[Cuis-dev] Allow debugger to step into quick return methods

Sat Nov 18 14:05:50 PST 2023

Hi Facu,

> I'm looking into it—these errors are really tough to debug!
> The problem arises when you try to debug an exception: in your code
> example, Customer class>>#importCustomers throws an exception because the
> file input.txt does not exist, therefore line is nil.
>

oh! that is because I forgot to send you the file, but create a file called
input.txt or replace the file with a ReadStream. That is not the problem I
had.
Replace the opening of the file with:
inputStream := ReadStream on: 'C,a,b,d,1122'.
That will help you reproduce the error. You have to step over until the [
line notNil ]

>
> 📝 Here's what I've found so far:
> In my previous changeset, I changed the InstructionStream>>#willReturn
> method so that it'll stop before actually performing a quick return once
> you step into it. This is used from ContextPart>>#stepToSendOrReturn (👈 notice
> the message name).
> While I was debugging this issue, I realized that there's also another
> place where something similar is done:
> ContextPart>>#runUntilErrorOrReturnFrom:. This is used, for example, when
> you perform a "through" action. As a quick return method can only return an
> object, I changed #runUntilErrorOrReturnFrom: to just do that instead of
> going through the rest of the logic.
>
> I attach a fileout of the changes to
> ContextPart>>#runUntilErrorOrReturnFrom:. It should be filed-in after
> having applied the original changeset, and it should fix the problem.
> I don't think this is an elegant solution, but I want you to try it to see
> if it works on your tests or if you find more problems.
>

With this fix, the problem I describe above is gone, so it fixes the issue.

Cheers!
Hernan.

> I'll keep looking into it!
> Cheers!
> Facu
>
>
>
> El mar, 14 nov 2023 a las 9:35, Hernán Wilkinson (<
> hernan.wilkinson at 10pines.com>) escribió:
>
>> Hi Facu,
>>  there is an error with this change. I do not know exactly what it is,
>> but you can reproduce it by filing in the attached file and debugging
>> importCustomers from Customer class (it is a class method). The error
>> happens when doing step over in [ line notNil ] whileTrue: ...
>>
>> On Tue, Nov 14, 2023 at 8:07 AM Hernán Wilkinson <
>> hernan.wilkinson at 10pines.com> wrote:
>>
>>> This is so great!! It is a really important feature when doing TDD and
>>> the first implementation of a method is a ^true or similar.
>>> The only concern I have is the change in Process>>#resume, because that
>>> impacts all the situations where #resume is sent... I know the impact is
>>> low, but is it possible to restrict that change to the debugger only or not?
>>>
>>> Cheers!
>>> Hernan.
>>>
>>> On Mon, Nov 13, 2023 at 8:28 PM Facundo Javier Gelatti via Cuis-dev <
>>> cuis-dev at lists.cuis.st> wrote:
>>>
>>>> Hi!
>>>> I attach some code to be able to step into quick return methods from
>>>> the debugger, and there's also a demo video
>>>> <https://drive.google.com/file/d/1Iv5-hJ4TNjmR0pG-qm02KpTxCvKzsDZC/view?usp=sharing>.
>>>> Being able to step into a quick return method is very useful, especially in
>>>> situations where we are doing TDD (because the first implementation of a
>>>> method probably ends up being a quick return).
>>>>
>>>> Most of these changes were developed during the Camp Smalltalk event of
>>>> the Smalltalks 2023 conference by me, Juan Vuletich and Felipe Zak (thank
>>>> you guys!).
>>>>
>>>> I included automated tests for various debugging scenarios. The class
>>>> QuickReturnDebuggingTest should probably be moved to an appropriate
>>>> category (it's currently in the "Smalltalks 2023" category, just because
>>>> the changes were developed during the conference) or be merged into another
>>>> existing test class (I wasn't sure where to put it).
>>>>
>>>> ℹ️ Extra interesting info: there are other places in which we're
>>>> currently treating quick return methods in a special way. See for example
>>>> Debugger>>#contents:notifying:, which handles the special case of a
>>>> normal method becoming a quick return method after saving the changes on
>>>> the debugger (the stack frame is removed in that case, try it!). As a
>>>> curiosity, another quirk related to quick returns is that you cannot debug
>>>> an expression that will compile to a quick return (e.g. ^2), the
>>>> debugger simply doesn't show up! None of this is modified on the code I'm
>>>> submitting.
>>>>
>>>> I include a summary of the changes below, that could be useful during
>>>> code review 👇
>>>>
>>>> Cheers!
>>>> Facu
>>>>
>>>> ------------------------------
>>>> 📝 Changes summary:
>>>>
>>>>    - Do not run a quick return as a primitive in
>>>>    ContextPart>>#send:to:with:lookupIn:, treat it as a normal
>>>>    instruction —before which we can stop— and create a new stack frame for it.
>>>>    - Refactor: extracted an isPrimitive variable in
>>>>    ContextPart>>#send:to:with:lookupIn:, to avoid having repeated code.
>>>>    - Changed InstructionStream>>#willReturn to include quick returns
>>>>    there. This ends up telling the debugger that it's possible to pause the
>>>>    execution there.
>>>>    - In Process>>#resume, resolve pending quick returns before running
>>>>    #primitiveResume, so that the VM can resume the process without
>>>>    having an unexpected stack frame (if you remove this, the VM crashes).
>>>>    - Refactor: extracted the method Debugger class>>#newDebugging:,
>>>>    which is useful for tests (because it does not open the debugger UI).
>>>>
>>>> --
>>>> Cuis-dev mailing list
>>>> Cuis-dev at lists.cuis.st
>>>> https://lists.cuis.st/mailman/listinfo/cuis-dev
>>>>
>>>
>>>
>>> --
>>>
>>> *Hernán WilkinsonAgile Software Development, Teaching & Coaching*
>>> *Phone: +54-011*-4893-2057
>>> *Twitter: @HernanWilkinson*
>>> *site: http://www.10Pines.com <http://www.10pines.com/>*
>>> Address: Alem 896, Floor 6, Buenos Aires, Argentina
>>>
>>
>>
>> --
>>
>> *Hernán WilkinsonAgile Software Development, Teaching & Coaching*
>> *Phone: +54-011*-4893-2057
>> *Twitter: @HernanWilkinson*
>> *site: http://www.10Pines.com <http://www.10pines.com/>*
>> Address: Alem 896, Floor 6, Buenos Aires, Argentina
>>
>

-- 

*Hernán WilkinsonAgile Software Development, Teaching & Coaching*
*Phone: +54-011*-4893-2057
*Twitter: @HernanWilkinson*
*site: http://www.10Pines.com <http://www.10pines.com/>*
Address: Alem 896, Floor 6, Buenos Aires, Argentina
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