Add information around `Exited` when "debugging" a project about what type of error happened

[FMorschel]

Yesterday, I was debugging some issues with the new plugin system and how it registers warnings (already filed) and trying to do a local patch so I can test my plugin on a separate project. I came back to it today, and I stumbled upon an error, so I manually opened the created plugin project and tried running it directly. This is the output:

Connecting to VM Service at ws://127.0.0.1:64559/aFo1eRDXgvk=/ws
Connected to the VM Service.
../../../../../.puro/shared/pub_cache/hosted/pub.dev/analysis_server_plugin-0.3.4/lib/src/registry.dart:59:48: Error: The argument type 'DiagnosticCode' can't be assigned to the parameter type 'LintCode'.
registry.dart:59
 - 'DiagnosticCode' is from 'package:_fe_analyzer_shared/src/base/errors.dart' ('../../../../../.puro/shared/pub_cache/hosted/pub.dev/_fe_analyzer_shared-92.0.0/lib/src/base/errors.dart').
 - 'LintCode' is from 'package:analyzer/src/dart/error/lint_codes.dart' ('../../../../../.puro/shared/pub_cache/hosted/pub.dev/analyzer-9.0.0/lib/src/dart/error/lint_codes.dart').
    registeredFixGenerators.registerFixForLint(code, generator);
                                               ^

Exited (254).

Since I saw at the beginning Connected to the VM Service, I assumed (mistakenly) that this was a runtime error and was trying to add breakpoints, but nothing worked. Then I remembered I was editing some cached dependencies to make things work, and that probably was a compile error.

---

This issue is requesting that we add some information around Exited to tell the user whether this was a compile or runtime error.

P.S.: If you know how to better phrase the title, please do so. Thanks!

CC @DanTup

[DanTup]

@FMorschel I couldn't reproduce seeing "Connected to VM Service" before a compile error:

Is there anything unusual about this project? You mention it's a plugin, is it something that is being compiled and run by code (eg. the main app does start running, then then it triggers compilation of something)?

[FMorschel]

TLDR: I suspect this has something to do with only dependencies not being correct, nothing about the code in the current project.

---

I'm on my bug-repro project (so, whatever you have should be good) with https://github.com/FMorschel/essential_lints/tree/base-lints (at the latest commit on this branch), set from path (git plugins still ongoing #61794).

If you try to run this as is, it should fail to launch the plugin. But that is not just it. I had edited: pub_cache\hosted\pub.dev\analysis_server_plugin-0.3.4\lib\src\correction\fix_generators.dart: to:

import 'package:analyzer/error/error.dart';

///...

  /// Associates the given correction producer [generator] with the lint with
  /// the given [lintCode].
  void registerFixForLint(DiagnostiCode lintCode, ProducerGenerator generator) {
    lintProducers.putIfAbsent(lintCode, () => []).add(generator);
  }

And that caused the problem you see above, where a DiagnosticCode (non-LintCode) was being assigned to lintProducers key (LintCode).

This caused my Insights plugins page to show a similar error (and that it was trying to do AOT compiling - which I missed), and what the plugin project under .dartServer hash was. So I opened it directly (.dartServer\.plugin_manager\40010cc439e108da47d1a13e366f63b2\) with Dart-Code and asked it to run. This gave me the error above.

[bwilkerson]

@srawlins

[srawlins]

Thumbs up

[DanTup]

@FMorschel I'm not sure I understand how to reproduce this from the description above. It sounds like this is a plugin (and therefore maybe related to how plugins are compiled?) but your screenshot showed the error in the Debug Console which suggests it was something you launched through a debug session.

Or do you mean it happens with any app, but only if the app itself compiles, and only dependencies do not compile (and therefore is not related to plugins)?

[FMorschel]

It sounds like this is a plugin (and therefore maybe related to how plugins are compiled?) but your screenshot showed the error in the Debug Console which suggests it was something you launched through a debug session.

All analysis_server_plugins named under plugins for any project you have, will generate a specific pub package listing them all under .dartServer\.plugin_manager\ (in my path: C:\Users\felip_0vh5fa6\AppData\Local\.dartServer\.plugin_manager\40010cc439e108da47d1a13e366f63b2 for this specific project, and you can find the path for it under the Plugins Insight page). So when things weren't running as I expected them to be, I opened the plugin project directly and used F5 to run the project. That is when I saw the above.

But that specific error only happens if you change the cached version for analysis_server_plugin in the way I specified above. I suspect that any incorrect character there, which would cause a compile-time error, would give a similar result and exemplify what I mean.

I'm home now, so I'll see if I can create a simpler repro with local-only projects so it is easier to understand. Testing/proving my theory above.

[FMorschel]

I did a small test with a simple package that contained a function:

void foo(double v) {
  int i = v;
}

And a separate project that calls foo.

We get:

Connecting to VM Service at ws://127.0.0.1:22741/WHb5D1eXz9c=/ws
Connected to the VM Service.
../package/lib/package.dart:3:13: Error: A value of type 'double' can't be assigned to a variable of type 'int'.
package.dart:3
    int i = v;
            ^

Exited (254).

So basically, what I experienced above. We can't compile our dependencies, so that is the message we get.

[DanTup]

Actually, I can reproduce "Connected to the VM Service" even without a dependency, I see it just generally if trying to start a Dart app that has a compilation error:

@bkonyi is it expected that we'd get a VM Service URL to connect to it in the case of a compile error? Is there any value in it? (if not, could we delay emitting the VM Service URL via --write-service-info until it has compiled?).

Runtime errors do start with "Unhandled exception:" so it's more obvious they are runtime errors, but compile errors are a bit less clear. I wonder if emitting some text prefix ("Compilation failed:\n") would make it clearer?

[bkonyi]

@bkonyi is it expected that we'd get a VM Service URL to connect to it in the case of a compile error? Is there any value in it? (if not, could we delay emitting the VM Service URL via --write-service-info until it has compiled?).

Actually, this is somewhat expected. The VM service starts in its own isolate immediately when the VM starts. Compilation of Dart sources happens in the kernel isolate, so it's possible for the VM service to finish starting up before compilation is complete, resulting in this situation.
We could add some logic to only advertise the VM service once the kernel isolate has completed its initial compilation and can start the main isolate, but I don't think we'd be able to prioritize that work at the moment.