bug #30247 Don't resolve the Deprecation error handler mode until a d…

…eprecation is triggered (ossinkine)

This PR was merged into the 3.4 branch.

Discussion
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Don't resolve the Deprecation error handler mode until a deprecation is triggered

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #30047
| License       | MIT

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If an error happens before `.env.test` is loaded the mode is set to 0 and cached so SYMFONY_DEPRECATIONS_HELPER is not read from `.env.test`.

Commits
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1090b8c Don't resolve the Deprecation error handler mode until a deprecation is triggered

src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler.php

@@ -105,8 +105,7 @@ public static function register($mode = 0)
             'remaining vendor' => array(),
         );
         $deprecationHandler = function ($type, $msg, $file, $line, $context = array()) use (&$deprecations, $getMode, $UtilPrefix, $inVendors) {
-            $mode = $getMode();
-            if ((E_USER_DEPRECATED !== $type && E_DEPRECATED !== $type) || DeprecationErrorHandler::MODE_DISABLED === $mode) {
+            if ((E_USER_DEPRECATED !== $type && E_DEPRECATED !== $type) || DeprecationErrorHandler::MODE_DISABLED === $mode = $getMode()) {
                 $ErrorHandler = $UtilPrefix.'ErrorHandler';
 
                 return $ErrorHandler::handleError($type, $msg, $file, $line, $context);