Defining and Processing Configuration Values
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Validating Configuration Values
After loading configuration values from all kinds of resources, the values
and their structure can be validated using the "Definition" part of the
Config Component. Configuration values are usually expected to show some
kind of hierarchy. Also, values should be of a certain type, be restricted
in number or be one of a given set of values. For example, the following
configuration (in YAML) shows a clear hierarchy and some validation rules
that should be applied to it (like: "the value for auto_connect
must
be a boolean value"):
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database:
auto_connect: true
default_connection: mysql
connections:
mysql:
host: localhost
driver: mysql
username: user
password: pass
sqlite:
host: localhost
driver: sqlite
memory: true
username: user
password: pass
When loading multiple configuration files, it should be possible to merge
and overwrite some values. Other values should not be merged and stay as
they are when first encountered. Also, some keys are only available when
another key has a specific value (in the sample configuration above: the
memory
key only makes sense when the driver
is sqlite
).
Defining a Hierarchy of Configuration Values Using the TreeBuilder
All the rules concerning configuration values can be defined using the TreeBuilder.
A TreeBuilder
instance should be returned from a custom Configuration
class which
implements the ConfigurationInterface:
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namespace Acme\DatabaseConfiguration;
use Symfony\Component\Config\Definition\Builder\TreeBuilder;
use Symfony\Component\Config\Definition\ConfigurationInterface;
class DatabaseConfiguration implements ConfigurationInterface
{
public function getConfigTreeBuilder()
{
$treeBuilder = new TreeBuilder('database');
// ... add node definitions to the root of the tree
// $treeBuilder->getRootNode()->...
return $treeBuilder;
}
}
4.2
Not passing the root node name to TreeBuilder
was deprecated in Symfony 4.2.
Adding Node Definitions to the Tree
Variable Nodes
A tree contains node definitions which can be laid out in a semantic way. This means, using indentation and the fluent notation, it is possible to reflect the real structure of the configuration values:
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$rootNode
->children()
->booleanNode('auto_connect')
->defaultTrue()
->end()
->scalarNode('default_connection')
->defaultValue('default')
->end()
->end()
;
The root node itself is an array node, and has children, like the boolean
node auto_connect
and the scalar node default_connection
. In general:
after defining a node, a call to end()
takes you one step up in the
hierarchy.
Node Type
It is possible to validate the type of a provided value by using the appropriate node definition. Node types are available for:
- scalar (generic type that includes booleans, strings, integers, floats
and
null
) - boolean
- integer
- float
- enum (similar to scalar, but it only allows a finite set of values)
- array
- variable (no validation)
and are created with node($name, $type)
or their associated shortcut
xxxxNode($name)
method.
Numeric Node Constraints
Numeric nodes (float and integer) provide two extra constraints - min() and max() - allowing to validate the value:
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$rootNode
->children()
->integerNode('positive_value')
->min(0)
->end()
->floatNode('big_value')
->max(5E45)
->end()
->integerNode('value_inside_a_range')
->min(-50)->max(50)
->end()
->end()
;
Enum Nodes
Enum nodes provide a constraint to match the given input against a set of values:
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$rootNode
->children()
->enumNode('delivery')
->values(['standard', 'expedited', 'priority'])
->end()
->end()
;
This will restrict the delivery
options to be either standard
,
expedited
or priority
.
Array Nodes
It is possible to add a deeper level to the hierarchy, by adding an array node. The array node itself, may have a predefined set of variable nodes:
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$rootNode
->children()
->arrayNode('connection')
->children()
->scalarNode('driver')->end()
->scalarNode('host')->end()
->scalarNode('username')->end()
->scalarNode('password')->end()
->end()
->end()
->end()
;
Or you may define a prototype for each node inside an array node:
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$rootNode
->children()
->arrayNode('connections')
->arrayPrototype()
->children()
->scalarNode('driver')->end()
->scalarNode('host')->end()
->scalarNode('username')->end()
->scalarNode('password')->end()
->end()
->end()
->end()
->end()
;
A prototype can be used to add a definition which may be repeated many times
inside the current node. According to the prototype definition in the example
above, it is possible to have multiple connection arrays (containing a driver
,
host
, etc.).
Sometimes, to improve the user experience of your application or bundle, you may
allow the use of a simple string or numeric value where an array value is required.
Use the castToArray()
helper to turn those variables into arrays:
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->arrayNode('hosts')
->beforeNormalization()->castToArray()->end()
// ...
