feature #19681 [DI] Allow injecting ENV parameters at runtime using %env(MY_ENV_VAR)% (nicolas-grekas)

This PR was merged into the 3.2-dev branch.

Discussion
----------

[DI] Allow injecting ENV parameters at runtime using %env(MY_ENV_VAR)%

| Q             | A
| ------------- | ---
| Branch?       | master
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |  #10138, #7555, #16403, #18155
| License       | MIT
| Doc PR        | https://github.com/symfony/symfony-docs/pull/6918

This is an alternative approach to #18155 for injecting env vars into container configurations.

With this PR, anywhere parameters are allowed, one can use `%env(ENV_VAR)%` to inject a dynamic env var. Additionally, if one sets a value to such parameters in e.g. the `parameter.yml` file (`env(ENV_VAR): foo`), this value will be used as a default value when the env var is not defined. If no default value is specified, an `EnvVarNotFoundException` will be thrown at runtime.

Unlike previous attempts that also used parameters (#16403), the implementation is compatible with DI extensions: before being dumped, env vars are resolved to uniquely identifiable string placeholders that can get through DI extensions manipulations. When dumped, these unique placeholders are replaced by dynamic calls to a getEnv method..

ping @magnusnordlander @dzuelke @fabpot

Commits
-------

bac2132 [DI] Allow injecting ENV parameters at runtime using %env(MY_ENV_VAR)% syntax

src/Symfony/Component/DependencyInjection/Compiler/Compiler.php

@@ -12,6 +12,7 @@
 namespace Symfony\Component\DependencyInjection\Compiler;
 
 use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\Exception\EnvParameterException;
 
 /**
  * This class is used to remove circular dependencies between individual passes.
@@ -108,8 +109,29 @@ class Compiler
      */
     public function compile(ContainerBuilder $container)
     {
-        foreach ($this->passConfig->getPasses() as $pass) {
-            $pass->process($container);
+        try {
+            foreach ($this->passConfig->getPasses() as $pass) {
+                $pass->process($container);
+            }
+        } catch (\Exception $e) {
+            $usedEnvs = array();
+            $prev = $e;
+
+            do {
+                $msg = $prev->getMessage();
+
+                if ($msg !== $resolvedMsg = $container->resolveEnvPlaceholders($msg, null, $usedEnvs)) {
+                    $r = new \ReflectionProperty($prev, 'message');
+                    $r->setAccessible(true);
+                    $r->setValue($prev, $resolvedMsg);
+                }
+            } while ($prev = $prev->getPrevious());
+
+            if ($usedEnvs) {
+                $e = new EnvParameterException($usedEnvs, $e);
+            }
+
+            throw $e;
         }
     }
 }

src/Symfony/Component/DependencyInjection/Container.php

@@ -11,11 +11,12 @@
 
 namespace Symfony\Component\DependencyInjection;
 
+use Symfony\Component\DependencyInjection\Exception\EnvNotFoundException;
 use Symfony\Component\DependencyInjection\Exception\InvalidArgumentException;
 use Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException;
 use Symfony\Component\DependencyInjection\Exception\ServiceCircularReferenceException;
 use Symfony\Component\DependencyInjection\ParameterBag\ParameterBagInterface;
-use Symfony\Component\DependencyInjection\ParameterBag\ParameterBag;
+use Symfony\Component\DependencyInjection\ParameterBag\EnvPlaceholderParameterBag;
 use Symfony\Component\DependencyInjection\ParameterBag\FrozenParameterBag;
 
 /**
@@ -70,13 +71,14 @@ class Container implements ResettableContainerInterface
     protected $loading = array();
 
     private $underscoreMap = array('_' => '', '.' => '_', '\\' => '_');
+    private $envCache = array();
 
     /**
      * @param ParameterBagInterface $parameterBag A ParameterBagInterface instance
      */
     public function __construct(ParameterBagInterface $parameterBag = null)
     {
-        $this->parameterBag = $parameterBag ?: new ParameterBag();
+        $this->parameterBag = $parameterBag ?: new EnvPlaceholderParameterBag();
     }
 
     /**
@@ -373,6 +375,33 @@ class Container implements ResettableContainerInterface
         return strtolower(preg_replace(array('/([A-Z]+)([A-Z][a-z])/', '/([a-z\d])([A-Z])/'), array('\\1_\\2', '\\1_\\2'), str_replace('_', '.', $id)));
     }
 
+    /**
+     * Fetches a variable from the environment.
+     *
+     * @param string The name of the environment variable
+     *
+     * @return scalar The value to use for the provided environment variable name
+     *
+     * @throws EnvNotFoundException When the environment variable is not found and has no default value
+     */
+    protected function getEnv($name)
+    {
+        if (isset($this->envCache[$name]) || array_key_exists($name, $this->envCache)) {
+            return $this->envCache[$name];
+        }
+        if (isset($_ENV[$name])) {
+            return $this->envCache[$name] = $_ENV[$name];
+        }
+        if (false !== $env = getenv($name)) {
+            return $this->envCache[$name] = $env;
+        }
+        if (!$this->hasParameter("env($name)")) {
+            throw new EnvNotFoundException($name);
+        }
+
+        return $this->envCache[$name] = $this->getParameter("env($name)");
+    }
+
     private function __clone()
     {
     }

src/Symfony/Component/DependencyInjection/ContainerBuilder.php

@@ -21,6 +21,7 @@ use Symfony\Component\DependencyInjection\Exception\RuntimeException;
 use Symfony\Component\DependencyInjection\Exception\ServiceCircularReferenceException;
 use Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException;
 use Symfony\Component\DependencyInjection\Extension\ExtensionInterface;
+use Symfony\Component\DependencyInjection\ParameterBag\EnvPlaceholderParameterBag;
 use Symfony\Component\Config\Resource\FileResource;
 use Symfony\Component\Config\Resource\ResourceInterface;
 use Symfony\Component\DependencyInjection\LazyProxy\Instantiator\InstantiatorInterface;
@@ -89,6 +90,16 @@ class ContainerBuilder extends Container implements TaggedContainerInterface
      */
     private $usedTags = array();
 
