Serverless-offline is unable to identify the GraphQL handler as a valid function

While attempting to transition my serverless nodejs graphql api to utilize typescript, I encountered an error in which serverless indicated that the graphql handler is not recognized as a function.

The following error message was generated:

Error: Serverless-offline: handler for 'hello' is not a function
    at Object.createHandler (/home/savnik/serverless-webpack-typescript-apollo/node_modules/serverless-offline/src/functionHelper.js:221:11)
    at handler (/home/savnik/serverless-webpack-typescript-apollo/node_modules/serverless-offline/src/ApiGateway.js:485:40)
    at module.exports.internals.Manager.execute (/home/savnik/serverless-webpack-typescript-apollo/node_modules/@hapi/hapi/lib/toolkit.js:41:33)
    at Object.internals.handler (/home/savnik/serverless-webpack-typescript-apollo/node_modules/@hapi/hapi/lib/handler.js:46:48)
    at exports.execute (/home/savnik/serverless-webpack-typescript-apollo/node_modules/@hapi/hapi/lib/handler.js:31:36)
    at Request._lifecycle (/home/savnik/serverless-webpack-typescript-apollo/node_modules/@hapi/hapi/lib/request.js:312:68)
    at processTicksAndRejections (internal/process/task_queues.js:93:5)
    at Request._execute (/home/savnik/serverless-webpack-typescript-apollo/node_modules/@hapi/hapi/lib/request.js:221:9)

The goal is to develop an apollo graphql api using typescript and have the ability to use it offline during development.

To demonstrate the issue, a replication has been created here: https://github.com/savnik/serverless-webpack-typescript-apollo

Any insights on the underlying cause of this problem would be appreciated.

typescriptwebpackapollo-serverserverless-offline

Answer №1

The reason for this issue is that you are still utilizing the 'export' syntax for a JavaScript module.

To resolve this problem, modify the final line in src/handler.ts from 

exports.graphqlHandler = server.createHandler()
to 
export const graphqlHandler = server.createHandler()

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