grafana/k6 · error

parsing setInputFiles parameter

Error message

parsing setInputFiles parameter: %w

What it means

Thrown when the files argument of ElementHandle.setInputFiles fails Files.Parse. The k6 browser module accepts only file descriptor objects {name, mimeType, buffer} (buffer is a base64 string) or arrays of them — unlike Playwright, plain file paths and strings are rejected with the wrapped error 'invalid parameter type : string', and a malformed object yields 'parsing file descriptor: ...'. This is the most common setInputFiles failure.

Solutions

1. Pass a descriptor object: setInputFiles({name: 'avatar.png', mimeType: 'image/png', buffer: '<base64>'})
2. For multiple files pass an array of descriptor objects
3. To use local file contents, load them as base64 in the script and put the base64 string in buffer — the module does not read paths from disk

Example fix

// before (Playwright style — not supported by k6)
await handle.setInputFiles('/uploads/avatar.png');
// after
await handle.setInputFiles({
  name: 'avatar.png',
  mimeType: 'image/png',
  buffer: 'iVBORw0KGgoAAAANSUhEUg...', // base64 string
});

function isFileDescriptor(v) {
  return typeof v?.name === 'string' && typeof v?.buffer === 'string';
}
const arr = Array.isArray(files) ? files : [files];
if (files != null && !arr.every(isFileDescriptor)) {
  throw new Error('setInputFiles requires {name, mimeType, buffer(base64)} objects, not paths');
}
await handle.setInputFiles(files);

function isFileDescriptor(v) {
  return v != null && typeof v === 'object' && !Array.isArray(v) &&
    typeof v.name === 'string' && typeof v.mimeType === 'string' &&
    typeof v.buffer === 'string';
}
function isInputFilesArg(v) {
  return v == null || isFileDescriptor(v) || (Array.isArray(v) && v.every(isFileDescriptor));
}

try {
  await handle.setInputFiles(files);
} catch (e) {
  if (String(e).includes('setInputFiles parameter')) {
    // a path string slipped in; convert it to a descriptor before retrying
    throw new Error('k6 setInputFiles does not accept file paths; pass {name, mimeType, buffer}');
  }
  throw e;
}

When it happens

Trigger: setInputFiles('/uploads/avatar.png') (string path — unsupported), setInputFiles(42), setInputFiles([{name: 'a.png'}]) with wrong/missing field types, or an array mixing strings and objects.

Common situations: Copying Playwright test code where setInputFiles('/path/to/file.pdf') is idiomatic; assuming k6 can read local files by path; passing a Buffer/ArrayBuffer instead of a base64 string for the buffer field.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• parsing setInputFiles options
• setting input files
• checking hit target
• getting element position
• getting injected script

AI-assisted analysis of grafana/k6@3fcf5388d7 (2026-08-18). Data as JSON: /api/errors/79a7d4cf5a2e5f91. Report an issue: GitHub.

Appendix: source

Thrown at internal/js/modules/k6/browser/browser/element_handle_mapping.go:244

			}), nil
		},
		"setChecked": func(checked bool, opts sobek.Value) (*sobek.Promise, error) {
			popts, err := parseElementHandleSetCheckedOptions(rt, opts, eh.DefaultTimeout())
			if err != nil {
				return nil, fmt.Errorf("parsing setChecked options: %w", err)
			}
			return promise(vu, func() (any, error) {
				return nil, eh.SetChecked(checked, popts) //nolint:wrapcheck
			}), nil
		},
		"setInputFiles": func(files sobek.Value, opts sobek.Value) (*sobek.Promise, error) {
			popts, err := parseElementHandleSetInputFilesOptions(rt, opts, eh.DefaultTimeout())
			if err != nil {
				return nil, fmt.Errorf("parsing setInputFiles options: %w", err)
			}
			var pfiles common.Files
			if err := pfiles.Parse(vu.Context(), files); err != nil {
				return nil, fmt.Errorf("parsing setInputFiles parameter: %w", err)
			}
			return promise(vu, func() (any, error) {
				return nil, eh.SetInputFiles(&pfiles, popts) //nolint:wrapcheck
			}), nil
		},
		"tap": func(opts sobek.Value) (*sobek.Promise, error) {
			popts, err := parseElementHandleTapOptions(rt, opts, eh.Timeout())
			if err != nil {
				return nil, fmt.Errorf("parsing element tap options: %w", err)
			}
			return promise(vu, func() (any, error) {
				return nil, eh.Tap(popts) //nolint:wrapcheck
			}), nil
		},
		"textContent": func() *sobek.Promise {
			return promise(vu, func() (any, error) {
				s, ok, err := eh.TextContent()
				if err != nil {

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