Fix mapJSHandle invalid memory address or nil pointer dereference

browser/frame_mapping.go

@@ -59,19 +59,25 @@ func mapFrame(vu moduleVU, f *common.Frame) mapping { //nolint:gocognit,cyclop
 				return nil, f.DispatchEvent(selector, typ, exportArg(eventInit), popts) //nolint:wrapcheck
 			}), nil
 		},
-		"evaluate": func(pageFunction sobek.Value, gargs ...sobek.Value) *sobek.Promise {
+		"evaluate": func(pageFunc sobek.Value, gargs ...sobek.Value) (*sobek.Promise, error) {
+			if sobekEmptyString(pageFunc) {
+				return nil, fmt.Errorf("evaluate requires a page function")
+			}
 			return k6ext.Promise(vu.Context(), func() (any, error) {
-				return f.Evaluate(pageFunction.String(), exportArgs(gargs)...) //nolint:wrapcheck
-			})
+				return f.Evaluate(pageFunc.String(), exportArgs(gargs)...)
+			}), nil
 		},
-		"evaluateHandle": func(pageFunction sobek.Value, gargs ...sobek.Value) *sobek.Promise {
+		"evaluateHandle": func(pageFunc sobek.Value, gargs ...sobek.Value) (*sobek.Promise, error) {
+			if sobekEmptyString(pageFunc) {
+				return nil, fmt.Errorf("evaluateHandle requires a page function")
+			}
 			return k6ext.Promise(vu.Context(), func() (any, error) {
-				jsh, err := f.EvaluateHandle(pageFunction.String(), exportArgs(gargs)...)
+				jsh, err := f.EvaluateHandle(pageFunc.String(), exportArgs(gargs)...)
 				if err != nil {
 					return nil, err //nolint:wrapcheck
 				}
 				return mapJSHandle(vu, jsh), nil
-			})
+			}), nil
 		},
 		"fill": func(selector, value string, opts sobek.Value) *sobek.Promise {
 			return k6ext.Promise(vu.Context(), func() (any, error) {

browser/helpers.go

@@ -3,6 +3,7 @@ package browser
 import (
 	"context"
 	"errors"
+	"strings"
 
 	"github.com/grafana/sobek"
 
@@ -61,3 +62,8 @@ func exportArgs(gargs []sobek.Value) []any {
 func sobekValueExists(v sobek.Value) bool {
 	return v != nil && !sobek.IsUndefined(v) && !sobek.IsNull(v)
 }
+
+// sobekEmptyString returns true if a given value is not nil or an empty string.
+func sobekEmptyString(v sobek.Value) bool {
+	return !sobekValueExists(v) || strings.TrimSpace(v.String()) == ""
+}

browser/helpers_test.go

@@ -0,0 +1,25 @@
+package browser
+
+import (
+	"testing"
+
+	"github.com/grafana/sobek"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSobekEmptyString(t *testing.T) {
+	// SobekEmpty string should return true if the argument
+	// is an empty string or not defined in the Sobek runtime.
+	rt := sobek.New()
+	require.NoError(t, rt.Set("sobekEmptyString", sobekEmptyString))
+	for _, s := range []string{"() => true", "'() => false'"} { // not empty
+		v, err := rt.RunString(`sobekEmptyString(` + s + `)`)
+		require.NoError(t, err)
+		require.Falsef(t, v.ToBoolean(), "got: true, want: false for %q", s)
+	}
+	for _, s := range []string{"", "  ", "null", "undefined"} { // empty
+		v, err := rt.RunString(`sobekEmptyString(` + s + `)`)
+		require.NoError(t, err)
+		require.Truef(t, v.ToBoolean(), "got: false, want: true for %q", s)
+	}
+}

browser/js_handle_mapping.go

@@ -1,6 +1,8 @@
 package browser
 
 import (
+	"fmt"
+
 	"github.com/grafana/sobek"
 
