Add-in Discovery

Add-in resolution follows a priority chain -- each resolver either returns a result or falls through to the next:

Manifest (devserver-addin.json)  -->  .targets parsing  -->  MSBuild fallback

Manifest-First (ManifestAddInResolver, instant)

File: Helpers/ManifestAddInResolver.cs

Looks for devserver-addin.json at the root of each NuGet package. Three return states:

Forward-compatibility: when manifest.Version > 1, the resolver logs a warning and returns null so older CLIs gracefully degrade to .targets parsing.

Data Model

Files: Helpers/AddInManifest.cs, Helpers/AddInManifestEntry.cs

{
  "version": 1,
  "addins": [
    {
      "entryPoint": "lib/net10.0/MyAddIn.dll",
      "minHostVersion": "5.6.0"
    }
  ]
}

• entryPoint -- relative DLL path (forward slashes normalized to platform separators)
• minHostVersion -- optional; skipped if current host version is lower

Validation

1. JSON parse (catches JsonException, IOException)
2. entryPoint is not null/whitespace
3. Entry point file exists on disk
4. minHostVersion semver check (if present)

.targets Parsing (TargetsAddInResolver, ~200ms)

File: Helpers/TargetsAddInResolver.cs

Parses packages.json from the Uno SDK and buildTransitive/*.targets files from NuGet packages to extract <UnoRemoteControlAddIns> items without invoking MSBuild.

MSBuild Fallback (Host-side, 10-30s)

File: ../Uno.UI.RemoteControl.Host/Extensibility/AddIns.cs

When the CLI fast paths fail, the Host falls back to dotnet build evaluation. The --addins flag on the Host bypasses this when paths are pre-resolved by the CLI.

Integration with DevServerMonitor

DevServerMonitor.RunMonitor() runs discovery via UnoToolsLocator.DiscoverAsync(), which invokes the resolvers. Resolved add-in paths are stored in LastDiscoveryInfo and passed to the Host via --addins when starting the process.

Adding a Manifest Field

1. Add the property to AddInManifest.cs or AddInManifestEntry.cs with [JsonPropertyName]
2. Update ManifestAddInResolver.cs to read and act on the new field
3. Add test in ManifestAddInResolverTests.cs covering the new field