bug #15794 [Console] default to stderr in the console helpers (alcohol)

This PR was squashed before being merged into the 2.3 branch (closes #15794).

Discussion
----------

[Console] default to stderr in the console helpers

Interactive input/output and informational output such as progress should go to `stderr` if available.

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

See #13730 also for previous discussion.

If someone explicitly wants to use `stdout`, they can simply pass `$output->getStream()` instead of `$output` in most use-cases.

Commits
-------

3d4e95e [Console] default to stderr in the console helpers

Helper/DialogHelper.php

@@ -11,6 +11,7 @@
 
 namespace Symfony\Component\Console\Helper;
 
+use Symfony\Component\Console\Output\ConsoleOutputInterface;
 use Symfony\Component\Console\Output\OutputInterface;
 use Symfony\Component\Console\Formatter\OutputFormatterStyle;
 
@@ -42,6 +43,10 @@ class DialogHelper extends Helper
      */
     public function select(OutputInterface $output, $question, $choices, $default = null, $attempts = false, $errorMessage = 'Value "%s" is invalid', $multiselect = false)
     {
+        if ($output instanceof ConsoleOutputInterface) {
+            $output = $output->getErrorOutput();
+        }
+
         $width = max(array_map('strlen', array_keys($choices)));
 
         $messages = (array) $question;
@@ -98,6 +103,10 @@ public function select(OutputInterface $output, $question, $choices, $default =
      */
     public function ask(OutputInterface $output, $question, $default = null, array $autocomplete = null)
     {
+        if ($output instanceof ConsoleOutputInterface) {
+            $output = $output->getErrorOutput();
+        }
+
         $output->write($question);
 
         $inputStream = $this->inputStream ?: STDIN;
@@ -255,6 +264,10 @@ public function askConfirmation(OutputInterface $output, $question, $default = t
      */
     public function askHiddenResponse(OutputInterface $output, $question, $fallback = true)
     {
+        if ($output instanceof ConsoleOutputInterface) {
+            $output = $output->getErrorOutput();
+        }
+
         if ('\\' === DIRECTORY_SEPARATOR) {
             $exe = __DIR__.'/../Resources/bin/hiddeninput.exe';
 
@@ -452,6 +465,10 @@ private function hasSttyAvailable()
      */
     private function validateAttempts($interviewer, OutputInterface $output, $validator, $attempts)
     {
+        if ($output instanceof ConsoleOutputInterface) {
+            $output = $output->getErrorOutput();
+        }
+
         $e = null;
         while (false === $attempts || $attempts--) {
             if (null !== $e) {

Helper/ProgressHelper.php

@@ -11,6 +11,7 @@
 
 namespace Symfony\Component\Console\Helper;
 
+use Symfony\Component\Console\Output\ConsoleOutputInterface;
 use Symfony\Component\Console\Output\OutputInterface;
 
 /**
@@ -182,6 +183,10 @@ public function setRedrawFrequency($freq)
      */
     public function start(OutputInterface $output, $max = null)
     {
+        if ($output instanceof ConsoleOutputInterface) {
+            $output = $output->getErrorOutput();
+        }
+
         $this->startTime = time();
         $this->current = 0;
         $this->max = (int) $max;

Tests/Helper/DialogHelperTest.php

@@ -14,6 +14,7 @@
 use Symfony\Component\Console\Helper\DialogHelper;
 use Symfony\Component\Console\Helper\HelperSet;
 use Symfony\Component\Console\Helper\FormatterHelper;
+use Symfony\Component\Console\Output\ConsoleOutput;
 use Symfony\Component\Console\Output\StreamOutput;
 
 class DialogHelperTest extends \PHPUnit_Framework_TestCase
@@ -50,6 +51,22 @@ public function testSelect()
         $this->assertEquals(array('0', '1'), $dialog->select($this->getOutputStream(), 'What is your favorite superhero?', $heroes, ' 0 , 1 ', false, 'Input "%s" is not a superhero!', true));
     }
 
