Merge branch '2.8' into 3.2

* 2.8:
  move provider after test
  update dataProvider function name
  cast substr result to string and remove empty function use
  rename dataset provider
  Add a test to prevent future regressions
  Switch to `empty` native function to check emptiness
  remove non relevant test case
  Switch to `is_string` native method
  Remove unnecessary parentheses
  Add a test case to prevent future regressions
  Move empty condition in return statement
  Use LF line separator
  fix coding standard to comply with fabbot
  Remove malformed EmailValidatorTest + Update UrlValidator test
  Add empty check on host in other methods + add unit tests
  [Validator] Allow checkMX() to return false when $host is empty
  [DI] Prevent AutowirePass from triggering irrelevant deprecations
  [DI] Fix the xml schema
  [Translation] avoid creating cache files for fallback locales.

Author: nicolas-grekas

Tests/TranslatorCacheTest.php

@@ -149,6 +149,17 @@ public function testDifferentTranslatorsForSameLocaleDoNotOverwriteEachOthersCac
         $this->assertEquals('OK', $translator->trans($msgid), '-> the cache was overwritten by another translator instance in '.($debug ? 'debug' : 'production'));
     }
 
+    public function testGeneratedCacheFilesAreOnlyBelongRequestedLocales()
+    {
+        $translator = new Translator('a', null, $this->tmpDir);
+        $translator->setFallbackLocales(array('b'));
+        $translator->trans('bar');
+
+        $cachedFiles = glob($this->tmpDir.'/*.php');
+
+        $this->assertCount(1, $cachedFiles);
+    }
+
     public function testDifferentCacheFilesAreUsedForDifferentSetsOfFallbackLocales()
     {
         /*

Translator.php

@@ -386,7 +386,7 @@ private function loadFallbackCatalogues($locale)
 
         foreach ($this->computeFallbackLocales($locale) as $fallback) {
             if (!isset($this->catalogues[$fallback])) {
-                $this->loadCatalogue($fallback);
+                $this->initializeCatalogue($fallback);
             }
 
             $fallbackCatalogue = new MessageCatalogue($fallback, $this->catalogues[$fallback]->all());