[DI][Config] Make accessing environment variables in configuration more convenient

Author: magnusnordlander

src/Symfony/Component/Config/Definition/Builder/ExpressionNodeDefinition.php

@@ -0,0 +1,32 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <[email protected]>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Config\Definition\Builder;
+
+use Symfony\Component\Config\Definition\ExpressionNode;
+
+/**
+ * This class provides a fluent interface for defining a node.
+ *
+ * @author Magnus Nordlander <[email protected]>
+ */
+class ExpressionNodeDefinition extends VariableNodeDefinition
+{
+    /**
+     * Instantiate a Node.
+     *
+     * @return VariableNode The node
+     */
+    protected function instantiateNode()
+    {
+        return new ExpressionNode($this->name, $this->parent);
+    }
+}

src/Symfony/Component/Config/Definition/Builder/NodeBuilder.php

@@ -34,6 +34,7 @@ public function __construct()
             'float' => __NAMESPACE__.'\\FloatNodeDefinition',
             'array' => __NAMESPACE__.'\\ArrayNodeDefinition',
             'enum' => __NAMESPACE__.'\\EnumNodeDefinition',
+            'expression' => __NAMESPACE__.'\\ExpressionNodeDefinition',
         );
     }
 
@@ -135,6 +136,18 @@ public function variableNode($name)
         return $this->node($name, 'variable');
     }
 
+    /**
+     * Creates a child variable node.
+     *
+     * @param string $name The name of the node
+     *
+     * @return VariableNodeDefinition The builder of the child node
+     */
+    public function expressionNode($name)
+    {
+        return $this->node($name, 'expression');
+    }
+
     /**
      * Returns the parent node.
      *

src/Symfony/Component/Config/Definition/Dumper/XmlReferenceDumper.php

@@ -16,6 +16,7 @@
 use Symfony\Component\Config\Definition\ArrayNode;
 use Symfony\Component\Config\Definition\EnumNode;
 use Symfony\Component\Config\Definition\PrototypedArrayNode;
+use Symfony\Component\ExpressionLanguage\Expression;
 
 /**
  * Dumps a XML reference configuration for the given configuration/node instance.
@@ -120,6 +121,10 @@ private function writeNode(NodeInterface $node, $depth = 0, $root = false, $name
                                 $prototypeValue = implode('|', array_map('json_encode', $prototype->getValues()));
                                 break;
 
+                            case 'Symfony\Component\Config\Definition\ExpressionNode':
+                                $prototypeValue = 'expression';
+                                break;
+
                             default:
                                 $prototypeValue = 'value';
                         }
@@ -297,6 +302,10 @@ private function writeValue($value)
             return '';
         }
 
+        if ($value instanceof Expression) {
+            return (string) $value;
+        }
+
         if (is_array($value)) {
             return implode(',', $value);
         }

src/Symfony/Component/Config/Definition/Dumper/YamlReferenceDumper.php

@@ -16,6 +16,7 @@
 use Symfony\Component\Config\Definition\ArrayNode;
 use Symfony\Component\Config\Definition\EnumNode;
 use Symfony\Component\Config\Definition\PrototypedArrayNode;
+use Symfony\Component\ExpressionLanguage\Expression;
 use Symfony\Component\Yaml\Inline;
 
 /**
@@ -106,6 +107,8 @@ private function writeNode(NodeInterface $node, $depth = 0)
                     } elseif (!is_array($example)) {
                         $default = '[]';
                     }
+                } elseif ($default instanceof Expression) {
+                    $default = Inline::dump((string) $default);
                 } else {
                     $default = Inline::dump($default);
                 }

