fix(session): default an unstated spawn cwd to the user's home

internal/session/registry.go

@@ -162,8 +162,22 @@ func (r *Registry) start(opts SpawnOpts, id string, preload []byte, restore Info
 		argv = []string{shell, "-l"}
 	}
 
+	// An empty Cwd is a caller with no preference, and it must not fall
+	// through to the daemon's own directory: a service-started daemon runs at
+	// / — neither unit in internal/service sets a working directory — and a
+	// hand-started one runs wherever it happened to be launched from, so
+	// every default session would open somewhere nobody chose. Home is what
+	// a terminal emulator or sshd would have picked, and it is where Revive
+	// already lands a session whose directory has vanished. When even home is
+	// unknowable the empty string stands and the shell inherits — the old
+	// behaviour, kept as the floor rather than the default.
+	cwd := opts.Cwd
+	if cwd == "" {
+		cwd, _ = os.UserHomeDir()
+	}
+
 	cmd := exec.Command(argv[0], argv[1:]...)
-	cmd.Dir = opts.Cwd
+	cmd.Dir = cwd
 	cmd.Env = sessionEnv(os.Environ(), shell)
 
 	cols, rows := opts.Cols, opts.Rows
@@ -184,7 +198,10 @@ func (r *Registry) start(opts SpawnOpts, id string, preload []byte, restore Info
 		size = DefaultRingSize
 	}
 
-	cwd := opts.Cwd
+	// The recorded cwd is the value resolved above, so what Info reports is
+	// where the shell actually started rather than a second opinion. It is
+	// only still empty when home was unresolvable, and then the child
+	// inherited the daemon's directory — so that is what gets recorded.
 	if cwd == "" {
 		cwd, _ = os.Getwd()
 	}

internal/session/registry_test.go

@@ -3,6 +3,7 @@ package session
 import (
 	"strings"
 	"testing"
+	"time"
 )
 
 func TestLoginShellPrefersSHELL(t *testing.T) {
@@ -82,6 +83,84 @@ func TestSessionEnvKeepsAnExistingSHELL(t *testing.T) {
 	}
 }
 
+// TestSpawnDefaultsCwdToHome pins where a session with no stated directory
+// opens: the user's home, like any terminal emulator or sshd. The alternative
+// — inheriting the daemon's own directory — is the launchd/systemd bug: a
+// service-started daemon runs at /, so every plain new session opened there.
+// os.UserHomeDir answers from $HOME on every platform flue targets, so
+// setting it is setting the expectation. Both the recorded cwd and the
+// child's real one are checked, because the fix is one resolution feeding
+// both — a seed that disagreed with the process would be the old split back
+// again. The poll and the symlink resolution are cwd_test.go's, for
+// cwd_test.go's reasons.
+func TestSpawnDefaultsCwdToHome(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	want := resolved(t, home)
+
+	r := NewRegistry(nil)
+	s, err := r.Spawn(SpawnOpts{Cmd: []string{"sleep", "5"}, Cols: 80, Rows: 24})
+	if err != nil {
+		t.Fatalf("Spawn: %v", err)
+	}
+	t.Cleanup(func() { _ = s.Close() })
+
+	s.mu.Lock()
+	seeded := s.info.Cwd
+	s.mu.Unlock()
+	if seeded != home {
+		t.Fatalf("recorded Cwd = %q, want the home %q", seeded, home)
+	}
+
+	deadline := time.Now().Add(5 * time.Second)
+	for {
+		got, err := processCwd(s.pid)
+		if err == nil && resolved(t, got) == want {
+			return
+		}
+		if time.Now().After(deadline) {
+			t.Fatalf("processCwd(%d) = %q, %v; want %q", s.pid, got, err, want)
+		}
+		time.Sleep(5 * time.Millisecond)
+	}
+}
+
+// TestSpawnKeepsExplicitCwd is the other half of the default: a caller that
+// states a directory gets that directory, and home never competes with it.
+// The stated one is deliberately not $HOME, so a spawn that reached for home
+// anyway could not pass by coincidence.
+func TestSpawnKeepsExplicitCwd(t *testing.T) {
+	t.Setenv("HOME", t.TempDir())
+	dir := t.TempDir()
+	want := resolved(t, dir)
+
+	r := NewRegistry(nil)
+	s, err := r.Spawn(SpawnOpts{Cwd: dir, Cmd: []string{"sleep", "5"}, Cols: 80, Rows: 24})
+	if err != nil {
+		t.Fatalf("Spawn: %v", err)
+	}
+	t.Cleanup(func() { _ = s.Close() })
+
+	s.mu.Lock()
+	seeded := s.info.Cwd
+	s.mu.Unlock()
+	if seeded != dir {
+		t.Fatalf("recorded Cwd = %q, want the stated %q", seeded, dir)
+	}
+
+	deadline := time.Now().Add(5 * time.Second)
+	for {
+		got, err := processCwd(s.pid)
+		if err == nil && resolved(t, got) == want {
+			return
+		}
+		if time.Now().After(deadline) {
+			t.Fatalf("processCwd(%d) = %q, %v; want %q", s.pid, got, err, want)
+		}
+		time.Sleep(5 * time.Millisecond)
+	}
+}
+
 func contains(env []string, kv string) bool {
 	for _, e := range env {
 		if e == kv {