feat: support building modctl for Windows

.github/workflows/ci.yml

@@ -51,3 +51,25 @@ jobs:
         run: |-
           go version
           go test -ldflags '-extldflags "-static"' -tags static,system_libgit2 -v ./...
+
+  cross-compile:
+    name: Cross Compile (windows/amd64)
+    timeout-minutes: 30
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1    # v4.3.1
+
+      - name: Install Go
+        uses: actions/setup-go@b7ad1dad31e06c5925ef5d2fc7ad053ef454303e    # v7.0.0
+        with:
+          go-version-file: go.mod
+
+      - name: Build and vet
+        env:
+          GOOS: windows
+          GOARCH: amd64
+          CGO_ENABLED: "0"
+        run: |-
+          go build ./...
+          go vet ./...

cmd/login.go

@@ -19,8 +19,8 @@ package cmd
 import (
 	"context"
 	"fmt"
+	"os"
 	"strings"
-	"syscall"
 
 	"golang.org/x/crypto/ssh/terminal"
 
@@ -84,7 +84,7 @@ func runLogin(ctx context.Context, registry string) error {
 		}
 	} else if loginConfig.PasswordStdin && loginConfig.Password == "" {
 		fmt.Print("Enter password: ")
-		password, err := terminal.ReadPassword(syscall.Stdin)
+		password, err := terminal.ReadPassword(int(os.Stdin.Fd()))
 		if err != nil {
 			return err
 		}

pkg/backend/build/builder.go

@@ -25,7 +25,6 @@ import (
 	"io"
 	"os"
 	"path/filepath"
-	"syscall"
 	"time"
 
 	sha256 "github.com/minio/sha256-simd"
@@ -417,10 +416,7 @@ func getFileMetadata(path string) (modelspec.FileMetadata, error) {
 	}
 
 	// UID and GID (Unix-specific).
-	if stat, ok := info.Sys().(*syscall.Stat_t); ok {
-		metadata.Uid = stat.Uid
-		metadata.Gid = stat.Gid
-	}
+	metadata.Uid, metadata.Gid = fileOwner(info)
 
 	return metadata, nil
 }

pkg/backend/build/builder_test.go

@@ -22,9 +22,7 @@ import (
 	"io"
 	"os"
 	"path/filepath"
-	"runtime"
 	"strings"
-	"syscall"
 	"testing"
 	"time"
 
@@ -499,18 +497,10 @@ func TestGetFileMetadata(t *testing.T) {
 		assert.Equal(t, byte(0), metadata.Typeflag, "Typeflag should be 0 for regular file")
 		assert.WithinDuration(t, fileInfo.ModTime(), metadata.ModTime, time.Second)
 
-		// Check UID/GID only on Unix-like systems
-		if stat, ok := fileInfo.Sys().(*syscall.Stat_t); ok {
-			assert.Equal(t, stat.Uid, metadata.Uid, "UID mismatch")
-			assert.Equal(t, stat.Gid, metadata.Gid, "GID mismatch")
-		} else if runtime.GOOS != "windows" {
-			// If not windows and not syscall.Stat_t, something is unexpected
-			t.Logf("Warning: Could not get syscall.Stat_t on non-Windows OS (%s)", runtime.GOOS)
-		} else {
-			// On Windows, expect 0 as syscall.Stat_t assertion fails
-			assert.Equal(t, uint32(0), metadata.Uid, "UID should be 0 on Windows")
-			assert.Equal(t, uint32(0), metadata.Gid, "GID should be 0 on Windows")
-		}
+		// UID and GID are only available on Unix-like systems and are 0 elsewhere.
+		wantUID, wantGID := expectedFileOwner(t, fileInfo)
+		assert.Equal(t, wantUID, metadata.Uid, "UID mismatch")
+		assert.Equal(t, wantGID, metadata.Gid, "GID mismatch")
 	})
 
