Refactor errors, introduce type parameter in Error

oauth2/src/main/scala/com/ocadotechnology/sttp/oauth2/AccessTokenProvider.scala

@@ -36,7 +36,7 @@ object AccessTokenProvider {
       override def requestToken(scope: Scope): F[ClientCredentialsToken.AccessTokenResponse] =
         ClientCredentials
           .requestToken(tokenUrl, clientId, clientSecret, scope)(backend)
-          .map(_.leftMap(OAuth2Exception).toTry)
+          .map(_.leftMap(_.toException).toTry)
           .flatMap(backend.responseMonad.fromTry)
 
     }

oauth2/src/main/scala/com/ocadotechnology/sttp/oauth2/ClientCredentialsToken.scala

@@ -4,19 +4,12 @@ import com.ocadotechnology.sttp.oauth2.common._
 import io.circe.Decoder
 import io.circe.refined._
 import sttp.client3.ResponseAs
-import com.ocadotechnology.sttp.oauth2.common.Error.OAuth2Error
 
 import scala.concurrent.duration.FiniteDuration
 
 object ClientCredentialsToken {
 
-  type Response = Either[Error, ClientCredentialsToken.AccessTokenResponse]
-
-  private[oauth2] implicit val bearerTokenResponseDecoder: Decoder[Either[OAuth2Error, AccessTokenResponse]] =
-    circe.eitherOrFirstError[AccessTokenResponse, OAuth2Error](
-      Decoder[AccessTokenResponse],
-      Decoder[OAuth2Error]
-    )
+  type Response = Either[Error[Throwable], ClientCredentialsToken.AccessTokenResponse]
 
   val response: ResponseAs[Response, Any] =
     common.responseWithCommonError[ClientCredentialsToken.AccessTokenResponse]

oauth2/src/main/scala/com/ocadotechnology/sttp/oauth2/Introspection.scala

@@ -11,7 +11,7 @@ import java.time.Instant
 
 object Introspection {
 
-  type Response = Either[common.Error, Introspection.TokenIntrospectionResponse]
+  type Response = Either[common.Error[Throwable], Introspection.TokenIntrospectionResponse]
 
   val response: ResponseAs[Response, Any] =
     common.responseWithCommonError[TokenIntrospectionResponse]

oauth2/src/main/scala/com/ocadotechnology/sttp/oauth2/OAuth2Token.scala

@@ -6,7 +6,7 @@ import sttp.client3.ResponseAs
 object OAuth2Token {
 
   // TODO: should be changed to Response[A] and allow custom responses, like in AuthorizationCodeGrant
-  type Response = Either[Error, ExtendedOAuth2TokenResponse]
+  type Response = Either[Error[Throwable], ExtendedOAuth2TokenResponse]
 
   val response: ResponseAs[Response, Any] =
     common.responseWithCommonError[ExtendedOAuth2TokenResponse]

oauth2/src/main/scala/com/ocadotechnology/sttp/oauth2/PasswordGrantProvider.scala

@@ -23,7 +23,7 @@ object PasswordGrantProvider {
   )(
     backend: SttpBackend[F, Any]
   ): PasswordGrantProvider[F] = { (user: User, scope: Scope) =>
-    PasswordGrant.requestToken(tokenUrl, user, clientId, clientSecret, scope)(backend).map(_.leftMap(OAuth2Exception)).rethrow
+    PasswordGrant.requestToken(tokenUrl, user, clientId, clientSecret, scope)(backend).map(_.leftMap(_.toException)).rethrow
   }
 
 }

oauth2/src/main/scala/com/ocadotechnology/sttp/oauth2/TokenIntrospection.scala

@@ -37,7 +37,7 @@ object TokenIntrospection {
       override def introspect(token: Secret[String]): F[Introspection.TokenIntrospectionResponse] =
         ClientCredentials
           .introspectToken(tokenIntrospectionUrl, clientId, clientSecret, token)(backend)
-          .map(_.leftMap(OAuth2Exception).toTry)
+          .map(_.leftMap(_.toException).toTry)
           .flatMap(backend.responseMonad.fromTry)
 
