[DI] Fix accepting null as default env param value

Author: nicolas-grekas

ParameterBag/EnvPlaceholderParameterBag.php

@@ -96,7 +96,7 @@ public function resolve()
             }
             if (is_numeric($default = $this->parameters[$name])) {
                 $this->parameters[$name] = (string) $default;
-            } elseif (!is_string($default)) {
+            } elseif (null !== $default && !is_string($default)) {
                 throw new RuntimeException(sprintf('The default value of env parameter "%s" must be string or null, %s given.', $env, gettype($default)));
             }
         }

Tests/ParameterBag/EnvPlaceholderParameterBagTest.php

@@ -113,21 +113,30 @@ public function testMergeWithDifferentIdentifiersForPlaceholders()
     public function testResolveEnvCastsIntToString()
     {
         $bag = new EnvPlaceholderParameterBag();
-        $bag->get('env(INT)');
-        $bag->set('env(INT)', 2);
+        $bag->get('env(INT_VAR)');
+        $bag->set('env(Int_Var)', 2);
         $bag->resolve();
-        $this->assertSame('2', $bag->all()['env(int)']);
+        $this->assertSame('2', $bag->all()['env(int_var)']);
+    }
+
+    public function testResolveEnvAllowsNull()
+    {
+        $bag = new EnvPlaceholderParameterBag();
+        $bag->get('env(NULL_VAR)');
+        $bag->set('env(Null_Var)', null);
+        $bag->resolve();
+        $this->assertNull($bag->all()['env(null_var)']);
     }
 
     /**
      * @expectedException \Symfony\Component\DependencyInjection\Exception\RuntimeException
-     * @expectedExceptionMessage The default value of env parameter "ARRAY" must be string or null, array given.
+     * @expectedExceptionMessage The default value of env parameter "ARRAY_VAR" must be string or null, array given.
      */
     public function testResolveThrowsOnBadDefaultValue()
     {
         $bag = new EnvPlaceholderParameterBag();
-        $bag->get('env(ARRAY)');
-        $bag->set('env(ARRAY)', array());
+        $bag->get('env(ARRAY_VAR)');
+        $bag->set('env(Array_Var)', array());
         $bag->resolve();
     }
 }