+    /**
+     * @var string[][] A map of env var names to their placeholders
+     */
+    private $envPlaceholders = array();
+
+    /**
+     * @var int[] A map of env vars to their resolution counter.
+     */
+    private $envCounters = array();
+
     private $compiled = false;
 
     /**
@@ -482,6 +493,18 @@ class ContainerBuilder extends Container implements TaggedContainerInterface
 
             $this->extensionConfigs[$name] = array_merge($this->extensionConfigs[$name], $container->getExtensionConfig($name));
         }
+
+        if ($this->getParameterBag() instanceof EnvPlaceholderParameterBag && $container->getParameterBag() instanceof EnvPlaceholderParameterBag) {
+            $this->getParameterBag()->mergeEnvPlaceholders($container->getParameterBag());
+        }
+
+        foreach ($container->envCounters as $env => $count) {
+            if (!isset($this->envCounters[$env])) {
+                $this->envCounters[$env] = $count;
+            } else {
+                $this->envCounters[$env] += $count;
+            }
+        }
     }
 
     /**
@@ -552,8 +575,11 @@ class ContainerBuilder extends Container implements TaggedContainerInterface
         }
 
         $this->extensionConfigs = array();
+        $bag = $this->getParameterBag();
 
         parent::compile();
+
+        $this->envPlaceholders = $bag instanceof EnvPlaceholderParameterBag ? $bag->getEnvPlaceholders() : array();
     }
 
     /**
@@ -996,6 +1022,56 @@ class ContainerBuilder extends Container implements TaggedContainerInterface
         return $this->expressionLanguageProviders;
     }
 
+    /**
+     * Resolves env parameter placeholders in a string.
+     *
+     * @param string      $string    The string to resolve
+     * @param string|null $format    A sprintf() format to use as replacement for env placeholders or null to use the default parameter format
+     * @param array       &$usedEnvs Env vars found while resolving are added to this array
+     *
+     * @return string The string with env parameters resolved
+     */
+    public function resolveEnvPlaceholders($string, $format = null, array &$usedEnvs = null)
+    {
+        $bag = $this->getParameterBag();
+        $envPlaceholders = $bag instanceof EnvPlaceholderParameterBag ? $bag->getEnvPlaceholders() : $this->envPlaceholders;
+
+        if (null === $format) {
+            $format = '%%env(%s)%%';
+        }
+
+        foreach ($envPlaceholders as $env => $placeholders) {
+            foreach ($placeholders as $placeholder) {
+                if (false !== stripos($string, $placeholder)) {
+                    $string = str_ireplace($placeholder, sprintf($format, $env), $string);
+                    $usedEnvs[$env] = $env;
+                    $this->envCounters[$env] = isset($this->envCounters[$env]) ? 1 + $this->envCounters[$env] : 1;
+                }
+            }
+        }
+
+        return $string;
+    }
+
+    /**
+     * Get statistics about env usage.
+     *
+     * @return int[] The number of time each env vars has been resolved
+     */
+    public function getEnvCounters()
+    {
+        $bag = $this->getParameterBag();
+        $envPlaceholders = $bag instanceof EnvPlaceholderParameterBag ? $bag->getEnvPlaceholders() : $this->envPlaceholders;
+
+        foreach ($envPlaceholders as $env => $placeholders) {
+            if (!isset($this->envCounters[$env])) {
+                $this->envCounters[$env] = 0;
+            }
+        }
+
+        return $this->envCounters;
+    }
+
     /**
      * Returns the Service Conditionals.
      *

src/Symfony/Component/DependencyInjection/Dumper/GraphvizDumper.php

@@ -81,7 +81,7 @@ class GraphvizDumper extends Dumper
             }
         }
 
-        return $this->startDot().$this->addNodes().$this->addEdges().$this->endDot();
+        return $this->container->resolveEnvPlaceholders($this->startDot().$this->addNodes().$this->addEdges().$this->endDot(), '__ENV_%s__');
     }
 
     /**

src/Symfony/Component/DependencyInjection/Dumper/PhpDumper.php

@@ -18,6 +18,7 @@ use Symfony\Component\DependencyInjection\Container;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\DependencyInjection\Reference;
 use Symfony\Component\DependencyInjection\Parameter;
+use Symfony\Component\DependencyInjection\Exception\EnvParameterException;
 use Symfony\Component\DependencyInjection\Exception\InvalidArgumentException;
 use Symfony\Component\DependencyInjection\Exception\RuntimeException;
 use Symfony\Component\DependencyInjection\Exception\ServiceCircularReferenceException;
@@ -98,6 +99,8 @@ class PhpDumper extends Dumper
      * @param array $options An array of options
      *
      * @return string A PHP class representing of the service container
+     *
+     * @throws EnvParameterException When an env var exists but has not been dumped
      */
     public function dump(array $options = array())
     {
@@ -156,6 +159,16 @@ class PhpDumper extends Dumper
         ;
         $this->targetDirRegex = null;
 
+        $unusedEnvs = array();
+        foreach ($this->container->getEnvCounters() as $env => $use) {
+            if (!$use) {
+                $unusedEnvs[] = $env;
+            }
+        }
+        if ($unusedEnvs) {
+            throw new EnvParameterException($unusedEnvs);
+        }
+
         return $code;
     }
 