+    public function testSelectOnErrorOutput()
+    {
+        $dialog = new DialogHelper();
+
+        $helperSet = new HelperSet(array(new FormatterHelper()));
+        $dialog->setHelperSet($helperSet);
+
+        $heroes = array('Superman', 'Batman', 'Spiderman');
+
+        $dialog->setInputStream($this->getInputStream("Stdout\n1\n"));
+        $this->assertEquals('1', $dialog->select($output = $this->getConsoleOutput($this->getOutputStream()), 'What is your favorite superhero?', $heroes, null, false, 'Input "%s" is not a superhero!', false));
+
+        rewind($output->getErrorOutput()->getStream());
+        $this->assertContains('Input "Stdout" is not a superhero!', stream_get_contents($output->getErrorOutput()->getStream()));
+    }
+
     public function testAsk()
     {
         $dialog = new DialogHelper();
@@ -63,6 +80,22 @@ public function testAsk()
         $this->assertEquals('What time is it?', stream_get_contents($output->getStream()));
     }
 
+    public function testAskOnErrorOutput()
+    {
+        if (!$this->hasSttyAvailable()) {
+            $this->markTestSkipped('`stderr` is required to test stderr output functionality');
+        }
+
+        $dialog = new DialogHelper();
+
+        $dialog->setInputStream($this->getInputStream("not stdout\n"));
+
+        $this->assertEquals('not stdout', $dialog->ask($output = $this->getConsoleOutput($this->getOutputStream()), 'Where should output go?', 'stderr'));
+
+        rewind($output->getErrorOutput()->getStream());
+        $this->assertEquals('Where should output go?', stream_get_contents($output->getErrorOutput()->getStream()));
+    }
+
     public function testAskWithAutocomplete()
     {
         if (!$this->hasSttyAvailable()) {
@@ -110,6 +143,25 @@ public function testAskHiddenResponse()
         $this->assertEquals('8AM', $dialog->askHiddenResponse($this->getOutputStream(), 'What time is it?'));
     }
 
+    /**
+     * @group tty
+     */
+    public function testAskHiddenResponseOnErrorOutput()
+    {
+        if ('\\' === DIRECTORY_SEPARATOR) {
+            $this->markTestSkipped('This test is not supported on Windows');
+        }
+
+        $dialog = new DialogHelper();
+
+        $dialog->setInputStream($this->getInputStream("8AM\n"));
+
+        $this->assertEquals('8AM', $dialog->askHiddenResponse($output = $this->getConsoleOutput($this->getOutputStream()), 'What time is it?'));
+
+        rewind($output->getErrorOutput()->getStream());
+        $this->assertContains('What time is it?', stream_get_contents($output->getErrorOutput()->getStream()));
+    }
+
     public function testAskConfirmation()
     {
         $dialog = new DialogHelper();
@@ -149,10 +201,12 @@ public function testAskAndValidate()
 
         $dialog->setInputStream($this->getInputStream("green\nyellow\norange\n"));
         try {
-            $this->assertEquals('white', $dialog->askAndValidate($this->getOutputStream(), $question, $validator, 2, 'white'));
+            $this->assertEquals('white', $dialog->askAndValidate($output = $this->getConsoleOutput($this->getOutputStream()), $question, $validator, 2, 'white'));
             $this->fail();
         } catch (\InvalidArgumentException $e) {
             $this->assertEquals($error, $e->getMessage());
+            rewind($output->getErrorOutput()->getStream());
+            $this->assertContains('What color was the white horse of Henry IV?', stream_get_contents($output->getErrorOutput()->getStream()));
         }
     }
 
@@ -170,6 +224,19 @@ protected function getOutputStream()
         return new StreamOutput(fopen('php://memory', 'r+', false));
     }
 
+    protected function getConsoleOutput($stderr)
+    {
+        $output = new ConsoleOutput();
+        $output->setErrorOutput($stderr);
+
+        return $output;
+    }
+
+    private function hasStderrSupport()
+    {
+        return false === $this->isRunningOS400();
+    }
+
     private function hasSttyAvailable()
     {
         exec('stty 2>&1', $output, $exitcode);