fix(cli): fallback to latest undone session in undo show when all sessions are undone

cmd/undo/main.go

@@ -3,6 +3,7 @@ package main
 
 import (
 	"bufio"
+	"errors"
 	"fmt"
 	"os"
 	"strconv"
@@ -141,17 +142,35 @@ func cmdList() {
 	}
 }
 
-func cmdShow(args []string) {
-	var s *session.Session
-	var err error
+func getShowSession(args []string) (*session.Session, bool, error) {
 	if len(args) > 0 {
-		s, err = session.Get(args[0])
-	} else {
-		s, err = session.Latest()
+		s, err := session.Get(args[0])
+		return s, false, err
+	}
+	s, err := session.Latest()
+	if errors.Is(err, os.ErrNotExist) {
+		// No non-undone session found. Fall back to the most recent
+		// session (including undone ones) so the user sees what happened
+		// rather than an opaque "no such session" error.
+		if all, lerr := session.List(); lerr == nil {
+			for _, candidate := range all {
+				if len(candidate.Entries) > 0 {
+					return candidate, true, nil
+				}
+			}
+		}
 	}
+	return s, false, err
+}
+
+func cmdShow(args []string) {
+	s, allUndone, err := getShowSession(args)
 	if err != nil {
 		fatal(fmt.Errorf("no such session"))
 	}
+	if allUndone {
+		fmt.Fprintln(os.Stderr, "(all sessions have been undone; showing the most recent)")
+	}
 	fmt.Printf("session %s (%s)\n$ %s\n\n", shortID(s.ID), when(s.ID), s.Cmd)
 	for i, e := range s.Entries {
 		fmt.Printf("  %2d  %s\n", i+1, e.Describe())

