through pay-1 stay out of the base.

Expected

An entry with package and branchedDatabases loads its application on its fork, the same as an entry without package. If the fork can't be created, the load fails, as it does today for an entry without package. It must never fall back to the base.

A regression test should deploy by package and check that a write through the application stays out of the base.

Context

• Parent: [Epic] PR preview deployments, whose preview shape (branchedDatabases on a CI deploy) depends on this.
• Feature: Branched databases for application isolation.
• Found while verifying the 5.3 branched-database and isolated-application docs against a local 5.3.0.