Config: show user friendly error message when ini change failed

Inspired by discussion 415.

Previously, when a PHP ini option which cannot be changed at runtime was passed to PHPCS, it would be silently ignored (by PHP, PHPCS would still try to handle it, but would not report that PHP did not change the value).

This commit changes that behaviour by adding a new "ERROR: Ini option %s cannot be set at runtime" error to alert the end-user to the fact that they are passing a PHP ini option which PHPCS cannot change.

The new error will be thrown both when the user passes the invalid ini setting via the command line, as well as when it is passed via a custom ruleset.

The behaviour when trying to change an ini setting which _doesn't exist_ (typo, extension not available) is unchanged. In that case, the ini directive will still be silently ignored.

Includes unit tests to safeguard the new behaviour.

Closes 416

Also note: when this error occurs due to an invalid setting being passed via a ruleset, the error will be thrown directly and not collected via the `MessageCollector`. This is due to the error coming from the `Config` class.
Once the `MessageCollector` would be implemented in the `Config` class, this can potentially be changed.

Author: jrfnl

.github/workflows/test.yml

@@ -65,6 +65,15 @@ jobs:
           - php: '8.4'
             skip_tests: true
 
+          # Run a couple of builds with custom extensions to allow for testing ini handling within PHPCS.
+          # Ref: https://github.com/PHPCSStandards/PHP_CodeSniffer/issues/416
+          - php: '7.3'
+            os: 'ubuntu-latest'
+            extensions: ':mysqli' # Run with mysqli disabled.
+          - php: '8.2'
+            os: 'ubuntu-latest'
+            extensions: ':mysqli' # Run with mysqli disabled.
+
           # The default libxml library on Ubuntu images is a little out of date.
           # To safeguard support for the latest libxml we need to update the library on the fly.
           # This only needs to be tested with one PHP version for each libxml minor to verify support.
@@ -183,6 +192,7 @@ jobs:
         with:
           php-version: ${{ matrix.php }}
           ini-values: ${{ steps.set_ini.outputs.PHP_INI }}
+          extensions: ${{ matrix.extensions }}
           coverage: none
           tools: cs2pr
 
@@ -269,10 +279,12 @@ jobs:
         custom_ini: [false]
 
         include:
-          # Also run one coverage build with custom ini settings.
+          # Also run one coverage build with custom ini settings for testing the DisallowShortOpenTag sniff.
+          # Also run with a disabled extension for testing the handling of unsettable ini settings by PHPCS.
           - php: '8.1'
             os: 'ubuntu-latest'
             custom_ini: true
+            extensions: ':mysqli' # Run with mysqli disabled.
 
     # yamllint disable-line rule:line-length
     name: "Coverage: ${{ matrix.php }} ${{ matrix.custom_ini && ' with custom ini settings' || '' }} (${{ matrix.os == 'ubuntu-latest' && 'Linux' || 'Win'  }})"
@@ -297,6 +309,7 @@ jobs:
         with:
           php-version: ${{ matrix.php }}
           ini-values: error_reporting=-1, display_errors=On${{ steps.set_ini.outputs.PHP_INI }}
+          extensions: ${{ matrix.extensions }}
           coverage: xdebug
 
       # Install dependencies and handle caching in one go.

src/Config.php

@@ -739,10 +739,23 @@ public function processShortArgument($arg, $pos)
         case 'd' :
             $ini = explode('=', $this->cliArgs[($pos + 1)]);
             $this->cliArgs[($pos + 1)] = '';
-            if (isset($ini[1]) === true) {
-                ini_set($ini[0], $ini[1]);
-            } else {
-                ini_set($ini[0], true);
+            if (isset($ini[1]) === false) {
+                // Set to true.
+                $ini[1] = '1';
+            }
+
+            $current = ini_get($ini[0]);
+            if ($current === false) {
+                // Ini setting which doesn't exist, or is from an unavailable extension.
+                // Silently ignore it.
+                break;
+            }
+
+            $changed = ini_set($ini[0], $ini[1]);
+            if ($changed === false && ini_get($ini[0]) !== $ini[1]) {
+                $error  = sprintf('ERROR: Ini option "%s" cannot be changed at runtime.', $ini[0]).PHP_EOL;
+                $error .= $this->printShortUsage(true);
+                throw new DeepExitException($error, 3);
             }
             break;
         case 'n' :