Unexpected '__typename not found on object'

[AlistairB]

Hi, possibly related to #493

I got around to using the changes for this feature. They are compiling as expected, however now I am getting a runtime error.

My query looks like:

defineByDocumentFile
  "../resource/minimal-github.graphql"
  [gql|
    query FetchRepoFile ($repoOwner: String!, $repoName: String!, $expression: String!) {
      repository(name: $repoName, owner: $repoOwner) {
        object(expression: $expression) {
          ... on Blob {
            isTruncated
            text
          }
        }
      }
    }
  |]

You can see the schema I am using here https://github.com/AlistairB/morpheus-repro/blob/master/minimal-github.graphql .

The error I am getting: Error in $.data.repository.object: key \"__typename\" not found on object

Running this in the github graphql explorer, eg. this query:

query { 
  repository(name: "react", owner: "facebook") {
    object(expression: "af219cc6e6c514099a667ffab4e2d80c5c0c1bcc:.nvmrc") {
      ... on Blob {
        isTruncated
        text
      }
    }
  }
}

produces this response:

{
  "data": {
    "repository": {
      "object": {
        "isTruncated": false,
        "text": "v12.16.2\n"
      }
    }
  }
}

I can include __typename in the query and will get back in the response "__typename": "Blob" (via the github graphql explorer).

Adding __typename to the query that morpheus is using causes compile time errors eg. Error: \"cant find field DataInterface.

Is this enough info? If not I can set up a repro in https://github.com/AlistairB/morpheus-repro

[nalchevanidze]

hi @AlistairB. please checkout #511

[AlistairB]

Thanks! This works if I change the query to:

defineByDocumentFile
  "../resource/minimal-github.graphql"
  [gql|
    query FetchRepoFile ($repoOwner: String!, $repoName: String!, $expression: String!) {
      repository(name: $repoName, owner: $repoOwner) {
        object(expression: $expression) {
          __typename
          ... on Blob {
            isTruncated
            text
          }
        }
      }
    }
  |]

This works for me as a solution.

However, if I don't add __typename to the query it still fails with the same error. This is a bit unintuitive since I don't need __typename for my purposes, but morpheus seems to require it. I think ideally morpheus would request __typename itself if it needs it even if it isn't in the query.

I could be wrong though. Happy to close if you think this is the right solution.

[nalchevanidze]

@AlistairB you are right, i fixed that too. please checkout #512

[AlistairB]

Unfortunately this is still producing the same error unless I manually include __typename.

I have updated master on https://github.com/AlistairB/morpheus-repro to reproduce the issue.

As per https://github.com/AlistairB/morpheus-repro/blob/master/src/Lib.hs#L50-L52 , you will need to create a github personal access token. Then you can reproduce the issue with stack run.

[AlistairB]

Hi, I've been playing with this a little bit more and noticed another minor issue. In the morpheus-repro example, the master version of morpheus will generate the following type:

data RepositoryObjectGitObject
  = RepositoryObjectGitObject {__typename :: Text} |
    RepositoryObjectBlob {__typename :: Text,
                          isTruncated :: Bool,
                          text :: (Maybe Text)}
  deriving Generic
  deriving Show
  deriving Eq

A sum type with record accessors is considered a bit of an anti-pattern. This is because isTruncated is now a partial function. ie. isTruncated (RepositoryObjectGitObject "blah") will compile, but will error at runtime. The data type will cause a ghc warning if compiled with -Wpartial-fields (which is not enabled by -Wall).

I pushed a new commit to https://github.com/AlistairB/morpheus-repro with the warning enabled to demonstrate the issue.

One solution is just to exclude the accessors, but this would get ugly if you had a lot of fields returned. I think the ideal solution would be something like:

data RepositoryObjectGitObject
  = RepositoryObjectGitObject RepositoryObjectGitObjectValues
  | RepositoryObjectBlob RepositoryObjectBlobValues
  deriving (Generic)
  deriving (Show)
  deriving (Eq)

data RepositoryObjectGitObjectValues = RepositoryObjectGitObjectValues {repositoryObjectGitObjectValues__typename :: Text}

data RepositoryObjectBlobValues = RepositoryObjectBlobValues
  { repositoryObjectBlobValues__typename :: Text, -- actually we need to prefix this now as there can't be overlapping `__typename`. Unless DuplicateRecordFields is enabled.
    isTruncated :: Bool,
    text :: (Maybe Text)
  }

Anyway, as mentioned I think this is minor. It could be a separate issue (I can create if you want), or not worried about. Just thought I'd mention it.

[nalchevanidze]

hi @AlistairB ,

Hi, I've been playing with this a little bit more and noticed another minor issue. In the morpheus-repro example, the master version of morpheus will generate the following type:

please address it in different issue :)

Unfortunately this is still producing the same error unless I manually include __typename.

i checked this out. i will address this problem later, as long as it is not as trivial as i thought

[nalchevanidze]

finally fixed it. see #773