Blazor WASM PWA Could not find any element matching selector 'app' - progressive-web-apps

I am using Visual Studio 2019 v16.8.5 and have a single Blazor WASM PWA project in my solution that I recently upgraded to .NET5. In between I got it to run, but lately I cannot get to start it anymore.
The screen says Loading... and that's it.
The console output (Firefox) shows the following error: Microsoft.JSInterop.JSException: Could not find any element matching selector 'app'.
At some point this was running without this issue, but even reverting the solution to an earlier state does not bring any change and I still get a blank screen.
I found a github source saying "just remove builder.RootComponents.Add<App>("app"); from Program Main". If I do this, the error disappears and I just get a blank page saying Loading... with no errors in Console output.
Additional information: I now do a full cache cleanup (cookies and website files) after running the project in Visual Studio to prevent any caching issues.
What am I doing wrong that I can't see any of my pages?
Even after explicitely calling them like https://192.168.188.31:5555/login?

Depending on the template version used to create the initial app, a slightly different HTML is used inside the index.html.
Older version could look like
<app>Loading...</app>
while newer should like
<div id="app">Loading...</div>
In case, the first is still true, the corresponding declaration should be
builder.RootComponents.Add<App>("app");
For the second the line should be
builder.RootComponents.Add<App>("#app");
The second uses the id selector #.
Usually, the index.html is seen as a "static" file and is cached by the browser. So changes, you have done in that file are not reflected immediately. The easiest way to disable the cache is to open the developer tools, go to the Network tab and disable the cache.

Related

Chrome Devtools empty file-list

I need to inspect the website but my scripts are not listed.
I already tried to uninstalled chrome and resintalled it again.
If I pause javascript and trigger any javascript action it opens a VM-version of jquery but I need the real file, not the vm-loaded one.
Any idea?
A but or not?
Any workaround?
Following the discussion from the comments above, the issue was unrelated to the web app but the environment in which the Chrome instance was run in. It was likely a Chrome Extension or modified setting that caused this misbehaviour.
The resolution was to create a new Chrome Profile, since extensions and settings are not shared between profile instances. The next step may be to identify the particular extension or plugin at fault to avoid this happening again.

Aurelia/Babel 6 sourcemaps shown as html

I have an aurelia application updated to the latest beta, 1.0.0-beta.1.2.1 at the time of this writing. This version of aurelia already uses Babel 6, and my application is based on the based on the ASP.NET 5 ES2016 navigation skeleton.
"All of a sudden", whenever I try to open my untranspiled javascript source files in Chrome (Version 49.0.2623.110 m (64-bit)) Developer tools, for instance main.js, all I get to see is the html of Index.cshtml.
It doesn't matter which javascript file I try to open, it always shows the html of Index.cshtml instead of javascript.
The transpiled files are displayed correctly in Chrome Dev Tools.
I've had this before but it usually meant I had a binding or templating error somewhere, but in this case the application works perfectly, so it probably has to do with the sourcemaps... Or does it?
My questions are:
What is the best way to track down a subtle binding or templating
error in Aurelia? Everything I've tried to do in my applcation works
fine, but I don't want to rule out this being my own fault just yet.
In case it's not my fault, has anybody come across this before? What
is the reason the sourcemaps are not working; is it Aurelia? is it
Babel 6? Is it Chrome?
Update
It doesn't seem to be a Chrome issue; the same problem occurs in Edge.
Update 2
By turning off Enable javascript sourcemaps on Chrome Developer Tools I can debug de transpiled code.
The transpilation gulp tasks I'm using are copy/pasted from the version mentioned above.
Has anybody else come across this issue?
Ok, I think I've found the problem.
I changed includeContent to true for sourcemaps.write in the build-system gulp task defined in build\tasks\build.js, so that line 23 of that file looks as follows:
.pipe(sourcemaps.write({ includeContent: true}))
This comes set to false in the navigation skeleton, so more people should have this same issue. Anyhow, this seems to have solved the problem.
I also removed the sourceRoot: "/src" parameter in that call, as it is only necessary when includeContent is false.

