mapsize 1.2.0: permanent delete and in-map reveal when headless

On a headless Linux or BSD system (no DISPLAY or WAYLAND_DISPLAY) nothing
empties the freedesktop trash, so trashing never freed space. There, d now
deletes permanently after an explicit confirmation, checking owner and type
against the scan and removing through an os.Root on the parent so a swapped
symlink cannot redirect it. o shows the folder in the map instead of
launching a file manager. Desktop sessions, macOS and Windows are unchanged.

internal/platform/delete_unix.go

@@ -0,0 +1,35 @@
+//go:build unix
+
+package platform
+
+import (
+	"errors"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"syscall"
+)
+
+// Delete permanently removes path (recursively for a directory) if it still
+// matches want. The check and the removal both go through an os.Root on the
+// parent directory, so a symlink swapped in since the scan cannot redirect
+// the removal outside it.
+func Delete(path string, want Expect) error {
+	if err := checkAbs(path); err != nil {
+		return err
+	}
+	dir, base := filepath.Dir(path), filepath.Base(path)
+	root, err := os.OpenRoot(dir)
+	if err != nil {
+		return err
+	}
+	defer root.Close()
+	fi, err := root.Lstat(base)
+	if err != nil {
+		return err
+	}
+	if fi.Sys().(*syscall.Stat_t).Uid != want.UID || fi.Mode()&fs.ModeType != want.Mode&fs.ModeType {
+		return errors.New("item changed since the scan (owner or type differs); rescan first")
+	}
+	return root.RemoveAll(base)
+}

internal/platform/ops_darwin.go

@@ -75,3 +75,7 @@ func volumeOf(path string) string {
 	}
 	return ""
 }
+
+// Headless is always false: macOS has Finder and the Trash even without
+// $DISPLAY (which it does not use).
+func Headless() bool { return false }

internal/platform/ops_linux.go

@@ -123,3 +123,10 @@ func mountTop(path string, dev uint64) string {
 		cur = parent
 	}
 }
+
+// Headless reports whether there is no graphical session (no X or Wayland
+// display), so there is no file manager to open and no desktop trash anyone
+// will empty.
+func Headless() bool {
+	return os.Getenv("DISPLAY") == "" && os.Getenv("WAYLAND_DISPLAY") == ""
+}

internal/platform/ops_linux_test.go

@@ -113,3 +113,43 @@ func TestTrashRefusesSwappedItem(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestDeletePermanently(t *testing.T) {
+	base := t.TempDir()
+	dir := filepath.Join(base, "S01")
+	os.MkdirAll(filepath.Join(dir, "extras"), 0o755)
+	os.WriteFile(filepath.Join(dir, "extras", "E01.mkv"), []byte("x"), 0o644)
+	// A symlink inside must be removed, not followed.
+	keep := filepath.Join(base, "keep")
+	os.WriteFile(keep, []byte("k"), 0o644)
+	os.Symlink(keep, filepath.Join(dir, "link"))
+
+	w := want(t, dir)
+	if err := Delete(dir, Expect{UID: w.UID, Mode: 0}); err == nil {
+		t.Fatal("type mismatch accepted")
+	}
+	if err := Delete(dir, w); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := os.Lstat(dir); !os.IsNotExist(err) {
+		t.Fatal("directory still present")
+	}
+	if _, err := os.Lstat(keep); err != nil {
+		t.Fatal("symlink target was deleted")
+	}
+	if err := Delete("relative/path", Expect{}); err == nil {
+		t.Fatal("relative paths must be refused")
+	}
+}
+
+func TestHeadless(t *testing.T) {
+	t.Setenv("DISPLAY", "")
+	t.Setenv("WAYLAND_DISPLAY", "")
+	if !Headless() {
+		t.Fatal("no display should be headless")
+	}
+	t.Setenv("WAYLAND_DISPLAY", "wayland-0")
+	if Headless() {
+		t.Fatal("wayland session reported headless")
+	}
+}

internal/platform/ops_other.go

@@ -2,7 +2,10 @@
 
 package platform
 
-import "errors"
+import (
+	"errors"
+	"os"
+)
 
 // TrashName is the user-facing name of the trash.
 const TrashName = "trash"
@@ -12,3 +15,10 @@ func Reveal(string) error { return errors.New("not supported on this platform")
 
 // Trash is unsupported on this platform.
 func Trash(string, Expect) error { return errors.New("trash not supported on this platform") }
+
+// Headless reports whether there is no graphical session (no X or Wayland
+// display), so there is no file manager to open and no desktop trash anyone
+// will empty.
+func Headless() bool {
+	return os.Getenv("DISPLAY") == "" && os.Getenv("WAYLAND_DISPLAY") == ""
+}

internal/platform/ops_windows.go

@@ -70,3 +70,9 @@ func Trash(path string, _ Expect) error {
 	}
 	return nil
 }
+
+// Headless is always false: Windows always has Explorer and the Recycle Bin.
+func Headless() bool { return false }
+
+// Delete is not offered on Windows; items go to the Recycle Bin.
+func Delete(string, Expect) error { return errors.New("permanent delete not supported on Windows") }