[Process] Add feature \"wait until callback\" to process class

src/Symfony/Component/Process/CHANGELOG.md

@@ -7,6 +7,8 @@ CHANGELOG
  * added the `Process::fromShellCommandline()` to run commands in a shell wrapper
  * deprecated passing a command as string when creating a `Process` instance
  * deprecated the `Process::setCommandline()` and the `PhpProcess::setPhpBinary()` methods
+ * added the `Process::waitUntil()` method to wait for the process only for a
+   specific output, then continue the normal execution of your application
 
 4.1.0
 -----

src/Symfony/Component/Process/Process.php

@@ -407,7 +407,7 @@ class Process implements \IteratorAggregate
         if (null !== $callback) {
             if (!$this->processPipes->haveReadSupport()) {
                 $this->stop(0);
-                throw new \LogicException('Pass the callback to the Process::start method or enableOutput to use a callback with Process::wait');
+                throw new \LogicException('Pass the callback to the "Process::start" method or call enableOutput to use a callback with "Process::wait"');
             }
             $this->callback = $this->buildCallback($callback);
         }
@@ -429,6 +429,45 @@ class Process implements \IteratorAggregate
         return $this->exitcode;
     }
 
+    /**
+     * Waits until the callback returns true.
+     *
+     * The callback receives the type of output (out or err) and some bytes
+     * from the output in real-time while writing the standard input to the process.
+     * It allows to have feedback from the independent process during execution.
+     *
+     * @param callable $callback
+     *
+     * @throws RuntimeException When process timed out
+     * @throws LogicException   When process is not yet started
+     */
+    public function waitUntil(callable $callback)
+    {
+        $this->requireProcessIsStarted(__FUNCTION__);
+        $this->updateStatus(false);
+
+        if (!$this->processPipes->haveReadSupport()) {
+            $this->stop(0);
+            throw new \LogicException('Pass the callback to the "Process::start" method or call enableOutput to use a callback with "Process::waitUntil".');
+        }
+        $callback = $this->buildCallback($callback);
+
+        $wait = true;
+        do {
+            $this->checkTimeout();
+            $running = '\\' === \DIRECTORY_SEPARATOR ? $this->isRunning() : $this->processPipes->areOpen();
+            $output = $this->processPipes->readAndWrite($running, '\\' !== \DIRECTORY_SEPARATOR || !$running);
+
+            foreach ($output as $type => $data) {
+                if (3 !== $type) {
+                    $wait = !$callback(self::STDOUT === $type ? self::OUT : self::ERR, $data);
+                } elseif (!isset($this->fallbackStatus['signaled'])) {
+                    $this->fallbackStatus['exitcode'] = (int) $data;
+                }
+            }
+        } while ($wait);
+    }
+
     /**
      * Returns the Pid (process identifier), if applicable.
      *
@@ -1264,7 +1303,7 @@ class Process implements \IteratorAggregate
         if ($this->outputDisabled) {
             return function ($type, $data) use ($callback) {
                 if (null !== $callback) {
-                    \call_user_func($callback, $type, $data);
+                    return \call_user_func($callback, $type, $data);
                 }
             };
         }
@@ -1279,7 +1318,7 @@ class Process implements \IteratorAggregate
             }
 
             if (null !== $callback) {
-                \call_user_func($callback, $type, $data);
+                return \call_user_func($callback, $type, $data);
             }
         };
     }

src/Symfony/Component/Process/Tests/KillableProcessWithOutput.php

@@ -0,0 +1,26 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+$outputs = array(
+    'First iteration output',
+    'Second iteration output',
+    'One more iteration output',
+    'This took more time',
+    'This one was sooooo slow',
+);
+
+$iterationTime = 10000;
+
+foreach ($outputs as $output) {
+    usleep($iterationTime);
+    $iterationTime *= 10;
+    echo $output."\n";
+}

src/Symfony/Component/Process/Tests/ProcessTest.php

@@ -133,6 +133,33 @@ class ProcessTest extends TestCase
         $this->assertLessThan(15, microtime(true) - $start);
     }
 
+    public function testWaitUntilSpecificOutput()
+    {
+        $p = $this->getProcess(array(self::$phpBin, __DIR__.'/KillableProcessWithOutput.php'));
+        $p->start();
+
+        $start = microtime(true);
+
+        $completeOutput = '';
+        $p->waitUntil(function ($type, $output) use (&$completeOutput) {
+            $completeOutput .= $output;
+            if (false !== strpos($output, 'One more')) {
+                return true;
+            }
+
+            return false;
+        });
+        $p->stop();
+
+        if ('\\' === \DIRECTORY_SEPARATOR) {
+            // Windows is slower
+            $this->assertLessThan(15, microtime(true) - $start);
+        } else {
+            $this->assertLessThan(2, microtime(true) - $start);
+        }
+        $this->assertEquals("First iteration output\nSecond iteration output\nOne more iteration output\n", $completeOutput);
+    }
+
     public function testAllOutputIsActuallyReadOnTermination()
     {
         // this code will result in a maximum of 2 reads of 8192 bytes by calling