Add more diagnostics on why we do not see crash dumps

Author: vmoroz

.ado/jobs/e2e-test.yml

@@ -139,6 +139,82 @@ jobs:
               condition: and(failed(), eq(variables.StartedFabricTests, 'true'))
               continueOnError: true
 
+            # Diagnostic: figure out where WER actually put the dumps. On packaged
+            # apps WER sometimes ignores the per-exe LocalDumps key and cabs to
+            # the system report queue, or silently drops if it can't write to our
+            # folder. We dump the WER config + ACLs and copy any dumps we find
+            # from common fallback locations into $(CrashDumpRootPath) so they
+            # ride the existing artifact publish.
+            - pwsh: |
+                Write-Host "=== CrashDumpRootPath: $(CrashDumpRootPath) ==="
+                if (Test-Path "$(CrashDumpRootPath)") {
+                  Write-Host "--- ACLs ---"
+                  Get-Acl "$(CrashDumpRootPath)" | Format-List | Out-String | Write-Host
+                  Write-Host "--- Contents ---"
+                  Get-ChildItem -Path "$(CrashDumpRootPath)" -Recurse -Force | Select-Object FullName, Length | Format-Table -AutoSize | Out-String | Write-Host
+                } else {
+                  Write-Host "(folder does not exist)"
+                }
+
+                Write-Host ""
+                Write-Host "=== WER LocalDumps registry ==="
+                $localDumpsRoot = 'HKLM:\SOFTWARE\Microsoft\Windows\Windows Error Reporting\LocalDumps'
+                if (Test-Path $localDumpsRoot) {
+                  Get-ChildItem $localDumpsRoot | ForEach-Object {
+                    Write-Host "--- $($_.Name) ---"
+                    Get-ItemProperty $_.PSPath | Format-List | Out-String | Write-Host
+                  }
+                  Write-Host "--- (global defaults) ---"
+                  Get-ItemProperty $localDumpsRoot -ErrorAction SilentlyContinue | Format-List | Out-String | Write-Host
+                } else {
+                  Write-Host "(no LocalDumps key)"
+                }
+
+                Write-Host ""
+                Write-Host "=== AeDebug AutoExclusionList ==="
+                Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug\AutoExclusionList' -ErrorAction SilentlyContinue | Format-List | Out-String | Write-Host
+
+                Write-Host ""
+                Write-Host "=== Searching for dumps in common WER locations ==="
+                $searchRoots = @(
+                  "$env:LOCALAPPDATA\CrashDumps",
+                  "$env:ProgramData\Microsoft\Windows\WER\ReportQueue",
+                  "$env:ProgramData\Microsoft\Windows\WER\ReportArchive",
+                  "$env:ProgramData\Microsoft\Windows\WER\Temp",
+                  "C:\Users",
+                  "$env:TEMP",
+                  "$env:windir\Temp"
+                )
+                $found = @()
+                foreach ($root in $searchRoots) {
+                  if (-not (Test-Path $root)) { continue }
+                  Write-Host "--- $root ---"
+                  $hits = Get-ChildItem -Path $root -Recurse -Include *.dmp,*.mdmp,*RNTesterApp*.* -ErrorAction SilentlyContinue -Force |
+                    Where-Object { -not $_.PSIsContainer -and $_.LastWriteTime -gt (Get-Date).AddHours(-2) }
+                  foreach ($h in $hits) {
+                    Write-Host ("  {0,-10} {1}" -f $h.Length, $h.FullName)
+                    $found += $h
+                  }
+                }
+
+                Write-Host ""
+                Write-Host "=== Copying any matching dumps into $(CrashDumpRootPath)\recovered ==="
+                if ($found.Count -gt 0) {
+                  $dest = Join-Path "$(CrashDumpRootPath)" 'recovered'
+                  New-Item -ItemType Directory -Path $dest -Force | Out-Null
+                  foreach ($h in $found) {
+                    $tag = ($h.FullName -replace '[:\\/]', '_')
+                    $target = Join-Path $dest $tag
+                    Copy-Item -LiteralPath $h.FullName -Destination $target -Force -ErrorAction SilentlyContinue
+                    Write-Host "Copied $($h.FullName) -> $target"
+                  }
+                } else {
+                  Write-Host "(no matching dumps found anywhere)"
+                }
+              displayName: Search for crash dumps in WER fallback locations
+              condition: and(failed(), eq(variables.StartedFabricTests, 'true'))
+              continueOnError: true
+
             - script: npx jest --clearCache
               displayName: clear jest cache
               workingDirectory: packages/e2e-test-app-fabric

.ado/templates/prepare-build-env.yml

@@ -51,8 +51,15 @@ steps:
     displayName: Check and enable Windows Error Reporting
 
   - pwsh: |
-        Write-Host "##vso[task.setvariable variable=CrashDumpRootPath]$(Build.StagingDirectory)\CrashDumps"
-        New-Item -Path '$(Build.StagingDirectory)\CrashDumps' -ItemType Directory
+        $path = '$(Build.StagingDirectory)\CrashDumps'
+        Write-Host "##vso[task.setvariable variable=CrashDumpRootPath]$path"
+        New-Item -Path $path -ItemType Directory -Force | Out-Null
+        # Grant full control to NT AUTHORITY\SYSTEM and Users so the WER service
+        # (running as LocalSystem) and any child process — including packaged
+        # apps — can write dumps here. Without this, per-exe LocalDumps can
+        # silently fail on agents that lock down the work directory.
+        & icacls $path /grant 'SYSTEM:(OI)(CI)F' 'Users:(OI)(CI)F' /T /C | Out-Null
+        & icacls $path
     displayName: Set CrashDumpRootPath
 
   - pwsh: |