Trait Visitor

pub trait Visitor<'a, Context = ()>: Sized {
    // Provided methods
    fn compose<V: Visitor<'a, Context>>(
        self,
        other: V,
    ) -> ComposedVisitor<'a, Context, Self, V> { ... }
    fn enter_document(
        &mut self,
        _ctx: &mut Context,
        _document: &'a Document<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn leave_document(
        &mut self,
        _ctx: &mut Context,
        _document: &'a Document<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn enter_operation(
        &mut self,
        _ctx: &mut Context,
        _operation: &'a OperationDefinition<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn leave_operation(
        &mut self,
        _ctx: &mut Context,
        _operation: &'a OperationDefinition<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn enter_fragment(
        &mut self,
        _ctx: &mut Context,
        _fragment: &'a FragmentDefinition<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn leave_fragment(
        &mut self,
        _ctx: &mut Context,
        _fragment: &'a FragmentDefinition<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn enter_variable_definition(
        &mut self,
        _ctx: &mut Context,
        _var_def: &'a VariableDefinition<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn leave_variable_definition(
        &mut self,
        _ctx: &mut Context,
        _var_def: &'a VariableDefinition<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn enter_selection_set(
        &mut self,
        _ctx: &mut Context,
        _selection_set: &'a SelectionSet<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn leave_selection_set(
        &mut self,
        _ctx: &mut Context,
        _selection_set: &'a SelectionSet<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn enter_fragment_spread(
        &mut self,
        _ctx: &mut Context,
        _fragment_spread: &'a FragmentSpread<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn leave_fragment_spread(
        &mut self,
        _ctx: &mut Context,
        _fragment_spread: &'a FragmentSpread<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn enter_inline_fragment(
        &mut self,
        _ctx: &mut Context,
        _inline_fragment: &'a InlineFragment<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn leave_inline_fragment(
        &mut self,
        _ctx: &mut Context,
        _inline_fragment: &'a InlineFragment<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn enter_field(
        &mut self,
        _ctx: &mut Context,
        _field: &'a Field<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn leave_field(
        &mut self,
        _ctx: &mut Context,
        _field: &'a Field<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn enter_directive(
        &mut self,
        _ctx: &mut Context,
        _directive: &'a Directive<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn leave_directive(
        &mut self,
        _ctx: &mut Context,
        _directive: &'a Directive<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn enter_argument(
        &mut self,
        _ctx: &mut Context,
        _argument: &'a Argument<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
    fn leave_argument(
        &mut self,
        _ctx: &mut Context,
        _argument: &'a Argument<'a>,
        _info: &VisitInfo,
    ) -> VisitFlow { ... }
}

Trait for a visitor that carries methods that are called as callback while AST nodes implementing the visitor pattern are traversed.

While the AST is traversed in depth-first order, callbacks that are prefixed with enter_ are called from top-to-bottom while the traversal is recursing, while callbacks that are prefixed with leave_ are called from bottom-to-top while the traversal is returning.

All callbacks have a default no-op implementation that returns VisitFlow::Next. The VisitFlow signals are returned from callbacks to alter the traversal and either continue it (Next), skip over a node during an enter_ callback with (Skip), or abort traversal entirely (Break).

The visitor must implement the Visitor trait which may also define a custom context structure that can be passed to the visit method. By default the context is an empty unit ().

This pattern is applicable to any AST node that implements the VisitNode trait.

Provided Methods

fn compose<V: Visitor<'a, Context>>( self, other: V, ) -> ComposedVisitor<'a, Context, Self, V>

Combines two visitors into one that will run both the original and passed visitor concurrently.

Both visitors must accept the same Context type.

fn enter_document( &mut self, _ctx: &mut Context, _document: &'a Document<'a>, _info: &VisitInfo, ) -> VisitFlow

Called when a Document is visited and before its child nodes are visited.

fn leave_document( &mut self, _ctx: &mut Context, _document: &'a Document<'a>, _info: &VisitInfo, ) -> VisitFlow

Called after a Document and its child nodes were visited.

fn enter_operation( &mut self, _ctx: &mut Context, _operation: &'a OperationDefinition<'a>, _info: &VisitInfo, ) -> VisitFlow

Called when an OperationDefinition node is visited and before its child nodes are visited.

fn leave_operation( &mut self, _ctx: &mut Context, _operation: &'a OperationDefinition<'a>, _info: &VisitInfo, ) -> VisitFlow

Called after an OperationDefinition and its child node were visited.

fn enter_fragment( &mut self, _ctx: &mut Context, _fragment: &'a FragmentDefinition<'a>, _info: &VisitInfo, ) -> VisitFlow

