Breaking change in how breakpoints are handled by the debugger

[bergwerf]

See: dart-lang/sdk#29988. I noticed that with dart 1.25.0-dev.1.0 the debugger did not pause at all breakpoints (in particular some inside a closure, where I did not experience any issues previously). It seems that something was updated in the SDK and something has to be fixed in this plugin.

[DanTup]

I'm struggling to reproduce this; I've got this:

main() {
  print(getThing().length);
}

getThing() {
  var result = [1, 2, 3, 4];
  return result.map((v) => v / 2).toList();
}

I'm putting a breakpoint on the map line and it always gets hit. I'm using v.1.25.0-dev.2.1. Are you able to make a simple repro?

[bergwerf]

It took me some tries to reproduce this as well, but this reproduces the bug:

lib/src/test.dart

part of test;

void doPrint() {
  print('Break!');
}

lib/test.dart

library test;
part 'src/test.dart';

test/test.dart

import 'dart:async';
import 'package:test/test.dart';
import 'package:yourpackage/test.dart';

Future main() async {
  test('Test', () {
    doPrint();
  });
}

(it doesn't reproduce the issue if you put the function directly in the primary library file)

Try to break on print('Break!');

[DanTup]

@hermanbergwerf Perfect; I can repro with these files. I'll investigate!

[DanTup]

Ok, I ran this same test in 1.24 and 1.25 and found this..

We currently send breakpoints twice because we previously found that depending on how a file was imported, the debugger would not break on it (some discussion in #134). So the request to add breakpoints looks like this:

==> {"id":"5","method":"addBreakpointWithScriptUri","params":{"isolateId":"isolates/11111111","scriptUri":"file:///c:/Users/danny/Desktop/DartDebugSample/lib/src/test.dart","line":4}}
==> {"id":"6","method":"addBreakpointWithScriptUri","params":{"isolateId":"isolates/11111111","scriptUri":"package:yourpackage/src/test.dart","line":4}}

In 1.24, both of these breakpoints are accepted:

<== {"jsonrpc":"2.0", "result":{"type":"Breakpoint","fixedId":true,"id":"breakpoints\/1","breakpointNumber":1,"resolved":false,"location":{"type":"UnresolvedSourceLocation","scriptUri":"file:\/\/\/c:\/Users\/danny\/Desktop\/DartDebugSample\/lib\/src\/test.dart","line":4}},"id":"5"}
<== {"jsonrpc":"2.0", "result":{"type":"Breakpoint","fixedId":true,"id":"breakpoints\/2","breakpointNumber":2,"resolved":false,"location":{"type":"UnresolvedSourceLocation","script":{"type":"@Script","fixedId":true,"id":"libraries\/@17134453\/scripts\/package%3Ayourpackage%2Fsrc%2Ftest.dart\/15cd52126c7","uri":"package:yourpackage\/src\/test.dart","_kind":"source"},"line":4}},"id":"6"}

and when we go on to execute, we stop at the second breakpoint - the "package" version.

However, here's what happens in 1.25. We send the same requests:

==> {"id":"5","method":"addBreakpointWithScriptUri","params":{"isolateId":"isolates/11111111","scriptUri":"file:///c:/Users/danny/Desktop/DartDebugSample/lib/src/test.dart","line":4}}
==> {"id":"6","method":"addBreakpointWithScriptUri","params":{"isolateId":"isolates/11111111","scriptUri":"package:yourpackage/src/test.dart","line":4}}

But here's the response:

<== {"jsonrpc":"2.0", "result":{"type":"Breakpoint","fixedId":true,"id":"breakpoints\/1","breakpointNumber":1,"resolved":false,"location":{"type":"UnresolvedSourceLocation","scriptUri":"file:\/\/\/c:\/Users\/danny\/Desktop\/DartDebugSample\/lib\/src\/test.dart","line":4}},"id":"5"}
<== {"jsonrpc":"2.0", "error":{"code":102,"message":"Cannot add breakpoint","data":{"request":{"method":"addBreakpointWithScriptUri","params":{"isolateId":"isolates\/11111111","scriptUri":"package:yourpackage\/src\/test.dart","line":"4"}},"details":"addBreakpointWithScriptUri: Cannot add breakpoint at line '4'"}},"id":"6"}

Note that the second breakpoint (which is the one that breaks in 1.24) is the one being rejected.

So, I have no idea how to fix this - the breakpoint we can't set is the one that would actually work.

DartDebugSample.zip

I'm gonna add this comment also to dart-lang/sdk#29988 because I need input from Google on how this is supposed to work.

[DanTup]

Looks like this has been fixed in Dart, so hopefully won't occur in any release SDKs.

[DanTup]

This seems fixed in SDK .dev.6.0 :-)

[bergwerf]

Again having issues in 1.25.0-dev.8.0 :-(

[DanTup]

I think it's best posting back in dart-lang/sdk#29988 or raising a new case there with a sample. You can get a log like I posted above by setting the "dart.observatoryLogFile" setting to a file path/name, which should help track things down. Feel free to post it here for me to have a look before you raise an SDK issue if you want.

[bergwerf]

Alright, will look into this a bit.
Also loading the scope variables for anything but the top of the stack trace is not working.

[DanTup]

@hermanbergwerf Using dev.8.0 and performing the same steps on the above repro I hit the breakpoint fine. If you can provide new repro steps/sample I can take a look.

[bergwerf]

I tried as well, and had no issues with the previous repro. I am quite sure I missed a breakpoint somewhere but I cannot find/reproduce it now. Will post back if I find something :-)

[DanTup]

@hermanbergwerf I'm just investigating an issue with breakpoints not being hit that may or may not be related - see #398. I think I know the cause and fix, but not why it's never been noticed before!

[bergwerf]

The number of developers effectively using breakpoints might be quite low, especially for Dart. I struggled with print/printf/console.log for years because no one had told me I should use breakpoints haha. Maybe people have noticed and not reported though.

…

On Mon, Jul 31, 2017, 21:27 Danny Tuppeny ***@***.***> wrote: @hermanbergwerf <https://github.com/hermanbergwerf> I'm just investigating an issue with breakpoints not being hit that may or may not be related - see #398 <#398>. I think I know the cause and fix, but not why it's never been noticed before! — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#334 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AEQJ1Y-fsHHWzpagiTC2Y7swjLaUA1MPks5sTdZKgaJpZM4OCxQv> .