@@ -384,7 +397,7 @@ class PhpDumper extends Dumper
 
         $class = $this->dumpValue($class);
 
-        if (0 === strpos($class, "'") && !preg_match('/^\'[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*(\\\{2}[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*)*\'$/', $class)) {
+        if (0 === strpos($class, "'") && false === strpos($class, '$') && !preg_match('/^\'[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*(\\\{2}[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*)*\'$/', $class)) {
             throw new InvalidArgumentException(sprintf('"%s" is not a valid class name for the "%s" service.', $class, $id));
         }
 
@@ -539,7 +552,7 @@ class PhpDumper extends Dumper
 
             $class = $this->dumpValue($callable[0]);
             // If the class is a string we can optimize call_user_func away
-            if (strpos($class, "'") === 0) {
+            if (0 === strpos($class, "'") && false === strpos($class, '$')) {
                 return sprintf("        %s::%s(\$%s);\n", $this->dumpLiteralClass($class), $callable[1], $variableName);
             }
 
@@ -572,6 +585,7 @@ class PhpDumper extends Dumper
         if ($definition->isSynthetic()) {
             $return[] = '@throws RuntimeException always since this service is expected to be injected dynamically';
         } elseif ($class = $definition->getClass()) {
+            $class = $this->container->resolveEnvPlaceholders($class);
             $return[] = sprintf('@return %s A %s instance', 0 === strpos($class, '%') ? 'object' : '\\'.ltrim($class, '\\'), ltrim($class, '\\'));
         } elseif ($definition->getFactory()) {
             $factory = $definition->getFactory();
@@ -595,6 +609,7 @@ class PhpDumper extends Dumper
         }
 
         $return = str_replace("\n     * \n", "\n     *\n", implode("\n     * ", $return));
+        $return = $this->container->resolveEnvPlaceholders($return);
 
         $doc = '';
         if ($definition->isShared()) {
@@ -654,7 +669,7 @@ EOF;
             $code .= sprintf("        throw new RuntimeException('You have requested a synthetic service (\"%s\"). The DIC does not know how to construct this service.');\n    }\n", $id);
         } else {
             if ($definition->isDeprecated()) {
-                $code .= sprintf("        @trigger_error(%s, E_USER_DEPRECATED);\n\n", var_export($definition->getDeprecationMessage($id), true));
+                $code .= sprintf("        @trigger_error(%s, E_USER_DEPRECATED);\n\n", $this->export($definition->getDeprecationMessage($id)));
             }
 
             $code .=
@@ -720,7 +735,7 @@ EOF;
 
                 $class = $this->dumpValue($callable[0]);
                 // If the class is a string we can optimize call_user_func away
-                if (strpos($class, "'") === 0) {
+                if (0 === strpos($class, "'") && false === strpos($class, '$')) {
                     if ("''" === $class) {
                         throw new RuntimeException(sprintf('Cannot dump definition: The "%s" service is defined to be created by a factory but is missing the service reference, did you forget to define the factory service id or class?', $id));
                     }
@@ -735,7 +750,7 @@ EOF;
                 return sprintf("        $return{$instantiation}call_user_func(array(%s, '%s')%s);\n", $this->dumpValue($callable[0]), $callable[1], $arguments ? ', '.implode(', ', $arguments) : '');
             }
 
-            return sprintf("        $return{$instantiation}\\%s(%s);\n", $callable, $arguments ? implode(', ', $arguments) : '');
+            return sprintf("        $return{$instantiation}%s(%s);\n", $this->dumpLiteralClass($this->dumpValue($callable)), $arguments ? implode(', ', $arguments) : '');
         }
 
         if (false !== strpos($class, '$')) {
@@ -904,7 +919,7 @@ EOF;
         $code = "        \$this->methodMap = array(\n";
         ksort($definitions);
         foreach ($definitions as $id => $definition) {
-            $code .= '            '.var_export($id, true).' => '.var_export($this->generateMethodName($id), true).",\n";
+            $code .= '            '.$this->export($id).' => '.$this->export($this->generateMethodName($id)).",\n";
         }
 
         return $code."        );\n";
@@ -925,7 +940,7 @@ EOF;
         ksort($definitions);
         foreach ($definitions as $id => $definition) {
             if (!$definition->isPublic()) {
-                $code .= '            '.var_export($id, true)." => true,\n";
+                $code .= '            '.$this->export($id)." => true,\n";
             }
         }
 
@@ -962,7 +977,7 @@ EOF;
             while (isset($aliases[$id])) {
                 $id = (string) $aliases[$id];
             }
-            $code .= '            '.var_export($alias, true).' => '.var_export($id, true).",\n";
+            $code .= '            '.$this->export($alias).' => '.$this->export($id).",\n";
         }
 
         return $code."        );\n";
@@ -979,7 +994,23 @@ EOF;
             return '';
         }
 
-        $parameters = $this->exportParameters($this->container->getParameterBag()->all());
+        $php = array();
+        $dynamicPhp = array();
+
+        foreach ($this->container->getParameterBag()->all() as $key => $value) {
+            if ($key !== $resolvedKey = $this->container->resolveEnvPlaceholders($key)) {
+                throw new InvalidArgumentException(sprintf('Parameter name cannot use env parameters: %s.', $resolvedKey));
+            }
+            $export = $this->exportParameters(array($value));
+            $export = explode('0 => ', substr(rtrim($export, " )\n"), 7, -1), 2);
+
+            if (preg_match("/\\\$this->(?:getEnv\('\w++'\)|targetDirs\[\d++\])/", $export[1])) {
+                $dynamicPhp[$key] = sprintf('%scase %s: $value = %s; break;', $export[0], $this->export($key), $export[1]);
+            } else {
+                $php[] = sprintf('%s%s => %s,', $export[0], $this->export($key), $export[1]);
+            }
+        }
+        $parameters = sprintf("array(\n%s\n%s)", implode("\n", $php), str_repeat(' ', 8));
 