 	// --- Test Case 2: Directory ---
@@ -528,15 +518,9 @@ func TestGetFileMetadata(t *testing.T) {
 		assert.Equal(t, byte(5), metadata.Typeflag, "Typeflag should be 5 for directory")
 		assert.WithinDuration(t, dirInfo.ModTime(), metadata.ModTime, time.Second)
 
-		// Check UID/GID only on Unix-like systems
-		if stat, ok := dirInfo.Sys().(*syscall.Stat_t); ok {
-			assert.Equal(t, stat.Uid, metadata.Uid, "UID mismatch")
-			assert.Equal(t, stat.Gid, metadata.Gid, "GID mismatch")
-		} else if runtime.GOOS != "windows" {
-			t.Logf("Warning: Could not get syscall.Stat_t on non-Windows OS (%s)", runtime.GOOS)
-		} else {
-			assert.Equal(t, uint32(0), metadata.Uid, "UID should be 0 on Windows")
-			assert.Equal(t, uint32(0), metadata.Gid, "GID should be 0 on Windows")
-		}
+		// UID and GID are only available on Unix-like systems and are 0 elsewhere.
+		wantUID, wantGID := expectedFileOwner(t, dirInfo)
+		assert.Equal(t, wantUID, metadata.Uid, "UID mismatch")
+		assert.Equal(t, wantGID, metadata.Gid, "GID mismatch")
 	})
 }

pkg/version/platform_darwin.go → pkg/backend/build/owner_other.go

@@ -1,5 +1,7 @@
+//go:build !unix
+
 /*
- *     Copyright 2025 The ModelPack Authors
+ *     Copyright 2026 The ModelPack Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,6 +16,11 @@
  * limitations under the License.
  */
 
-package version
+package build
+
+import "os"
 
-const platform = "darwin"
+// fileOwner returns zero IDs because the platform has no numeric file owners.
+func fileOwner(info os.FileInfo) (uid, gid uint32) {
+	return 0, 0
+}

pkg/version/platform_linux.go → pkg/backend/build/owner_other_test.go

@@ -1,5 +1,7 @@
+//go:build !unix
+
 /*
- *     Copyright 2025 The ModelPack Authors
+ *     Copyright 2026 The ModelPack Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,6 +16,17 @@
  * limitations under the License.
  */
 
-package version
+package build
+
+import (
+	"os"
+	"testing"
+)
+
+// expectedFileOwner returns zero IDs because the platform has no numeric file
+// owners.
+func expectedFileOwner(t *testing.T, info os.FileInfo) (uid, gid uint32) {
+	t.Helper()
 
-const platform = "linux"
+	return 0, 0
+}

pkg/backend/build/owner_unix.go

@@ -0,0 +1,33 @@
+//go:build unix
+
+/*
+ *     Copyright 2026 The ModelPack Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package build
+
+import (
+	"os"
+	"syscall"
+)
+
+// fileOwner returns the numeric user and group IDs that own the file.
+func fileOwner(info os.FileInfo) (uid, gid uint32) {
+	if stat, ok := info.Sys().(*syscall.Stat_t); ok {
+		return stat.Uid, stat.Gid
+	}
+
+	return 0, 0
+}

pkg/backend/build/owner_unix_test.go

@@ -0,0 +1,37 @@
+//go:build unix
+
+/*
+ *     Copyright 2026 The ModelPack Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package build
+
+import (
+	"os"
+	"syscall"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// expectedFileOwner returns the numeric owner IDs reported by the OS.
+func expectedFileOwner(t *testing.T, info os.FileInfo) (uid, gid uint32) {
+	t.Helper()
+
+	stat, ok := info.Sys().(*syscall.Stat_t)
+	require.True(t, ok, "expected *syscall.Stat_t, got %T", info.Sys())
+
+	return stat.Uid, stat.Gid
+}

pkg/diskspace/check.go

@@ -1,3 +1,5 @@
+//go:build linux || darwin || windows
+
 /*
  *     Copyright 2025 The CNAI Authors
  *
@@ -14,17 +16,12 @@
  * limitations under the License.
  */
 
