Enumerate and display blocking processes when installer exits with packageInUse / packageInUseByApplication

[tonicofonico]

Relevant area(s)

WinGet CLI

Description of the new feature / enhancement

Problem Statement

When an installer exits due to locked files (e.g. exit code 6 mapped to packageInUse or packageInUseByApplication in the manifest schema), WinGet outputs a localized message:

"The files modified by the installer are currently being used by another application. Please close the applications, then try again."
However, WinGet provides no visibility into which specific application or process is holding the lock.
In automated workflows, silent upgrades (-h / --silent), or scenarios involving shared DLLs/drivers, users are left completely in the dark.

Real-World Example

Upgrading OBSProject.OBSStudio from 32.2.1 to 32.2.2 silently fails with exit code 6 when an Electron/Chromium app (such as VS Code, Discord, Slack, or Antigravity) has loaded obs-virtualcam-module64.dll via DirectShow camera device enumeration. Even if the user closes OBS Studio itself, the lock remains held by an unrelated background process. Identifying the culprit currently requires manual inspection of process modules or handles.

User Value

Displaying the locking process names and PIDs allows users to immediately identify and close the conflicting application without guesswork, without running interactive installers, and without opening external tools like Process Explorer.

Proposed technical implementation details

Proposed Architecture

1. Trigger Condition:
   In AppInstallerCLICore (InstallFlow.cpp / ShellExecuteInstallerHandler.cpp), execute the detection flow only when an installer returns an exit code mapped to ReturnResponse::packageInUse or ReturnResponse::packageInUseByApplication (e.g. exit code 6).
2. Process Enumeration via Windows Restart Manager:
   Utilize the native Win32 Restart Manager API (rstrtmgr.h / rstrtmgr.dll):
   • Call RmStartSession to obtain a session handle.
   • Register the target package install path or modified files via RmRegisterResources.
   • Call RmGetList to obtain the array of RM_PROCESS_INFO structures (retrieving strAppName and Process.dwProcessId).
   • Clean up with RmEndSession.
3. CLI Output Format:
   Render the list of blocking processes directly in the error block:

   The files modified by the installer are currently being used by another application:
     - Antigravity (PID: 9468)
   Please close these applications and try again.
   Installer failed with exit code: '6'