Documentation

Visitor
in package

Utility for efficient AST traversal and modification.

visit() will walk through an AST using a depth first traversal, calling the visitor's enter function at each node in the traversal, and calling the leave function after visiting that node and all of it's child nodes.

By returning different values from the enter and leave functions, the behavior of the visitor can be altered, including skipping over a sub-tree of the AST (by returning false), editing the AST by returning a value or null to remove the value, or to stop the whole traversal by returning BREAK.

When using visit() to edit an AST, the original AST will not be modified, and a new version of the AST with the changes applied will be returned from the visit function.

$editedAST = Visitor::visit($ast, [
  'enter' => function ($node, $key, $parent, $path, $ancestors) {
    // return
    //   null: no action
    //   Visitor::skipNode(): skip visiting this node
    //   Visitor::stop(): stop visiting altogether
    //   Visitor::removeNode(): delete this node
    //   any value: replace this node with the returned value
  },
  'leave' => function ($node, $key, $parent, $path, $ancestors) {
    // return
    //   null: no action
    //   Visitor::stop(): stop visiting altogether
    //   Visitor::removeNode(): delete this node
    //   any value: replace this node with the returned value
  }
]);

Alternatively to providing enter() and leave() functions, a visitor can instead provide functions named the same as the kinds of AST nodes, or enter/leave visitors at a named key, leading to four permutations of visitor API:

  1. Named visitors triggered when entering a node a specific kind.

    Visitor::visit($ast, [ 'Kind' => function ($node) { // enter the "Kind" node } ]);

  2. Named visitors that trigger upon entering and leaving a node of a specific kind.

    Visitor::visit($ast, [ 'Kind' => [ 'enter' => function ($node) { // enter the "Kind" node } 'leave' => function ($node) { // leave the "Kind" node } ] ]);

  3. Generic visitors that trigger upon entering and leaving any node.

    Visitor::visit($ast, [ 'enter' => function ($node) { // enter any node }, 'leave' => function ($node) { // leave any node } ]);

  4. Parallel visitors for entering and leaving nodes of a specific kind.

    Visitor::visit($ast, [ 'enter' => [ 'Kind' => function($node) { // enter the "Kind" node } }, 'leave' => [ 'Kind' => function ($node) { // leave the "Kind" node } ] ]);

Table of Contents

$visitorKeys  : array<string|int, array<string|int, string>>
getVisitFn()  : callable|null
removeNode()  : VisitorOperation
Returns marker for removing a node
skipNode()  : VisitorOperation
Returns marker for skipping current node
stop()  : VisitorOperation
Returns marker for visitor break
visit()  : Node|mixed
Visit the AST (see class description for details)
visitInParallel()  : array<string, callable>
visitWithTypeInfo()  : mixed
Creates a new visitor instance which maintains a provided TypeInfo instance along with visiting visitor.

