Re: cleaning perl code

> On Apr 11, 2020, at 9:47 AM, Andrew Dunstan <andrew.dunstan@2ndquadrant.com> wrote:
> 
> 
> On 4/11/20 12:28 PM, Mark Dilger wrote:
>> 
>>> On Apr 11, 2020, at 9:13 AM, Andrew Dunstan <andrew.dunstan@2ndquadrant.com> wrote:
>> Hi Andrew.  I appreciate your interest and efforts here.  I hope you don't mind a few questions/observations about this effort:
> 
> 
> Not at all.
> 
> 
>> 
>>> The
>>> last one fixes the mixture of high and low precedence boolean operators,
>> I did not spot examples of this in your diffs, but I assume you mean to prohibit conditionals like:
>> 
>>    if ($a || $b and $c || $d)
>> 
>> As I understand it, perl introduced low precedence operators precisely to allow this.  Why disallow it?
> 
> 
> The docs say:
> 
> 
>    Conway advises against combining the low-precedence booleans ( |and
>    or not| ) with the high-precedence boolean operators ( |&& || !| )
>    in the same expression. Unless you fully understand the differences
>    between the high and low-precedence operators, it is easy to
>    misinterpret expressions that use both. And even if you do
>    understand them, it is not always clear if the author actually
>    intended it.
> 
>    |next| |if| |not ||$foo| ||| ||$bar||;  ||#not ok|
>    |next| |if| |!||$foo| ||| ||$bar||;     ||#ok|
>    |next| |if| |!( ||$foo| ||| ||$bar| |); ||#ok|

I don't think any of those three are ok, from a code review perspective, but it's not because high and low precedence operators were intermixed.

>> 
>>> and the use of commas to separate statements
>> I don't understand the prejudice against commas used this way.  What is wrong with:
>> 
>>    $i++, $j++ if defined $k;
>> 
>> rather than:
>> 
>>    if (defined $k)
>>    {
>>        $i++;
>>        $j++;
>>    }
>> 
> 
> 
> I don't think the example is terribly clear. I have to look at it and
> think "Does it do $i++ if $k isn't defined?"

It works like the equivalent C-code:

    if (k)
        i++, j++;

which to my eyes is also fine.

I'm less concerned with which perlcritic features you enable than I am with accidentally submitting perl which looks fine to me but breaks the build.  I mostly use perl from within TAP tests, which I run locally before submission to the project.  Can your changes be integrated into the TAP_TESTS makefile target so that I get local errors about this stuff and can fix it before submitting a regression test to -hackers?

—
Mark Dilger
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company