fix(windows): #399 ignore stale App Paths values in the install-folder fallback

The App Paths directory search doesn't check that lightcraft.exe exists, and
when the old installers' unquoted path is gone, Windows Installer falls back
to the text before the first space: a deleted
C:\Program Files\LightCraft\lightcraft.exe resolved to C:\, so an upgrade
would install into the drive root. Gate the fallback on a second search of
the same value with a FileSearch for lightcraft.exe.

The install-folder test gains legacy-folder-deleted (failed before this fix)
and legacy-exe-deleted cases, and removes its empty parent registry key.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

packaging/windows/lightcraft.wxs

@@ -51,9 +51,19 @@
       <RegistrySearch Id="LegacyInstallFolder" Root="HKLM"
           Key="Software\Microsoft\Windows\CurrentVersion\App Paths\lightcraft.exe" Type="file" />
     </Property>
+    <!-- That directory search doesn't check the executable exists, and when its unquoted path is
+         gone it falls back to the text before the first space: a deleted
+         "C:\Program Files\LightCraft\lightcraft.exe" yields "C:\". Only use the folder when this
+         search, which does require lightcraft.exe, finds it too. -->
+    <Property Id="LEGACYINSTALLEXE">
+      <RegistrySearch Id="LegacyInstallExe" Root="HKLM"
+          Key="Software\Microsoft\Windows\CurrentVersion\App Paths\lightcraft.exe" Type="file">
+        <FileSearch Id="LegacyInstallExeFile" Name="lightcraft.exe" />
+      </RegistrySearch>
+    </Property>
     <SetProperty Id="INSTALLFOLDER" Action="SetInstallFolderFromAppPaths" Value="[LEGACYINSTALLFOLDER]"
         After="SetINSTALLFOLDER" Sequence="both"
-        Condition="LEGACYINSTALLFOLDER AND NOT PREVIOUSINSTALLFOLDER AND NOT INSTALLFOLDER" />
+        Condition="LEGACYINSTALLFOLDER AND LEGACYINSTALLEXE AND NOT PREVIOUSINSTALLFOLDER AND NOT INSTALLFOLDER" />
     <StandardDirectory Id="ProgramMenuFolder" />
 
     <Feature Id="Main" Title="LightCraft" Level="1">

packaging/windows/test-install-folder.ps1

@@ -12,7 +12,8 @@ $ErrorActionPreference = 'Stop'
 $PSNativeCommandUseErrorActionPreference = $false
 $id = [Guid]::NewGuid().ToString('N')
 $root = Join-Path ([IO.Path]::GetTempPath()) "lightcraft-install-folder-$id"
-$key = "Software\LightCraftInstallerTests\$id"
+$testsKey = 'Software\LightCraftInstallerTests'
+$key = "$testsKey\$id"
 $product = [Guid]::NewGuid().ToString('B')
 $upgrade = [Guid]::NewGuid().ToString('B')
 $view = if ($Arch -eq 'x86') { [Microsoft.Win32.RegistryView]::Registry32 } else { [Microsoft.Win32.RegistryView]::Registry64 }
@@ -72,20 +73,25 @@ try {
   $legacy = Join-Path $root 'legacy app café'
   $modern = Join-Path $root 'remembered app'
   $explicit = Join-Path $root 'explicit app'
-  New-Item -ItemType Directory -Path $legacy, $modern, $explicit | Out-Null
-  [IO.File]::WriteAllText((Join-Path $legacy 'lightcraft.exe'), 'test placeholder; never executed')
+  $emptied = Join-Path $root 'emptied app'
+  New-Item -ItemType Directory -Path $legacy, $modern, $explicit, $emptied | Out-Null
+  $legacyExe = Join-Path $legacy 'lightcraft.exe'
+  [IO.File]::WriteAllText($legacyExe, 'test placeholder; never executed')
   $programFiles = if ($Arch -eq 'x86' -and ${env:ProgramFiles(x86)}) { ${env:ProgramFiles(x86)} } else { $env:ProgramFiles }
   $cases = @(
     @{ Name = 'fresh'; Expected = (Join-Path $programFiles 'LightCraft') },
-    @{ Name = 'legacy-app-paths'; Legacy = $true; Expected = $legacy },
+    @{ Name = 'legacy-app-paths'; Legacy = $legacyExe; Expected = $legacy },
+    # A stale unquoted path with a space used to resolve to the parent of the text before the space.
+    @{ Name = 'legacy-folder-deleted'; Legacy = (Join-Path $root 'deleted app\lightcraft.exe'); Expected = (Join-Path $programFiles 'LightCraft') },
+    @{ Name = 'legacy-exe-deleted'; Legacy = (Join-Path $emptied 'lightcraft.exe'); Expected = (Join-Path $programFiles 'LightCraft') },
     @{ Name = 'remembered-folder'; Modern = $true; Expected = $modern },
-    @{ Name = 'remembered-beats-legacy'; Modern = $true; Legacy = $true; Expected = $modern },
-    @{ Name = 'explicit-beats-legacy'; Legacy = $true; Explicit = $true; Expected = $explicit },
-    @{ Name = 'explicit-beats-both'; Modern = $true; Legacy = $true; Explicit = $true; Expected = $explicit }
+    @{ Name = 'remembered-beats-legacy'; Modern = $true; Legacy = $legacyExe; Expected = $modern },
+    @{ Name = 'explicit-beats-legacy'; Legacy = $legacyExe; Explicit = $true; Expected = $explicit },
+    @{ Name = 'explicit-beats-both'; Modern = $true; Legacy = $legacyExe; Explicit = $true; Expected = $explicit }
   )
   foreach ($case in $cases) {
     $registry.DeleteSubKeyTree($key, $false)
-    if ($case.Legacy) { Set-TestValue 'Software\Microsoft\Windows\CurrentVersion\App Paths\lightcraft.exe' '' (Join-Path $legacy 'lightcraft.exe') }
+    if ($case.Legacy) { Set-TestValue 'Software\Microsoft\Windows\CurrentVersion\App Paths\lightcraft.exe' '' $case.Legacy }
     if ($case.Modern) { Set-TestValue 'Software\LightCraft' 'InstallFolder' "$modern\" }
     $arguments = @('/i', "`"$msi`"")
     if ($case.Explicit) { $arguments += "INSTALLFOLDER=`"$explicit`"" }
@@ -108,6 +114,12 @@ try {
     if ($installed) { Invoke-Msi @('/x', $product) (Join-Path $root 'cleanup.log') -AllowAbsent }
   } finally {
     $registry.DeleteSubKeyTree($key, $false)
+    $tests = $registry.OpenSubKey($testsKey)
+    if ($tests) {
+      $empty = $tests.SubKeyCount -eq 0 -and $tests.ValueCount -eq 0
+      $tests.Dispose()
+      if ($empty) { $registry.DeleteSubKey($testsKey, $false) }
+    }
     $registry.Dispose()
     # Keep logs on failure; they explain MSI failures that otherwise only report an exit code.
     if ($passed) { Remove-Item -Recurse -Force $root } else { Write-Output "Test artifacts retained: $root" }