Parsing SDL allows true, false, and null for enum value names

[Yogu]

There is a schema validator that forbids true, false, and null as enum value names sinde https://github.com/graphql/graphql-js/pull/812/files. The parse function together with the specifiedSDLRules rules however allow these strings to be used as enum value names/values (they're the same there). This means you can parse and successfully validate an SDL which generates a validation error when creating the schema.

I'm not quite sure whether this is a bug in the parser or a missing SDL validator. parseEnumValueDefinition uses parseName and states that the EnumValue non-terminal is equivalent to the name non-terminal:

  /**
   * EnumValueDefinition : Description? EnumValue Directives[Const]?
   *
   * EnumValue : Name
   */
  ;

  _proto.parseEnumValueDefinition = function parseEnumValueDefinition() {
    var start = this._lexer.token;
    var description = this.parseDescription();
    var name = this.parseName();
    var directives = this.parseDirectives(true);
    return {
      kind: Kind.ENUM_VALUE_DEFINITION,
      description: description,
      name: name,
      directives: directives,
      loc: this.loc(start)
    };
  }

There also is an EnumValue non-terminal which is defined as follows:

EnumValue : Name but not true, false or null

So an enum declaration either should switch from EnumName to EnumValue, or there should be an SDL validator that rejects the three forbidden words when used as enum value names/values.

[renatobenks]

what a catch, sounds like a missing thing, interesting 🤔

I had a problem related a couple years ago, using schema-stitching from graphql-tools, which he was re-creating the entire schema, and the enums became syntactically problematic, probably because of this.

[Yogu]

I looked into the specification. It's actually a bug in the parser. Section 3.9 defines the EnumValueDefinition as follows:

EnumValueDefinition :
Description[opt] EnumValue Directives[Const][opt]

And section 2.9.6 defines EnumValue:

EnumValue :
Name but not true or false or null

I'll create a PR for this fix.

[IvanGoncharov]

@Yogu Thanks for reporting and especially for working on a fix 👍
Closing and we will track progress in #3223