Use vswhere as defaultVS2017+ contain an utility named vswhere, which discovers installed VS's.VS2019 abolished the registry that contains the infomation of the installed version.

Author: tats-u

Code/Import-VisualStudioEnvironment.ps1

@@ -1,4 +1,4 @@
-#requires -version 5.0
+#requires -version 5.0
 ###############################################################################
 # WintellectPowerShell Module
 # Copyright (c) 2010-2017 - John Robbins/Wintellect
@@ -74,6 +74,10 @@ https://github.com/Wintellect/WintellectPowerShell
         [string]$AdditionalOptions = ""
     )  
 
+    # VS2017+
+    $vswherePath = "C:\Program Files (x86)\Microsoft Visual Studio\Installer\vswhere.exe"
+
+    # for VS2017 and older
     $versionSearchKey = "HKLM:\SOFTWARE\Wow6432Node\Microsoft\VisualStudio\SxS\VS7"
     if ([IntPtr]::size -ne 8)
     {
@@ -87,20 +91,32 @@ https://github.com/Wintellect/WintellectPowerShell
 
     if ($VSVersion -eq 'Latest')
     {
-        # Find the largest number in the install lookup directory and that will
-        # be the latest version.
-        $biggest = 0.0
-        Get-RegistryKeyPropertiesAndValues $versionSearchKey  | 
-            ForEach-Object { 
-                                if ([System.Convert]::ToDecimal($_.Property, [CultureInfo]::InvariantCulture) -gt `
-                                    [System.Convert]::ToDecimal($biggest, [CultureInfo]::InvariantCulture))
-                                {
-                                    $biggest = $_.Property
-                                    $vsDirectory = $_.Value 
-                                }
-                            }  
+        if (Test-Path -PathType Leaf $vswherePath)
+        {
+            $latestVSInfo = & $vswherePath -latest -legacy -format json | ConvertFrom-Json
+            if ($latestVSInfo)
+            {
+                $usingVersion = [System.Convert]::ToDecimal(($latestVSInfo.installationVersion -replace "^(\d+\.\d+)[^\d].*", "`$1"), [CultureInfo]::InvariantCulture)
+                $vsDirectory = $latestVSInfo.installationPath
+            }
+        }
+        else
+        {
+            # Find the largest number in the install lookup directory and that will
+            # be the latest version.
+            $biggest = 0.0
+            Get-RegistryKeyPropertiesAndValues $versionSearchKey  | 
+                ForEach-Object { 
+                                    if ([System.Convert]::ToDecimal($_.Property, [CultureInfo]::InvariantCulture) -gt `
+                                        [System.Convert]::ToDecimal($biggest, [CultureInfo]::InvariantCulture))
+                                    {
+                                        $biggest = $_.Property
+                                        $vsDirectory = $_.Value 
+                                    }
+                                }  
 
-        $usingVersion = $biggest
+            $usingVersion = $biggest
+        }
     }
     else
     {
@@ -115,7 +131,16 @@ https://github.com/Wintellect/WintellectPowerShell
 
         $usingVersion = [System.Convert]::ToDecimal($propVal, [CultureInfo]::InvariantCulture)
 
-        if (Test-PathReg -Path $versionSearchKey -Property $propVal)
+        if (Test-Path -PathType Leaf $vswherePath)
+        {
+            $vsInfo = & $vswherePath -version "[${usingVersion},$($usingVersion + 1))" -legacy -format json | ConvertFrom-Json
+            if ($vsInfo)
+            {
+                $usingVersion = [System.Convert]::ToDecimal(($vsInfo.installationVersion -replace "^(\d+\.\d+)[^\d].*", "`$1"), [CultureInfo]::InvariantCulture)
+                $vsDirectory = $vsInfo.installationPath
+            }
+        }
+        elseif (Test-PathReg -Path $versionSearchKey -Property $propVal)
         {
             $vsDirectory = (Get-ItemProperty -Path $versionSearchKey -WarningAction SilentlyContinue).$propVal
         }

Code/Internal.ps1

@@ -93,19 +93,33 @@ function Get-RegistryKeyPropertiesAndValues
 
 function LatestVSRegistryKeyVersion
 {
+    # 2017+
+    $vswherePath = "C:\Program Files (x86)\Microsoft Visual Studio\Installer\vswhere.exe"
+    # 2017 and older
     $versionSearchKey = "HKLM:\SOFTWARE\Wow6432Node\Microsoft\VisualStudio\SxS\VS7"
     if ([IntPtr]::size -ne 8)
     {
         $versionSearchKey = "HKLM:\SOFTWARE\Microsoft\VisualStudio\SxS\VS7"    
     }
     $biggest = 0.0
-    Get-RegistryKeyPropertiesAndValues $versionSearchKey  | 
-        ForEach-Object { 
-                            if ([System.Convert]::ToDecimal($_.Property) -gt [System.Convert]::ToDecimal($biggest))
-                            {
-                                $biggest = $_.Property
-                            }
-                        }  
+    if (Test-Path -PathType Leaf $vswherePath)
+    {
+        $latestVSInfo = & $vswherePath -latest -legacy -format json | ConvertFrom-Json
+        if ($latestVSInfo)
+        {
+            $biggest = [System.Convert]::ToDecimal(($latestVSInfo.installationVersion -replace "^(\d+\.\d+)[^\d].*", "`$1"), [CultureInfo]::InvariantCulture)
+        }
+    }
+    else
+    {
+        Get-RegistryKeyPropertiesAndValues $versionSearchKey  | 
+            ForEach-Object { 
+                                if ([System.Convert]::ToDecimal($_.Property) -gt [System.Convert]::ToDecimal($biggest))
+                                {
+                                    $biggest = $_.Property
+                                }
+                            }  
+    }
 
     $biggest
 }