fix: finch run panic without arguments

Signed-off-by: Arjun Raja Yogidas <arjunry@amazon.com>

Author: coderbirju

cmd/finch/nerdctl_remote.go

@@ -94,9 +94,12 @@ func (nc *nerdctlCommand) run(cmdName string, args []string) error {
 	case "container run", "exec", "compose":
 		// check if an option flag is present; immediately following the command
 		switch {
-		case args[0] == "run" && strings.HasPrefix(args[1], "-"):
+		case len(args) > 1 && args[0] == "run" && strings.HasPrefix(args[1], "-"):
 			firstOptPos = 1
-		case strings.HasPrefix(args[0], "-"):
+		case len(args) > 0 && strings.HasPrefix(args[0], "-"):
+			firstOptPos = 0
+		case len(args) == 0:
+			args = append(args, "--help")
 			firstOptPos = 0
 		default:
 			firstOptPos = -1

cmd/finch/nerdctl_remote_test.go

@@ -14,6 +14,7 @@ import (
 	"github.com/stretchr/testify/assert"
 	"go.uber.org/mock/gomock"
 
+	"github.com/runfinch/finch/pkg/command"
 	"github.com/runfinch/finch/pkg/config"
 	"github.com/runfinch/finch/pkg/mocks"
 )
@@ -132,3 +133,96 @@ func TestNerdctlCommand_withVMErrors(t *testing.T) {
 		})
 	}
 }
+
+func TestNerdctlCommand_withEmptyArgs(t *testing.T) {
+	t.Parallel()
+
+	testCases := []struct {
+		name    string
+		cmdName string
+		args    []string
+	}{
+		{
+			name:    "finch run with no arguments",
+			cmdName: "container run",
+			args:    []string{},
+		},
+		{
+			name:    "finch compose with no arguments",
+			cmdName: "compose",
+			args:    []string{},
+		},
+		{
+			name:    "finch exec with no arguments",
+			cmdName: "exec",
+			args:    []string{},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			ctrl := gomock.NewController(t)
+			ecc := mocks.NewCommandCreator(ctrl)
+			ncc := mocks.NewNerdctlCmdCreator(ctrl)
+			ncsd := mocks.NewNerdctlCommandSystemDeps(ctrl)
+			logger := mocks.NewLogger(ctrl)
+			fs := afero.NewMemMapFs()
+			fc := &config.Finch{}
+
+			// Mock VM status check to return running
+			getVMStatusC := mocks.NewCommand(ctrl)
+			ncc.EXPECT().CreateWithoutStdio("ls", "-f", "{{.Status}}", limaInstanceName).Return(getVMStatusC)
+			getVMStatusC.EXPECT().Output().Return([]byte("Running"), nil)
+			logger.EXPECT().Debugf("Status of virtual machine: %s", "Running")
+
+			// Mock environment variable lookups (these happen in the run method)
+			envVars := []string{
+				"COSIGN_PASSWORD", "AWS_ACCESS_KEY_ID", "AWS_SECRET_ACCESS_KEY",
+				"AWS_SESSION_TOKEN", "COMPOSE_FILE", "SOURCE_DATE_EPOCH",
+				"AWS_ECR_DISABLE_CACHE", "AWS_ECR_CACHE_DIR", "AWS_ECR_IGNORE_CREDS_STORAGE",
+			}
+			for _, envVar := range envVars {
+				ncsd.EXPECT().LookupEnv(envVar).Return("", false).AnyTimes()
+			}
+
+			// Mock Windows-specific system calls (GetCmdArgs method calls these)
+			ncsd.EXPECT().GetWd().Return("C:\\test", nil).AnyTimes()
+			ncsd.EXPECT().FilePathAbs(gomock.Any()).DoAndReturn(func(path string) (string, error) {
+				return path, nil
+			}).AnyTimes()
+			ncsd.EXPECT().FilePathToSlash(gomock.Any()).DoAndReturn(func(path string) string {
+				return path
+			}).AnyTimes()
+			ncsd.EXPECT().FilePathJoin(gomock.Any()).DoAndReturn(func(elem ...string) string {
+				return "/mnt/c/test"
+			}).AnyTimes()
+
+			// Mock the RunWithReplacingStdout method (used when --help is present)
+			ncc.EXPECT().RunWithReplacingStdout(gomock.Any(), gomock.Any()).DoAndReturn(
+				func(replacements []command.Replacement, args ...string) error {
+					// Verify that --help was added to the arguments
+					found := false
+					for _, arg := range args {
+						if arg == "--help" {
+							found = true
+							break
+						}
+					}
+					assert.True(t, found, "Expected --help to be added to arguments")
+
+					// Verify the replacement is correct (nerdctl -> finch)
+					assert.Len(t, replacements, 1, "Expected one replacement")
+					assert.Equal(t, "nerdctl", replacements[0].Source, "Expected source to be 'nerdctl'")
+					assert.Equal(t, "finch", replacements[0].Target, "Expected target to be 'finch'")
+
+					return nil
+				})
+
+			// This should not panic and should complete successfully
+			err := newNerdctlCommand(ncc, ecc, ncsd, logger, fs, fc).run(tc.cmdName, tc.args)
+			assert.NoError(t, err)
+		})
+	}
+}