How to fix "Oracle Developer Tools for Visual Studio 2017 is already installed. Please uninstall and try again."

How to fix "Oracle Developer Tools for Visual Studio 2017 is already installed. Please uninstall and try again."

I recently uninstalled Oracle Developer Tools for Visual Studio to try and pinpoint the source of another issue I was having. However, the uninstall failed with the following log (apparently, there was still a Visual Studio process running):

10/18/2018 2:52:09 PM - Microsoft VSIX Installer
10/18/2018 2:52:09 PM - -------------------------------------------
10/18/2018 2:52:09 PM - vsixinstaller.exe version:
10/18/2018 2:52:09 PM - 15.8.3252
10/18/2018 2:52:09 PM - -------------------------------------------
10/18/2018 2:52:09 PM - Command line parameters:

...

10/18/2018 2:52:23 PM - Pre-check verification: The following process is running and needs to be closed. Select Continue to save its current state, close it, and restart it when the installation is done:
 * vsls-agent
10/18/2018 2:52:23 PM - Pre-check verification failed with warning(s) :  VSProcessesRunning.
10/18/2018 2:52:23 PM - System.OperationCanceledException: Pre-check verification failed with warning(s) :  VSProcessesRunning.
   at Microsoft.VisualStudio.Setup.PrecheckManager.RunPrechecks(PrecheckParameters precheckParameters, VariableCollection properties)
   at Microsoft.VisualStudio.Setup.Engine.RunPrecheck(String destination, Product product, ExecuteAction action, IWindowsRestartManager rmService, ITelemetryOperation installOperation, InstallOperation install)
   at Microsoft.VisualStudio.Setup.Engine.Install(Product product, String destination, CancellationToken token)
   at Microsoft.VisualStudio.ExtensionManager.ExtensionEngineImpl.PerformSetupEngineUnInstall(IInstalledExtension extension, InstallFlags installFlags, Boolean downgrade)
   at Microsoft.VisualStudio.ExtensionManager.ExtensionEngineImpl.UninstallInternal(IInstalledExtension extension, Boolean forceDelete, Version targetedVSVersion, InstallFlags installFlags, Boolean downgrade)
   at Microsoft.VisualStudio.ExtensionManager.ExtensionEngineImpl.Uninstall(IInstalledExtension extension, InstallFlags installFlags, Version targetedVSVersion)
   at VSIXInstaller.App.UninstallExtensionFromSKU(String vsixID, SupportedVSSKU sku)
   at VSIXInstaller.App.UninstallSilently(String vsixId, IEnumerable`1 validSKUs)
   at VSIXInstaller.App.OnStartup(StartupEventArgs e)

The uninstaller did not fail gracefully and left my computer in a bad state. When I attempted to re-run the installer for Oracle Developer Tools for Visual Studio, I received the following error dialog:

Oracle Developer Tools for Visual Studio 2017 is already installed. Please uninstall and try again.

After more research, I was finally able to come up with a solution. Basically, the installer was looking to see if the Oracle.VsDevTools.15.0.vsix ins already installed. If so, it will present that error.

I had to uninstall the vsix from Visual Studio to continue. Using a great post by Rick Strahl, I was able to run the command to uninstall the vsix (you need to open the Visual Studio 2017 Command Prompt) :

vsixinstaller /a /u:"Oracle.VsDevTools.15.0"

Then, simply run the installer for Oracle Developer Tools for Visual Studio 2017 and it should run all the way through this time.