fix(playground): absorb malformed HTML + warn when runner script is swallowed - #1705
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Add `id="mdn-play-js"` and `id="mdn-play-js-end"` markers to the runner script and the script following it, and check from the head after `DOMContentLoaded` that both are present as script elements. If either is missing, log a console warning. Unclosed or malformed tags in the HTML input can absorb the runner script, so the JavaScript never executes and the playground silently does nothing.
…lags Insert `<!-- "" '' -->` after the HTML so an unclosed tag, attribute value, or comment ends there instead of swallowing the runner script. Set `window.__mdnPlayJsStarted` and `window.__mdnPlayJsEnded` around the runner and check those in `<head>`, since the script elements disappear when user JS replaces the body's children (a false positive in live samples using `document.body.innerHTML`).
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(⚠️ Mirrored to mdn/dex#435. ⚠️ )
Description
Fix the Playground runner (
vendor/yari/libs/play/index.js) so malformed HTML no longer swallows the user's JS, and warn when it still does:<!-- "" '' -->after the HTML, which closes an unclosed tag, attribute value, or comment before the runner script.window.__mdnPlayJsStartedin a script before the runner andwindow.__mdnPlayJsEndedin the script after it.<head>check onDOMContentLoadedthat warns viaconsole.warnif either flag is missing.test/unit/play/runner.test.js).Motivation
Ensure a typo like
<oin the HTML no longer renders the JS as text, and that users get a hint in the remaining cases (e.g. an unclosed<textarea>), where the JS silently does not run.Additional details
Flags instead of marker elements: user JS that replaces the body's children (e.g.
document.body.innerHTML = ..., as several live samples do) removes the script elements but not the flags.Verified with headless Chrome:
<p>ok</p>annn <o jwj,<div class=", unclosed<!--document.bodychildren<textarea>,<template>,<math>The file is mirrored in
mdn/dex(cloud-function/src/internal/play/index.js), which serves the runner in deployed environments, so the fix only takes effect there once mdn/dex#435 lands.Related issues and pull requests
Fixes #1440.