     }

oauth2/src/main/scala/com/ocadotechnology/sttp/oauth2/common.scala

@@ -1,7 +1,7 @@
 package com.ocadotechnology.sttp.oauth2
 
 import cats.syntax.all._
-import com.ocadotechnology.sttp.oauth2.common.Error.OAuth2Error
+import com.ocadotechnology.sttp.oauth2.common.Error.{OAuth2Error, errorDecoder}
 import com.ocadotechnology.sttp.oauth2.common.Error.OAuth2ErrorResponse.InvalidClient
 import com.ocadotechnology.sttp.oauth2.common.Error.OAuth2ErrorResponse.InvalidGrant
 import com.ocadotechnology.sttp.oauth2.common.Error.OAuth2ErrorResponse.InvalidRequest
@@ -40,21 +40,30 @@ object common {
     def refine: RefineMPartiallyApplied[Refined, ValidScope] = refineMV[ValidScope]
   }
 
-  sealed trait Error extends Throwable with Product with Serializable
+  final case class OAuth2Exception[E <: Throwable](inner: Error[E]) extends Exception(s"${inner.message}: ${inner.error.getMessage}", inner.error)
+
+  sealed trait Error[E] extends Product with Serializable {
+    def error: E
+    def message: String
+  }
 
   object Error {
 
-    final case class HttpClientError(statusCode: StatusCode, cause: Throwable)
-      extends Exception(s"Client call resulted in error ($statusCode): ${cause.getMessage}", cause)
-      with Error
+    final case class HttpClientError(statusCode: StatusCode, error: Throwable) extends Error[Throwable] {
+      val message: String = s"Client call resulted in error ($statusCode)"
+    }
 
-    sealed trait OAuth2Error extends Error
+    sealed trait OAuth2Error[E] extends Error[E]
 
     /** Token errors as listed in documentation: https://tools.ietf.org/html/rfc6749#section-5.2
       */
-    final case class OAuth2ErrorResponse(errorType: OAuth2ErrorResponse.OAuth2ErrorResponseType, errorDescription: Option[String])
-      extends Exception(errorDescription.fold(s"$errorType")(description => s"$errorType: $description"))
-      with OAuth2Error
+    final case class OAuth2ErrorResponse[E](
+      errorType: OAuth2ErrorResponse.OAuth2ErrorResponseType,
+      errorDescription: Option[String],
+      error: E
+    ) extends OAuth2Error[E] {
+      val message: String = errorDescription.fold(s"$errorType")(description => s"$errorType: $description")
+    }
 
     object OAuth2ErrorResponse {
 
@@ -74,41 +83,45 @@ object common {
 
     }
 
-    final case class UnknownOAuth2Error(error: String, errorDescription: Option[String])
-      extends Exception(
-        errorDescription.fold(s"Unknown OAuth2 error type: $error")(description =>
-          s"Unknown OAuth2 error type: $error, description: $description"
-        )
+    final case class UnknownOAuth2Error[E](errorString: String, errorDescription: Option[String], error: E)
+      extends OAuth2Error[E] {
+
+      val message: String = errorDescription.fold(s"Unknown OAuth2 error type: $errorString")(description =>
+        s"Unknown OAuth2 error type: $errorString, description: $description"
       )
-      with OAuth2Error
 
-    implicit val errorDecoder: Decoder[OAuth2Error] =
-      Decoder.forProduct2[OAuth2Error, String, Option[String]]("error", "error_description") { (error, description) =>
+    }
+
+    def errorDecoder[E](cause: E): Decoder[OAuth2Error[E]] =
+      Decoder.forProduct2[OAuth2Error[E], String, Option[String]]("error", "error_description") { (error, description) =>
         error match {
-          case "invalid_request"        => OAuth2ErrorResponse(InvalidRequest, description)
-          case "invalid_client"         => OAuth2ErrorResponse(InvalidClient, description)
-          case "invalid_grant"          => OAuth2ErrorResponse(InvalidGrant, description)
-          case "unauthorized_client"    => OAuth2ErrorResponse(UnauthorizedClient, description)
-          case "unsupported_grant_type" => OAuth2ErrorResponse(UnsupportedGrantType, description)
-          case "invalid_scope"          => OAuth2ErrorResponse(InvalidScope, description)
-          case unknown                  => UnknownOAuth2Error(unknown, description)
+          case "invalid_request"        => OAuth2ErrorResponse(InvalidRequest, description, cause)
+          case "invalid_client"         => OAuth2ErrorResponse(InvalidClient, description, cause)
+          case "invalid_grant"          => OAuth2ErrorResponse(InvalidGrant, description, cause)
+          case "unauthorized_client"    => OAuth2ErrorResponse(UnauthorizedClient, description, cause)
+          case "unsupported_grant_type" => OAuth2ErrorResponse(UnsupportedGrantType, description, cause)
+          case "invalid_scope"          => OAuth2ErrorResponse(InvalidScope, description, cause)
+          case unknown                  => UnknownOAuth2Error(unknown, description, cause)
         }
       }
 
