Compatibility for Jest 28

[EvHaus]

jest-transform-graphql module fails in Jest 28 with this error:

Invalid return value:
      `process()` or/and `processAsync()` method of code transformer found at 
      "/Users/evhaus/Git/zenhub/node_modules/jest-transform-graphql/index.js" 
      should return an object or a Promise resolving to an object. The object 
      must have `code` property with a string of processed code.
      This error may be caused by a breaking change in Jest 28:
      https://jestjs.io/docs/upgrading-to-jest28#transformer
      Code Transformation Documentation:
      https://jestjs.io/docs/code-transformation

This is due to the change here: https://jestjs.io/docs/upgrading-to-jest28#transformer

Unfortunately this PR will make jest-transform-graphql no longer compatible with Jest <=27, so it would need to be published a new major version change.

You can test this PR by installing it your project via this npm dependency definition:

"devDependencies": {
    "jest-transform-graphql": "remind101/jest-transform-graphql#pull/11/head",
}

[benrowe-chuffed]

I think you mean Jest 28, but im having the same issue.

[JiaboHou]

Unfortunately this PR will make jest-transform-graphql no longer compatible with Jest <=27, so it would need to be published a new major version change.

Are you sure? I've tried installing this version to a private repo of mine still on jest 27.5.1, and the tests are still working for me. Could I be doing something wrong?

[EvHaus]

Are you sure?

Not at all. I assumed that because of the API syntax change older versions might not support it, but I'm happy to be wrong here. I do suspect though that not all older versions of Jest will support it. It's good that 27 does but what about 26, 25, 24? I haven't tested to see where it falls apart.

[JiaboHou]

That's fair. Better safe than sorry to mention that for sure. I did some quick digging and it looks like according to the types definition file at least, strings and TransformedSource types have been supported for quite some time.

Looks like support for returning a TransformedSource type was introduced here, in version... v20?: Aftabnack/jest@c6d2b08#diff-0edc0d624e256a618a4b6ca7fe68e9a198c70b4a7c20144b0ca2e4410c7efb94R45

[gerisztein]

any update on this?

[chrisbruford]

for anyone waiting for this to be merged - you can just put the contents of index.js into a file in your own repo and then refer to that file in your jest config e.g.

transform: {
    '\\.(gql|graphql)$': './src/utils/gqlTransformer',
    '\\.[jt]sx?$': 'babel-jest'
}

[dobesv]

This change should be good, but I guess the project is no longer maintained.

[neatcoding]

It would be great if the maintainer released this.

Solves issue #13

[andypearson]

Has anyone managed to get this fix working with TypeScript, Apollo, and Jest 29?

I've implemented this change to the process function, but now I seem to be getting:

TypeError: Cannot convert object to primitive value
    at String.concat (<anonymous>)

At the point that the GraphQL is used in my client code, for example:

const { ... } = useQuery(getViewerQuery)

Any thoughts would be appreciated, I've already lost 4 hours :D