[wildfly-dev] CLI batches in control flow blocks

[Alexey Loubyansky]

Yes, that could be another reason. Thanks.

Although, this is where it gets complicated and confusing.

By multi-level, did you mean nested batches? Like nested transactions?
If so, I don't think we'll go for that. It's just too complicated.

Removing auto-batch from if/else and using them in a batch like you 
described could still be confusing. The batch won't be executed until 
all the lines preceding run-batch are added to the batch. Now we have if 
in the middle. What if the condition depends on the operations between 
batch and if? The evaluation of the if condition w/o executing those 
won't be correct. And we won't be able to predict the effects of the 
operations on the model w/o actually sending them to the controller 
(because unless it's write-attribute, the operations may do whatever).

So, that would be an improvement to be able to use if/else in the batch 
but the condition should not depend on the operations preceding the if.

Thanks,
Alexey

On 09/04/2015 12:36 PM, Tom Fonteyne wrote:
> IMHO.... you cannot use if/then in batches anyhow, e.g:
>
> batch
> ...
> if ...
> ...
> then
> ...
> fi
> ...
> run-batch
>
> fails. So the use of if/then was of very limited use anyhow.
>
> Having multi-level batch would be ideal.
> Removing auto-batch from if/then blocks would at least allow batches
> "around" them to work properly which would be a big win anyhow.
>
> just my £0.02 of course
> Tom
>
>
> On 04/09/15 06:55, Alexey Loubyansky wrote:
>> On 09/04/2015 12:10 AM, Brian Stansberry wrote:
>>> The risk is this can break existing scripts, which we've sought to
>>> avoid. A couple breakage scenarios:
>>>
>>> 1) Step 1 needs to happen in a batch with Step 2; now it won't so the
>>> script breaks.
>>> 2) Step 1 works but for some reason Step 2 fails, and now Step 1 isn't
>>> rolled back.
>>>
>>> The first one is more likely, but the second one is a bigger concern, as
>>> the user may not be aware Step 1 wasn't rolled back.
>>>
>>> Do you have any sense of how common either of those scenarios would be?
>> Unfortunately, no. I don't get much feedback on this except for created
>> issues that I referenced.
>> I wouldn't bring it up unless this wasn't a major version release, of
>> course.
>>
>>> Below are bad ideas that I wrote down and then thought better of, but
>>> I'll send them in case it sparks a thought.
>>>
>>> I. Since there is already logic for dropping out of the batch for things
>>> like cd, ls, could it be modified as follows?
>>>
>>> a) Close any current batch and execute that batch.
>>> b) Execute the cd, ls, etc
>>> c) Proceed, and if the next statement isn't a cd, ls etc, start a new
>>> batch.
>>>
>>> That seems like a better semantic for cd and ls anyway.
>> I don't think so. The batch mode is also a composition/editing mode. cd
>> and ls are useful when writing commands/operations that should be added
>> to the batch. Imagine editing a batch and wishing to cd before entering
>> next lines. That won't be possible without explicit holback-batch, cd
>> and then batch again. That would be inconvenient.
>>
>>> With that, reload and shutdown can be treated the same as cd, ls.
>> For reload and shutdown that does seem to make sense. So, a possible
>> alternative is making them exceptions.
>>
>>> Why a bad idea? Doing it as I suggest has the same two drawbacks as
>>> requiring the user to declare the batch. :( Just perhaps less likely to
>>> occur.
>>>
>>> II. Is an --auto-batch=true|false param to if/else/try/catch/finally
>>> possible? Why a bad idea? To solve the breakage problem it would need to
>>> be 'true' by default, thus forcing users forever to declare that they
>>> want the non-broken mode, *plus* they have to declare the batches.
>> As a param to if/else/try/catch/finally this doesn't make sense to me.
>> Because then the user could simply explicitly start bodies with batch.
>> This kind of argument could make sense as a launching script argument
>> for the whole cli session, imo.
>>
>> Thanks,
>> Alexey
>>
>>>
>>> On 9/3/15 10:42 AM, Alexey Loubyansky wrote:
>>>> Hello everyone,
>>>>
>>>> I've been thinking about changing how the bodies of if-else and
>>>> try-catch-finally are treated by the CLI.
>>>>
>>>> Up until now every control flow block (i.e. between if and else,
>>>> between
>>>> else and end-if, etc) was executed as a batch. So, when a block was
>>>> selected for the execution, the CLI would enter the batch mode and
>>>> proceed adding operations (and commands translated to operations) to
>>>> it.
>>>> If a command can't be translated to an operation, it would be executed
>>>> outside the batch immediately (that's done for commands like cd, ls,
>>>> etc). After the last line of the body processed, the batch (if not
>>>> empty) is executed.
>>>>
>>>> But this doesn't work when mixing operations with shutdown or reload
>>>> commands (they do translate to operations but they have additional
>>>> logic
>>>> related to re-connecting). shutdown/reload will be executed outside the
>>>> batch and before the batch is complete.
>>>>
>>>> Currently open issues for this
>>>> https://issues.jboss.org/browse/WFCORE-876
>>>> https://issues.jboss.org/browse/WFCORE-533
>>>>
>>>> So, I think it was a mistake to execute the bodies of control flow
>>>> blocks as batches. It would be better leave them as usual sequences of
>>>> command lines and if the user wants a batch, he/she could add batch
>>>> command explicitly.
>>>>
>>>> I wanted to ask for opinions. Could we make this change in WildFly 10?
>>>>
>>>> Thanks,
>>>> Alexey
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>>>>
>>>
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