Fix Update-PSResource re-installing dependency packages which already meet dependency criteria (#1919)

Author: anamnavi

src/code/InstallHelper.cs

@@ -587,6 +587,16 @@ private List<PSResourceInfo> InstallPackages(
                                     }
                                 }
 
+                                string depPkgNameVersion = $"{depPkg.Name}{depPkg.Version.ToString()}";
+                                if (_packagesOnMachine.Contains(depPkgNameVersion) && !depPkg.IsPrerelease)
+                                {
+                                    // if a dependency package is already installed, do not install it again.
+                                    // to determine if the package version is already installed, _packagesOnMachine is used but it only contains name, version info, not version with prerelease info
+                                    // if the dependency package is found to be prerelease, it is safer to install it (and worse case it reinstalls)
+                                    _cmdletPassedIn.WriteVerbose($"Dependency '{depPkg.Name}' with version '{depPkg.Version}' is already installed.");
+                                    continue;
+                                }
+
                                 packagesHash = BeginPackageInstall(
                                             searchVersionType: VersionType.SpecificVersion,
                                             specificVersion: depVersion,

src/code/UpdatePSResource.cs

@@ -25,6 +25,7 @@ public sealed class UpdatePSResource : PSCmdlet
     {
         #region Members
         private List<string> _pathsToInstallPkg;
+        private HashSet<string> _packagesOnMachine;
         private CancellationTokenSource _cancellationTokenSource;
         private FindHelper _findHelper;
         private InstallHelper _installHelper;
@@ -157,6 +158,8 @@ protected override void BeginProcessing()
             RepositorySettings.CheckRepositoryStore();
 
             _pathsToInstallPkg = Utils.GetAllInstallationPaths(this, Scope);
+            List<string> pathsToSearch = Utils.GetAllResourcePaths(this, Scope);
+            _packagesOnMachine = Utils.GetInstalledPackages(pathsToSearch, this);
             _cancellationTokenSource = new CancellationTokenSource();
             var networkCred = Credential != null ? new NetworkCredential(Credential.UserName, Credential.Password) : null;
 
@@ -216,7 +219,7 @@ protected override void ProcessRecord()
                 pathsToInstallPkg: _pathsToInstallPkg,
                 scope: Scope,
                 tmpPath: _tmpPath,
-                pkgsInstalled: new HashSet<string>(StringComparer.InvariantCultureIgnoreCase));
+                pkgsInstalled: _packagesOnMachine);
 
             if (PassThru)
             {