csboling/parser

A lexer and parser for GraphQL in .NET

GraphQL Dotnet Parser

This library contains a lexer and parser classes as well as the complete GraphQL AST model.

The parser from this library is used in GraphQL for .NET.

Lexer

Generates token based on input text.

Usage

var lexer = new Lexer();
var token = lexer.Lex(new Source("\"str\""));

Lex method always returns the first token it finds. In this case case the result would look like following.

Also lexer can use the cache to save on memory allocations for named tokens in the managed heap:

var cache = new DictionaryCache(); // for single-threaded usage
var cache = new ConcurrentDictionaryCache(); // for multi-threaded usage
var lexer = new Lexer { Cache = cache };           

By default the cache is not used. You can find some results of testing with and without the cache in this file. Keep in mind that the advantages and disadvantages of using the cache appear depending on the specific usage scenario, so it is strongly recommended that you obtain some metrics before and after using the cache to ensure that you achieve the desired result.

Parser

Parses provided GraphQL expression into AST (abstract syntax tree).

Usage

var lexer = new Lexer();
var parser = new Parser(lexer);
var ast = parser.Parse(new Source(@"
{
  field
}"));

Json representation of the resulting AST would be:

{
	"Definitions": [{
		"Directives": [],
		"Kind": 2,
		"Name": null,
		"Operation": 0,
		"SelectionSet": {
			"Kind": 5,
			"Selections": [{
				"Alias": null,
				"Arguments": [],
				"Directives": [],
				"Kind": 6,
				"Name": {
					"Kind": 0,
					"Value": "field",
					"Location": {
						"End": 50,
						"Start": 31
					}
				},
				"SelectionSet": null,
				"Location": {
					"End": 50,
					"Start": 31
				}
			}],
			"Location": {
				"End": 50,
				"Start": 13
			}
		},
		"VariableDefinitions": null,
		"Location": {
			"End": 50,
			"Start": 13
		}
	}],
	"Kind": 1,
	"Location": {
		"End": 50,
		"Start": 13
	}
}