Make Metal availability check static and platform-aware

- Updated usemetal() to be a static check that returns false on non-Apple platforms
- Modified MetalLUFactorization constructor to check platform with @static
- Updated test files to skip Metal tests on non-Apple platforms
- This fixes CI failures on Linux where Metal is not available

Following the same pattern as AppleAccelerateLUFactorization for consistency.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: claude

src/LinearSolve.jl

@@ -410,7 +410,13 @@ appleaccelerate_isavailable() = HAS_APPLE_ACCELERATE[]
 # Extension availability checking functions
 useblis() = Base.get_extension(@__MODULE__, :LinearSolveBLISExt) !== nothing
 usecuda() = Base.get_extension(@__MODULE__, :LinearSolveCUDAExt) !== nothing
-usemetal() = Base.get_extension(@__MODULE__, :LinearSolveMetalExt) !== nothing
+
+# Metal is only available on Apple platforms
+@static if !Sys.isapple()
+    usemetal() = false
+else
+    usemetal() = Base.get_extension(@__MODULE__, :LinearSolveMetalExt) !== nothing
+end
 
 PrecompileTools.@compile_workload begin
     A = rand(4, 4)

src/extension_algs.jl

@@ -633,11 +633,19 @@ sol = solve(prob, alg)
 """
 struct MetalLUFactorization <: AbstractFactorization 
     function MetalLUFactorization(; throwerror = true)
-        ext = Base.get_extension(@__MODULE__, :LinearSolveMetalExt)
-        if ext === nothing && throwerror
-            error("MetalLUFactorization requires that Metal.jl is loaded, i.e. `using Metal`")
+        @static if !Sys.isapple()
+            if throwerror
+                error("MetalLUFactorization is only available on Apple platforms")
+            else
+                return new()
+            end
         else
-            return new()
+            ext = Base.get_extension(@__MODULE__, :LinearSolveMetalExt)
+            if ext === nothing && throwerror
+                error("MetalLUFactorization requires that Metal.jl is loaded, i.e. `using Metal`")
+            else
+                return new()
+            end
         end
     end
 end

test/nopre/jet.jl

@@ -63,7 +63,8 @@ end
 
     # CUDA/Metal factorizations (only test if CUDA/Metal are loaded)
     # CudaOffloadFactorization requires CUDA to be loaded, skip if not available
-    if @isdefined(MetalLUFactorization)
+    # Metal is only available on Apple platforms
+    if Sys.isapple() && @isdefined(MetalLUFactorization)
         JET.@test_opt solve(prob, MetalLUFactorization()) broken=true
     end
     if @isdefined(BLISLUFactorization)

test_new_solvers.jl

@@ -35,13 +35,27 @@ end
     alg2 = LinearSolve.CudaOffloadLUFactorization(throwerror=false)
     @test alg2 isa LinearSolve.CudaOffloadLUFactorization
 
-    alg3 = LinearSolve.MetalLUFactorization(throwerror=false)
-    @test alg3 isa LinearSolve.MetalLUFactorization
+    # Metal is only available on Apple platforms
+    if Sys.isapple()
+        alg3 = LinearSolve.MetalLUFactorization(throwerror=false)
+        @test alg3 isa LinearSolve.MetalLUFactorization
+    else
+        # On non-Apple platforms, it should still not error with throwerror=false
+        alg3 = LinearSolve.MetalLUFactorization(throwerror=false)
+        @test alg3 isa LinearSolve.MetalLUFactorization
+    end
 
     # These should throw errors with throwerror=true (default)
     @test_throws ErrorException LinearSolve.BLISLUFactorization()
     @test_throws ErrorException LinearSolve.CudaOffloadLUFactorization()
-    @test_throws ErrorException LinearSolve.MetalLUFactorization()
+    
+    # Metal error message depends on platform
+    if Sys.isapple()
+        @test_throws ErrorException LinearSolve.MetalLUFactorization()
+    else
+        # On non-Apple platforms, should error with platform message
+        @test_throws ErrorException LinearSolve.MetalLUFactorization()
+    end
 end
 
 # Test that preferences system recognizes the new algorithms