Uncaught Instance of 'minified:b0' when using proxy

[odogy]

Running proxy middleware in this Express app to serve JS files from the Dart web dev server is giving an "client.js:367 Uncaught Instance of 'minified:b0'" error.

This may be the same issue or related to #2333 . However, build_web_compilers 2.1.2 does not seem to fix this, though it does fix #2333 for me (so I could just be screwing something up with configuration here). This worked before in a much older version of build_web_compilers (0.4.4+3) with build_runner 1.1.2 - I don't have any info for in-between versions.

• Dart SDK 2.4.0
• build_runner: 1.6.1, build_web_compilers: 2.1.2
• Windows 10
• Chrome

minified_b0_issue.zip

1. Download and unzip attached folder
2. run 'pub get' in client subfolder
3. run 'webdev serve' in client subfolder
4. run 'npm install' in server subfolder
5. run 'npm run start' in server subfolder
6. open http://localhost:3000/ in Chrome and check the console

If I'm just pursuing a silly strategy with the proxy middleware, and there's a better option, please let me know. Just figuring this stuff out.

[natebosch]

This worked before in a much older version of build_web_compilers (0.4.4+3) with build_runner 1.1.2

This is coming from dart2js and it is very unlikely to be impacted by the version of build_runner or build_web_compilers you are using since we've changed very little about how we invoke dart2js. The details for ddc have changed a lot and so differences in dev mode are more likely to be caused by changing version of build_web_compilers.

You might try disabling minification and debugging with the dart2js version to get a more specific error.
https://github.com/dart-lang/build/blob/master/docs/faq.md#how-can-i-debug-my-release-mode-web-app-dart2js

[odogy]

I'm a little confused. I didn't know I was using dart2js here, since I'm just running webdev serve with default configuration. Is dart2js always used? As far as the error itself goes, the stack trace is identical to the one I see in #2333 which was resolved to be a pathing issue. I was sort of thinking this might be a similar issue due to the HTML being located on a different server. I will try using dart2js later today. Thanks!

[evanweible-wf]

I can't remember the exact error, but I saw a similar client.js exception when using a proxy and refreshing at a URL that was not in the root directory. In order to fix that, I had to include a <base href="/"> in the HTML that was being served.

[natebosch]

I didn't know I was using dart2js here, since I'm just running webdev serve with default configuration

I would also expect DDC in that configuration, but I would not expect to see anything like minified:b0 in that case. That looks like something coming from dart2js compiled code...

It looks like it may be related to dart2js code compiled by us for hot reload stuff maybe?
#2334 was intended to fix it but you would have been using a version with that fix at 2.1.2

@jakemac53 @grouma do you have any more context here?

[grouma]

client.js corresponds to this code here:
https://github.com/dart-lang/webdev/blob/master/webdev/web/client.dart

This is precompiled with Dart2JS and shipped with Webdev.
See: https://github.com/dart-lang/webdev/blob/master/webdev/lib/src/serve/injected/client.js

The client is injected by Webdev and handles the handshake between server and browser. It also sets up various listeners to support the debugging and development workflows e.g. alt + d.

It would be helpful to get the unminified error. I created a PR which has the unoptimized client. Simply activate Webdev from this branch:
dart-lang/webdev#472

[mhrst]

The branch created for dart-lang/webdev#472 has been deleted. Is there still a branch somewhere with the unminified version of webdev? I'm trying to provide an unminified version of the following error:

Uncaught Instance of 'minified:p'
    at Object.b (http://localhost:8888/web/webdev/src/serve/injected/client.js:367:3)
    at nq.$0 (http://localhost:8888/web/webdev/src/serve/injected/client.js:5445:20)
    at Object.uK (http://localhost:8888/web/webdev/src/serve/injected/client.js:1268:5)
    at kK.uP (http://localhost:8888/web/webdev/src/serve/injected/client.js:1270:7)
    at lL.$1 (http://localhost:8888/web/webdev/src/serve/injected/client.js:4865:3)
    at vk (http://localhost:8888/web/webdev/src/serve/injected/client.js:441:17)
    at MutationObserver.<anonymous> (http://localhost:8888/web/webdev/src/serve/injected/client.js:449:51)

Edit -- This is the exact issue I'm having btw:

I can't remember the exact error, but I saw a similar client.js exception when using a proxy and refreshing at a URL that was not in the root directory. In order to fix that, I had to include a <base href="/"> in the HTML that was being served.

Note: Using a base-href of / does resolve this issue for me, but the base-href of my website is not /.

[grouma]

The branch was deleted as we no longer minify the client:
dart-lang/webdev#497

Note that I will be publishing a new version of webdev later today which will include that change.

[grouma]

I just published a new version of webdev (2.3.0) which does not minify the injected client.

[mhrst]

Thanks!~
Here is the unminified error (web/ is my base-href):

client.js:1016 Uncaught Instance of 'Event'
    at Object.wrapException (http://localhost:8888/web/dwds/src/injected/client.js:1016:17)
    at _rootHandleUncaughtError_closure.call$0 (http://localhost:8888/web/dwds/src/injected/client.js:12697:17)
    at Object._microtaskLoop (http://localhost:8888/web/dwds/src/injected/client.js:3253:21)
    at StaticClosure._startMicrotaskLoop (http://localhost:8888/web/dwds/src/injected/client.js:3259:11)
    at _AsyncRun__initializeScheduleImmediate_internalCallback.call$1 (http://localhost:8888/web/dwds/src/injected/client.js:11368:9)
    at invokeClosure (http://localhost:8888/web/dwds/src/injected/client.js:1206:26)
    at MutationObserver.<anonymous> (http://localhost:8888/web/dwds/src/injected/client.js:1225:18)