Crate apollo_parser
source · [−]Expand description
Features
- Typed GraphQL AST as per October 2021 specification
- Error resilience
- lexing and parsing does not fail or
panic
if a lexical or a syntax error is found
- lexing and parsing does not fail or
- The AST produced is lossless, meaning all ignored tokens like whitespace and commas are kept in the tree
- GraphQL lexer
- GraphQL parser
Getting started
Add this to your Cargo.toml
to start using apollo-parser
:
[dependencies]
apollo-parser = "0.2.1"
Or using cargo-edit:
cargo add apollo-parser
Usage
apollo-parser
is built to parse both GraphQL schemas and queries according to the latest October 2021 specification. It produces
a typed syntax tree that then can be walked, extracting all the necessary
information. You can quick start with:
use apollo_parser::Parser;
let input = "union SearchResult = Photo | Person | Cat | Dog";
let parser = Parser::new(input);
let ast = parser.parse();
apollo-parser
is built to be error-resilient. This means we don’t abort parsing (or lexing) if an error occurs. That means parser.parse()
will always produce an AST, and it will be accompanied by any errors that are encountered:
use apollo_parser::Parser;
let input = "union SearchResult = Photo | Person | Cat | Dog";
let parser = Parser::new(input);
let ast = parser.parse();
// ast.errors() returns an errors slice encountered during lexing and parsing
assert_eq!(0, ast.errors().len());
// ast.document() get the Document, or root node, of the tree that you can
// start iterating on.
let doc = ast.document();
Examples
Two examples outlined here:
The examples directory in this repository has a few more useful implementations such as:
- using apollo-rs with miette to display error diagnostics
- using apollo-rs with annotate_snippets to display error diagnostics
- checking for unused variables
Get field names in an object
use apollo_parser::{ast, Parser};
let input = "
type ProductDimension {
size: String
weight: Float @tag(name: \"hi from inventory value type field\")
}
";
let parser = Parser::new(input);
let ast = parser.parse();
assert_eq!(0, ast.errors().len());
let doc = ast.document();
for def in doc.definitions() {
if let ast::Definition::ObjectTypeDefinition(object_type) = def {
assert_eq!(object_type.name().unwrap().text(), "ProductDimension");
for field_def in object_type.fields_definition().unwrap().field_definitions() {
println!("{}", field_def.name().unwrap().text()); // size weight
}
}
}
Get variables used in a query
use apollo_parser::{ast, Parser};
let input = "
query GraphQuery($graph_id: ID!, $variant: String) {
service(id: $graph_id) {
schema(tag: $variant) {
document
}
}
}
";
let parser = Parser::new(input);
let ast = parser.parse();
assert_eq!(0, ast.errors().len());
let doc = ast.document();
for def in doc.definitions() {
if let ast::Definition::OperationDefinition(op_def) = def {
assert_eq!(op_def.name().unwrap().text(), "GraphQuery");
let variable_defs = op_def.variable_definitions();
let variables: Vec<String> = variable_defs
.iter()
.map(|v| v.variable_definitions())
.flatten()
.filter_map(|v| Some(v.variable()?.text().to_string()))
.collect();
assert_eq!(
variables.as_slice(),
["graph_id".to_string(), "variant".to_string()]
);
}
}
License
Licensed under either of
- Apache License, Version 2.0 (LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or https://opensource.org/licenses/MIT)
at your option.
Modules
Typed AST module to access nodes in the tree.
Macros
Structs
An Error
type for operations performed in the lexer and the parser.
Parse GraphQL schemas or queries into a typed AST.
An AST generated by the parser. Consists of a syntax tree and a Vec<Error>
if any.