Ignore a mismatched system Zig during native restore

Resolve-ZigPath returned any zig on PATH without checking its version, so
a newer system Zig (e.g. 0.17) broke dotnet build: Zig's build API changes
between minor releases and the pinned Ghostty sources only build with 0.16.

A zig on PATH is now used only when it matches the pinned major.minor
(patch and dev builds included); otherwise it is skipped and the pinned Zig
is used from, or downloaded into, artifacts/tools. An explicit -ZigPath is
still honored but warns on a version mismatch.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: mamoreau-devolutions

CONTRIBUTING.md

@@ -73,7 +73,8 @@ Do not point that tool at this repository.
 - Windows Explorer/toast helpers: `native/windows-shell` (MSVC, gitignored `bin/`)
 
 `dotnet build` restores Ghostty and `dt-pty-host` for the host RID (Zig is
-downloaded into `artifacts/tools` on first use). See
+downloaded into `artifacts/tools` on first use; a system `zig` of a different
+minor version than the pinned one is ignored, so it does not break the build). See
 [`native/ghostty/README.md`](native/ghostty/README.md). Pass
 `-p:SkipNativeRestore=true` to skip.
 

native/Zig.ps1

@@ -111,6 +111,50 @@ function Install-Zig {
     return $found.FullName
 }
 
+function Get-ZigVersion {
+    param(
+        [Parameter(Mandatory)]
+        [string] $ZigPath
+    )
+
+    try {
+        $output = & $ZigPath version 2>$null
+        if ($LASTEXITCODE -ne 0) {
+            return $null
+        }
+
+        return ([string]$output).Trim()
+    }
+    catch {
+        return $null
+    }
+}
+
+# Zig's build API changes between minor releases, so only the pinned major.minor can build the
+# pinned sources; patch releases (and dev builds of that minor) are accepted.
+function Test-ZigVersionCompatible {
+    param(
+        [string] $Actual,
+        [Parameter(Mandatory)]
+        [string] $Required
+    )
+
+    if ([string]::IsNullOrWhiteSpace($Actual)) {
+        return $false
+    }
+
+    $actualCore = ($Actual -split '[-+]', 2)[0]
+    $requiredCore = ($Required -split '[-+]', 2)[0]
+    $actualVersion = $null
+    $requiredVersion = $null
+    if (-not [version]::TryParse($actualCore, [ref]$actualVersion) -or
+        -not [version]::TryParse($requiredCore, [ref]$requiredVersion)) {
+        return $false
+    }
+
+    return $actualVersion.Major -eq $requiredVersion.Major -and $actualVersion.Minor -eq $requiredVersion.Minor
+}
+
 function Resolve-ZigPath {
     param(
         [string] $ZigPath,
@@ -122,12 +166,24 @@ function Resolve-ZigPath {
     )
 
     if (-not [string]::IsNullOrWhiteSpace($ZigPath) -and (Test-Path -LiteralPath $ZigPath)) {
+        $explicitVersion = Get-ZigVersion -ZigPath $ZigPath
+        if (-not (Test-ZigVersionCompatible -Actual $explicitVersion -Required $Version)) {
+            Write-Warning "Using explicit Zig '$ZigPath' ($explicitVersion); the pinned sources expect Zig $Version."
+        }
+
         return $ZigPath
     }
 
+    # A different system Zig (for example a newer release on PATH) is ignored rather than failing
+    # the build: the pinned version is used from, or downloaded into, artifacts/tools instead.
     $command = Get-Command zig -ErrorAction SilentlyContinue | Select-Object -First 1
     if ($null -ne $command) {
-        return $command.Source
+        $pathVersion = Get-ZigVersion -ZigPath $command.Source
+        if (Test-ZigVersionCompatible -Actual $pathVersion -Required $Version) {
+            return $command.Source
+        }
+
+        Write-Host "Ignoring Zig $pathVersion at '$($command.Source)'; native libraries require Zig $Version."
     }
 
     $zigName = if (Test-HostWindows) { "zig.exe" } else { "zig" }

native/ghostty/README.md

@@ -12,7 +12,9 @@ The optional Ghostty terminal engine uses `libghostty-vt` built from
 Binaries are **not** committed. `dotnet build` / `dotnet test` restore the host
 RID via [`../Restore-NativeLibraries.ps1`](../Restore-NativeLibraries.ps1),
 which downloads Zig 0.16.0 if needed and compiles `libghostty-vt` into
-`native/ghostty/<rid>/` (gitignored). ABI checks use the type manifest, not a
+`native/ghostty/<rid>/` (gitignored). A `zig` on `PATH` is used only when it is
+Zig 0.16.x; any other version (for example a newer system install) is ignored
+and the pinned Zig is downloaded into `artifacts/tools` instead. ABI checks use the type manifest, not a
 file hash.
 
 Linux: glibc **2.31+**. macOS: **13.0+** (`aarch64-macos.13.0` /