From d99b4c1df17657f6bc177ee778a85d9226da21c1 Mon Sep 17 00:00:00 2001
From: "Steve Lee (POWERSHELL HE/HIM) (from Dev Box)"
 <slee@ntdev.microsoft.com>
Date: Fri, 10 Apr 2026 21:50:00 -0700
Subject: [PATCH] Add error when using dism resources via Appx

---
 resources/dism_dsc/locales/en-us.toml | 1 +
 resources/dism_dsc/src/dism.rs        | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/resources/dism_dsc/locales/en-us.toml b/resources/dism_dsc/locales/en-us.toml
index 5cd2f39ad..19a945a67 100644
--- a/resources/dism_dsc/locales/en-us.toml
+++ b/resources/dism_dsc/locales/en-us.toml
@@ -49,6 +49,7 @@ failedSerializeOutput = "Failed to serialize output: %{err}"
 failedLoadLibrary = "Failed to load dismapi.dll. Ensure DISM is available on this system."
 functionNotFound = "Failed to find function '%{name}' in dismapi.dll"
 initializeFailed = "DismInitialize failed: HRESULT %{hr}"
+notSupportedAppx = "This resource currently is not supported when installed via Appx"
 openSessionFailed = "DismOpenSession failed: HRESULT %{hr}"
 getFeatureInfoFailed = "DismGetFeatureInfo failed for '%{name}': HRESULT %{hr}"
 enableFeatureFailed = "DismEnableFeature failed for '%{name}': HRESULT %{hr}"
diff --git a/resources/dism_dsc/src/dism.rs b/resources/dism_dsc/src/dism.rs
index 167b20597..aa693d8b0 100644
--- a/resources/dism_dsc/src/dism.rs
+++ b/resources/dism_dsc/src/dism.rs
@@ -14,6 +14,7 @@ const DISM_PACKAGE_NONE: i32 = 0;
 const ERROR_SUCCESS_REBOOT_REQUIRED: i32 = 3010;
 const DISMAPI_E_UNKNOWN_FEATURE: i32 = 0x800F080Cu32 as i32;
 const DISMAPI_E_CAPABILITY_NOT_APPLICABLE: i32 = 0x800F0825u32 as i32;
+const REGDB_E_CLASSNOTREG: i32 = 0x80040154u32 as i32;
 const LOAD_LIBRARY_SEARCH_SYSTEM32: u32 = 0x0000_0800;
 
 #[link(name = "kernel32")]
@@ -243,6 +244,9 @@ impl DismSessionHandle {
 
         unsafe {
             let hr = dism_initialize(DISM_LOG_ERRORS, std::ptr::null(), std::ptr::null());
+            if hr == REGDB_E_CLASSNOTREG {
+                return Err(t!("dism.notSupportedAppx").to_string());
+            }
             if hr < 0 {
                 return Err(t!("dism.initializeFailed", hr = format!("0x{:08X}", hr as u32)).to_string());
             }
@@ -255,6 +259,10 @@ impl DismSessionHandle {
                 std::ptr::null(),
                 &mut session,
             );
+            if hr == REGDB_E_CLASSNOTREG {
+                (api.shutdown)();
+                return Err(t!("dism.notSupportedAppx").to_string());
+            }
             if hr < 0 {
                 (api.shutdown)();
                 return Err(t!("dism.openSessionFailed", hr = format!("0x{:08X}", hr as u32)).to_string());