Installed Add-ons

pkg/addons reads what is installed in Microsoft Flight Simulator. It only reads files and the process list; no SimConnect connection is needed. It reports what is there and leaves the meaning to the caller: which package or process stands for ATC, a network client, GSX or a traffic add-on is the application’s catalogue, not the library’s.

in, err := addons.Find() // MSFS 2024 before 2020
if err != nil {
    return err // addons.ErrNotFound
}
pkgs, err := addons.Scan(in.Packages)
fp := addons.Fingerprint(pkgs) // drop scenery caches when this changes
procs, _ := addons.Processes()  // "Couatl64.exe", "FlightSimulator2024.exe", ...

Where the packages are

Installs reads InstalledPackagesPath from each UserCfg.opt it finds:

Only the 2024 Steam path has been checked on a real install; the others are the usual locations. ReadPackagesPath reads one file directly.

Packages

Scan returns one Package per folder in Community, Community2024, Official2024\<store>, Official2020\<store> and StreamedPackages, sorted by source and folder.

• Community and Official. Title, creator, content_type and package_version come from manifest.json, kept as written. content_type is not reliable: GSX Pro and navigraph-nav-base both say SCENERY. Linked folders (symlinks, junctions) count; an unreadable manifest leaves only the folder name.

• Streamed. These folders have no manifest, only content\*.fsarchive. When the name reads as an airport, Publisher and ICAO are filled (ParseStreamedName):

  Folder	Publisher	ICAO
  fs20-orbx-airport-lkpr-prague	orbx	LKPR
  fs20-gaya-simulations-airport-loww-vienna	gaya-simulations	LOWW
  fs24-asobo-airport-c53-lowerloon	asobo	C53
  fs20-fps-lkmt-ostrava-airport	fps	LKMT

  Names with no airport code (fs20-microsoft-airport-voloport, fs24-asobo-modellib-airport-generic, travel books) are left without one.

What a streamed folder means

This was looked at on one MSFS 2024 Steam install, with 1,248 streamed folders:

• Every folder holds content\minimal.fsarchive, a small stub.
• 788 of them also hold further .fsarchive files, here or in subfolders. That is content the sim downloaded and keeps on disk; Package.Cached counts those files.
• Airports: 198 folders read as an airport; 23 had cached content, the others only the stub.

Stock and marketplace items appear alike. So a streamed folder shows that the sim knows the package, not that it is owned or active. Treat a streamed airport as a hint, not proof that its scenery will load.

The loaded aircraft’s package

AircraftPackage(pkgs, path) takes the path the sim reports for the AircraftLoaded system state or event. For example, SimObjects\Airplanes\FNX_32X\presets\fnx\FNX_319_CFM_WF_HD\config\aircraft.CFG gives fnx-aircraft-319-321.

• Packages with a manifest are matched on their layout.json file list.
• Streamed packages match when their content holds the aircraft’s folder (content\SimObjects\Airplanes\Asobo_Baron_G58).
• Order: Community packages are tried first, since they override the others.

Fingerprint

Fingerprint is a SHA-256 over each package’s source, folder (lower case) and version, in any order. It changes when a package is added, removed or updated:

• use it as the key of a cache built from scenery, such as airport layouts;
• streamed packages count by name only, because their cached content comes and goes.

Processes

Processes returns the executable names running now, sorted and without duplicates, from a Toolhelp snapshot. Matching them against known add-ons is up to the caller.