bug #18635 [Console] Prevent fatal error when calling Command::getHel…

…per without helperSet (chalasr)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #18635).

Discussion
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[Console] Prevent fatal error when calling Command::getHelper without helperSet

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #18619
| License       | MIT
| Doc PR        | n/a

Patch attached to #18619

Commits
-------

31285c2 [Console][#18619] Prevent fatal error when calling Command#getHelper() without helperSet

src/Symfony/Component/Console/Command/Command.php

@@ -537,10 +537,15 @@ public function getSynopsis()
      *
      * @return mixed The helper value
      *
+     * @throws \LogicException           if no HelperSet is defined
      * @throws \InvalidArgumentException if the helper is not defined
      */
     public function getHelper($name)
     {
+        if (null === $this->helperSet) {
+            throw new \LogicException(sprintf('Cannot retrieve helper "%s" because there is no HelperSet defined. Did you forget to add your command to the application or to set the application on the command using the setApplication() method? You can also set the HelperSet directly using the setHelperSet() method.', $name));
+        }
+
         return $this->helperSet->get($name);
     }
 

src/Symfony/Component/Console/Tests/Command/CommandTest.php

@@ -173,6 +173,16 @@ public function testGetHelper()
         $this->assertEquals($formatterHelper->getName(), $command->getHelper('formatter')->getName(), '->getHelper() returns the correct helper');
     }
 
+    /**
+     * @expectedException        \LogicException
+     * @expectedExceptionMessage Cannot retrieve helper "formatter" because there is no HelperSet defined.
+     */
+    public function testGetHelperWithoutHelperSet()
+    {
+        $command = new \TestCommand();
+        $command->getHelper('formatter');
+    }
+
     public function testMergeApplicationDefinition()
     {
         $application1 = new Application();