Feature suggestion: Improve information available about installed standards

[jrfnl]

Repost from squizlabs/PHP_CodeSniffer#2600:

(I seem to remember seeing a discussion about something like this before, but can't find it anymore, so hoping I'm not opening a duplicate issue)

At this moment, there is the --version option to show the version of PHPCS itself, the -i option to show which (external) standards are installed and the --config-show option which provides information on the configuration used.

# phpcs --version
PHP_CodeSniffer version 3.5.0 (stable) by Squiz (http://www.squiz.net)

# phpcs -i
The installed coding standards are MySource, PEAR, PSR1, PSR12, PSR2, Squiz, Zend, PHPCompatibility, Debug, PHPCSDev, WordPress, WordPress-Core, WordPress-Docs, WordPress-Extra, WPThemeReview, Joomla and Symfony

# phpcs --config-show
Using config file: /path/to/PHP_CodeSniffer/CodeSniffer.conf                                                                                     
                                                                                                                                                            
installed_paths: /path/to/PHPCompatibility,/path/to/PHPCSDevTools,/path/to/WordPress,/path/to/WPThemeReview,/path/to/Joomla-coding-standards,/path/to/Symfony-coding-standard
report_width:    90                                                                                                                                         

I believe it would be helpful if there was a command-line option available which would combine some of this information.

For this to work as I envision, external standards would need to be allowed to pass their version number on to PHPCS through the XML ruleset.

Something along the lines of:

<ruleset
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    name="PHPCSDev"
    namespace="PHPCSStandards\PHPCSDev"
    version="1.0.0"
    xsi:noNamespaceSchemaLocation="https://raw.githubusercontent.com/squizlabs/PHP_CodeSniffer/master/phpcs.xsd">
    ...
</ruleset>

This would require a change to the phpcs.xsd file along the lines of adding the below to the <xs:element name="ruleset"> block:

            <xs:attribute name="version" type="xs:string"></xs:attribute>

Secondly, either one of the above mentioned command-line options would need to be adjusted or a new one should be introduced, let's call it --list-standards for now.

I imagine the output could then look something like this:

# phpcs --list-standards
PHP_CodeSniffer version 3.5.0 (stable) by Squiz (http://www.squiz.net)

Standards        | Version   | Installed path
---------------------------------------------------------------
MySource         | 3.5.0     | N/A (build-in)
PEAR             | 3.5.0     | N/A (build-in)
PSR1             | 3.5.0     | N/A (build-in)
PSR2             | 3.5.0     | N/A (build-in)
PSR12            | 3.5.0     | N/A (build-in)
Squiz            | 3.5.0     | N/A (build-in)
Zend             | 3.5.0     | N/A (build-in)
Debug            | 1.0.0     | /path/to/PHPCSDevTools
Joomla           | 2.0.0-rc3 | /path/to/Joomla-coding-standards
PHPCompatibility | 9.3.0     | /path/to/PHPCompatibility
PHPCSDev         | 1.0.0     | /path/to/PHPCSDevTools
Symfony          | 3.9.0     | /path/to/Symfony-coding-standard
WordPress        | 2.1.1     | /path/to/WordPress
WordPress-Core   | 2.1.1     | /path/to/WordPress
WordPress-Docs   | 2.1.1     | /path/to/WordPress
WordPress-Extra  | 2.1.1     | /path/to/WordPress
WPThemeReview    | 0.2.0     | /path/to/WPThemeReview

For standards which do not (yet) supply the version number via the ruleset.xml file, it could be tried to retrieve the version number via a composer --show in case of a Composer based install.

For non-Composer based installs, the version could either be left empty of be listed as Unknown.

Also take note of the ordering of the list: build-in standards first and then external standards in alphabetic order using natsort.

Opinions ?

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See the original issue for additional considerations.