Fix options parsing error printing the most of the options (#4629)

The original idea of #4602 was to report at least the key with
potentially the option in question. Due to the lack of support from the
error - it can't parse it. The commit was trying to get everything
between the previous and next new line.

But in practice was getting anything until the end, both because of
error in the coed to get the index, but also because there were no
newlines due to how we marshal the data before that.

This should fix both and make it less likely we just get everything
until the end.


Co-authored-by: Oleg Bespalov <oleg.bespalov@grafana.com>
Co-authored-by: Ivan <2103732+codebien@users.noreply.github.com>

Author: 3 people

internal/js/bundle.go

@@ -208,7 +208,7 @@ func (b *Bundle) populateExports(updateOptions bool, bi *BundleInstance) error {
 					continue
 				}
 				var data []byte
-				data, err = json.Marshal(v.Export())
+				data, err = json.MarshalIndent(v.Export(), "", "  ")
 				if err != nil {
 					err = fmt.Errorf("error parsing script options: %w", err)
 					return
@@ -217,7 +217,8 @@ func (b *Bundle) populateExports(updateOptions bool, bi *BundleInstance) error {
 				dec.DisallowUnknownFields()
 				if err = dec.Decode(&b.Options); err != nil {
 					if uerr := json.Unmarshal(data, &b.Options); uerr != nil {
-						uerr = beautifyJSONUnmarshalError(data, uerr)
+						// Beautify the error so we can try to show the user the key and potential value that is failing to parse
+						uerr = beautifyOptionsJSONUnmarshalError(data, uerr)
 						err = errext.WithAbortReasonIfNone(
 							errext.WithExitCodeIfNone(uerr, exitcodes.InvalidConfig),
 							errext.AbortedByScriptError,
@@ -248,12 +249,12 @@ func (b *Bundle) populateExports(updateOptions bool, bi *BundleInstance) error {
 	return nil
 }
 
-func beautifyJSONUnmarshalError(data []byte, err error) error {
+func beautifyOptionsJSONUnmarshalError(data []byte, err error) error {
 	unmarshalTypError := new(json.UnmarshalTypeError)
 	if errors.As(err, &unmarshalTypError) {
 		e := unmarshalTypError
 		previousNewLineIndex := max(bytes.LastIndexByte(data[:e.Offset], '\n'), 0)
-		nextNewLineIndex := max(bytes.IndexByte(data[e.Offset:], '\n'), len(data)-1)
+		nextNewLineIndex := max(min(bytes.IndexByte(data[e.Offset:], '\n'), len(data)-1), (int)(e.Offset))
 
 		info := strings.TrimSpace(string(data[previousNewLineIndex:nextNewLineIndex]))
 		err = fmt.Errorf("parsing options from script got error while parsing %q: %w", info, e)

internal/js/bundle_test.go

@@ -236,8 +236,12 @@ func TestNewBundle(t *testing.T) {
 						`json: cannot unmarshal array into Go value of type lib.Options`,
 				},
 				"Bad value": {
-					`{"tags":["something"]}`,
-					`parsing options from script got error while parsing "{\"tags\":[\"something\"]": ` +
+					`{
+						"duration": "5m",
+						"tags":["something"],
+						"vus": 5
+					}`,
+					`parsing options from script got error while parsing "\"tags\": [": ` +
 						`json: cannot unmarshal array into Go struct field Options.tags of type map[string]string`,
 				},
 				"Function": {