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To: Rowan Tommins <rowan.collins@gmail.com>, "internals@lists.php.net"
	<internals@lists.php.net>
Thread-Topic: [PHP-DEV] [RFC] var_representation() : readable alternative to
 var_export()
Thread-Index: AQHW8R1wWWGP+37l0kiexDpDbUAmVKo1egmAgAAyURKAAR7sgIAAHRck
Date: Sun, 24 Jan 2021 16:17:19 +0000
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Subject: Re: [PHP-DEV] [RFC] var_representation() : readable alternative to
 var_export()
From: tysonandre775@hotmail.com (tyson andre)

Hi Rowan Tommins,=0A=
=0A=
> > var_representation=A0 may be useful to a user when any of the following=
 apply:=0A=
> >=0A=
> > - You are generating a snippet of code to eval() in a situation where t=
he snippet will occasionally or frequently be read by a human=A0 (If the ou=
tput never needs to be read by a human, `return unserialize(' . var_export(=
serialize($data), true) . ');` can be used)=0A=
> =0A=
> =0A=
> As far as I know I have never had any reason to generate code and then =
=0A=
> eval() it, and can't think of a situation where I ever would. If I =0A=
> wanted a machine-readable output from a variable, I would use =0A=
> serialize() or json_encode().=0A=
>=0A=
> That's not to say that there aren't cases where those requirements do =0A=
> happen, but I think it is a very niche use case to dedicate two =0A=
> different built-in functions to.=0A=
=0A=
Even if a developer such as yourself doesn't need to generate code and don'=
t expect to directly use it,=0A=
**some of the applications and libraries they do use everyday would need to=
 generate human and machine readable code.**=0A=
That output is then shown to users of those libraries/applications,=0A=
or saved to files that would need to be looked at by users submitting bug r=
eports or trying to understand the issue,=0A=
e.g. trying to understand why a unit test mock isn't doing what they'd expe=
ct.=0A=
=0A=
For example, the output of some composer autoload files are generated using=
 var_export,=0A=
and composer uses var_export for generating some exception messages,=0A=
and it may be useful to have $e->getMessage() be a single line.=0A=
https://github.com/composer/composer/blob/master/src/Composer/Repository/Fi=
lesystemRepository.php#L205-L208=0A=
(if users were trying to diagnose composer not autoloading the class, havin=
g these files be more readable would be useful=0A=
many years from now if composer's minimum version became php 8.1)=0A=
=0A=
And a subset of the uses of var_export in the dependencies of a project I'm=
 using:=0A=
=0A=
```=0A=
vendor/sebastian/global-state/src/CodeExporter.php=0A=
// in protected function recursiveExport=0A=
67:            return \var_export($variable, true);=0A=
=0A=
70:        return 'unserialize(' . \var_export(\serialize($variable), true)=
 . ')';=0A=
=0A=
vendor/phpunit/php-code-coverage/src/Report/PHP.php=0A=
16: * Uses var_export() to write a SebastianBergmann\CodeCoverage\CodeCover=
age object to a file.=0A=
=0A=
37:            \var_export($coverage->getData(true), true),=0A=
=0A=
vendor/phpspec/prophecy/src/Prophecy/Doubler/Generator/ClassCodeGenerator.p=
hp=0A=
104:                $php .=3D ' =3D '.var_export($argument->getDefault(), t=
rue);=0A=
=0A=
vendor/symfony/console/Descriptor/MarkdownDescriptor.php=0A=
62:            .'* Default: `'.str_replace("\n", '', var_export($argument->=
getDefault(), true)).'`'=0A=
```=0A=
=0A=
If you want to distinguish between array, stdClass, and MyClass, json_encod=
e isn't adequate.=0A=
=0A=
> > - You are writing unit tests for applications supporting PHP 8.1+ (or a=
 var_representation polyfill) that test the exact string representation of =
the output (e.g. phpt tests of php-src and PECL extensions)=0A=
> =0A=
> =0A=
> Since test output doesn't need to be executable, I would have thought =0A=
> var_dump would be more appropriate than var_export here.=0A=
=0A=
https://www.php.net/var_dump does not have an option to save to a string - =
it outputs to stdout.=0A=
if __debugInfo or an error handler echoes anything that would get captured =
