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