Add {{.Temp}} variable to host templates

Allows writing the temp mount as

mounts:
- location: "{{.Temp}}/lima"
  mountPoint: /tmp/lima

Note that on macOS this would use $TMPDIR and not /tmp, so would be a change
in behaviour. It would not affect existing instances though.

Signed-off-by: Jan Dubois <jan.dubois@suse.com>

Author: jandubois

pkg/limayaml/defaults.go

@@ -738,7 +738,7 @@ func FillDefault(y, d, o *LimaYAML, filePath string, warn bool) {
 	location := make(map[string]int)
 	for _, mount := range slices.Concat(d.Mounts, y.Mounts, o.Mounts) {
 		if out, err := executeHostTemplate(mount.Location, instDir, y.Param); err == nil {
-			mount.Location = out.String()
+			mount.Location = filepath.Clean(out.String())
 		} else {
 			logrus.WithError(err).Warnf("Couldn't process mount location %q as a template", mount.Location)
 		}
@@ -955,14 +955,22 @@ func executeHostTemplate(format, instDir string, param map[string]string) (bytes
 	tmpl, err := template.New("").Parse(format)
 	if err == nil {
 		limaHome, _ := dirnames.LimaDir()
+		globalTempDir := "/tmp"
+		if runtime.GOOS == "windows" {
+			// On Windows the global temp directory "%SystemRoot%\Temp" (normally "C:\Windows\Temp")
+			// is not writable by regular users.
+			globalTempDir = os.TempDir()
+		}
 		data := map[string]any{
 			"Dir":  instDir,
 			"Name": filepath.Base(instDir),
 			// TODO: add hostname fields for the host and the guest
-			"UID":   currentUser.Uid,
-			"User":  currentUser.Username,
-			"Home":  userHomeDir,
-			"Param": param,
+			"UID":           currentUser.Uid,
+			"User":          currentUser.Username,
+			"Home":          userHomeDir,
+			"Param":         param,
+			"GlobalTempDir": globalTempDir,
+			"TempDir":       os.TempDir(),
 
 			"Instance": filepath.Base(instDir), // DEPRECATED, use `{{.Name}}`
 			"LimaHome": limaHome,               // DEPRECATED, use `{{.Dir}}` instead of `{{.LimaHome}}/{{.Instance}}`

pkg/limayaml/defaults_test.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"net"
 	"os"
+	"path"
 	"path/filepath"
 	"runtime"
 	"slices"
@@ -146,10 +147,9 @@ func TestFillDefault(t *testing.T) {
 			},
 		},
 		Mounts: []Mount{
-			// Location will be passed through localpathutil.Expand() which will normalize the name
-			// (add a drive letter). So we must start with a valid local path to match it again later.
-			{Location: filepath.Clean(t.TempDir())},
-			{Location: "{{.Dir}}/{{.Param.ONE}}", MountPoint: ptr.Of("/mnt/{{.Param.ONE}}")},
+			//nolint:usetesting // We need the OS temp directory name here; it is not used to create temp files for testing
+			{Location: filepath.Clean(os.TempDir())},
+			{Location: filepath.Clean("{{.Dir}}/{{.Param.ONE}}"), MountPoint: ptr.Of("/mnt/{{.Param.ONE}}")},
 		},
 		MountType: ptr.Of(NINEP),
 		Provision: []Provision{
@@ -240,7 +240,7 @@ func TestFillDefault(t *testing.T) {
 	expect.Mounts[0].Virtiofs.QueueSize = nil
 	// Only missing Mounts field is Writable, and the default value is also the null value: false
 	expect.Mounts[1].Location = filepath.Join(instDir, y.Param["ONE"])
-	expect.Mounts[1].MountPoint = ptr.Of(fmt.Sprintf("/mnt/%s", y.Param["ONE"]))
+	expect.Mounts[1].MountPoint = ptr.Of(path.Join("/mnt", y.Param["ONE"]))
 	expect.Mounts[1].Writable = ptr.Of(false)
 	expect.Mounts[1].SSHFS.Cache = ptr.Of(true)
 	expect.Mounts[1].SSHFS.FollowSymlinks = ptr.Of(false)

templates/_default/mounts.yaml

@@ -1,4 +1,6 @@
 mounts:
 - location: "~"
-- location: "/tmp/lima"
+
+- location: "{{.GlobalTempDir}}/lima"
+  mountPoint: /tmp/lima
   writable: true

templates/default.yaml

@@ -34,7 +34,8 @@ memory: null
 disk: null
 
 # Expose host directories to the guest, the mount point might be accessible from all UIDs in the guest
-# "location" can use these template variables: {{.Home}}, {{.Dir}}, {{.Name}}, {{.UID}}, {{.User}}, and {{.Param.Key}}.
+# "location" can use these template variables: {{.Home}}, {{.Dir}}, {{.Name}}, {{.UID}}, {{.User}}, {{.Param.Key}},
+# {{.GlobalTempDir}}, and {{.TempDir}}. The global temp dir is always "/tmp" on Unix.
 # "mountPoint" can use these template variables: {{.Home}}, {{.Name}}, {{.Hostname}}, {{.UID}}, {{.User}}, and {{.Param.Key}}.
 # 🟢 Builtin default: [] (Mount nothing)
 # 🔵 This file: Mount the home as read-only, /tmp/lima as writable  (inherited via the `base` mechanism later in this file)