         $code = '';
         if ($this->container->isFrozen()) {
@@ -992,9 +1023,12 @@ EOF;
     {
         $name = strtolower($name);
 
-        if (!(isset($this->parameters[$name]) || array_key_exists($name, $this->parameters))) {
+        if (!(isset($this->parameters[$name]) || array_key_exists($name, $this->parameters) || isset($this->loadedDynamicParameters[$name]))) {
             throw new InvalidArgumentException(sprintf('The parameter "%s" must be defined.', $name));
         }
+        if (isset($this->loadedDynamicParameters[$name])) {
+            return $this->loadedDynamicParameters[$name] ? $this->dynamicParameters[$name] : $this->getDynamicParameter($name);
+        }
 
         return $this->parameters[$name];
     }
@@ -1006,7 +1040,7 @@ EOF;
     {
         $name = strtolower($name);
 
-        return isset($this->parameters[$name]) || array_key_exists($name, $this->parameters);
+        return isset($this->parameters[$name]) || array_key_exists($name, $this->parameters) || isset($this->loadedDynamicParameters[$name]);
     }
 
     /**
@@ -1023,7 +1057,11 @@ EOF;
     public function getParameterBag()
     {
         if (null === $this->parameterBag) {
-            $this->parameterBag = new FrozenParameterBag($this->parameters);
+            $parameters = $this->parameters;
+            foreach ($this->loadedDynamicParameters as $name => $loaded) {
+                $parameters[$name] = $loaded ? $this->dynamicParameters[$name] : $this->getDynamicParameter($name);
+            }
+            $this->parameterBag = new FrozenParameterBag($parameters);
         }
 
         return $this->parameterBag;
@@ -1033,6 +1071,46 @@ EOF;
             if ('' === $this->docStar) {
                 $code = str_replace('/**', '/*', $code);
             }
+
+            if ($dynamicPhp) {
+                $loadedDynamicParameters = $this->exportParameters(array_combine(array_keys($dynamicPhp), array_fill(0, count($dynamicPhp), false)), '', 8);
+                $getDynamicParameter = <<<'EOF'
+        switch ($name) {
+%s
+            default: throw new InvalidArgumentException(sprintf('The dynamic parameter "%%s" must be defined.', $name));
+        }
+        $this->loadedDynamicParameters[$name] = true;
+
+        return $this->dynamicParameters[$name] = $value;
+EOF;
+                $getDynamicParameter = sprintf($getDynamicParameter, implode("\n", $dynamicPhp));
+            } else {
+                $loadedDynamicParameters = 'array()';
+                $getDynamicParameter = str_repeat(' ', 8).'throw new InvalidArgumentException(sprintf(\'The dynamic parameter "%s" must be defined.\', $name));';
+            }
+
+            $code .= <<<EOF
+
+    private \$loadedDynamicParameters = {$loadedDynamicParameters};
+    private \$dynamicParameters = array();
+
+    /*{$this->docStar}
+     * Computes a dynamic parameter.
+     *
+     * @param string The name of the dynamic parameter to load
+     *
+     * @return mixed The value of the dynamic parameter
+     *
+     * @throws InvalidArgumentException When the dynamic parameter does not exist
+     */
+    private function getDynamicParameter(\$name)
+    {
+{$getDynamicParameter}
+    }
+
+EOF;
+        } elseif ($dynamicPhp) {
+            throw new RuntimeException('You cannot dump a not-frozen container with dynamic parameters.');
         }
 
         $code .= <<<EOF
@@ -1081,7 +1159,7 @@ EOF;
                 $value = $this->export($value);
             }
 
-            $php[] = sprintf('%s%s => %s,', str_repeat(' ', $indent), var_export($key, true), $value);
+            $php[] = sprintf('%s%s => %s,', str_repeat(' ', $indent), $this->export($key), $value);
         }
 
         return sprintf("array(\n%s\n%s)", implode("\n", $php), str_repeat(' ', $indent - 4));
@@ -1283,7 +1361,7 @@ EOF;
                 $factory = $value->getFactory();
 
                 if (is_string($factory)) {
-                    return sprintf('\\%s(%s)', $factory, implode(', ', $arguments));
+                    return sprintf('%s(%s)', $this->dumpLiteralClass($this->dumpValue($factory)), implode(', ', $arguments));
                 }
 
                 if (is_array($factory)) {
@@ -1358,7 +1436,7 @@ EOF;
     private function dumpLiteralClass($class)
     {
         if (false !== strpos($class, '$')) {
-            throw new RuntimeException('Cannot dump definitions which have a variable class name.');
+            return sprintf('${($_ = %s) && false ?: "_"}', $class);
         }
         if (0 !== strpos($class, "'") || !preg_match('/^\'[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*(\\\{2}[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*)*\'$/', $class)) {
             throw new RuntimeException(sprintf('Cannot dump definition because of invalid class name (%s)', $class ?: 'n/a'));
@@ -1534,9 +1612,9 @@ EOF;
     private function export($value)
     {
         if (null !== $this->targetDirRegex && is_string($value) && preg_match($this->targetDirRegex, $value, $matches, PREG_OFFSET_CAPTURE)) {
-            $prefix = $matches[0][1] ? var_export(substr($value, 0, $matches[0][1]), true).'.' : '';
+            $prefix = $matches[0][1] ? $this->doExport(substr($value, 0, $matches[0][1])).'.' : '';
             $suffix = $matches[0][1] + strlen($matches[0][0]);
-            $suffix = isset($value[$suffix]) ? '.'.var_export(substr($value, $suffix), true) : '';
+            $suffix = isset($value[$suffix]) ? '.'.$this->doExport(substr($value, $suffix)) : '';
             $dirname = '__DIR__';
 
             if (0 < $offset = 1 + $this->targetDirMaxMatches - count($matches)) {
@@ -1550,6 +1628,23 @@ EOF;
             return $dirname;
         }
 
