Expose Platform API from SMA and uses that in NuGetProvider

src/Microsoft.PackageManagement.NuGetProvider/NugetLightRequest.cs

@@ -171,6 +171,10 @@
                 // or  $env:programfiles\NuGet\Packages\  if you are an admin.
                 try
                 {
+#if LINUX
+                    // there is only 1 installation location by default for linux ("HOME/.local/share/powershell/PackageManagement/NuGet/Packages")
+                    string basePath = CurrentUserDefaultInstallLocation;
+#else
                     var scope = (Scope == null) ? null : Scope.Value;
                     scope = string.IsNullOrWhiteSpace(scope) ? Constants.AllUsers : scope;
                     string basePath;
@@ -192,6 +196,7 @@
                             Constants.Messages.InstallRequiresCurrentUserScopeParameterForNonAdminUser, AllUserDefaultInstallLocation, CurrentUserDefaultInstallLocation);
                         return string.Empty;
                     }
+#endif
 
                     if (!Directory.Exists(basePath))
                     {
@@ -215,7 +220,11 @@
             get
             {
 #if CORECLR
+#if LINUX
+                return Path.Combine(Platform.SelectProductNameForDirectory(Platform.XDG_Type.POWERSHELL), "PackageManagement", "NuGet", "Packages");
+#else
                 return Path.Combine(Environment.GetEnvironmentVariable("LocalAppData"), "PackageManagement", "NuGet", "Packages"); 
+#endif
 #else
                 return Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), "PackageManagement", "NuGet", "Packages");
 #endif
@@ -228,7 +237,11 @@
             get
             {
 #if CORECLR
+#if LINUX
+                return Path.Combine(Platform.SelectProductNameForDirectory(Platform.XDG_Type.POWERSHELL), "PackageManagement", "NuGet", "Packages");
+#else
                 return Path.Combine(Environment.GetEnvironmentVariable("ProgramFiles"), "NuGet", "Packages"); 
+#endif
 #else
                 return Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles), "NuGet", "Packages");
 #endif
@@ -1289,7 +1302,11 @@
                         }
 
                     } else {
+#if LINUX
+                        var appdataFolder = Platform.SelectProductNameForDirectory(Platform.XDG_Type.PROFILE);
+#else
                         var appdataFolder = Environment.GetEnvironmentVariable("appdata");
+#endif
                         _configurationFileLocation = Path.Combine(appdataFolder, "NuGet", NuGetConstant.SettingsFileName);
 
                         //create directory if does not exist

src/System.Management.Automation/CoreCLR/CorePsPlatform.cs

@@ -28,7 +28,7 @@ namespace System.Management.Automation
     /// All these properties are calling into platform specific static classes, to make
     /// sure the platform implementations are switched at runtime (including pinvokes).
     /// </summary>
-    internal static class Platform
+    public static class Platform
     {
 
         // Platform variables used to defined corresponding PowerShell built-in variables
@@ -50,6 +50,7 @@ namespace System.Management.Automation
             PROFILE,
             MODULES,
             CACHE,
+            POWERSHELL,
             DEFAULT
         }
 
@@ -115,7 +116,8 @@ namespace System.Management.Automation
             string xdgdatahome = System.Environment.GetEnvironmentVariable("XDG_DATA_HOME");
             string xdgcachehome = System.Environment.GetEnvironmentVariable("XDG_CACHE_HOME");
             string xdgConfigHomeDefault =  Path.Combine ( System.Environment.GetEnvironmentVariable("HOME"), ".config", "powershell");
-            string xdgModuleDefault = Path.Combine ( System.Environment.GetEnvironmentVariable("HOME"), ".local", "share", "powershell", "Modules");
+            string xdgPowerShellDefault = Path.Combine( System.Environment.GetEnvironmentVariable("HOME"), ".local", "share", "powershell");
+            string xdgModuleDefault = Path.Combine ( xdgPowerShellDefault, "Modules");
             string xdgCacheDefault = Path.Combine (System.Environment.GetEnvironmentVariable("HOME"), ".cache", "powershell");
 
             switch (dirpath){
@@ -132,6 +134,22 @@ namespace System.Management.Automation
                         return Path.Combine(xdgconfighome, "powershell");
                     }
 
+                case Platform.XDG_Type.POWERSHELL:
+                    //the user has set XDG_DATA_HOME corresponding to module path
+                    if (String.IsNullOrEmpty(xdgdatahome)){
+
+                    // create the xdg folder if needed
+                    if (!Directory.Exists(xdgPowerShellDefault))
+                    {
+                        Directory.CreateDirectory(xdgPowerShellDefault);
+                    }
+                       return xdgPowerShellDefault;
+                    }
+                    else
+                    {
+                        return Path.Combine(xdgdatahome, "powershell");
+                    }
+
                 case Platform.XDG_Type.MODULES:
                     //the user has set XDG_DATA_HOME corresponding to module path
                     if (String.IsNullOrEmpty(xdgdatahome)){