setLibraryDebuggable doesn't work as expected

[DanTup]

It's entirely possible this is user error, but I'm not sure how to debug further.

For now, I'm trying to set all libraries as not-debuggable for testing; my startup code looks something like this:

return Promise.all(
    isolate.libraries.map(library => 
        this.observatory.setLibraryDebuggable(isolateRef.id, library.id, false)
    )
);

I can see the requests all being sent and success responses:

==> {"id":"4","method":"setExceptionPauseMode","params":{"isolateId":"isolates/360410364","mode":"Unhandled"}}
==> {"id":"5","method":"setLibraryDebuggable","params":{"isolateId":"isolates/360410364","libraryId":"libraries/0","isDebuggable":false}}
==> {"id":"6","method":"setLibraryDebuggable","params":{"isolateId":"isolates/360410364","libraryId":"libraries/1","isDebuggable":false}}
==> {"id":"7","method":"setLibraryDebuggable","params":{"isolateId":"isolates/360410364","libraryId":"libraries/2","isDebuggable":false}}
==> {"id":"8","method":"setLibraryDebuggable","params":{"isolateId":"isolates/360410364","libraryId":"libraries/3","isDebuggable":false}}
// SNIP

<== {"jsonrpc":"2.0", "result":{"type":"Success"},"id":"5"}
<== {"jsonrpc":"2.0", "result":{"type":"Success"},"id":"6"}
<== {"jsonrpc":"2.0", "result":{"type":"Success"},"id":"7"}
<== {"jsonrpc":"2.0", "result":{"type":"Success"},"id":"8"}
// SNIP

However, it doesn't seem to do what I expect. Here's my sample program:

main() {
  print("Danny");
}

I have a breakpoint on line 2 and I'm pressing Step Into after it's hit. I end up in broken inside print, but I expected it to just step over.

[DanTup]

FYI @johnmccutchan

[johnmccutchan]

@mhausner @turnidge

[mhausner]

I can reproduce this using the Observatory debugger. This is a bug in the VM. The VM side of the debugger ignores the "isDebuggable" property of libraries and thus pauses even in libraries that are marked as not debuggable.

This is a relic from a time when the VM supported two debuggers.

@turnidge wants to think about how to fix this the right way.

[mhausner]

The culprit is in this code:

bool Debugger::IsDebuggable(const Function& func) {
  if (!func.is_debuggable()) {
    return false;
  }
  if (ServiceIsolate::IsRunning()) {
    return true;  <<<<<<<<<
  }
  const Class& cls = Class::Handle(func.Owner());
  const Library& lib = Library::Handle(cls.library());
  return lib.IsDebuggable();
}