-//go:build linux || darwin
-
 package diskspace
 
 import (
 	"fmt"
-	"math"
 	"os"
 	"path/filepath"
-
-	"golang.org/x/sys/unix"
 )
 
 const (
@@ -42,7 +39,7 @@ func Check(dir string, requiredBytes int64) error {
 		return nil
 	}
 
-	// Ensure the directory exists for statfs; walk up to find an existing parent.
+	// Ensure the directory exists for the disk space query; walk up to find an existing parent.
 	checkDir := dir
 	for {
 		if _, err := os.Stat(checkDir); err == nil {
@@ -56,22 +53,11 @@ func Check(dir string, requiredBytes int64) error {
 		checkDir = parent
 	}
 
-	var stat unix.Statfs_t
-	if err := unix.Statfs(checkDir, &stat); err != nil {
+	availableBytes, err := availableSpace(checkDir)
+	if err != nil {
 		return fmt.Errorf("failed to check disk space for %s: %w", dir, err)
 	}
 
-	// Available space for non-root users.
-	// Guard against overflow: on Linux Bavail is uint64, and values exceeding
-	// math.MaxInt64 would wrap negative when cast to int64. Cap at MaxInt64.
-	bavail := stat.Bavail
-	bsize := uint64(stat.Bsize)
-	var availableBytes int64
-	if bavail > 0 && bsize > uint64(math.MaxInt64)/bavail {
-		availableBytes = math.MaxInt64
-	} else {
-		availableBytes = int64(bavail * bsize)
-	}
 	requiredWithMargin := int64(float64(requiredBytes) * safetyMargin)
 
 	if availableBytes < requiredWithMargin {

pkg/diskspace/check_other.go

@@ -1,3 +1,5 @@
+//go:build !linux && !darwin && !windows
+
 /*
  *     Copyright 2025 The CNAI Authors
  *
@@ -14,16 +16,13 @@
  * limitations under the License.
  */
 
-//go:build !linux && !darwin
-
 package diskspace
 
 import "github.com/sirupsen/logrus"
 
 // Check is a no-op stub for platforms that do not yet have a disk-space
 // implementation. It always returns nil so callers can compile and run on
-// Windows and other non-Unix systems, at the cost of losing the pre-check
-// warning. Native Windows support is tracked upstream.
+// those systems, at the cost of losing the pre-check warning.
 func Check(dir string, requiredBytes int64) error {
 	logrus.Debugf("diskspace: pre-check skipped on this platform (dir=%s, required=%d)", dir, requiredBytes)
 	return nil

pkg/diskspace/check_test.go

@@ -1,3 +1,5 @@
+//go:build linux || darwin || windows
+
 /*
  *     Copyright 2025 The CNAI Authors
  *
@@ -14,8 +16,6 @@
  * limitations under the License.
  */
 
-//go:build linux || darwin
-
 package diskspace
 
 import (

pkg/diskspace/space_unix.go

@@ -0,0 +1,44 @@
+//go:build linux || darwin
+
+/*
+ *     Copyright 2026 The ModelPack Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package diskspace
+
+import (
+	"math"
+
+	"golang.org/x/sys/unix"
+)
+
+// availableSpace returns the number of bytes available to non-root users on
+// the filesystem containing dir.
+func availableSpace(dir string) (int64, error) {
+	var stat unix.Statfs_t
+	if err := unix.Statfs(dir, &stat); err != nil {
+		return 0, err
+	}
+
+	// Guard against overflow: on Linux Bavail is uint64, and values exceeding
+	// math.MaxInt64 would wrap negative when cast to int64. Cap at MaxInt64.
+	bavail := stat.Bavail
+	bsize := uint64(stat.Bsize)
+	if bavail > 0 && bsize > uint64(math.MaxInt64)/bavail {
+		return math.MaxInt64, nil
+	}
+
+	return int64(bavail * bsize), nil
+}