-        return var_export($value, true);
+        return $this->doExport($value);
+    }
+
+    private function doExport($value)
+    {
+        $export = var_export($value, true);
+
+        if ("'" === $export[0] && $export !== $resolvedExport = $this->container->resolveEnvPlaceholders($export, "'.\$this->getEnv('%s').'")) {
+            $export = $resolvedExport;
+            if ("'" === $export[1]) {
+                $export = substr($export, 3);
+            }
+            if (".''" === substr($export, -3)) {
+                $export = substr($export, 0, -3);
+            }
+        }
+
+        return $export;
     }
 }

src/Symfony/Component/DependencyInjection/Dumper/XmlDumper.php

@@ -55,7 +55,7 @@ class XmlDumper extends Dumper
         $xml = $this->document->saveXML();
         $this->document = null;
 
-        return $xml;
+        return $this->container->resolveEnvPlaceholders($xml);
     }
 
     /**

src/Symfony/Component/DependencyInjection/Dumper/YamlDumper.php

@@ -46,7 +46,7 @@ class YamlDumper extends Dumper
             $this->dumper = new YmlDumper();
         }
 
-        return $this->addParameters()."\n".$this->addServices();
+        return $this->container->resolveEnvPlaceholders($this->addParameters()."\n".$this->addServices());
     }
 
     /**

src/Symfony/Component/DependencyInjection/Exception/EnvNotFoundException.php

@@ -0,0 +1,25 @@
+<?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.
+ */
+
+namespace Symfony\Component\DependencyInjection\Exception;
+
+/**
+ * This exception is thrown when an environment variable is not found.
+ *
+ * @author Nicolas Grekas <p@tchwork.com>
+ */
+class EnvNotFoundException extends InvalidArgumentException
+{
+    public function __construct($name)
+    {
+        parent::__construct(sprintf('Environment variable not found: "%s".', $name));
+    }
+}

src/Symfony/Component/DependencyInjection/Exception/EnvParameterException.php

@@ -0,0 +1,25 @@
+<?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.
+ */
+
+namespace Symfony\Component\DependencyInjection\Exception;
+
+/**
+ * This exception wraps exceptions whose messages contain a reference to an env parameter.
+ *
+ * @author Nicolas Grekas <p@tchwork.com>
+ */
+class EnvParameterException extends InvalidArgumentException
+{
+    public function __construct(array $usedEnvs, \Exception $previous = null)
+    {
+        parent::__construct(sprintf('Incompatible use of dynamic environment variables "%s" found in parameters.', implode('", "', $usedEnvs)), 0, $previous);
+    }
+}

src/Symfony/Component/DependencyInjection/ParameterBag/EnvPlaceholderParameterBag.php

@@ -0,0 +1,69 @@
+<?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.
+ */
+
+namespace Symfony\Component\DependencyInjection\ParameterBag;
+
+use Symfony\Component\DependencyInjection\Exception\RuntimeException;
+
+/**
+ * @author Nicolas Grekas <p@tchwork.com>
+ */
+class EnvPlaceholderParameterBag extends ParameterBag
+{
+    private $envPlaceholders = array();
+
+    /**
+     * {@inheritdoc}
+     */
+    public function get($name)
+    {
+        if (0 === strpos($name, 'env(') && ')' === substr($name, -1) && 'env()' !== $name) {
+            $env = substr($name, 4, -1);
+
+            if (isset($this->envPlaceholders[$env])) {
+                return $this->envPlaceholders[$env][0];
+            }
+            if (preg_match('/\W/', $env)) {
+                throw new InvalidArgumentException(sprintf('Invalid %s name: only "word" characters are allowed.', $name));
+            }
+
+            if ($this->has($name)) {
+                $defaultValue = parent::get($name);
+
+                if (!is_scalar($defaultValue)) {
+                    throw new RuntimeException(sprintf('The default value of an env() parameter must be scalar, but "%s" given to "%s".', gettype($defaultValue), $name));
+                }
+            }
+
+            return $this->envPlaceholders[$env][] = sprintf('env_%s_%s', $env, md5($name.uniqid(mt_rand(), true)));
+        }
+
+        return parent::get($name);
+    }
+
+    /**
+     * Returns the map of env vars used in the resolved parameter values to their placeholders.
+     *
+     * @return string[][] A map of env var names to their placeholders
+     */
+    public function getEnvPlaceholders()
+    {
+        return $this->envPlaceholders;
+    }
+
+    /**
+     * Merges the env placeholders of another EnvPlaceholderParameterBag.
+     */
+    public function mergeEnvPlaceholders(self $bag)
+    {
+        $this->envPlaceholders = array_merge_recursive($this->envPlaceholders, $bag->getEnvPlaceholders());
+    }
+}

src/Symfony/Component/DependencyInjection/ParameterBag/ParameterBag.php

@@ -205,13 +205,14 @@ class ParameterBag implements ParameterBagInterface
         // as the preg_replace_callback throw an exception when trying
         // a non-string in a parameter value
         if (preg_match('/^%([^%\s]+)%$/', $value, $match)) {
-            $key = strtolower($match[1]);
+            $key = $match[1];
+            $lcKey = strtolower($key);
 
-            if (isset($resolving[$key])) {
+            if (isset($resolving[$lcKey])) {
                 throw new ParameterCircularReferenceException(array_keys($resolving));
             }
 
