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Name resolution
===============
Since the introduction of namespaces in PHP 5.3, literal names in PHP code are subject to a
relatively complex name resolution process, which is based on the current namespace, the current
import table state, as well the type of the referenced symbol. PHP-Parser implements name
resolution and related functionality, both as reusable logic (NameContext), as well as a node
visitor (NameResolver) based on it.
The NameResolver visitor
------------------------
The `NameResolver` visitor can (and for nearly all uses of the AST, should) be applied to resolve names
to their fully-qualified form, to the degree that this is possible.
```php
$nameResolver = new PhpParser\NodeVisitor\NameResolver;
$nodeTraverser = new PhpParser\NodeTraverser;
$nodeTraverser->addVisitor($nameResolver);
// Resolve names
$stmts = $nodeTraverser->traverse($stmts);
```
In the default configuration, the name resolver will perform three actions:
* Declarations of functions, classes, interfaces, traits, enums and global constants will have a
`namespacedName` property added, which contains the function/class/etc name including the
namespace prefix. For historic reasons this is a **property** rather than an attribute.
* Names will be replaced by fully qualified resolved names, which are instances of
`Node\Name\FullyQualified`.
* Unqualified function and constant names inside a namespace cannot be statically resolved. Inside
a namespace `Foo`, a call to `strlen()` may either refer to the namespaced `\Foo\strlen()`, or
the global `\strlen()`. Because PHP-Parser does not have the necessary context to decide this,
such names are left unresolved. Additionally, a `namespacedName` **attribute** is added to the
name node.
The name resolver accepts an option array as the second argument, with the following default values:
```php
$nameResolver = new PhpParser\NodeVisitor\NameResolver(null, [
'preserveOriginalNames' => false,
'replaceNodes' => true,
]);
```
If the `preserveOriginalNames` option is enabled, then the resolved (fully qualified) name will have
an `originalName` attribute, which contains the unresolved name.
If the `replaceNodes` option is disabled, then names will no longer be resolved in-place. Instead, a
`resolvedName` attribute will be added to each name, which contains the resolved (fully qualified)
name. Once again, if an unqualified function or constant name cannot be resolved, then the
`resolvedName` attribute will not be present, and instead a `namespacedName` attribute is added.
The `replaceNodes` attribute is useful if you wish to perform modifications on the AST, as you
probably do not wish the resulting code to have fully resolved names as a side-effect.
The NameContext
---------------
The actual name resolution logic is implemented in the `NameContext` class, which has the following
public API:
```php
class NameContext {
public function __construct(ErrorHandler $errorHandler);
public function startNamespace(Name $namespace = null);
public function addAlias(Name $name, string $aliasName, int $type, array $errorAttrs = []);
public function getNamespace();
public function getResolvedName(Name $name, int $type);
public function getResolvedClassName(Name $name) : Name;
public function getPossibleNames(string $name, int $type) : array;
public function getShortName(string $name, int $type) : Name;
}
```
The `$type` parameters accept one of the `Stmt\Use_::TYPE_*` constants, which represent the three
basic symbol types in PHP (functions, constants and everything else).
Next to name resolution, the `NameContext` also supports the reverse operation of finding a short
representation of a name given the current name resolution environment.
The name context is intended to be used for name resolution operations outside the AST itself, such
as class names inside doc comments. A visitor running in parallel with the name resolver can access
the name context using `$nameResolver->getNameContext()`. Alternatively a visitor can use an
independent context and explicitly feed `Namespace` and `Use` nodes to it.
|