   }
 
-  private[oauth2] def responseWithCommonError[A](implicit decoder: Decoder[A]): ResponseAs[Either[Error, A], Any] =
-    asJson[A].mapWithMetadata { case (either, meta) =>
-      either match {
-        case Left(HttpError(response, statusCode)) if statusCode.isClientError =>
-          decode[OAuth2Error](response)
-            .fold(error => Error.HttpClientError(statusCode, DeserializationException(response, error)).asLeft[A], _.asLeft[A])
-        case Left(sttpError)                                                   => Left(Error.HttpClientError(meta.code, sttpError))
-        case Right(value)                                                      => value.asRight[Error]
-      }
+  private[oauth2] def responseWithCommonError[A](implicit decoder: Decoder[A]): ResponseAs[Either[Error[Throwable], A], Any] =
+    asJson[A].mapWithMetadata {
+      case (either, meta) =>
+        either match {
+          case Left(HttpError(response, statusCode)) if statusCode.isClientError =>
+            decode[OAuth2Error[Throwable]](response)(errorDecoder(HttpError(response, statusCode)))
+              .fold(error => Error.HttpClientError(statusCode, DeserializationException(response, error)).asLeft[A], _.asLeft[A])
+          case Left(sttpError)                                                           => Left(Error.HttpClientError(meta.code, sttpError))
+          case Right(value)                                                              => value.asRight[Error[Throwable]]
+        }
     }
 
-  final case class OAuth2Exception(error: Error) extends Exception(error.getMessage, error)
+  final implicit class ErrorToException[E <: Throwable](error: Error[E]) {
+    def toException: Throwable = OAuth2Exception(error)
+  }
 
   final case class ParsingException(msg: String) extends Exception(msg)
 

oauth2/src/test/scala/com/ocadotechnology/sttp/oauth2/ClientCredentialsSpec.scala

@@ -2,20 +2,20 @@ package com.ocadotechnology.sttp.oauth2
 
 import com.ocadotechnology.sttp.oauth2.common.Scope
 import com.ocadotechnology.sttp.oauth2.common.Error
-
 import org.scalatest.wordspec.AnyWordSpec
 import org.scalatest.matchers.should.Matchers
 import sttp.model.Uri
 import sttp.client3.testing._
 import sttp.monad.TryMonad
+
 import scala.util.Try
 import eu.timepit.refined.types.string.NonEmptyString
 import eu.timepit.refined.auto._
 import org.scalatest.TryValues
 import org.scalatest.EitherValues
 import sttp.model.StatusCode
 import sttp.model.Method
-import sttp.client3.Request
+import sttp.client3.{HttpError, Request}
 
 import scala.concurrent.duration._
 
@@ -72,20 +72,19 @@ class ClientCredentialsSpec extends AnyWordSpec with Matchers with TryValues wit
 
     oauth2Errors.foreach { case (errorKey, errorDescription, statusCode, error) =>
       s"support $errorKey OAuth2 error" in {
+        val body = s"""
+                  |{
+                  |"error":"$errorKey",
+                  |"error_description":"$errorDescription"
+                  |}
+                  |""".stripMargin
 
         val testingBackend = SttpBackendStub(TryMonad)
           .whenRequestMatches(validTokenRequest)
-          .thenRespond(
-            s"""
-            {
-            "error":"$errorKey",
-            "error_description":"$errorDescription"
-            }
-            """,
-            statusCode
-          )
-
-        requestToken(testingBackend).success.value.left.value shouldBe Error.OAuth2ErrorResponse(error, Some(errorDescription))
+          .thenRespond(body, statusCode)
+
+        requestToken(testingBackend).success.value.left.value shouldBe
+          Error.OAuth2ErrorResponse(error, Some(errorDescription), HttpError(body, statusCode))
       }
     }
 
