From a041f2aa07531428520c37149a4dd4b0d277344f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Rodr=C3=ADguez?= <juandresrodca@gmail.com>
Date: Fri, 31 Jul 2026 22:31:23 +0100
Subject: [PATCH] Update existing assignment instead of duplicating

Add Assignment always appended the new assignment and re-posted the full set to
/assign. When the chosen target was already assigned (e.g. All Devices), Graph
received two assignments for the same target and ignored the new one, so changes
such as adding an include filter never took effect - the user had to delete the
assignment and re-create it (issue #57).

Before appending, drop any existing assignment that targets the same audience
(matched on @odata.type, plus groupId for group targets) so the new selection
replaces it. This lets an existing assignment be edited - for example adding a
filter to an All Devices assignment - without delete-then-re-add.

Fixes #57
---
 Scripts/AddAssignmentButton.ps1 | 39 +++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/Scripts/AddAssignmentButton.ps1 b/Scripts/AddAssignmentButton.ps1
index c27989d..629c63c 100644
--- a/Scripts/AddAssignmentButton.ps1
+++ b/Scripts/AddAssignmentButton.ps1
@@ -22,6 +22,37 @@ $AddAssignmentButton.Add_Click({
 })
 #>
 
+#--------------------------------------------------------------------------------
+# Helper: Test-SameAssignmentTarget
+# Returns $true when an existing Graph assignment targets the same audience as the
+# assignment the user is adding. Used so that re-adding an already-assigned target
+# (for example, to add an include filter to an existing "All Devices" assignment)
+# updates that assignment instead of being silently ignored by Graph as a duplicate
+# target (issue #57).
+#
+# "All Users" / "All Devices" are virtual targets with no groupId, so they are matched
+# on their @odata.type alone; group include/exclude targets are matched on both the
+# @odata.type and the groupId.
+#--------------------------------------------------------------------------------
+function Test-SameAssignmentTarget {
+    param (
+        [Parameter(Mandatory = $true)] $ExistingTarget,
+        [Parameter(Mandatory = $true)] $NewTarget
+    )
+
+    $existingType = [string]$ExistingTarget.'@odata.type'
+    $newType      = [string]$NewTarget.'@odata.type'
+    if ($existingType -ne $newType) { return $false }
+
+    if ($existingType -eq "#microsoft.graph.groupAssignmentTarget" -or
+        $existingType -eq "#microsoft.graph.exclusionGroupAssignmentTarget") {
+        return ([string]$ExistingTarget.groupId -eq [string]$NewTarget.groupId)
+    }
+
+    # All Users / All Devices (and any other group-less target) match on type alone.
+    return $true
+}
+
 $AddAssignmentButton.Add_Click({
     # Log the button click event.
     Write-IntuneToolkitLog "AddAssignmentButton clicked" -component "AddAssignment-Button" -file "AddAssignmentButton.ps1"
@@ -240,6 +271,14 @@ $AddAssignmentButton.Add_Click({
                 $target = @{ '@odata.type' = $targetType }
                 if ($groupId) { $target.groupId = $groupId }
 
+                # Issue #57: if this policy already has an assignment for the same target,
+                # drop the existing one so the new selection (which may add or change a
+                # filter / intent) replaces it, instead of being ignored by Graph as a
+                # duplicate target. This is what lets an assignment be "edited" (e.g. adding
+                # an include filter to an existing All Devices assignment) without having to
+                # delete and re-create it.
+                $currentAssignments = @($currentAssignments | Where-Object { -not (Test-SameAssignmentTarget -ExistingTarget $_.target -NewTarget $target) })
+
                 # Build the new assignment based on the policy type.
                 if ($global:CurrentPolicyType -eq "mobileApps") {
                     $newAssignment = @{