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        | symfony/symfony-docs#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 @@ public function getLog()
      */
     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 @@ public static function underscore($id)
         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\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 @@ public function merge(ContainerBuilder $container)
 
             $this->extensionConfigs[$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 @@ public function compile()
         }
 
         $this->extensionConfigs = array();
+        $bag = $this->getParameterBag();
 
         parent::compile();
+
+        $this->envPlaceholders = $bag instanceof EnvPlaceholderParameterBag ? $bag->getEnvPlaceholders() : array();
     }
 
     /**
@@ -996,6 +1022,56 @@ public function getExpressionLanguageProviders()
         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 @@ public function dump(array $options = array())
             }
         }
 
-        return $this->startDot().$this->addNodes().$this->addEdges().$this->endDot();
+        return $this->container->resolveEnvPlaceholders($this->startDot().$this->addNodes().$this->addEdges().$this->endDot(), '__ENV_%s__');
     }
 
     /**