Add support for custom event serialization (Was: Serialization is breaking Dates)

I’m using the Date type as in this documentation page https://www.apollographql.com/docs/graphql-tools/scalars.html

  Date: new GraphQLScalarType({
    name: 'Date',
    description: 'Date custom scalar type',
    parseValue(value) {
      return new Date(value); // value from the client
    },
    serialize(value) {
      return value.getTime(); // value sent to the client
    },
    parseLiteral(ast) {
      if (ast.kind === Kind.INT) {
        return parseInt(ast.value, 10); // ast value is always in string format
      }
      return null;
    },
  }),

I’m doing a findOne with Mongoose, and pass the returned document to the pubsub like this:

pubsub.publish('bookUpdated', { bookUpdated: book });

In my network tab, in the websocket, I’m getting the following error:

value.getTime is not a function in ["bookUpdated", "events", 1, "timestamp"]

The same code works without problem with the in-memory PubSub. This bug only affects RedisPubSub. Certainly because of the use of JSON.stringify and JSON.parse. See https://stackoverflow.com/questions/4511705/how-to-parse-json-to-receive-a-date-object-in-javascript

So I’m not sure if this can be considered a graphql-redis-subscriptions bug, but both PubSub are supposed to give the same result, I think.

[awwong1]

I thought about this some more and made this a configurable option instead. Probably don’t want to make all users suffer a performance hit. Not setting the reviver defaults to existing functionality.

Took 10939.090882ms	 for 2000000 * JSON.parse(val)
Took 1097.195139ms	 for 200000 * JSON.parse(val)
Took 117.38736ms	 for 20000 * JSON.parse(val)
Took 14.088721ms	 for 2000 * JSON.parse(val)
Took 1.155448ms		 for 200 * JSON.parse(val)
Took 0.164362ms		 for 20 * JSON.parse(val)
Took 0.03583ms		 for 2 * JSON.parse(val)
Took 18939.705402ms	 for 2000000 * JSON.parse(val, dateRevier)
Took 1946.931366ms	 for 200000 * JSON.parse(val, dateRevier)
Took 200.24652ms	 for 20000 * JSON.parse(val, dateRevier)
Took 18.73888ms		 for 2000 * JSON.parse(val, dateRevier)
Took 2.133128ms		 for 200 * JSON.parse(val, dateRevier)
Took 0.377002ms		 for 20 * JSON.parse(val, dateRevier)
Took 0.069415ms		 for 2 * JSON.parse(val, dateRevier)

I think, in the future, better serialization and deserialization support is ideal (flattening the json object, handling custom constructors, etc.) but this works for our use case right now and has minimal impact.

[davidyaha]

Hey @awwong1! Sorry for the delay, just published graphql-redis-subscriptions@1.5.0 Let me know if there are any problems with the new release.