k6 v0.52.0 is here 🎉! Some special mentions included in this release:

• We've switched to our own fork of goja named sobek.
• Panics are no longer captured.
• We've added experimental support for TypeScript and ES6+.
• k6/browser has graduated from an experimental module, and now has a fully Async API.

Breaking changes

Switch goja to our own fork named sobek #3775

To accelerate the development speed and bring ECMAScript Modules (ESM) support to k6 earlier (https://github.com/grafana/k6/issues/3265), we have decided to create a fork of the goja project under the Grafana GitHub organization, named sobek.

Starting on this release, k6 (and its extensions) now use sobek instead of the original goja, for all (of the publicly exposed parts of the API) except for a couple of packages that are only used internally by k6.

All k6 extensions linked in the docs have had a PR for this transition opened, as explained in this comment. Any extension author who hasn't gotten a PR can follow the same steps.

Find further details in #3772 and #3773.

Panics are no longer being captured #3777

Since this release, Go panics are no longer being captured by k6. This means that if a panic occurs while running a test, the k6 process will crash, and the panic stack trace will be printed to the console.

We decided to change this behavior because it's something that was left from the past as a safeguard, but it's not as good as it might seem. For most cases with multiple goroutines/async, it's not enough and also makes a bunch of potential bugs seem like less of an issue.

Thus, this will help us to identify and fix bugs earlier, improve the overall stability of k6, and most likely make the experience of developing k6 extensions friendlier.

lib.State no longer has Group #3750

As the result of refactoring the implementation of group and check methods, in order to decouple them, and thus enable other future improvements, the lib.State object no longer has a Group field.

This change should not affect most users, except for a couple of extensions, for which the use of Group was already questionable:

• xk6-fasthttp
• xk6-g0

Other breaking changes

• #3797 starts using - as a special value for --archive-out to output the archive to stdout.
• browser#1318 makes the Mouse.up and Mouse.down methods no longer take x and y coordinates. Instead, they dispatch events on the current mouse position.

New features

Experimental support for TypeScript and ES6+ using esbuild #3738

This release of k6 introduces experimental support for TypeScript and ES6+ using esbuild, thanks to a new compatibility mode named experimental_enhanced.

k6 run --compatibility-mode=experimental_enhanced script.js

With this new compatibility mode, the test source code is transformed using esbuild instead of Babel, which also means that source files with the extension ".ts" are loaded by esbuild's TypeScript loader, which results in partial TypeScript support: it removes the type information but doesn't provide type safety.

k6/browser has graduated from an experimental module #3793

The browser module is now available as k6/browser instead of k6/experimental/browser. The previous k6/experimental/browser module will be removed on September 23rd, 2024. Refer to the migration guide for more information on how to update your scripts.

k6/browser has now a fully Async API browser#428

This release introduces a fully Async API for the k6/browser module. This means that nearly all the methods in the module now return promises. This change is part of the ongoing effort to make the browser module more user-friendly and easier to use. Please see the browser documentation for more information on how to use the new Async API.

Related Changes:

• browser#1310, browser#1311, browser#1312, browser#1316, browser#1328, browser#1337, browser#1367, browser#1366, browser#1314, browser#1332, browser#1323, browser#1355, browser#1348, browser#1364 Migrates Browser, BrowserContext, ElementHandle, Frame, JSHandle, Keyboard, Locator, Mouse, Page, Request, Response APIs to async.

UX improvements and enhancements

• #3740 enables k6 extensions to initialize ReadableStream objects from Go code (io.Reader).
• #3798 adjusts a severity level of a log message from warn to debug for cases when k6 can't detect the terminal's size.
• #3797 makes it possible to output the archive to stdout by using - as the --archive-out. Thanks to @roobre! :bow: :tada:
• browser#1370 makes the GetAttribute method now return false when the attribute is missing, making it easier to check for the presence of an attribute.
• browser#1371 makes the TextContent method now return false when the element's text content cannot be grabbed (like a JS document), making it easier to check for the presence of text content.
• browser#1376 makes Request.headerValue and Response.headerValue to be case-insensitive.
• browser#1368 enhances await usage in Javascript examples.
• browser#1326 adds forgotten BrowserContext.browser and Page.context mappings.
• browser#1360, browser#1327, browser#1335, browser#1365, browser#1313, browser#1322, browser#1330, browser#1343, browser#1345, browser#1352 turns the Browser, BrowserContext, ElementHandle, JSHandle, Keyboard, Mouse, Locator, and Page types' panics into errors for stability and better error handling.

Bug fixes

• #3774 fixes a require warning for those tests using the stdin.
• #3776 fixes a panic caused by passing an undefined handler to timers.
• #3779 fixes a panic caused by registering an undefined handler in gRPC streams.
• xk6-websockets#73 fixes a panic caused by registering an undefined handler in WebSockets.
• browser#1369 improves valueFromRemoteObject null detection by returning a Go nil instead of "null" as a string.
• browser#1386 correctly handles empty string flags that don't have a value.
• browser#1380 ensures that JSHandle.evaluate and JSHandle.evaluateHandle both set themselves as the first argument.
• browser#1346 fixes an IFrame panic ("we either navigate top level or have old version of the navigated frame") that happens during navigation.
• browser#1349, browser#1354 fixes Request mappings.
• browser#1334 fixes an issue where clicking on a link that opens a new tab never navigates to the href link.
• browser#1318 fixes the Mouse.move to correctly dispatch a down event.
• browser#1301 fixes an error that occurs when working with a second tab and navigating to a URL.
• browser#1387 fixes a panic when the new document or request is missing.

Maintenance and internal improvements

• #3752, #3767, #3770, #3780, #3782, #3795 updates several dependencies.
• #3786, #3787, #3788, #3789, #3803 updates experimental modules.
• #3749 stops printing goja stack traces on panics, which has been empty since a while.
• #3760 fixes race conditions in ramping-vus tests.
• #3769 removes a linter setting no longer used.
• #3800 adds test coverage for outputting the archive to stdout.
• browser#1298 splits browser mappings into separate files for better organization and maintainability.
• browser#1321 adds test helpers for async VU execution to reduce the boilerplate in the tests.
• browser#1357 updates Group and Tag usage for the latest k6.
• browser#1361 precalculates the browser version information to prevent I/O calls when the version and userAgent methods are called. This change allows the browser module to expose these methods as a sync API to be consistent with the Playwright's API.
• browser#1377 uses the goja fork called sobek in the browser module.
• browser#1373 provides sync and async APIs within the browser module for making the migration to the async API easier.

Roadmap

Native ECMAScript modules

As mentioned above, the k6 team has forked goja into sobek and is currently working on native ECMAScript modules support. The current work in progress can be found in this PR and any feedback is welcome.

As part of that there likely will be some breaking changes due to the current not native support allowing stuff that shouldn't work. Like for example mixing CommonJS and ESM in the same file. Which is for example why we have added a warning that it won't work.

Support across multiple files is also not standard but due to amount of users that seems to be mixing them across files a lot of work has been done to support it. It is still likely that in the future warnings and potentially at some point future breaking changes will be enacted.

OpenTelemetry metrics output

We're also happy to share that this release cycle, we've been working on xk6-output-opentelemetry, a k6 output extension that allows you to send k6 metrics to OpenTelemetry-compatible backends. We're looking for feedback from the community. If you're interested, please try it and let us know via the extension repository!

Depending on the feedback, we plan to include this extension as an experimental output in the next k6 release.