fix(update): replace active binary during self-update

internal/cli/update.go

@@ -1,10 +1,13 @@
 package cli
 
 import (
+	"encoding/json"
 	"fmt"
 	"os"
 	"os/exec"
+	"path/filepath"
 	"runtime"
+	"strings"
 
 	"github.com/spf13/cobra"
 
@@ -41,28 +44,64 @@ func newUpdateCmd() *cobra.Command {
 			}
 
 			_, _ = fmt.Fprintf(w, "\nUpdating...\n")
-			return runInstaller(cmd)
+			executable, err := os.Executable()
+			if err != nil {
+				return fmt.Errorf("failed to locate active executable: %w", err)
+			}
+			return runInstaller(cmd, executable, result.LatestVersion)
 		},
 	}
 
 	cmd.Flags().BoolVar(&flagCheck, "check", false, "Only check for updates, do not install")
 	return cmd
 }
 
-func runInstaller(cmd *cobra.Command) error {
+func runInstaller(cmd *cobra.Command, executable, expectedVersion string) error {
+	isWindows := runtime.GOOS == "windows"
 	name, args := installerCommandSpec(runtime.GOOS, update.InstallShellURL(), update.InstallPowerShellURL())
 	c := exec.Command(name, args...)
 
 	c.Stdout = cmd.OutOrStdout()
 	c.Stderr = cmd.ErrOrStderr()
 	c.Stdin = os.Stdin
+	installedName := "flashduty"
 	c.Env = update.InstallerEnv(os.Environ())
+	if !isWindows {
+		installedName = filepath.Base(executable)
+		env := c.Env[:0]
+		for _, item := range c.Env {
+			if strings.HasPrefix(item, "FLASHDUTY_INSTALL_DIR=") || strings.HasPrefix(item, "INSTALLED_NAME=") {
+				continue
+			}
+			env = append(env, item)
+		}
+		c.Env = append(env,
+			"FLASHDUTY_INSTALL_DIR="+filepath.Dir(executable),
+			"INSTALLED_NAME="+installedName,
+		)
+	}
 
 	if err := c.Run(); err != nil {
 		return fmt.Errorf("update failed: %w", err)
 	}
 
-	_, _ = fmt.Fprintf(cmd.OutOrStdout(), "\nUpdate complete. Run 'flashduty version' to verify.\n")
+	if !isWindows {
+		out, err := exec.Command(executable, "version", "--json").Output()
+		if err != nil {
+			return fmt.Errorf("update installed but active executable %s could not be verified: %w", executable, err)
+		}
+		var info struct {
+			Version string `json:"version"`
+		}
+		if err := json.Unmarshal(out, &info); err != nil {
+			return fmt.Errorf("update installed but active executable %s returned unparseable version output: %w", executable, err)
+		}
+		if update.StripV(info.Version) != update.StripV(expectedVersion) {
+			return fmt.Errorf("update installed but active executable %s is still stale: expected %s, got %s", executable, expectedVersion, info.Version)
+		}
+	}
+
+	_, _ = fmt.Fprintf(cmd.OutOrStdout(), "\nUpdate complete. Run '%s version' to verify.\n", installedName)
 	return nil
 }
 

internal/cli/update_test.go

@@ -1,11 +1,109 @@
 package cli
 
 import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"runtime"
 	"slices"
 	"strings"
 	"testing"
+
+	"github.com/spf13/cobra"
 )
 
+func writeExecutable(t *testing.T, path, body string) {
+	t.Helper()
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(path, []byte(body), 0o755); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestRunInstallerUpdatesInvokedBinary(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("shell installer test")
+	}
+
+	dir := t.TempDir()
+	executable := filepath.Join(dir, ".flashduty", "bin", "fduty")
+	writeExecutable(t, executable, `#!/bin/sh
+if [ "$1" = "version" ] && [ "$2" = "--json" ]; then
+  echo '{"version":"1.3.6"}'
+else
+  echo 'flashduty version 1.3.6 (old) built old'
+fi
+`)
+
+	fakeBin := filepath.Join(dir, "fake-bin")
+	writeExecutable(t, filepath.Join(fakeBin, "sh"), `#!/bin/sh
+cat > "$FLASHDUTY_INSTALL_DIR/$INSTALLED_NAME" <<'EOF'
+#!/bin/sh
+if [ "$1" = "version" ] && [ "$2" = "--json" ]; then
+  echo '{"version":"1.3.24"}'
+else
+  echo 'flashduty version 1.3.24 (new) built now'
+fi
+EOF
+chmod +x "$FLASHDUTY_INSTALL_DIR/$INSTALLED_NAME"
+`)
+	t.Setenv("PATH", fakeBin+string(os.PathListSeparator)+os.Getenv("PATH"))
+	t.Setenv("FLASHDUTY_INSTALL_DIR", filepath.Join(dir, "wrong-dir"))
+	t.Setenv("INSTALLED_NAME", "wrong-name")
+
+	var stdout, stderr bytes.Buffer
+	cmd := &cobra.Command{}
+	cmd.SetOut(&stdout)
+	cmd.SetErr(&stderr)
+	if err := runInstaller(cmd, executable, "v1.3.24"); err != nil {
+		t.Fatalf("runInstaller: %v; stderr=%s", err, stderr.String())
+	}
+
+	out, err := os.ReadFile(executable)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(string(out), "version 1.3.24") {
+		t.Fatalf("active executable was not replaced: %s", out)
+	}
+	if !strings.Contains(stdout.String(), "Update complete") {
+		t.Fatalf("stdout = %q, want update success", stdout.String())
+	}
+}
+
+func TestRunInstallerRejectsShadowedInstall(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("shell installer test")
+	}
+
+	dir := t.TempDir()
+	executable := filepath.Join(dir, ".flashduty", "bin", "fduty")
+	writeExecutable(t, executable, `#!/bin/sh
+if [ "$1" = "version" ] && [ "$2" = "--json" ]; then
+  echo '{"version":"1.3.6"}'
+else
+  echo 'flashduty version 1.3.6 (old) built old'
+fi
+`)
+
+	fakeBin := filepath.Join(dir, "fake-bin")
+	writeExecutable(t, filepath.Join(fakeBin, "sh"), "#!/bin/sh\nexit 0\n")
+	t.Setenv("PATH", fakeBin+string(os.PathListSeparator)+os.Getenv("PATH"))
+
+	var stdout bytes.Buffer
+	cmd := &cobra.Command{}
+	cmd.SetOut(&stdout)
+	err := runInstaller(cmd, executable, "v1.3.24")
+	if err == nil || !strings.Contains(err.Error(), executable) || !strings.Contains(err.Error(), "1.3.6") {
+		t.Fatalf("runInstaller error = %v, want active path and stale version", err)
+	}
+	if strings.Contains(stdout.String(), "Update complete") {
+		t.Fatalf("reported success for stale executable: %q", stdout.String())
+	}
+}
+
 func TestInstallerCommandSpecPassesInstallerURLAsArgument(t *testing.T) {
 	shellURL := `https://mirror.example.com/fduty/install.sh; echo injected`
 	psURL := `https://mirror.example.com/fduty/install.ps1; Write-Host injected`