[debugger] Existing processes break after a breakpoint is removed

[robertoaloi]

Describe the bug

The debugger which comes with Erlang LS uses the Erlang interpreter behind the scenes.

If the user removes a breakpoint via the UI, existing processes will still break at the removed breakpoint, creating confusion for the user.

To Reproduce

Given:

-module(fact).

-compile(export_all).

fact(0) ->
    1;
fact(N) when N > 0 ->
    N * fact(N-1).

And:

-module(test).
-compile(export_all).
test() ->
    {module, fact} = int:i(fact),
    int:break(fact, 8),
    spawn(fun() -> fact:fact(5) end),
    timer:sleep(100),
    [{Pid, _, _, _}] = int:snapshot(),
    int:no_break(fact),
    %% int:no_break(),
    int:continue(Pid),
    timer:sleep(100),
    is_process_alive(Pid).

Using the following commands:

➜  /tmp erl
Erlang/OTP 25 [erts-13.2] [source] [64-bit] [smp:16:16] [ds:16:16:10] [async-threads:1] [jit:ns]

Eshell V13.2  (abort with ^G)
1>  c(fact, [debug_info]).
{ok,fact}
2> c(test).
{ok,test}
3> test:test().

This produces:

true

By replacing the int_no_break(fact) with the commented line, instead:

false

Expected behavior
Once a breakpoint is removed and the continue command is issued, existing processes should not break.

Affected versions
OTP 25 (at least).

Additional context
This seems related to the way breakpoints are stored and updated in the process dictionary in idbg_eval.

[bjorng]

This bug seems to have existed for a very long time. I have fixed it for OTP 24 and forward in the linked pull request.