fix(config): respect $HOME when resolving the default storage directory

pkg/config/root.go

@@ -17,6 +17,7 @@
 package config
 
 import (
+	"os"
 	"os/user"
 	"path/filepath"
 )
@@ -31,17 +32,35 @@ type Root struct {
 }
 
 func NewRoot() (*Root, error) {
-	user, err := user.Current()
+	homeDir, err := userHomeDir()
 	if err != nil {
 		return nil, err
 	}
 
 	return &Root{
-		StorageDir:      filepath.Join(user.HomeDir, ".modctl"),
+		StorageDir:      filepath.Join(homeDir, ".modctl"),
 		Pprof:           false,
 		PprofAddr:       "localhost:6060",
 		DisableProgress: false,
-		LogDir:          filepath.Join(user.HomeDir, ".modctl/logs"),
+		LogDir:          filepath.Join(homeDir, ".modctl/logs"),
 		LogLevel:        "info",
 	}, nil
 }
+
+// userHomeDir returns the home directory of the current user. It prefers
+// os.UserHomeDir, which honors $HOME (%USERPROFILE% on Windows), so that an
+// overridden home directory is respected. os/user.Current queries the user
+// database, which may ignore $HOME, so it is only used as a fallback when the
+// environment variable is not set.
+func userHomeDir() (string, error) {
+	if dir, err := os.UserHomeDir(); err == nil {
+		return dir, nil
+	}
+
+	u, err := user.Current()
+	if err != nil {
+		return "", err
+	}
+
+	return u.HomeDir, nil
+}

pkg/config/root_test.go

@@ -0,0 +1,51 @@
+/*
+ *     Copyright 2024 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 config
+
+import (
+	"os/user"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestNewRootRespectsHomeEnv(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	// os.UserHomeDir reads USERPROFILE on Windows.
+	t.Setenv("USERPROFILE", home)
+
+	root, err := NewRoot()
+	require.NoError(t, err)
+	assert.Equal(t, filepath.Join(home, ".modctl"), root.StorageDir)
+	assert.Equal(t, filepath.Join(home, ".modctl", "logs"), root.LogDir)
+}
+
+func TestNewRootFallsBackToCurrentUser(t *testing.T) {
+	u, err := user.Current()
+	require.NoError(t, err)
+
+	t.Setenv("HOME", "")
+	t.Setenv("USERPROFILE", "")
+
+	root, err := NewRoot()
+	require.NoError(t, err)
+	assert.Equal(t, filepath.Join(u.HomeDir, ".modctl"), root.StorageDir)
+	assert.Equal(t, filepath.Join(u.HomeDir, ".modctl", "logs"), root.LogDir)
+}