[Bug] Network errors are discarded.

[dogweather]

If there's an HTTP error, calls to GraphQL::Client can return this:

KeyError: key not found: "data" (KeyError)

E.g., when I try the example in the readme to https://example.com/graphql, I expect some kind of network or HTTP error. Instead, I get the above KeyError.

I got this when making changes to my infrastructure. It made it very hard to debug problems.

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I looked at load_schema, and found:

pry(main)> GraphQL::Client.load_schema(HTTP)
KeyError: key not found: "data" (KeyError)
from gems/3.4.0/gems/graphql-2.5.2/lib/graphql/schema/loader.rb:17:in 'Hash#fetch'

The load_schema call turns into load_schema(dump_schema(HTTP)). dump_schema seems to return full error info. So, between those two function calls, the information is lost:

[pry(main)> GraphQL::Client.dump_schema(HTTP)
=> {"errors" => [{"message" => "403 Forbidden"}]}

This happens other places that call execute, I believe, like .query().

---

In my opinion, the core problem is, the library uses fp-style Either error returns. However, Ruby doesn't have a way (like Rust or Haskell do) to enforce the handling of the error case. And so, it's possible to simply not handle them appropriately, like here.

Either-style API:

graphql-client/lib/graphql/client/http.rb

Lines 62 to 63 in aff5882

	# Returns { "data" => ... , "errors" => ... } Hash.
	def execute(document:, operation_name: nil, variables: {}, context: {})

IMO, the fix is to use Ruby's Exception/Error facility so that library clients can meaningfully handle errors.

[dogweather]

I've added exceptions in a fork. Instead of KeyError, I now get an HTTP exception:

HTTP Error accessing http://127.0.0.1:5000/graphql: 403 Forbidden.
(GraphQL::Client::HTTP::ClientError)

Are you interested in a PR?

[rmosolgo]

Yes, I think this would be a good improvement! All GraphQL responses are supposed to return 200, so it's a safe bet that anything else should be raised. A PR would be great!