->end()
Array Node Options
Before defining the children of an array node, you can provide options like:
useAttributeAsKey()
- Provide the name of a child node, whose value should be used as the key in the resulting array. This method also defines the way config array keys are treated, as explained in the following example.
requiresAtLeastOneElement()
-
There should be at least one element in the array (works only when
isRequired()
is also called). addDefaultsIfNotSet()
- If any child nodes have default values, use them if explicit values haven't been provided.
normalizeKeys(false)
-
If called (with
false
), keys with dashes are not normalized to underscores. It is recommended to use this with prototype nodes where the user will define a key-value map, to avoid an unnecessary transformation. ignoreExtraKeys()
- Allows extra config keys to be specified under an array without throwing an exception.
A basic prototyped array configuration can be defined as follows:
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$node
->fixXmlConfig('driver')
->children()
->arrayNode('drivers')
->scalarPrototype()->end()
->end()
->end()
;
When using the following YAML configuration:
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drivers: ['mysql', 'sqlite']
Or the following XML configuration:
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<driver>mysql</driver>
<driver>sqlite</driver>
The processed configuration is:
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Array(
[0] => 'mysql'
[1] => 'sqlite'
)
A more complex example would be to define a prototyped array with children:
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$node
->fixXmlConfig('connection')
->children()
->arrayNode('connections')
->arrayPrototype()
->children()
->scalarNode('table')->end()
->scalarNode('user')->end()
->scalarNode('password')->end()
->end()
->end()
->end()
->end()
;
When using the following YAML configuration:
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connections:
- { table: symfony, user: root, password: ~ }
- { table: foo, user: root, password: pa$$ }
Or the following XML configuration:
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<connection table="symfony" user="root" password="null"/>
<connection table="foo" user="root" password="pa$$"/>
The processed configuration is:
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Array(
[0] => Array(
[table] => 'symfony'
[user] => 'root'
[password] => null
)
[1] => Array(
[table] => 'foo'
[user] => 'root'
[password] => 'pa$$'
)
)
The previous output matches the expected result. However, given the configuration tree, when using the following YAML configuration:
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connections:
sf_connection:
table: symfony
user: root
password: ~
default:
table: foo
user: root
password: pa$$
The output configuration will be exactly the same as before. In other words, the
sf_connection
and default
configuration keys are lost. The reason is that
the Symfony Config component treats arrays as lists by default.
Note
As of writing this, there is an inconsistency: if only one file provides the
configuration in question, the keys (i.e. sf_connection
and default
)
are not lost. But if more than one file provides the configuration, the keys
are lost as described above.
In order to maintain the array keys use the useAttributeAsKey()
method:
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$node
->fixXmlConfig('connection')
->children()
->arrayNode('connections')
->useAttributeAsKey('name')
->arrayPrototype()
->children()
->scalarNode('table')->end()
->scalarNode('user')->end()
->scalarNode('password')->end()
->end()
->end()
->end()
->end()
;
Note
In YAML, the 'name'
argument of useAttributeAsKey()
has a special
meaning and refers to the key of the map (sf_connection
and default
in this example). If a child node was defined for the connections
node
with the key name
, then that key of the map would be lost.
The argument of this method (name
in the example above) defines the name of
the attribute added to each XML node to differentiate them. Now you can use the
same YAML configuration shown before or the following XML configuration:
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<connection name="sf_connection"
table="symfony" user="root" password="null"/>
<connection name="default"
table="foo" user="root" password="pa$$"/>
In both cases, the processed configuration maintains the sf_connection
and
default
keys:
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Array(
[sf_connection] => Array(
[table] => 'symfony'
[user] => 'root'
[password] => null
)
[default] => Array(
[table] => 'foo'
[user] => 'root'
[password] => 'pa$$'
)
)
Default and Required Values
For all node types, it is possible to define default values and replacement values in case a node has a certain value:
defaultValue()
- Set a default value
isRequired()
- Must be defined (but may be empty)
cannotBeEmpty()
- May not contain an empty value
default*()
-
(
null
,true
,false
), shortcut fordefaultValue()
treat*Like()
-
(
null
,true
,false
), provide a replacement value in case the value is*.
