SwiftGraphQl

Use SwiftGraphQl to parse GraphQL documents (queries and type definitions). SwiftGraphQl defines a complete abstract syntax tree for programmatically working with GraphQL documents. It aims to be (though is not quite yet) fully compliant with the latest working draft of the GraphQL spec.

SwiftGraphQl has only one dependency which is SwiftParse, a purely swift-based parser combinator library.

Example

let source = """
query GetPost($postId: ID!) {
  post(id: $postId) {
    title
    created_at
  }
}
"""
let document = try! parseGraphQl(source: source)
print(document)

The code snippet above produces the following AST:

[
    SwiftGraphQl.ExecutableDefinition.opDefinition (
        SwiftGraphQl.OperationDefinition (
            selectionSet : [
                SwiftGraphQl.Selection.field (
                    SwiftGraphQl.Field (
                        alias : nil,
                        name : "post",
                        arguments : [
                            SwiftGraphQl.Argument (
                                name : "id",
                                value : SwiftGraphQl.Value.variable ("postId")
                            )
                        ],
                        directives : [],
                        selectionSet : [
                            SwiftGraphQl.Selection.field (
                                SwiftGraphQl.Field (
                                    alias : nil,
                                    name : "title",
                                    arguments : [],
                                    directives : [],
                                    selectionSet : []
                                )
                            ),
                            SwiftGraphQl.Selection.field (
                                SwiftGraphQl.Field (
                                    alias : nil,
                                    name : "created_at",
                                    arguments : [],
                                    directives : [],
                                    selectionSet : []
                                )
                            )
                        ]
                    )
                )
            ],
            operationType : SwiftGraphQl.OperationType.query,
            name : Optional ("GetPost"),
            variableDefinitions : [
                SwiftGraphQl.VariableDefinition (
                    name : "postId",
                    type : SwiftGraphQl.Type.required (SwiftGraphQl.Type.named("ID")),
                    defaultValue : nil,
                    directives : []
                )
            ],
            directives : []
        )
    )
]

Not exactly for human consumption but great for your programmatic needs.

Command line interface

SwiftGraphQl also comes with a command line interface: graphql-cli.

graphql-cli --help
usage: graphql-cli parse [filename]
Use `-` in place of `[filename]` to read from stdin.

If the document can be parsed successfully, the program exits with success status (0). If it cannot be parsed, a terse error message is emitted to standard error and the program exists with status code of 1.

Pass - in place of [filename] if the document to be parsed is available for reading on stdin instead of from a file:

echo "query TotallyValidQuery { foo }" | graphql-cli parse -