by output buffering and interfere with that test.=0A=
=0A=
Additionally, humans need to update the test expectations and to read the t=
est output when it fails.=0A=
If that output contains control characters or unexpectedly mixes line endin=
gs, it is inconvenient to work with files using the raw output of in var_ex=
port/var_dump.=0A=
=0A=
> > As I mentioned before, var_export suffers from many shortcomings such a=
s the fact=0A=
> > that it can have more lines of output than var_dump for complex datastr=
uctures,=0A=
> > and doesn't escape control characters.=0A=
> =0A=
> Checking on php-src master, this does seem to be the case in the =0A=
> majority of tests:=0A=
> =0A=
> - var_export appears 703 times in 136 different *.phpt files (0.8% of fil=
es)=0A=
> - print_r appears 827 times in 342 different *.phpt files (2.1% of files)=
=0A=
> - var_dump appears 33503 times in 9599 different *.phpt files (59.7% of =
=0A=
files)=0A=
> =0A=
> So if we want to improve anything for that use case, we need to improve =
=0A=
> or replace var_dump, not var_export.=0A=
=0A=
**php-src phpt tests are for tests of php itself, which puts strict and aty=
pical limitations on the test framework.**=0A=
php-src's phpt test framework may represent needs of php-src and some pecl =
maintainers, not userland.=0A=
In a userland project, I could easily choose to add a whole lot of utility =
functions/methods such as=0A=
`function dump_repr($value) { echo var_representation($value), "\n"; }` and=
 use that to replace var_dump.=0A=
=0A=
I consider adding those helper methods **to php-src itself** impractical be=
cause tests of php-src should be self-contained.=0A=
If you encounter an issue with the engine, opcache or JIT, it's much, much =
harder to diagnose if dozens of userland helper functions=0A=
were loaded and invoked before the snippet in question was invoked.=0A=
=0A=
So I do use var_dump in phpt tests itself, mainly because:=0A=
=0A=
1. Currently, control characters such as `\r` are not escaped, so I'm more =
confident `string(4) "test"` has no control characters =0A=
2. var_export does not append a newline, it's more convenient to copy the .=
out file into the `--OUT--` section=0A=
3. I'm avoiding adding reusable helpers in a self-contained test case =0A=
4. var_export output make the overall test output longer for arrays of arra=
ys=0A=
=0A=
Still, I would prefer using var_representation over var_dump in phpt for ma=
ny use cases, especially with VAR_REPRESENTATION_SINGLE_LINE available.=0A=
=0A=
> > - You need to copy the output into a codebase that's following a modern=
 coding style guideline such as modern coding guidelines such as PSR-2. It =
also saves time if you don't have to remove array keys of lists and convert=
 array() to [].=0A=
> =0A=
> =0A=
> Trying to match any particular coding style seems rather outside the =0A=
> remit of a built-in function - do we need flags for tabs vs spaces, =0A=
> trailing commas, etc, etc? Surely it's simpler for users to take the =0A=
> existing var_export format and use their IDE or dev scripts to re-format =
=0A=
> it to taste.=0A=
=0A=
=0A=
Again, the IDE may have issues with the control characters in strings or un=
expectedly remove or add them=0A=
(e.g. windows vs unix newlines)=0A=
=0A=
For tabs vs spaces, Sara Golemon suggested an `'indent'` option=0A=
where users could choose what string prefix to use as spaces/tabs,=0A=
but I feel this would increase the initial scope of the RFC too much.=0A=
=0A=
For a new developer, they may not have those features or plugins installed =
in their IDE,=0A=
or may not be aware of the existence of the shortcut/command to invoke thos=
e features on a range.=0A=
(phpcbf, or for reindenting Ctrl+space in eclipse, `=3D` in vim, etc.)=0A=
Additionally, scripts to reindent may not remove the `0 =3D>`, `1 =3D>`, et=
c,=0A=
either not containing a php parser or assuming the user deliberately added =
those keys.=0A=
=0A=
It would be much easier to reindent the output of var_representation than t=
o rewrite+reindent the output of var_export.=0A=
=0A=
=0A=
Regards,=0A=
Tyson=