Properties

$visitorKeys

public static array<string|int, array<string|int, string>> $visitorKeys = [\GraphQL\Language\AST\NodeKind::NAME => [], \GraphQL\Language\AST\NodeKind::DOCUMENT => ['definitions'], \GraphQL\Language\AST\NodeKind::OPERATION_DEFINITION => ['name', 'variableDefinitions', 'directives', 'selectionSet'], \GraphQL\Language\AST\NodeKind::VARIABLE_DEFINITION => ['variable', 'type', 'defaultValue', 'directives'], \GraphQL\Language\AST\NodeKind::VARIABLE => ['name'], \GraphQL\Language\AST\NodeKind::SELECTION_SET => ['selections'], \GraphQL\Language\AST\NodeKind::FIELD => ['alias', 'name', 'arguments', 'directives', 'selectionSet'], \GraphQL\Language\AST\NodeKind::ARGUMENT => ['name', 'value'], \GraphQL\Language\AST\NodeKind::FRAGMENT_SPREAD => ['name', 'directives'], \GraphQL\Language\AST\NodeKind::INLINE_FRAGMENT => ['typeCondition', 'directives', 'selectionSet'], \GraphQL\Language\AST\NodeKind::FRAGMENT_DEFINITION => [ 'name', // Note: fragment variable definitions are experimental and may be changed // or removed in the future. 'variableDefinitions', 'typeCondition', 'directives', 'selectionSet', ], \GraphQL\Language\AST\NodeKind::INT => [], \GraphQL\Language\AST\NodeKind::FLOAT => [], \GraphQL\Language\AST\NodeKind::STRING => [], \GraphQL\Language\AST\NodeKind::BOOLEAN => [], \GraphQL\Language\AST\NodeKind::NULL => [], \GraphQL\Language\AST\NodeKind::ENUM => [], \GraphQL\Language\AST\NodeKind::LST => ['values'], \GraphQL\Language\AST\NodeKind::OBJECT => ['fields'], \GraphQL\Language\AST\NodeKind::OBJECT_FIELD => ['name', 'value'], \GraphQL\Language\AST\NodeKind::DIRECTIVE => ['name', 'arguments'], \GraphQL\Language\AST\NodeKind::NAMED_TYPE => ['name'], \GraphQL\Language\AST\NodeKind::LIST_TYPE => ['type'], \GraphQL\Language\AST\NodeKind::NON_NULL_TYPE => ['type'], \GraphQL\Language\AST\NodeKind::SCHEMA_DEFINITION => ['directives', 'operationTypes'], \GraphQL\Language\AST\NodeKind::OPERATION_TYPE_DEFINITION => ['type'], \GraphQL\Language\AST\NodeKind::SCALAR_TYPE_DEFINITION => ['description', 'name', 'directives'], \GraphQL\Language\AST\NodeKind::OBJECT_TYPE_DEFINITION => ['description', 'name', 'interfaces', 'directives', 'fields'], \GraphQL\Language\AST\NodeKind::FIELD_DEFINITION => ['description', 'name', 'arguments', 'type', 'directives'], \GraphQL\Language\AST\NodeKind::INPUT_VALUE_DEFINITION => ['description', 'name', 'type', 'defaultValue', 'directives'], \GraphQL\Language\AST\NodeKind::INTERFACE_TYPE_DEFINITION => ['description', 'name', 'interfaces', 'directives', 'fields'], \GraphQL\Language\AST\NodeKind::UNION_TYPE_DEFINITION => ['description', 'name', 'directives', 'types'], \GraphQL\Language\AST\NodeKind::ENUM_TYPE_DEFINITION => ['description', 'name', 'directives', 'values'], \GraphQL\Language\AST\NodeKind::ENUM_VALUE_DEFINITION => ['description', 'name', 'directives'], \GraphQL\Language\AST\NodeKind::INPUT_OBJECT_TYPE_DEFINITION => ['description', 'name', 'directives', 'fields'], \GraphQL\Language\AST\NodeKind::SCALAR_TYPE_EXTENSION => ['name', 'directives'], \GraphQL\Language\AST\NodeKind::OBJECT_TYPE_EXTENSION => ['name', 'interfaces', 'directives', 'fields'], \GraphQL\Language\AST\NodeKind::INTERFACE_TYPE_EXTENSION => ['name', 'interfaces', 'directives', 'fields'], \GraphQL\Language\AST\NodeKind::UNION_TYPE_EXTENSION => ['name', 'directives', 'types'], \GraphQL\Language\AST\NodeKind::ENUM_TYPE_EXTENSION => ['name', 'directives', 'values'], \GraphQL\Language\AST\NodeKind::INPUT_OBJECT_TYPE_EXTENSION => ['name', 'directives', 'fields'], \GraphQL\Language\AST\NodeKind::DIRECTIVE_DEFINITION => ['description', 'name', 'arguments', 'locations'], \GraphQL\Language\AST\NodeKind::SCHEMA_EXTENSION => ['directives', 'operationTypes']]

Methods

getVisitFn()

public static getVisitFn(array<string|int, callable>|null $visitor, string $kind, bool $isLeaving) : callable|null
Parameters
$visitor : array<string|int, callable>|null
$kind : string
$isLeaving : bool
Return values
callable|null —

visit()

Visit the AST (see class description for details)

public static visit(Node|ArrayObject|stdClass $root, array<string|int, callable> $visitor[, array<string|int, mixed>|null $keyMap = null ]) : Node|mixed
Parameters
$root : Node|ArrayObject|stdClass
$visitor : array<string|int, callable>
$keyMap : array<string|int, mixed>|null = null
Tags
throws
Exception
Return values
Node|mixed —

visitInParallel()

public static visitInParallel(array<string|int, array<string|int, callable>> $visitors) : array<string, callable>
Parameters
$visitors : array<string|int, array<string|int, callable>>
Return values
array<string, callable> —

visitWithTypeInfo()

Creates a new visitor instance which maintains a provided TypeInfo instance along with visiting visitor.

public static visitWithTypeInfo(TypeInfo $typeInfo, mixed $visitor) : mixed
Parameters
$typeInfo : TypeInfo
$visitor : mixed
Return values
mixed —

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