browser: tag API errors with module "browser"

Async rejects (promise helper) and sync throws (Panicf) now
attach module=browser via WithFields. This lets Cloud Logs
filter browser-originated errors without overriding the
existing source field used by other systems.

Author: inancgumus

internal/js/modules/k6/browser/browser/helpers.go

@@ -93,7 +93,7 @@ func promise(vu moduleVU, fn func() (result any, reason error)) *sobek.Promise {
 	go func() {
 		v, err := fn()
 		if err != nil {
-			reject(err)
+			reject(k6ext.BrowserError(err))
 			return
 		}
 		resolve(v)

internal/js/modules/k6/browser/browser/mapping.go

@@ -9,6 +9,7 @@ import (
 	"github.com/grafana/sobek"
 
 	"go.k6.io/k6/v2/internal/js/modules/k6/browser/common"
+	"go.k6.io/k6/v2/internal/js/modules/k6/browser/k6ext"
 
 	k6common "go.k6.io/k6/v2/js/common"
 )
@@ -30,7 +31,7 @@ func mapBrowserToSobek(vu moduleVU) *sobek.Object {
 	for k, v := range mapBrowser(vu) {
 		err := obj.Set(k, rt.ToValue(v))
 		if err != nil {
-			k6common.Throw(rt, fmt.Errorf("mapping: %w", err))
+			k6common.Throw(rt, k6ext.BrowserError(fmt.Errorf("mapping: %w", err)))
 		}
 	}
 

internal/js/modules/k6/browser/k6ext/panic.go

@@ -32,7 +32,7 @@ func Abortf(ctx context.Context, format string, a ...any) {
 // TODO: test.
 func Panicf(ctx context.Context, format string, a ...any) {
 	failFunc := func(rt *sobek.Runtime, a ...any) {
-		k6common.Throw(rt, fmt.Errorf(format, a...))
+		k6common.Throw(rt, BrowserError(fmt.Errorf(format, a...)))
 	}
 	sharedPanic(ctx, failFunc, a...)
 }
@@ -100,3 +100,8 @@ func (e *UserFriendlyError) Error() string {
 		return "canceled"
 	}
 }
+
+// BrowserError tags err as originating from the browser module.
+func BrowserError(err error) error {
+	return errext.WithFields(err, map[string]any{"module": "browser"})
+}

internal/js/modules/k6/browser/tests/page_test.go

@@ -25,6 +25,7 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
+	"go.k6.io/k6/v2/errext"
 	"go.k6.io/k6/v2/internal/js/modules/k6/browser/common"
 	"go.k6.io/k6/v2/internal/js/modules/k6/browser/k6ext/k6test"
 	k6metrics "go.k6.io/k6/v2/metrics"
@@ -299,6 +300,24 @@ func TestPageEvaluateMappingError(t *testing.T) { //nolint:tparallel
 	}
 }
 
+func TestPageEvaluateErrorHasBrowserModule(t *testing.T) {
+	t.Parallel()
+
+	tb := newTestBrowser(t)
+	tb.vu.ActivateVU()
+	tb.vu.StartIteration(t)
+	defer tb.vu.EndIteration(t)
+
+	_, err := tb.vu.RunAsync(t, `
+		const page = await browser.newPage();
+		await page.evaluate("() => { throw new Error('expected'); }");
+	`)
+	require.ErrorContains(t, err, "evaluating JS: Error: expected")
+
+	_, fields := errext.Format(err)
+	assert.Equal(t, "browser", fields["module"])
+}
+
 func TestPageGoto(t *testing.T) {
 	t.Parallel()