Sync eng/common directory with azure-sdk-tools for PR 9799 (#2015)

* resolve issue with matrix collation when multiple matrix configs are being resolved

---------

Co-authored-by: Scott Beddall <[email protected]>

eng/common/scripts/Helpers/Package-Helpers.ps1

@@ -210,14 +210,33 @@ function Group-ByObjectKey {
   $groupedDictionary = @{}
 
   foreach ($item in $Items) {
-    $key = Get-ObjectKey $item."$GroupByProperty"
+    # if the item is an array, we need to group by each element in the array
+    # however if it's an empty array we want to treat it as a single item
+    if ($item."$GroupByProperty" -and $item."$GroupByProperty" -is [array]) {
+      foreach ($GroupByPropertyValue in $item."$GroupByProperty") {
+        $key = Get-ObjectKey $GroupByPropertyValue
 
-    if (-not $groupedDictionary.ContainsKey($key)) {
-      $groupedDictionary[$key] = @()
+        if (-not $groupedDictionary.ContainsKey($key)) {
+          $groupedDictionary[$key] = @()
+        }
+
+        $groupedDictionary[$key] += $item
+      }
     }
+    else {
+      if ($item."$GroupByProperty") {
+        $key = Get-ObjectKey $item."$GroupByProperty"
+      }
+      else {
+        $key = "unset"
+      }
+
+      if (-not $groupedDictionary.ContainsKey($key)) {
+        $groupedDictionary[$key] = @()
+      }
 
-    # Add the current item to the array for this key
-    $groupedDictionary[$key] += $item
+      $groupedDictionary[$key] += $item
+    }
   }
 
   return $groupedDictionary