Remote Scala Eval

The remote Scala evaluator is a server based application that allows remote evaluation of arbitrary Scala code.

Run from sources

sbt "project evaluator-server" "run"

Authentication

The remote Scala eval uses JWT to encode / decode tokens. The secretKey used for encoding/decoding is configurable as part of the service configuration in server/src/main/resources/application.conf.

Please change secretKey by overriding it or providing the EVAL_SECRET_KEY env var.

eval.auth {
  secretKey = "secretKey"
  secretKey = ${?EVAL_SECRET_KEY}
}

Generate an auth token

In order to generate an auth token you may use the scala console and invoke the org.scalaexercises.evaluator.auth#generateToken like so

sbt "project evaluator-server" "console"

scala> import org.scalaexercises.evaluator.auth._

scala> generateToken("your identity")
res0: String = eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eW91ciBpZGVudGl0eQ.cfH43Wa7k_w1i0W2pQhV1k21t2JqER9lw5EpJcENRMI

Note your identity is exclusively to identify incoming requests for logging purposes. The Scala evaluator will authorize any incoming request generated with the secretKey

Request

Requests are sent in JSON format via HTTP POST and are authenticated via the x-scala-eval-api-token header.

Sample Request

Given the token above a sample request may look like:

curl -X POST -H "Content-Type: application/json" -H "x-scala-eval-api-token: eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eW91ciBpZGVudGl0eQ.cfH43Wa7k_w1i0W2pQhV1k21t2JqER9lw5EpJcENRMI" -d '{
   "resolvers":[
      "https://oss.sonatype.org/content/repositories/releases"
   ],
   "dependencies":[
      {
         "groupId":"org.typelevel",
         "artifactId":"cats-core_2.11",
         "version":"0.4.1"
      }
   ],
   "code":"{import cats._; Monad[Id].pure(42)}"
}
' "http://localhost:8080/eval"

Headers

Content-Type : application/json
x-scala-eval-api-token : eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eW91ciBpZGVudGl0eQ.cfH43Wa7k_w1i0W2pQhV1k21t2JqER9lw5EpJcENRMI 

Body

{
   "resolvers":[
      "https://oss.sonatype.org/content/repositories/releases"
   ],
   "dependencies":[
      {
         "groupId":"org.typelevel",
         "artifactId":"cats-core_2.11",
         "version":"0.4.1"
      }
   ],
   "code":"{import cats._; Monad[Id].pure(42)}"
}

• resolvers : A list of resolvers where artifacts dependencies are hosted
• dependencies : A List of artifacts required to eval the code
• code : Some Scala Code

Response

After compiling and attempting to evaluate the server will return a response payload with the following fields:

• msg : A message indicating the result of the compilation and evaluation. Note failing to compile still yields http status 200 as the purpose of the service is to output a result without judging if the input was correct or not.
• value : The result of the evaluation or null if it didn't compile or an exception is thrown.
• valueType : The type of result or null if it didn't compile or an exception is thrown
• compilationInfos : A map of compilation severity errors and their associated message

For ilustration purposes here is a few Response Payload examples:

Successful compilation and Evaluation

{
  "msg": "Ok",
  "value": "42",
  "valueType": "java.lang.Integer",
  "compilationInfos": {}
}

Compilation Failure

{
  "msg": "Compilation Error",
  "value": null,
  "valueType": null,
  "compilationInfos": {
    "ERROR": [
      {
        "message": "value x is not a member of cats.Monad[cats.Id]",
        "pos": {
          "start": 165,
          "point": 165,
          "end": 165
        }
      }
    ]
  }
}

Evaluating code that may result in a thrown exception

{
  "msg": "Runtime Error",
  "value": null,
  "valueType": null,
  "compilationInfos": {}
}