-            $resolving[$key] = true;
+            $resolving[$lcKey] = true;
 
             return $this->resolved ? $this->get($key) : $this->resolveValue($this->get($key), $resolving);
         }
@@ -222,8 +223,9 @@ class ParameterBag implements ParameterBagInterface
                 return '%%';
             }
 
-            $key = strtolower($match[1]);
-            if (isset($resolving[$key])) {
+            $key = $match[1];
+            $lcKey = strtolower($key);
+            if (isset($resolving[$lcKey])) {
                 throw new ParameterCircularReferenceException(array_keys($resolving));
             }
 
@@ -234,7 +236,7 @@ class ParameterBag implements ParameterBagInterface
             }
 
             $resolved = (string) $resolved;
-            $resolving[$key] = true;
+            $resolving[$lcKey] = true;
 
             return $this->isResolved() ? $resolved : $this->resolveString($resolved, $resolving);
         }, $value);

src/Symfony/Component/DependencyInjection/Tests/ContainerBuilderTest.php

@@ -26,6 +26,7 @@ use Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException;
 use Symfony\Component\DependencyInjection\Loader\ClosureLoader;
 use Symfony\Component\DependencyInjection\Reference;
 use Symfony\Component\DependencyInjection\ParameterBag\ParameterBag;
+use Symfony\Component\DependencyInjection\ParameterBag\EnvPlaceholderParameterBag;
 use Symfony\Component\Config\Resource\FileResource;
 use Symfony\Component\ExpressionLanguage\Expression;
 
@@ -505,6 +506,14 @@ class ContainerBuilderTest extends \PHPUnit_Framework_TestCase
         $config->setDefinition('foo', new Definition('BazClass'));
         $container->merge($config);
         $this->assertEquals('BazClass', $container->getDefinition('foo')->getClass(), '->merge() overrides already defined services');
+
+        $container = new ContainerBuilder();
+        $bag = new EnvPlaceholderParameterBag();
+        $bag->get('env(Foo)');
+        $config = new ContainerBuilder($bag);
+        $config->resolveEnvPlaceholders($bag->get('env(Bar)'));
+        $container->merge($config);
+        $this->assertEquals(array('Foo' => 0, 'Bar' => 1), $container->getEnvCounters());
     }
 
     /**

src/Symfony/Component/DependencyInjection/Tests/Dumper/PhpDumperTest.php

@@ -11,11 +11,13 @@
 
 namespace Symfony\Component\DependencyInjection\Tests\Dumper;
 
+use Symfony\Component\Config\FileLocator;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\Dumper\PhpDumper;
 use Symfony\Component\DependencyInjection\ParameterBag\ParameterBag;
 use Symfony\Component\DependencyInjection\Reference;
 use Symfony\Component\DependencyInjection\Definition;
+use Symfony\Component\DependencyInjection\Loader\YamlFileLoader;
 use Symfony\Component\DependencyInjection\Variable;
 use Symfony\Component\ExpressionLanguage\Expression;
 
@@ -285,6 +287,30 @@ class PhpDumperTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals(file_get_contents(self::$fixturesPath.'/php/services24.php'), $dumper->dump());
     }
 
+    public function testEnvParameter()
+    {
+        $container = new ContainerBuilder();
+        $loader = new YamlFileLoader($container, new FileLocator(self::$fixturesPath.'/yaml'));
+        $loader->load('services26.yml');
+        $container->compile();
+        $dumper = new PhpDumper($container);
+
+        $this->assertStringEqualsFile(self::$fixturesPath.'/php/services26.php', $dumper->dump(), '->dump() dumps inline definitions which reference service_container');
+    }
+
+    /**
+     * @expectedException \Symfony\Component\DependencyInjection\Exception\EnvParameterException
+     * @expectedExceptionMessage Incompatible use of dynamic environment variables "FOO" found in parameters.
+     */
+    public function testUnusedEnvParameter()
+    {
+        $container = new ContainerBuilder();
+        $container->getParameter('env(FOO)');
+        $container->compile();
+        $dumper = new PhpDumper($container);
+        $dumper->dump();
+    }
+
     public function testInlinedDefinitionReferencingServiceContainer()
     {
         $container = new ContainerBuilder();

src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services10.php

@@ -69,9 +69,12 @@ class ProjectServiceContainer extends Container
     {
         $name = strtolower($name);
 
-        if (!(isset($this->parameters[$name]) || array_key_exists($name, $this->parameters))) {
+        if (!(isset($this->parameters[$name]) || array_key_exists($name, $this->parameters) || isset($this->loadedDynamicParameters[$name]))) {
             throw new InvalidArgumentException(sprintf('The parameter "%s" must be defined.', $name));
         }
+        if (isset($this->loadedDynamicParameters[$name])) {
+            return $this->loadedDynamicParameters[$name] ? $this->dynamicParameters[$name] : $this->getDynamicParameter($name);
+        }
 
         return $this->parameters[$name];
     }
@@ -83,7 +86,7 @@ class ProjectServiceContainer extends Container
     {
         $name = strtolower($name);
 
-        return isset($this->parameters[$name]) || array_key_exists($name, $this->parameters);
+        return isset($this->parameters[$name]) || array_key_exists($name, $this->parameters) || isset($this->loadedDynamicParameters[$name]);
     }
 