src/Symfony/Component/Config/Definition/ExpressionNode.php

@@ -0,0 +1,86 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <[email protected]>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Config\Definition;
+
+use Symfony\Component\Config\Definition\Exception\InvalidTypeException;
+use Symfony\Component\ExpressionLanguage\Expression;
+
+/**
+ * This node represents a Symfony Expression Language Expression.
+ *
+ * @author Magnus Nordlander <[email protected]>
+ */
+class ExpressionNode extends VariableNode
+{
+    /**
+     * {@inheritdoc}
+     */
+    protected function validateType($value)
+    {
+        if (!$value instanceof Expression) {
+            $e = new InvalidTypeException(sprintf('Invalid type for path "%s": expected Symfony\\Component\\ExpressionLanguage\\Expression , but got %s.', $this->getPath(), gettype($value)));
+
+            if ($hint = $this->getInfo()) {
+                $e->addHint($hint);
+            }
+            $e->setPath($this->getPath());
+
+            throw $e;
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function preNormalize($value)
+    {
+        $value = parent::preNormalize($value);
+
+        return $this->transformToExpression($value);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getDefaultValue()
+    {
+        $value = parent::getDefaultValue();
+
+        return $this->transformToExpression($value);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function isValueEmpty($value)
+    {
+        // a boolean value cannot be empty
+        return null === $value;
+    }
+
+    private function transformToExpression($value)
+    {
+        if (null === $value) {
+            return;
+        }
+
+        if ($value instanceof Expression) {
+            return $value;
+        }
+
+        if (!class_exists(Expression::class) {
+            throw new \RuntimeException('The Symfony Expression Language component must be installed to use expression nodes in configurations.');
+        }
+
+        return new Expression($value);
+    }
+}

src/Symfony/Component/Config/composer.json

@@ -20,7 +20,8 @@
         "symfony/filesystem": "~2.8|~3.0"
     },
     "suggest": {
-        "symfony/yaml": "To use the yaml reference dumper"
+        "symfony/yaml": "To use the yaml reference dumper",
+        "symfony/expression-language": "To use the expression node type"
     },
     "autoload": {
         "psr-4": { "Symfony\\Component\\Config\\": "" },

src/Symfony/Component/DependencyInjection/Container.php

@@ -11,6 +11,7 @@
 
 namespace Symfony\Component\DependencyInjection;
 
+use Symfony\Component\DependencyInjection\Exception\EnvironmentVariableNotFoundException;
 use Symfony\Component\DependencyInjection\Exception\InvalidArgumentException;
 use Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException;
 use Symfony\Component\DependencyInjection\Exception\ServiceCircularReferenceException;
@@ -151,6 +152,26 @@ public function setParameter($name, $value)
         $this->parameterBag->set($name, $value);
     }
 
+    /**
+     * @internal
+     */
+    public function getEnvironmentVariable($name, $default = null)
+    {
+        if (isset($_ENV[$name])) {
+            return $_ENV[$name];
+        }
+
+        if (false !== $value = getenv($name)) {
+            return $value;
+        }
+
+        if (2 > func_num_args()) {
+            throw new EnvironmentVariableNotFoundException($name);
+        }
+
+        return $default;
+    }
+
     /**
      * Sets a service.
      *

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

@@ -0,0 +1,25 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <[email protected]>
+ *
+ * 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 was not found.
+ *
+ * @author Magnus Nordlander <[email protected]>
+ */
+class EnvironmentVariableNotFoundException extends InvalidArgumentException
+{
+    public function __construct($name)
+    {
+        parent::__construct(sprintf('You have requested a non-existent environment variable "%s".', $sourceId, $name));
+    }
+}

src/Symfony/Component/DependencyInjection/ExpressionLanguageProvider.php

@@ -19,6 +19,7 @@
  *
  * To get a service, use service('request').
  * To get a parameter, use parameter('kernel.debug').
+ * To get an environment variable, use env('UID').
  *
  * @author Fabien Potencier <[email protected]>
  */
@@ -38,6 +39,20 @@ public function getFunctions()
             }, function (array $variables, $value) {
                 return $variables['container']->getParameter($value);
             }),
+
+            new ExpressionFunction('env', function ($arg, $default = null) {
+                if (2 > func_num_args()) {
+                    return sprintf('$this->getEnvironmentVariable(%s)', $arg);
+                }
+
+                return sprintf('$this->getEnvironmentVariable(%s, %s)', $arg, $default);
+            }, function (array $variables, $value, $default = null) {
+                if (2 > func_num_args()) {
+                    return $variables['container']->getEnvironmentVariable($value);
+                }
+
+                return $variables['container']->getEnvironmentVariable($value, $default);
+            }),
         );
     }
 }