cmd/undo/show_test.go

@@ -0,0 +1,179 @@
+package main
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/edaywalid/undo/internal/session"
+)
+
+// Helper to create a test session with a specified command and optional journal entry
+func createTestSession(t *testing.T, cmd string, withJournal bool) *session.Session {
+	t.Helper()
+	s, err := session.Create(cmd)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := s.MarkDone(); err != nil {
+		t.Fatal(err)
+	}
+	if withJournal {
+		if err := os.WriteFile(filepath.Join(s.Dir, "journal"), []byte("unlink\t/tmp/file\t/tmp/file_bak\n"), 0o600); err != nil {
+			t.Fatal(err)
+		}
+	}
+	return s
+}
+
+// 1. Edge Case: Empty Session Store
+func TestGetShowSessionEmptyStore(t *testing.T) {
+	t.Setenv("UNDO_DATA_DIR", t.TempDir())
+
+	s, allUndone, err := getShowSession(nil)
+	if !errors.Is(err, os.ErrNotExist) {
+		t.Errorf("expected os.ErrNotExist, got %v", err)
+	}
+	if allUndone {
+		t.Errorf("expected allUndone=false, got true")
+	}
+	if s != nil {
+		t.Errorf("expected s=nil, got %v", s)
+	}
+}
+
+// 2. Edge Case: Only Empty Sessions (0 journal entries)
+func TestGetShowSessionOnlyEmptySessions(t *testing.T) {
+	t.Setenv("UNDO_DATA_DIR", t.TempDir())
+
+	createTestSession(t, "ls -la", false)
+	createTestSession(t, "cat README.md", false)
+
+	s, allUndone, err := getShowSession(nil)
+	if !errors.Is(err, os.ErrNotExist) {
+		t.Errorf("expected os.ErrNotExist for empty sessions, got %v", err)
+	}
+	if allUndone {
+		t.Errorf("expected allUndone=false, got true")
+	}
+	if s != nil {
+		t.Errorf("expected s=nil, got %v", s)
+	}
+}
+
+// 3. Edge Case: Explicit Session ID Argument Provided
+func TestGetShowSessionExplicitID(t *testing.T) {
+	t.Setenv("UNDO_DATA_DIR", t.TempDir())
+
+	s1 := createTestSession(t, "rm -rf dir1", true)
+	if err := s1.MarkUndone(); err != nil {
+		t.Fatal(err)
+	}
+
+	got, allUndone, err := getShowSession([]string{s1.ID})
+	if err != nil {
+		t.Fatalf("unexpected error looking up explicit ID: %v", err)
+	}
+	if got.ID != s1.ID {
+		t.Errorf("got ID %s, want %s", got.ID, s1.ID)
+	}
+	if allUndone {
+		t.Errorf("expected allUndone=false for explicit ID lookup")
+	}
+}
+
+// 4. Edge Case: Mix of Active and Undone Sessions
+func TestGetShowSessionMixActiveAndUndone(t *testing.T) {
+	t.Setenv("UNDO_DATA_DIR", t.TempDir())
+
+	s1 := createTestSession(t, "rm file1", true)
+	if err := s1.MarkUndone(); err != nil {
+		t.Fatal(err)
+	}
+
+	time.Sleep(10 * time.Millisecond)
+	s2 := createTestSession(t, "rm file2", true)
+
+	got, allUndone, err := getShowSession(nil)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if got.ID != s2.ID {
+		t.Errorf("got session ID %s, want active session %s", got.ID, s2.ID)
+	}
+	if allUndone {
+		t.Errorf("expected allUndone=false when an active session exists")
+	}
+}
+
+// 5. Edge Case: All Sessions Undone -> Fallback to Latest
+func TestGetShowSessionAllUndone(t *testing.T) {
+	tmpDir := t.TempDir()
+	t.Setenv("UNDO_DATA_DIR", tmpDir)
+
+	s1 := createTestSession(t, "rm -rf old_file", true)
+	if err := s1.MarkUndone(); err != nil {
+		t.Fatal(err)
+	}
+
+	got, allUndone, err := getShowSession(nil)
+	if err != nil {
+		t.Fatalf("unexpected error on fallback: %v", err)
+	}
+	if !allUndone {
+		t.Errorf("expected allUndone=true when all sessions are undone")
+	}
+	if got.ID != s1.ID {
+		t.Errorf("got session %s, want %s", got.ID, s1.ID)
+	}
+}
+
+// Full Output Verification Test for cmdShow
+func TestCmdShowOutputFormatting(t *testing.T) {
+	tmpDir := t.TempDir()
+	t.Setenv("UNDO_DATA_DIR", tmpDir)
+
+	s := createTestSession(t, "rm -rf target_folder", true)
+	if err := s.MarkUndone(); err != nil {
+		t.Fatal(err)
+	}
+
+	oldStdout := os.Stdout
+	oldStderr := os.Stderr
+	rOut, wOut, _ := os.Pipe()
+	rErr, wErr, _ := os.Pipe()
+	os.Stdout = wOut
+	os.Stderr = wErr
+
+	defer func() {
+		os.Stdout = oldStdout
+		os.Stderr = oldStderr
+	}()
+
+	cmdShow(nil)
+
+	wOut.Close()
+	wErr.Close()
+
+	var outBuf, errBuf bytes.Buffer
+	_, _ = io.Copy(&outBuf, rOut)
+	_, _ = io.Copy(&errBuf, rErr)
+
+	stderrStr := errBuf.String()
+	stdoutStr := outBuf.String()
+
+	if !strings.Contains(stderrStr, "(all sessions have been undone; showing the most recent)") {
+		t.Errorf("expected stderr warning, got: %q", stderrStr)
+	}
+	if !strings.Contains(stdoutStr, "rm -rf target_folder") {
+		t.Errorf("expected stdout command string, got: %q", stdoutStr)
+	}
+	if !strings.Contains(stdoutStr, "currently undone") {
+		t.Errorf("expected stdout undone footer, got: %q", stdoutStr)
+	}
+}