[webview_flutter_web] Add WebWebViewController.runJavaScript #9835
Conversation
|
Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA). View this failed invocation of the CLA check for more information. For the most up to date status, view the checks section at the bottom of the pull request. |
There was a problem hiding this comment.
Code Review
This pull request introduces the runJavaScript method for the web implementation of WebView and refactors loadHtmlString to better support the baseUrl parameter. The changes are generally good, but there are a few areas for improvement regarding event listener management and robustness against race conditions. I've identified a potential memory leak in loadHtmlString and a high-severity issue in _getIFrameDocument that could lead to an infinite loop. I've provided suggestions to address these issues by using one-time event listeners and replacing polling with a more robust event-based approach.
| Future<web.Document> _getIFrameDocument() async { | ||
| while (_webWebViewParams.iFrame.contentDocument == null) { | ||
| await Future<void>.delayed(_webWebViewParams._iFrameWaitDelay); | ||
| } | ||
|
|
||
| return _webWebViewParams.iFrame.contentDocument!; | ||
| } |
There was a problem hiding this comment.
The polling mechanism in _getIFrameDocument can lead to an infinite loop if it's called before any content has been loaded (e.g., on a newly created controller). In this scenario, the iframe's src is empty, contentDocument remains null, and the while loop never terminates.
Instead of polling, it's more robust to use the load event to wait for the document to be ready. If no src is set, you can default to loading about:blank to ensure a document context is always available for methods like runJavaScript.
Future<web.Document> _getIFrameDocument() async {
// If the document is not yet available, wait for the 'load' event.
if (_webWebViewParams.iFrame.contentDocument == null) {
final Completer<void> completer = Completer<void>();
_webWebViewParams.iFrame.addEventListener(
'load',
(web.Event _) {
completer.complete();
}.toJS,
AddEventListenerOptions(once: true),
);
// If src is not set, the iframe will never load.
if (_webWebViewParams.iFrame.src.isEmpty) {
_webWebViewParams.iFrame.src = 'about:blank';
}
await completer.future;
}
return _webWebViewParams.iFrame.contentDocument!;
}
| _webWebViewParams.iFrame.addEventListener( | ||
| 'load', | ||
| () { | ||
| _webWebViewParams.iFrame.contentDocument?.write(html.toJS); | ||
| loading.complete(); | ||
| }.toJS); |
There was a problem hiding this comment.
The load event listener is added every time loadHtmlString is called but is never removed. This can lead to a memory leak if this method is called multiple times on the same controller, as multiple listeners will be attached.
To ensure the listener is only called once per loadHtmlString call, you can use the once option in addEventListener. This will automatically remove the listener after it has been invoked.
_webWebViewParams.iFrame.addEventListener(
'load',
(web.Event _) {
_webWebViewParams.iFrame.contentDocument?.write(html.toJS);
loading.complete();
}.toJS,
AddEventListenerOptions(once: true),
);
| script.addEventListener( | ||
| 'load', | ||
| () { | ||
| body.removeChild(script); | ||
| run.complete(); | ||
| }.toJS); |
There was a problem hiding this comment.
The load event listener on the script element is only intended to fire once. It's good practice to make this explicit by using the once: true option in addEventListener. This also ensures the listener is removed automatically, preventing any potential for lingering listeners, even though the script element is removed from the DOM.
script.addEventListener(
'load',
(web.Event _) {
body.removeChild(script);
run.complete();
}.toJS,
AddEventListenerOptions(once: true),
);
This PR adds an implementation for
WebWebViewController.runJavaScriptand changes the wayWebWebViewController.loadHtmlStringinjects HTML code while also adding support for thebaseUrloption.The following issues are fixed:
runJavaScriptfor Web when the content has the same origin flutter#173899Pre-Review Checklist
[shared_preferences]pubspec.yamlwith an appropriate new version according to the pub versioning philosophy, or I have commented below to indicate which version change exemption this PR falls under1.CHANGELOG.mdto add a description of the change, following repository CHANGELOG style, or I have commented below to indicate which CHANGELOG exemption this PR falls under1.///).If you need help, consider asking for advice on the #hackers-new channel on Discord.
Note: The Flutter team is currently trialing the use of Gemini Code Assist for GitHub. Comments from the
gemini-code-assistbot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed.Footnotes
Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling. ↩ ↩2 ↩3