Called when a FragmentDefinition node is visited and before its child nodes are visited.

fn leave_fragment( &mut self, _ctx: &mut Context, _fragment: &'a FragmentDefinition<'a>, _info: &VisitInfo, ) -> VisitFlow

Called after a FragmentDefinition node and its child nodes were visited.

fn enter_variable_definition( &mut self, _ctx: &mut Context, _var_def: &'a VariableDefinition<'a>, _info: &VisitInfo, ) -> VisitFlow

Called when a VariableDefinition node is visited and before its child nodes are visited.

fn leave_variable_definition( &mut self, _ctx: &mut Context, _var_def: &'a VariableDefinition<'a>, _info: &VisitInfo, ) -> VisitFlow

Called after a VariableDefinition node and its child nodes were visited.

fn enter_selection_set( &mut self, _ctx: &mut Context, _selection_set: &'a SelectionSet<'a>, _info: &VisitInfo, ) -> VisitFlow

Called when a SelectionSet node is visited and before its child nodes are visited.

fn leave_selection_set( &mut self, _ctx: &mut Context, _selection_set: &'a SelectionSet<'a>, _info: &VisitInfo, ) -> VisitFlow

Called after a SelectionSet node and its child nodes were visited.

fn enter_fragment_spread( &mut self, _ctx: &mut Context, _fragment_spread: &'a FragmentSpread<'a>, _info: &VisitInfo, ) -> VisitFlow

Called when a FragmentSpread node is visited and before its child nodes are visited.

fn leave_fragment_spread( &mut self, _ctx: &mut Context, _fragment_spread: &'a FragmentSpread<'a>, _info: &VisitInfo, ) -> VisitFlow

Called after a FragmentSpread node and its child nodes were visited.

fn enter_inline_fragment( &mut self, _ctx: &mut Context, _inline_fragment: &'a InlineFragment<'a>, _info: &VisitInfo, ) -> VisitFlow

Called when an InlineFragment node is visited and before its child nodes are visited.

fn leave_inline_fragment( &mut self, _ctx: &mut Context, _inline_fragment: &'a InlineFragment<'a>, _info: &VisitInfo, ) -> VisitFlow

Called after an InlineFragment node and its child nodes were visited.

fn enter_field( &mut self, _ctx: &mut Context, _field: &'a Field<'a>, _info: &VisitInfo, ) -> VisitFlow

Called when a Field node is visited and before its child nodes are visited.

fn leave_field( &mut self, _ctx: &mut Context, _field: &'a Field<'a>, _info: &VisitInfo, ) -> VisitFlow

Called after a Field node and its child nodes were visited.

fn enter_directive( &mut self, _ctx: &mut Context, _directive: &'a Directive<'a>, _info: &VisitInfo, ) -> VisitFlow

Called when a Directive node is visited and before its child nodes are visited.

fn leave_directive( &mut self, _ctx: &mut Context, _directive: &'a Directive<'a>, _info: &VisitInfo, ) -> VisitFlow

Called after a Directive node and its child nodes were visited.

fn enter_argument( &mut self, _ctx: &mut Context, _argument: &'a Argument<'a>, _info: &VisitInfo, ) -> VisitFlow

Called when an Argument node is visited and before its child nodes are visited.

fn leave_argument( &mut self, _ctx: &mut Context, _argument: &'a Argument<'a>, _info: &VisitInfo, ) -> VisitFlow

Called after an Argument node and its child nodes were visited.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl<'a> Visitor<'a, ValidationContext<'a>> for KnownFragmentNames<'a>

impl<'a> Visitor<'a, ValidationContext<'a>> for LoneAnonymousOperation

impl<'a> Visitor<'a, ValidationContext<'a>> for NoFragmentCycles<'a>

impl<'a> Visitor<'a, ValidationContext<'a>> for NoUndefinedVariables<'a>

impl<'a> Visitor<'a, ValidationContext<'a>> for NoUnusedFragments<'a>

impl<'a> Visitor<'a, ValidationContext<'a>> for UniqueArgumentNames<'a>

impl<'a> Visitor<'a, ValidationContext<'a>> for UniqueFragmentNames<'a>

impl<'a> Visitor<'a, ValidationContext<'a>> for UniqueOperationNames<'a>

impl<'a> Visitor<'a, ValidationContext<'a>> for UniqueVariableNames<'a>

impl<'a, C, A: Visitor<'a, C>, B: Visitor<'a, C>> Visitor<'a, C> for ComposedVisitor<'a, C, A, B>