The following example shows these methods in practice:
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$rootNode
->children()
->arrayNode('connection')
->children()
->scalarNode('driver')
->isRequired()
->cannotBeEmpty()
->end()
->scalarNode('host')
->defaultValue('localhost')
->end()
->scalarNode('username')->end()
->scalarNode('password')->end()
->booleanNode('memory')
->defaultFalse()
->end()
->end()
->end()
->arrayNode('settings')
->addDefaultsIfNotSet()
->children()
->scalarNode('name')
->isRequired()
->cannotBeEmpty()
->defaultValue('value')
->end()
->end()
->end()
->end()
;
Deprecating the Option
You can deprecate options using the setDeprecated() method:
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$rootNode
->children()
->integerNode('old_option')
// this outputs the following generic deprecation message:
// The child node "old_option" at path "..." is deprecated.
->setDeprecated()
// you can also pass a custom deprecation message (%node% and %path% placeholders are available):
->setDeprecated('The "%node%" option is deprecated. Use "new_config_option" instead.')
->end()
->end()
;
If you use the Web Debug Toolbar, these deprecation notices are shown when the configuration is rebuilt.
Documenting the Option
All options can be documented using the info() method:
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$rootNode
->children()
->integerNode('entries_per_page')
->info('This value is only used for the search results page.')
->defaultValue(25)
->end()
->end()
;
The info will be printed as a comment when dumping the configuration tree
with the config:dump-reference
command.
In YAML you may have:
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# This value is only used for the search results page.
entries_per_page: 25
and in XML:
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<!-- entries-per-page: This value is only used for the search results page. -->
<config entries-per-page="25"/>
Optional Sections
If you have entire sections which are optional and can be enabled/disabled, you can take advantage of the shortcut canBeEnabled() and canBeDisabled() methods:
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$arrayNode
->canBeEnabled()
;
// is equivalent to
$arrayNode
->treatFalseLike(['enabled' => false])
->treatTrueLike(['enabled' => true])
->treatNullLike(['enabled' => true])
->children()
->booleanNode('enabled')
->defaultFalse()
;
The canBeDisabled()
method looks about the same except that the section
would be enabled by default.
Merging Options
Extra options concerning the merge process may be provided. For arrays:
performNoDeepMerging()
- When the value is also defined in a second configuration array, don't try to merge an array, but overwrite it entirely
For all nodes:
cannotBeOverwritten()
- don't let other configuration arrays overwrite an existing value for this node
Appending Sections
If you have a complex configuration to validate, then the tree can grow to
be large and you may want to split it up into sections. You can do this
by making a section a separate node and then appending it into the main
tree with append()
:
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public function getConfigTreeBuilder()
{
$treeBuilder = new TreeBuilder('database');
$treeBuilder->getRootNode()
->children()
->arrayNode('connection')
->children()
->scalarNode('driver')
->isRequired()
->cannotBeEmpty()
->end()
->scalarNode('host')
->defaultValue('localhost')
->end()
->scalarNode('username')->end()
->scalarNode('password')->end()
->booleanNode('memory')
->defaultFalse()
->end()
->end()
->append($this->addParametersNode())
->end()
->end()
;
return $treeBuilder;
}
public function addParametersNode()
{
$treeBuilder = new TreeBuilder('parameters');
$node = $treeBuilder->getRootNode()
->isRequired()
->requiresAtLeastOneElement()
->useAttributeAsKey('name')
->arrayPrototype()
->children()
->scalarNode('value')->isRequired()->end()
->end()
->end()
;
return $node;
}
This is also useful to help you avoid repeating yourself if you have sections of the config that are repeated in different places.
The example results in the following:
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database:
connection:
driver: ~ # Required
host: localhost
username: ~
password: ~
memory: false
parameters: # Required
# Prototype
name:
value: ~ # Required
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<database>
<!-- driver: Required -->
<connection
driver=""
host="localhost"
username=""
password=""
memory="false"
>
<!-- prototype -->
<!-- value: Required -->
<parameters
name="parameters name"
value=""
/>
</connection>
</database>
Normalization
When the config files are processed they are first normalized, then merged and finally the tree is used to validate the resulting array. The normalization process is used to remove some of the differences that result from different configuration formats, mainly the differences between YAML and XML.
The separator used in keys is typically _
in YAML and -
in XML.
For example, auto_connect
in YAML and auto-connect
in XML. The
normalization would make both of these auto_connect
.
Caution
The target key will not be altered if it's mixed like
foo-bar_moo
or if it already exists.