Google Chrome Dev Tools inspect element styles not showing

Starting a couple of weeks ago....on some of our sites, but not all, when inspecting an element, the styles tab only shows the "styles box", but not the actual styles relating to css?? - Again, this is ONLY on some sites - weird
It should look like this (with styles showing on the right relating to css)
BUT......instead, on SOME of our sites, this just started a couple of weeks ago looking like this....with no css showing in the styles tab:
NOTE: it has worked for 2 years - The page looks fine and all styles are being applied to the DOM, but do NOT show up in the styles tab when inspecting element.
Any ideas??
I just had this same issue and to resolve it I went into Chrome Developer Tools -> Settings -> Scroll to the bottom and click "Restore defaults and reload" then it all magically came back!
I hadn't changed anything between it working and when it stopped so not sure why it broke but hopefully this helps you too.
I just close the tab, and reopen it, and then right click > inspect element. Don't need to restore the whole dev tools to default settings. It's a waste. Try it, it works! :)
I had to go to Chrome Developer Tools -> Settings -> Enable JavaScript source maps and then disable that checkbox. It has probably got do with sourcemaps and the fact that I'm building the scss to css.
something that worked for me: chrome:flags>Enable Developer Tools experiments>Disable. I had enabled it at some point, used it for years w/o issue, then could not see any style details as OP described. After updating, resetting devtools prefs to default, even trying incognito, this was the one thing that seemed to get it working again. There were some neat experiments, but i'd much rather be able to do my job...
I was also facing this problem, in addition to the suggestions the other users made it worked for me accessing:
Chrome Developer Tools -> CSS -> Relaoad Linked Style Sheets
Image Ilustrating the procedure
Another one for the mix - using CSS variables but one of the variables was referencing another variable that didn't exist.
Elements using that missing variable in the chain just don't show up in chromium at all (it hid all references to h2s in the case of my site).
Interestingly, it still shows the elements in Firefox's dev tool panel.
Look for errors in the CSS file, in my in my case it was on the global CSS variables, fixing the errors solved the problem.
This tool can help you find the errors:
https://jigsaw.w3.org/css-validator/
I was just having the same odd issue. I'm not 100% sure what triggered this to happen but we use build tools to build SCSS into CSS. I went into my CSS file and removed the source map reference -
/*# sourceMappingURL=myCSS.map */
And all of the sudden it started showing up again. Then I added it back and I can still see it. I am not sure if this is because a version of the map is cached now or not but this worked for me.
Even i faced this issue !!!
style.css file was causing this issue..
I just created a new css file (Ex: style1.css) and cut pasted the older css file content (all lines in style.css) to style1.css file. It works
Note: Don't forget to update link tag, which is loading css file.
I think your CSS files are not loaded properly. Just check the syntax for referencing the external stylesheets.
It should be like this
<link rel="stylesheet" type="text/css" href="mystyle.css">
If you are skipping the rel="stylesheet", browser may think it as a plain file. To confirm the loading of stylesheets go for Chrome Inspector -> Sources
Check the site resources
No need of resetting anything. Hope it helps :)
I use Dreamweaver and Breckets.
Could see that the problem occurred only when I used Dreamweaver.
Solved the problem by changing Dreamweaver's preferences
--> Code Format --> Line Break Type --> CR LF (Windows)
Sometimes it can be the server!
I just had this error on a page that appeared to be fully loaded but the style panel was completely empty.
A complete restart of Chrome (and verifying no processes) did not work.
Restarting my server (in this case a .NET Core app running locally in Visual Studio) then allowed the style panel to show.
I think there was some sort of connection leak or web socket limit - something of that nature which was confusing Chrome.
I think this may helpfull.. If it is an angular project > then simply run
ng serve --extract-css.

What does Ctrl-S specifically do in Chrome Dev tools Sources tab?

The local save feature of the Chrome Dev tools Sources tab is very powerful.
However, I can't completely tell what kind of changes actually hold.
What changes are actually activated?
Ctrl-S applies your changes into v8.
So the the dynamic page behavior will work differently according to the changed code.
The star symbol in the file title indicates that the recent changes in the file haven't been sent to v8.
You have to save the changed file to the place where the web server gets it if you want to see the changes after reloading the page. You could do that with help of context menu.

Waiting mouse cursor in my GWT application stays infinitely (only in Chrome, only in Production)

Could you please tell me why I have waiting mouse cursor in my gwt application as if page not fully loaded ? It doesn't happen on dev server. It only happens in production. Also it's happening in Chrome but doesn't in IE.
Link to my app is here.
Screenshot
I checked it again in Chrome, but for me no wait cursor is Displayed. But i think, your Google Chrome is trying to open the Google Translate Menu. For me it came quickly and the page loading stopped and the mouse was at normal position.
I prefer you try updating your chrome.
I have also checked the same in my co-workers Laptop and its working fine too.
If problem still persists, please use CCleaner Software and clear all Temporary files, Browser Cache, Recent files etc. Why because, GWT creates a lot of temporary files which may reduce your system performance. So after each cleaning, just restart the system also. I had few such resolutions recently.
I opened your link in Firefox and got the following error
ERROR: Possible problem with your *.gwt.xml module file. The compile
time user.agent value (safari) does not match the runtime user.agent
value (gecko1_8). Expect more errors
This is because, you have compiled your code for Webkit browsers only. If you have added a line as below in your gwt module xml file,
<define-property name="user.agent" values="ie6">
you may either remove it or you can add more browser support via this.