 	"github.com/grafana/xk6-browser/common"
@@ -15,26 +17,32 @@ func mapJSHandle(vu moduleVU, jsh common.JSHandleAPI) mapping {
 		},
 		"dispose": func() *sobek.Promise {
 			return k6ext.Promise(vu.Context(), func() (any, error) {
-				return nil, jsh.Dispose() //nolint:wrapcheck
+				return nil, jsh.Dispose()
 			})
 		},
-		"evaluate": func(pageFunc sobek.Value, gargs ...sobek.Value) *sobek.Promise {
+		"evaluate": func(pageFunc sobek.Value, gargs ...sobek.Value) (*sobek.Promise, error) {
+			if sobekEmptyString(pageFunc) {
+				return nil, fmt.Errorf("evaluate requires a page function")
+			}
 			return k6ext.Promise(vu.Context(), func() (any, error) {
 				args := make([]any, 0, len(gargs))
 				for _, a := range gargs {
 					args = append(args, exportArg(a))
 				}
-				return jsh.Evaluate(pageFunc.String(), args...) //nolint:wrapcheck
-			})
+				return jsh.Evaluate(pageFunc.String(), args...)
+			}), nil
 		},
-		"evaluateHandle": func(pageFunc sobek.Value, gargs ...sobek.Value) *sobek.Promise {
+		"evaluateHandle": func(pageFunc sobek.Value, gargs ...sobek.Value) (*sobek.Promise, error) {
+			if sobekEmptyString(pageFunc) {
+				return nil, fmt.Errorf("evaluateHandle requires a page function")
+			}
 			return k6ext.Promise(vu.Context(), func() (any, error) {
 				h, err := jsh.EvaluateHandle(pageFunc.String(), exportArgs(gargs)...)
 				if err != nil {
 					return nil, err //nolint:wrapcheck
 				}
 				return mapJSHandle(vu, h), nil
-			})
+			}), nil
 		},
 		"getProperties": func() *sobek.Promise {
 			return k6ext.Promise(vu.Context(), func() (any, error) {

browser/page_mapping.go

@@ -80,19 +80,25 @@ func mapPage(vu moduleVU, p *common.Page) mapping { //nolint:gocognit,cyclop
 				return nil, p.EmulateVisionDeficiency(typ) //nolint:wrapcheck
 			})
 		},
-		"evaluate": func(pageFunction sobek.Value, gargs ...sobek.Value) *sobek.Promise {
+		"evaluate": func(pageFunc sobek.Value, gargs ...sobek.Value) (*sobek.Promise, error) {
+			if sobekEmptyString(pageFunc) {
+				return nil, fmt.Errorf("evaluate requires a page function")
+			}
 			return k6ext.Promise(vu.Context(), func() (any, error) {
-				return p.Evaluate(pageFunction.String(), exportArgs(gargs)...) //nolint:wrapcheck
-			})
+				return p.Evaluate(pageFunc.String(), exportArgs(gargs)...)
+			}), nil
 		},
-		"evaluateHandle": func(pageFunc sobek.Value, gargs ...sobek.Value) *sobek.Promise {
+		"evaluateHandle": func(pageFunc sobek.Value, gargs ...sobek.Value) (*sobek.Promise, error) {
+			if sobekEmptyString(pageFunc) {
+				return nil, fmt.Errorf("evaluateHandle requires a page function")
+			}
 			return k6ext.Promise(vu.Context(), func() (any, error) {
 				jsh, err := p.EvaluateHandle(pageFunc.String(), exportArgs(gargs)...)
 				if err != nil {
 					return nil, err //nolint:wrapcheck
 				}
 				return mapJSHandle(vu, jsh), nil
-			})
+			}), nil
 		},
 		"fill": func(selector string, value string, opts sobek.Value) *sobek.Promise {
 			return k6ext.Promise(vu.Context(), func() (any, error) {

tests/page_test.go

@@ -264,6 +264,11 @@ func TestPageEvaluateMappingError(t *testing.T) {
 			script:  "(6)",
 			wantErr: "Given expression does not evaluate to a function",
 		},
+		{
+			name:    "void",
+			script:  "",
+			wantErr: "evaluate requires a page function",
+		},
 	}
 
 	for _, tt := range tests {