Another difference between YAML and XML is in the way arrays of values may be represented. In YAML you may have:
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twig:
extensions: ['twig.extension.foo', 'twig.extension.bar']
and in XML:
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<twig:config>
<twig:extension>twig.extension.foo</twig:extension>
<twig:extension>twig.extension.bar</twig:extension>
</twig:config>
This difference can be removed in normalization by pluralizing the key used
in XML. You can specify that you want a key to be pluralized in this way
with fixXmlConfig()
:
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$rootNode
->fixXmlConfig('extension')
->children()
->arrayNode('extensions')
->scalarPrototype()->end()
->end()
->end()
;
If it is an irregular pluralization you can specify the plural to use as a second argument:
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$rootNode
->fixXmlConfig('child', 'children')
->children()
->arrayNode('children')
// ...
->end()
->end()
;
As well as fixing this, fixXmlConfig()
ensures that single XML elements
are still turned into an array. So you may have:
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<connection>default</connection>
<connection>extra</connection>
and sometimes only:
1
<connection>default</connection>
By default, connection
would be an array in the first case and a string
in the second, making it difficult to validate. You can ensure it is always
an array with fixXmlConfig()
.
You can further control the normalization process if you need to. For example,
you may want to allow a string to be set and used as a particular key or
several keys to be set explicitly. So that, if everything apart from name
is optional in this config:
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connection:
name: my_mysql_connection
host: localhost
driver: mysql
username: user
password: pass
you can allow the following as well:
1
connection: my_mysql_connection
By changing a string value into an associative array with name
as the key:
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$rootNode
->children()
->arrayNode('connection')
->beforeNormalization()
->ifString()
->then(function ($v) { return ['name' => $v]; })
->end()
->children()
->scalarNode('name')->isRequired()->end()
// ...
->end()
->end()
->end()
;
Validation Rules
More advanced validation rules can be provided using the ExprBuilder. This builder implements a fluent interface for a well-known control structure. The builder is used for adding advanced validation rules to node definitions, like:
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$rootNode
->children()
->arrayNode('connection')
->children()
->scalarNode('driver')
->isRequired()
->validate()
->ifNotInArray(['mysql', 'sqlite', 'mssql'])
->thenInvalid('Invalid database driver %s')
->end()
->end()
->end()
->end()
->end()
;
A validation rule always has an "if" part. You can specify this part in the following ways:
ifTrue()
ifString()
ifNull()
ifEmpty()
(since Symfony 3.2)ifArray()
ifInArray()
ifNotInArray()
always()
A validation rule also requires a "then" part:
then()
thenEmptyArray()
thenInvalid()
thenUnset()
Usually, "then" is a closure. Its return value will be used as a new value for the node, instead of the node's original value.
Configuring the Node Path Separator
Consider the following config builder example:
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$treeBuilder = new TreeBuilder('database');
$treeBuilder->getRootNode()
->children()
->arrayNode('connection')
->children()
->scalarNode('driver')->end()
->end()
->end()
->end()
;
By default, the hierarchy of nodes in a config path is defined with a dot
character (.
):
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// ...
$node = $treeBuilder->buildTree();
$children = $node->getChildren();
$childChildren = $children['connection']->getChildren();
$path = $childChildren['driver']->getPath();
// $path = 'database.connection.driver'
Use the setPathSeparator()
method on the config builder to change the path
separator:
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// ...
$treeBuilder->setPathSeparator('/');
$node = $treeBuilder->buildTree();
$children = $node->getChildren();
$childChildren = $children['connection']->getChildren();
$path = $childChildren['driver']->getPath();
// $path = 'database/connection/driver'
Processing Configuration Values
The Processor uses the tree as it was built using the TreeBuilder to process multiple arrays of configuration values that should be merged. If any value is not of the expected type, is mandatory and yet undefined, or could not be validated in some other way, an exception will be thrown. Otherwise the result is a clean array of configuration values:
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use Acme\DatabaseConfiguration;
use Symfony\Component\Config\Definition\Processor;
use Symfony\Component\Yaml\Yaml;
$config = Yaml::parse(
file_get_contents(__DIR__.'/src/Matthias/config/config.yaml')
);
$extraConfig = Yaml::parse(
file_get_contents(__DIR__.'/src/Matthias/config/config_extra.yaml')
);
$configs = [$config, $extraConfig];
$processor = new Processor();
$databaseConfiguration = new DatabaseConfiguration();
$processedConfiguration = $processor->processConfiguration(
$databaseConfiguration,
$configs
);