     /**
@@ -100,12 +103,33 @@ class ProjectServiceContainer extends Container
     public function getParameterBag()
     {
         if (null === $this->parameterBag) {
-            $this->parameterBag = new FrozenParameterBag($this->parameters);
+            $parameters = $this->parameters;
+            foreach ($this->loadedDynamicParameters as $name => $loaded) {
+                $parameters[$name] = $loaded ? $this->dynamicParameters[$name] : $this->getDynamicParameter($name);
+            }
+            $this->parameterBag = new FrozenParameterBag($parameters);
         }
 
         return $this->parameterBag;
     }
 
+    private $loadedDynamicParameters = array();
+    private $dynamicParameters = array();
+
+    /**
+     * Computes a dynamic parameter.
+     *
+     * @param string The name of the dynamic parameter to load
+     *
+     * @return mixed The value of the dynamic parameter
+     *
+     * @throws InvalidArgumentException When the dynamic parameter does not exist
+     */
+    private function getDynamicParameter($name)
+    {
+        throw new InvalidArgumentException(sprintf('The dynamic parameter "%s" must be defined.', $name));
+    }
+
     /**
      * Gets the default parameters.
      *

src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services12.php

@@ -73,9 +73,12 @@ class ProjectServiceContainer extends Container
     {
         $name = strtolower($name);
 
-        if (!(isset($this->parameters[$name]) || array_key_exists($name, $this->parameters))) {
+        if (!(isset($this->parameters[$name]) || array_key_exists($name, $this->parameters) || isset($this->loadedDynamicParameters[$name]))) {
             throw new InvalidArgumentException(sprintf('The parameter "%s" must be defined.', $name));
         }
+        if (isset($this->loadedDynamicParameters[$name])) {
+            return $this->loadedDynamicParameters[$name] ? $this->dynamicParameters[$name] : $this->getDynamicParameter($name);
+        }
 
         return $this->parameters[$name];
     }
@@ -87,7 +90,7 @@ class ProjectServiceContainer extends Container
     {
         $name = strtolower($name);
 
-        return isset($this->parameters[$name]) || array_key_exists($name, $this->parameters);
+        return isset($this->parameters[$name]) || array_key_exists($name, $this->parameters) || isset($this->loadedDynamicParameters[$name]);
     }
 
     /**
@@ -104,12 +107,43 @@ class ProjectServiceContainer extends Container
     public function getParameterBag()
     {
         if (null === $this->parameterBag) {
-            $this->parameterBag = new FrozenParameterBag($this->parameters);
+            $parameters = $this->parameters;
+            foreach ($this->loadedDynamicParameters as $name => $loaded) {
+                $parameters[$name] = $loaded ? $this->dynamicParameters[$name] : $this->getDynamicParameter($name);
+            }
+            $this->parameterBag = new FrozenParameterBag($parameters);
         }
 
         return $this->parameterBag;
     }
 
+    private $loadedDynamicParameters = array(
+        'foo' => false,
+        'buz' => false,
+    );
+    private $dynamicParameters = array();
+
+    /**
+     * Computes a dynamic parameter.
+     *
+     * @param string The name of the dynamic parameter to load
+     *
+     * @return mixed The value of the dynamic parameter
+     *
+     * @throws InvalidArgumentException When the dynamic parameter does not exist
+     */
+    private function getDynamicParameter($name)
+    {
+        switch ($name) {
+            case 'foo': $value = ('wiz'.$this->targetDirs[1]); break;
+            case 'buz': $value = $this->targetDirs[2]; break;
+            default: throw new InvalidArgumentException(sprintf('The dynamic parameter "%s" must be defined.', $name));
+        }
+        $this->loadedDynamicParameters[$name] = true;
+
+        return $this->dynamicParameters[$name] = $value;
+    }
+
     /**
      * Gets the default parameters.
      *
@@ -118,10 +152,8 @@ class ProjectServiceContainer extends Container
     protected function getDefaultParameters()
     {
         return array(
-            'foo' => ('wiz'.$this->targetDirs[1]),
             'bar' => __DIR__,
             'baz' => (__DIR__.'/PhpDumperTest.php'),
-            'buz' => $this->targetDirs[2],
         );
     }
 }