@@ -133,20 +132,19 @@ class ClientCredentialsSpec extends AnyWordSpec with Matchers with TryValues wit
 
     oauth2Errors.foreach { case (errorKey, errorDescription, statusCode, error) =>
       s"support $errorKey OAuth2 error" in {
+        val body = s"""
+            |{
+            |"error":"$errorKey",
+            |"error_description":"$errorDescription"
+            |}
+            |""".stripMargin
 
         val testingBackend = SttpBackendStub(TryMonad)
           .whenRequestMatches(validIntrospectRequest)
-          .thenRespond(
-            s"""
-            {
-            "error":"$errorKey",
-            "error_description":"$errorDescription"
-            }
-            """,
-            statusCode
-          )
-
-        introspectToken(testingBackend).success.value.left.value shouldBe Error.OAuth2ErrorResponse(error, Some(errorDescription))
+          .thenRespond(body, statusCode)
+
+        introspectToken(testingBackend).success.value.left.value shouldBe
+          Error.OAuth2ErrorResponse(error, Some(errorDescription), HttpError(body, statusCode))
       }
     }
 

oauth2/src/test/scala/com/ocadotechnology/sttp/oauth2/ClientCredentialsTokenDeserializationSpec.scala

@@ -3,6 +3,7 @@ package com.ocadotechnology.sttp.oauth2
 import com.ocadotechnology.sttp.oauth2.ClientCredentialsToken.AccessTokenResponse
 import com.ocadotechnology.sttp.oauth2.common.Error.OAuth2ErrorResponse.InvalidClient
 import com.ocadotechnology.sttp.oauth2.common._
+import io.circe.Decoder
 import io.circe.DecodingFailure
 import io.circe.literal._
 import org.scalatest.EitherValues
@@ -15,6 +16,13 @@ import scala.concurrent.duration._
 
 class ClientCredentialsTokenDeserializationSpec extends AnyFlatSpec with Matchers with EitherValues {
 
+
+  private[oauth2] implicit val bearerTokenResponseDecoder: Decoder[Either[OAuth2Error[Unit], AccessTokenResponse]] =
+    circe.eitherOrFirstError[AccessTokenResponse, OAuth2Error[Unit]](
+      Decoder[AccessTokenResponse],
+      Decoder[OAuth2Error[Unit]](common.Error.errorDecoder(()))
+    )
+
   "token response JSON" should "be deserialized to proper response" in {
     val json =
       // language=JSON
@@ -27,7 +35,7 @@ class ClientCredentialsTokenDeserializationSpec extends AnyFlatSpec with Matcher
             "token_type": "Bearer"
         }"""
 
-    val response = json.as[Either[OAuth2Error, AccessTokenResponse]]
+    val response = json.as[Either[OAuth2Error[Unit], AccessTokenResponse]]
     response shouldBe Right(
       Right(
         ClientCredentialsToken.AccessTokenResponse(
@@ -52,7 +60,7 @@ class ClientCredentialsTokenDeserializationSpec extends AnyFlatSpec with Matcher
             "token_type": "VeryBadType"
         }"""
 
-    json.as[Either[OAuth2Error, AccessTokenResponse]].left.value shouldBe a[DecodingFailure]
+    json.as[Either[OAuth2Error[Unit], AccessTokenResponse]].left.value shouldBe a[DecodingFailure]
   }
 
   "JSON with error" should "be deserialized to proper type" in {
@@ -64,8 +72,8 @@ class ClientCredentialsTokenDeserializationSpec extends AnyFlatSpec with Matcher
               "error_uri": "https://pandasso.pages.tech.lastmile.com/documentation/support/panda-errors/token/#invalid_client_client_invalid"
           }"""
 
-    json.as[Either[OAuth2Error, AccessTokenResponse]] shouldBe Right(
-      Left(OAuth2ErrorResponse(InvalidClient, Some("Client is missing or invalid.")))
+    json.as[Either[OAuth2Error[Unit], AccessTokenResponse]] shouldBe Right(
+      Left(OAuth2ErrorResponse(InvalidClient, Some("Client is missing or invalid."), ()))
     )
   }
 
@@ -76,8 +84,8 @@ class ClientCredentialsTokenDeserializationSpec extends AnyFlatSpec with Matcher
               "error": "invalid_client"
           }"""
 
-    json.as[Either[OAuth2Error, AccessTokenResponse]] shouldBe Right(
-      Left(OAuth2ErrorResponse(InvalidClient, None))
+    json.as[Either[OAuth2Error[Unit], AccessTokenResponse]] shouldBe Right(
+      Left(OAuth2ErrorResponse(InvalidClient, None, ()))
     )
   }