Merge nucleic/humble-fern-egret-60xo into dev

build.ps1

@@ -33,6 +33,12 @@
 .PARAMETER Test
     Run the leg's tests instead of just building it.
 
+.PARAMETER VcpkgRoot
+    An existing vcpkg checkout to use. Otherwise the script looks at %VCPKG_INSTALLATION_ROOT%,
+    the %LOCALAPPDATA%\vcpkg\vcpkg.path.txt breadcrumb, %LOCALAPPDATA%\Programs\vcpkg,
+    %USERPROFILE%\vcpkg and C:\vcpkg, and clones one into %LOCALAPPDATA%\Programs\vcpkg if none
+    of those hold a vcpkg.exe.
+
 .PARAMETER Persist
     Also save CPATH to your *user* environment, so future shells and editors resolve
     sqlite3.h without going through this script.
@@ -70,22 +76,44 @@ function Initialize-SQLite {
         $script:Triplet = "$arch-windows-static-md"
     }
 
-    $root = $VcpkgRoot
-    if (-not $root) { $root = $env:VCPKG_INSTALLATION_ROOT }
-    if (-not $root -or -not (Test-Path (Join-Path $root 'vcpkg.exe'))) {
-        $root = Join-Path $env:LOCALAPPDATA 'vcpkg'
-    }
+    # `%LOCALAPPDATA%\vcpkg` is NOT a candidate install root, and must never be a clone target:
+    # that path is vcpkg's own per-user DATA directory (registries, downloads, and the
+    # `vcpkg.path.txt` breadcrumb naming the real root), so it exists — non-empty, no `.git` —
+    # on any machine where vcpkg has merely *run* once. Cloning into it fails with "destination
+    # path already exists and is not an empty directory". We only ever read it, for that
+    # breadcrumb; a clone of our own goes to the conventional per-user install location.
+    $breadcrumb = Join-Path $env:LOCALAPPDATA 'vcpkg\vcpkg.path.txt'
+    $known = @(
+        $VcpkgRoot
+        $env:VCPKG_INSTALLATION_ROOT
+        $(if (Test-Path $breadcrumb) { (Get-Content $breadcrumb -Raw).Trim() })
+        (Join-Path $env:LOCALAPPDATA 'Programs\vcpkg')
+        (Join-Path $env:USERPROFILE 'vcpkg')
+        'C:\vcpkg'
+    )
+    $root = $known | Where-Object { $_ -and (Test-Path (Join-Path $_ 'vcpkg.exe')) } | Select-Object -First 1
 
+    if (-not $root) {
+        # Nothing usable found. Clone into the per-user install location — unless the caller
+        # named a root, in which case honour it (they may be pointing at a fresh directory).
+        $root = if ($VcpkgRoot) { $VcpkgRoot } else { Join-Path $env:LOCALAPPDATA 'Programs\vcpkg' }
         if (-not (Test-Path (Join-Path $root '.git'))) {
+            # `git clone` refuses a non-empty destination, and the resulting error says nothing
+            # about what to do — so diagnose it here, where the remedy is known.
+            if ((Test-Path $root) -and (Get-ChildItem $root -Force | Select-Object -First 1)) {
+                throw ("$root exists, is not empty, and holds neither vcpkg.exe nor a git " +
+                    "checkout. Point the script at your vcpkg with -VcpkgRoot <path>, or " +
+                    "remove that directory.")
+            }
             Write-Step "Cloning vcpkg to $root (one time)"
             git clone --depth 1 https://github.com/microsoft/vcpkg $root | Out-Host
             if ($LASTEXITCODE -ne 0) { throw "vcpkg clone failed" }
         }
-    if (-not (Test-Path (Join-Path $root 'vcpkg.exe'))) {
         Write-Step 'Bootstrapping vcpkg (one time)'
         & (Join-Path $root 'bootstrap-vcpkg.bat') -disableMetrics | Out-Host
         if ($LASTEXITCODE -ne 0) { throw "vcpkg bootstrap failed" }
     }
+    Write-Note "vcpkg root: $root"
 
     $prefix = Join-Path $root "installed\$Triplet"
     if (-not (Test-Path (Join-Path $prefix 'include\sqlite3.h'))) {