ClickOnce Upgrade doesn't cleanup old version

[jochenwezel]

Problem description

After upgrade, the new version exists in parallel of an older version of the same channel.

Expected situation - Ideal situation

• ClickOnce Upgrade feature automatically detects that older version needs to be uninstalled or be replaced before new install

Expected situation - 2nd best option

• App realizes: in parent directory are more App Directories with same name (except version/GUID name parts of directory)
• Directory/File Scan in those parallel app directories finds older app versions of same channel (also see/check e.g. static JSON file)
• Ask user to cleanup those older directories with app version XY and same channel XZ -> if yes, remove those directories, if no, remember this directory to never report in future any more, if cancel just abort cleanup feature

[jochenwezel]

Design note from implementation discussion:

The current cleanup-state approach only covers the in-app update flow:

1. The running old app detects an available update.
2. The user confirms the update in the app.
3. The old app writes %APPDATA%\GuacamoleClient\clickonce-cleanup-state.json with its current install path.
4. ClickOnce starts the update.
5. The new app instance reads the cleanup state and can offer to remove the old directory.

There is still a conceptual gap for updates initiated by ClickOnce before our application code runs, for example when the user starts the app through the ClickOnce shortcut and ClickOnce updates the deployment before launching the executable. In that case the old app instance never runs and cannot write the cleanup candidate.

To close that gap, the new app should additionally support a scan fallback: inspect sibling/parallel ClickOnce application directories and identify older installations by their app-info.json metadata. This scan must be very conservative.

Important guardrail: the scan fallback should only run when the current app version has a non-zero major version number. Local/debug builds from Visual Studio use major version 0 and must not scan or propose deleting ClickOnce directories. Official GitHub workflow builds use major versions such as 2026, so only those builds should enable the scan fallback.

The explicit cleanup-state file remains useful as the precise path for the normal in-app update flow; the scan fallback is needed for ClickOnce-before-app-start updates.

[jochenwezel]

Implementation summary:

• Added ClickOnce cleanup state handling for the normal in-app update flow. The old instance records its current install directory before starting the update, and the new instance can offer cleanup after startup.
• Added conservative fallback scanning for sibling ClickOnce application directories when running an official build with a non-zero major version. Local/debug builds with major version 0 do not scan or propose cleanup.
• Cleanup candidates are matched through app metadata so app variant and deployment type stay separated.
• The current installation directory is protected from self-deletion.
• Successfully removed cleanup entries are pruned from the JSON state file, and the file is removed when no entries remain.
• Avalonia ClickOnce support was added separately as a Windows deployment type using appId=avalonia and deploymentType=clickonce. Existing WinForms ClickOnce URLs and metadata remain unchanged.

Validation performed:

• Built WinForms and Avalonia projects locally.
• Ran GuacamoleCommon.Tests successfully.
• Published dev release 2026.07.08.1 and verified GitHub Pages, app-updates.json, WinForms ClickOnce dev endpoint, and Avalonia ClickOnce dev endpoint.

Remaining action before closing:

Manual testing is still required with real ClickOnce update scenarios, especially:

• In-app update writes cleanup state and the updated app offers/removes the old directory.
• ClickOnce-before-app-start update path exercises the fallback scan.
• A local/debug build with major version 0 does not scan or suggest cleanup.
• Avalonia ClickOnce and WinForms ClickOnce do not cross-detect or cross-clean each other.