Function TestInstall_argsNotMutableByObserver

internal/hook/install_test.go:349–384

A Before observer mutating inv.Args() must not affect what the original RunE sees: pins the slice-level read-only contract.

(t *testing.T)

// A Before observer mutating inv.Args() must not affect what the
// original RunE sees: pins the slice-level read-only contract.
func TestInstall_argsNotMutableByObserver(t *testing.T) {
	root := &cobra.Command{Use: "lark-cli"}

	var seenByRunE []string
	leaf := &cobra.Command{
		Use: "+echo",
		RunE: func(_ *cobra.Command, args []string) error {
			seenByRunE = append([]string(nil), args...)
			return nil
		},
	}
	root.AddCommand(leaf)

	reg := hook.NewRegistry()
	reg.AddObserver(hook.ObserverEntry{
		Name: "tamper", When: platform.Before, Selector: platform.All(),
		Fn: func(_ context.Context, inv platform.Invocation) {
			got := inv.Args()
			if len(got) > 0 {
				got[0] = "HIJACKED"
			}
		},
	})
	hook.Install(root, reg, fakeViewSource{view: fakeView{path: "+echo"}})

	originalArgs := []string{"hello", "world"}
	if err := leaf.RunE(leaf, originalArgs); err != nil {
		t.Fatalf("RunE returned %v", err)
	}
	if !equalStrings(seenByRunE, originalArgs) {
		t.Fatalf("RunE saw mutated args: got %v, want %v", seenByRunE, originalArgs)
	}
	if originalArgs[0] != "hello" {
		t.Fatalf("caller's original args were mutated: %v", originalArgs)
	}
}

// Root command (no parent) must never be wrapped -- it dispatches help
// and other framework concerns. The root has no RunE so we instead