Module apollo_parser::ast
source · Expand description
Typed AST module to access nodes in the tree.
The nodes described here are those also described in the GraphQL grammar,
with a few exceptions. For example, for easy of querying the AST we do not
separate Definition into ExecutableDefinition and
TypeSystemDefinitionOrExtension. Instead, all possible definitions and
extensions can be accessed with Definition.
Each struct in this module has getter methods to access information that’s
part of its node. For example, as per spec a UnionTypeDefinition is defined as follows:
UnionTypeDefinition =
Description? 'union' Name Directives? UnionMemberTypes?
It will then have getters for Description, union token, Name,
Directives and UnionMemberTypes. Checkout documentation for the Struct
you’re working with to find out its exact API.
Example
This example parses a subgraph schema and looks at the various Definition Names.
use apollo_parser::{ast, Parser};
let schema = r#"
directive @tag(name: String!) repeatable on FIELD_DEFINITION
type ProductVariation {
id: ID!
}
scalar UUID @specifiedBy(url: "https://tools.ietf.org/html/rfc4122")
union SearchResult = Photo | Person
extend type Query {
allProducts: [Product]
product(id: ID!): Product
}
"#;
let parser = Parser::new(schema);
let ast = parser.parse();
assert_eq!(0, ast.errors().len());
let document = ast.document();
for definition in document.definitions() {
match definition {
ast::Definition::DirectiveDefinition(directive) => {
assert_eq!(
directive
.name()
.expect("Cannot get directive name.")
.text()
.as_ref(),
"tag"
)
}
ast::Definition::ObjectTypeDefinition(object_type) => {
assert_eq!(
object_type
.name()
.expect("Cannot get object type definition name.")
.text()
.as_ref(),
"ProductVariation"
)
}
ast::Definition::UnionTypeDefinition(union_type) => {
assert_eq!(
union_type
.name()
.expect("Cannot get union type definition name.")
.text()
.as_ref(),
"SearchResult"
)
}
ast::Definition::ScalarTypeDefinition(scalar_type) => {
assert_eq!(
scalar_type
.name()
.expect("Cannot get scalar type definition name.")
.text()
.as_ref(),
"UUID"
)
}
ast::Definition::ObjectTypeExtension(object_type) => {
assert_eq!(
object_type
.name()
.expect("Cannot get object type extension name.")
.text()
.as_ref(),
"Query"
)
}
_ => unimplemented!(),
}
}Structs
SyntaxNode children of a particular AST type.Enums
Traits
SyntaxNode to a typed ast. The
conversion itself has zero runtime cost: ast and syntax nodes have exactly
the same representation: a pointer to the tree root and a pointer to the
node itself.AstNode, but wraps tokens rather than interior nodes.Type Definitions
SyntaxNodePtr.