Chris@13: Name resolution
Chris@13: ===============
Chris@13: 
Chris@13: Since the introduction of namespaces in PHP 5.3, literal names in PHP code are subject to a
Chris@13: relatively complex name resolution process, which is based on the current namespace, the current
Chris@13: import table state, as well the type of the referenced symbol. PHP-Parser implements name
Chris@13: resolution and related functionality, both as reusable logic (NameContext), as well as a node
Chris@13: visitor (NameResolver) based on it.
Chris@13: 
Chris@13: The NameResolver visitor
Chris@13: ------------------------
Chris@13: 
Chris@13: The `NameResolver` visitor can (and for nearly all uses of the AST, is) be applied to resolve names
Chris@13: to their fully-qualified form, to the degree that this is possible.
Chris@13: 
Chris@13: ```php
Chris@13: $nameResolver = new PhpParser\NodeVisitor\NameResolver;
Chris@13: $nodeTraverser = new PhpParser\NodeTraverser;
Chris@13: $nodeTraverser->addVisitor($nameResolver);
Chris@13: 
Chris@13: // Resolve names
Chris@13: $stmts = $nodeTraverser->traverse($stmts);
Chris@13: ```
Chris@13: 
Chris@13: In the default configuration, the name resolver will perform three actions:
Chris@13: 
Chris@13:  * Declarations of functions, classes, interfaces, traits and global constants will have a
Chris@13:    `namespacedName` property added, which contains the function/class/etc name including the
Chris@13:    namespace prefix. For historic reasons this is a **property** rather than an attribute.
Chris@13:  * Names will be replaced by fully qualified resolved names, which are instances of
Chris@13:    `Node\Name\FullyQualified`.
Chris@13:  * Unqualified function and constant names inside a namespace cannot be statically resolved. Inside
Chris@13:    a namespace `Foo`, a call to `strlen()` may either refer to the namespaced `\Foo\strlen()`, or
Chris@13:    the global `\strlen()`. Because PHP-Parser does not have the necessary context to decide this,
Chris@13:    such names are left unresolved. Additionally a `namespacedName` **attribute** is added to the
Chris@13:    name node.
Chris@13: 
Chris@13: The name resolver accepts an option array as the second argument, with the following default values:
Chris@13: 
Chris@13: ```php
Chris@13: $nameResolver = new PhpParser\NodeVisitor\NameResolver(null, [
Chris@13:     'preserveOriginalNames' => false,
Chris@13:     'replaceNodes' => true,
Chris@13: ]);
Chris@13: ```
Chris@13: 
Chris@13: If the `preserveOriginalNames` option is enabled, then the resolved (fully qualified) name will have
Chris@13: an `originalName` attribute, which contains the unresolved name.
Chris@13: 
Chris@13: If the `replaceNodes` option is disabled, then names will no longer be resolved in-place. Instead a
Chris@13: `resolvedName` attribute will be added to each name, which contains the resolved (fully qualified)
Chris@13: name. Once again, if an unqualified function or constant name cannot be resolved, then the
Chris@13: `resolvedName` attribute will not be present, and instead a `namespacedName` attribute is added.
Chris@13: 
Chris@13: The `replaceNodes` attribute is useful if you wish to perform modifications on the AST, as you
Chris@13: probably do not wish the resoluting code to have fully resolved names as a side-effect.
Chris@13: 
Chris@13: The NameContext
Chris@13: ---------------
Chris@13: 
Chris@13: The actual name resolution logic is implemented in the `NameContext` class, which has the following
Chris@13: public API:
Chris@13: 
Chris@13: ```php
Chris@13: class NameContext {
Chris@13:     public function __construct(ErrorHandler $errorHandler);
Chris@13:     public function startNamespace(Name $namespace = null);
Chris@13:     public function addAlias(Name $name, string $aliasName, int $type, array $errorAttrs = []);
Chris@13: 
Chris@13:     public function getNamespace();
Chris@13:     public function getResolvedName(Name $name, int $type);
Chris@13:     public function getResolvedClassName(Name $name) : Name;
Chris@13:     public function getPossibleNames(string $name, int $type) : array;
Chris@13:     public function getShortName(string $name, int $type) : Name;
Chris@13: }
Chris@13: ```
Chris@13: 
Chris@13: The `$type` parameters accept on of the `Stmt\Use_::TYPE_*` constants, which represent the three
Chris@13: basic symbol types in PHP (functions, constants and everything else).
Chris@13: 
Chris@13: Next to name resolution, the `NameContext` also supports the reverse operation of finding a short
Chris@13: representation of a name given the current name resolution environment.
Chris@13: 
Chris@13: The name context is intended to be used for name resolution operations outside the AST itself, such
Chris@13: as class names inside doc comments. A visitor running in parallel with the name resolver can access
Chris@13: the name context using `$nameResolver->getNameContext()`. Alternatively a visitor can use an
Chris@13: independent context and explicitly feed `Namespace` and `Use` nodes to it.