Schema parsing fails when a union has a leading pipe

[mattcosta7]

Describe the bug

Prettier version 3.2.0 started formatting unions in schemas with a leading bar when they are defined across lines
When consuming/validating a schema using this gem, however, we get an error when using that formatting standard.

see: prettier/prettier#15870

Which notes that this syntax has been support for years (since graphql 0.10.3) - prettier/prettier#15870 (comment) https://github.com/graphql/graphql-js/releases/tag/v0.10.3

see: https://prettier.io/blog/2024/01/12/3.2.0#graphql

this gem's parser fails on schemas like this with

    it "is parsed for union definitions when the union has a leading bar" do
      document = subject.parse <<-GRAPHQL
        "Thing description"
        union Thing = 
          | Int 
          | String
      GRAPHQL

      thing_defn = document.definitions[0]
      assert_equal "Thing", thing_defn.name
      assert_equal "Thing description", thing_defn.description
    end

Error:
GraphQL::Language::Parser::string description#test_0004_is parsed for union definitions:
GraphQL::ParseError: Expected NAME, actual: PIPE ("|") at [3, 11]
    lib/graphql/language/parser.rb:799:in `raise_parse_error'
    lib/graphql/language/parser.rb:788:in `expect_token'
    lib/graphql/language/parser.rb:627:in `parse_name'
    lib/graphql/language/parser.rb:640:in `parse_type_name'
    lib/graphql/language/parser.rb:401:in `parse_union_members'
    lib/graphql/language/parser.rb:335:in `definition'
    lib/graphql/language/parser.rb:103:in `document'
    lib/graphql/language/parser.rb:45:in `block in parse'
    lib/graphql/tracing/trace.rb:24:in `parse'
    lib/graphql/language/parser.rb:44:in `parse'
    lib/graphql/language/parser.rb:16:in `parse'
    lib/graphql.rb:38:in `parse'
    spec/graphql/language/parser_spec.rb:253:in `block (3 levels) in <top (required)>'

Versions

graphql version: all as far as I can tell

GraphQL schema

Include relevant types and fields (in Ruby is best, in GraphQL IDL is ok). Any custom extensions, etc?

GraphQL schema

union Thing = 
    | Int 
    | String

Additional context

Add any other context about the problem here.

With these details, we can efficiently hunt down the bug!

[rmosolgo]

Hey, thanks for the detailed report! I never noticed that a leading pipe was valid syntax, but sure enough: https://github.com/graphql/graphql-spec/blame/f8f2fac7478df812af885f7f8470cdb5a6c1659b/spec/Section%203%20--%20Type%20System.md#L1410-L1411

I agree, the parser should handle this without a hitch 👍