src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services26.php

@@ -0,0 +1,154 @@
+<?php
+
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\DependencyInjection\Container;
+use Symfony\Component\DependencyInjection\Exception\InvalidArgumentException;
+use Symfony\Component\DependencyInjection\Exception\LogicException;
+use Symfony\Component\DependencyInjection\Exception\RuntimeException;
+use Symfony\Component\DependencyInjection\ParameterBag\FrozenParameterBag;
+
+/**
+ * ProjectServiceContainer.
+ *
+ * This class has been auto-generated
+ * by the Symfony Dependency Injection Component.
+ */
+class ProjectServiceContainer extends Container
+{
+    private $parameters;
+    private $targetDirs = array();
+
+    /**
+     * Constructor.
+     */
+    public function __construct()
+    {
+        $this->parameters = $this->getDefaultParameters();
+
+        $this->services = array();
+        $this->methodMap = array(
+            'test' => 'getTestService',
+        );
+
+        $this->aliases = array();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function compile()
+    {
+        throw new LogicException('You cannot compile a dumped frozen container.');
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function isFrozen()
+    {
+        return true;
+    }
+
+    /**
+     * Gets the 'test' service.
+     *
+     * This service is shared.
+     * This method always returns the same instance of the service.
+     *
+     * @return object A %env(FOO)% instance
+     */
+    protected function getTestService()
+    {
+        $class = $this->getEnv('FOO');
+
+        return $this->services['test'] = new $class($this->getEnv('Bar'), 'foo'.$this->getEnv('FOO').'baz');
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getParameter($name)
+    {
+        $name = strtolower($name);
+
+        if (!(isset($this->parameters[$name]) || array_key_exists($name, $this->parameters) || isset($this->loadedDynamicParameters[$name]))) {
+            throw new InvalidArgumentException(sprintf('The parameter "%s" must be defined.', $name));
+        }
+        if (isset($this->loadedDynamicParameters[$name])) {
+            return $this->loadedDynamicParameters[$name] ? $this->dynamicParameters[$name] : $this->getDynamicParameter($name);
+        }
+
+        return $this->parameters[$name];
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function hasParameter($name)
+    {
+        $name = strtolower($name);
+
+        return isset($this->parameters[$name]) || array_key_exists($name, $this->parameters) || isset($this->loadedDynamicParameters[$name]);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function setParameter($name, $value)
+    {
+        throw new LogicException('Impossible to call set() on a frozen ParameterBag.');
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getParameterBag()
+    {
+        if (null === $this->parameterBag) {
+            $parameters = $this->parameters;
+            foreach ($this->loadedDynamicParameters as $name => $loaded) {
+                $parameters[$name] = $loaded ? $this->dynamicParameters[$name] : $this->getDynamicParameter($name);
+            }
+            $this->parameterBag = new FrozenParameterBag($parameters);
+        }
+
+        return $this->parameterBag;
+    }
+
+    private $loadedDynamicParameters = array(
+        'bar' => false,
+    );
+    private $dynamicParameters = array();
+
+    /**
+     * Computes a dynamic parameter.
+     *
+     * @param string The name of the dynamic parameter to load
+     *
+     * @return mixed The value of the dynamic parameter
+     *
+     * @throws InvalidArgumentException When the dynamic parameter does not exist
+     */
+    private function getDynamicParameter($name)
+    {
+        switch ($name) {
+            case 'bar': $value = $this->getEnv('FOO'); break;
+            default: throw new InvalidArgumentException(sprintf('The dynamic parameter "%s" must be defined.', $name));
+        }
+        $this->loadedDynamicParameters[$name] = true;
+
+        return $this->dynamicParameters[$name] = $value;
+    }
+
+    /**
+     * Gets the default parameters.
+     *
+     * @return array An array of the default parameters
+     */
+    protected function getDefaultParameters()
+    {
+        return array(
+            'env(foo)' => 'foo',
+        );
+    }
+}

src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services9_compiled.php

@@ -357,9 +357,12 @@ class ProjectServiceContainer extends Container
     {
         $name = strtolower($name);
 
-        if (!(isset($this->parameters[$name]) || array_key_exists($name, $this->parameters))) {
+        if (!(isset($this->parameters[$name]) || array_key_exists($name, $this->parameters) || isset($this->loadedDynamicParameters[$name]))) {
             throw new InvalidArgumentException(sprintf('The parameter "%s" must be defined.', $name));
         }
+        if (isset($this->loadedDynamicParameters[$name])) {
+            return $this->loadedDynamicParameters[$name] ? $this->dynamicParameters[$name] : $this->getDynamicParameter($name);
+        }
 
         return $this->parameters[$name];
     }
@@ -371,7 +374,7 @@ class ProjectServiceContainer extends Container
     {
         $name = strtolower($name);
 
-        return isset($this->parameters[$name]) || array_key_exists($name, $this->parameters);
+        return isset($this->parameters[$name]) || array_key_exists($name, $this->parameters) || isset($this->loadedDynamicParameters[$name]);
     }
 
     /**
@@ -388,12 +391,33 @@ class ProjectServiceContainer extends Container
     public function getParameterBag()
     {
         if (null === $this->parameterBag) {
-            $this->parameterBag = new FrozenParameterBag($this->parameters);
+            $parameters = $this->parameters;
+            foreach ($this->loadedDynamicParameters as $name => $loaded) {
+                $parameters[$name] = $loaded ? $this->dynamicParameters[$name] : $this->getDynamicParameter($name);
+            }
+            $this->parameterBag = new FrozenParameterBag($parameters);
         }
 
         return $this->parameterBag;
     }
 
+    private $loadedDynamicParameters = array();
+    private $dynamicParameters = array();
+
+    /**
+     * Computes a dynamic parameter.
+     *
+     * @param string The name of the dynamic parameter to load
+     *
+     * @return mixed The value of the dynamic parameter
+     *
+     * @throws InvalidArgumentException When the dynamic parameter does not exist
+     */
+    private function getDynamicParameter($name)
+    {
+        throw new InvalidArgumentException(sprintf('The dynamic parameter "%s" must be defined.', $name));
+    }
+
     /**
      * Gets the default parameters.
      *

src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/services26.yml

@@ -0,0 +1,10 @@
+parameters:
+    env(FOO): foo
+    bar: '%env(FOO)%'
+
+services:
+    test:
+        class: '%env(FOO)%'
+        arguments:
+            - '%env(Bar)%'
+            - 'foo%bar%baz'

src/Symfony/Component/HttpKernel/Kernel.php

@@ -16,7 +16,6 @@ use Symfony\Bridge\ProxyManager\LazyProxy\PhpDumper\ProxyDumper;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\Dumper\PhpDumper;
-use Symfony\Component\DependencyInjection\ParameterBag\ParameterBag;
 use Symfony\Component\DependencyInjection\Loader\XmlFileLoader;
 use Symfony\Component\DependencyInjection\Loader\YamlFileLoader;
 use Symfony\Component\DependencyInjection\Loader\IniFileLoader;
@@ -611,7 +610,8 @@ abstract class Kernel implements KernelInterface, TerminableInterface
      */
     protected function getContainerBuilder()
     {
-        $container = new ContainerBuilder(new ParameterBag($this->getKernelParameters()));
+        $container = new ContainerBuilder();
+        $container->getParameterBag()->add($this->getKernelParameters());
 
         if (class_exists('ProxyManager\Configuration') && class_exists('Symfony\Bridge\ProxyManager\LazyProxy\Instantiator\RuntimeInstantiator')) {
             $container->setProxyInstantiator(new RuntimeInstantiator());