diff --git a/CHANGELOG.md b/CHANGELOG.md new file mode 100644 --- /dev/null +++ b/CHANGELOG.md @@ -0,0 +1,15 @@ +# Changelog + +## 0.2.0 + +### Added +- Initial release. +- Core JSON-RPC 2.0 types: `JSONRPCRequest`, `JSONRPCResponse`, `JSONRPCError`, + `JSONRPCNotification`, `JSONRPCMessage`, `JSONRPCErrorInfo`, `RequestId`. +- Type classes for deriving JSON-RPC serialisation: `IsJSONRPCRequest`, + `IsJSONRPCNotification` with `ViaJSONRPCRequest` / `ViaJSONRPCNotification` + newtype wrappers for `DerivingVia`. +- Standard JSON-RPC 2.0 error codes: `pARSE_ERROR`, `iNVALID_REQUEST`, + `mETHOD_NOT_FOUND`, `iNVALID_PARAMS`, `iNTERNAL_ERROR`. +- `rPC_VERSION` constant (`"2.0"`). +- `EmptyParams` placeholder type for methods with no parameters. diff --git a/LICENSE b/LICENSE new file mode 100644 --- /dev/null +++ b/LICENSE @@ -0,0 +1,373 @@ +Mozilla Public License Version 2.0 +================================== + +1. Definitions +-------------- + +1.1. "Contributor" + means each individual or legal entity that creates, contributes to + the creation of, or owns Covered Software. + +1.2. "Contributor Version" + means the combination of the Contributions of others (if any) used + by a Contributor and that particular Contributor's Contribution. + +1.3. "Contribution" + means Covered Software of a particular Contributor. + +1.4. "Covered Software" + means Source Code Form to which the initial Contributor has attached + the notice in Exhibit A, the Executable Form of such Source Code + Form, and Modifications of such Source Code Form, in each case + including portions thereof. + +1.5. "Incompatible With Secondary Licenses" + means + + (a) that the initial Contributor has attached the notice described + in Exhibit B to the Covered Software; or + + (b) that the Covered Software was made available under the terms of + version 1.1 or earlier of the License, but not also under the + terms of a Secondary License. + +1.6. "Executable Form" + means any form of the work other than Source Code Form. + +1.7. "Larger Work" + means a work that combines Covered Software with other material, in + a separate file or files, that is not Covered Software. + +1.8. "License" + means this document. + +1.9. "Licensable" + means having the right to grant, to the maximum extent possible, + whether at the time of the initial grant or subsequently, any and + all of the rights conveyed by this License. + +1.10. "Modifications" + means any of the following: + + (a) any file in Source Code Form that results from an addition to, + deletion from, or modification of the contents of Covered + Software; or + + (b) any new file in Source Code Form that contains any Covered + Software. + +1.11. "Patent Claims" of a Contributor + means any patent claim(s), including without limitation, method, + process, and apparatus claims, in any patent Licensable by such + Contributor that would be infringed, but for the grant of the + License, by the making, using, selling, offering for sale, having + made, import, or transfer of either its Contributions or its + Contributor Version. + +1.12. "Secondary License" + means either the GNU General Public License, Version 2.0, the GNU + Lesser General Public License, Version 2.1, the GNU Affero General + Public License, Version 3.0, or any later versions of those + licenses. + +1.13. "Source Code Form" + means the form of the work preferred for making modifications. + +1.14. "You" (or "Your") + means an individual or a legal entity exercising rights under this + License. For legal entities, "You" includes any entity that + controls, is controlled by, or is under common control with You. For + purposes of this definition, "control" means (a) the power, direct + or indirect, to cause the direction or management of such entity, + whether by contract or otherwise, or (b) ownership of more than + fifty percent (50%) of the outstanding shares or beneficial + ownership of such entity. + +2. License Grants and Conditions +-------------------------------- + +2.1. Grants + +Each Contributor hereby grants You a world-wide, royalty-free, +non-exclusive license: + +(a) under intellectual property rights (other than patent or trademark) + Licensable by such Contributor to use, reproduce, make available, + modify, display, perform, distribute, and otherwise exploit its + Contributions, either on an unmodified basis, with Modifications, or + as part of a Larger Work; and + +(b) under Patent Claims of such Contributor to make, use, sell, offer + for sale, have made, import, and otherwise transfer either its + Contributions or its Contributor Version. + +2.2. Effective Date + +The licenses granted in Section 2.1 with respect to any Contribution +become effective for each Contribution on the date the Contributor first +distributes such Contribution. + +2.3. Limitations on Grant Scope + +The licenses granted in this Section 2 are the only rights granted under +this License. No additional rights or licenses will be implied from the +distribution or licensing of Covered Software under this License. +Notwithstanding Section 2.1(b) above, no patent license is granted by a +Contributor: + +(a) for any code that a Contributor has removed from Covered Software; + or + +(b) for infringements caused by: (i) Your and any other third party's + modifications of Covered Software, or (ii) the combination of its + Contributions with other software (except as part of its Contributor + Version); or + +(c) under Patent Claims infringed by Covered Software in the absence of + its Contributions. + +This License does not grant any rights in the trademarks, service marks, +or logos of any Contributor (except as may be necessary to comply with +the notice requirements in Section 3.4). + +2.4. Subsequent Licenses + +No Contributor makes additional grants as a result of Your choice to +distribute the Covered Software under a subsequent version of this +License (see Section 10.2) or under the terms of a Secondary License (if +permitted under the terms of Section 3.3). + +2.5. Representation + +Each Contributor represents that the Contributor believes its +Contributions are its original creation(s) or it has sufficient rights +to grant the rights to its Contributions conveyed by this License. + +2.6. Fair Use + +This License is not intended to limit any rights You have under +applicable copyright doctrines of fair use, fair dealing, or other +equivalents. + +2.7. Conditions + +Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted +in Section 2.1. + +3. Responsibilities +------------------- + +3.1. Distribution of Source Form + +All distribution of Covered Software in Source Code Form, including any +Modifications that You create or to which You contribute, must be under +the terms of this License. You must inform recipients that the Source +Code Form of the Covered Software is governed by the terms of this +License, and how they can obtain a copy of this License. You may not +attempt to alter or restrict the recipients' rights in the Source Code +Form. + +3.2. Distribution of Executable Form + +If You distribute Covered Software in Executable Form then: + +(a) such Covered Software must also be made available in Source Code + Form, as described in Section 3.1, and You must inform recipients of + the Executable Form how they can obtain a copy of such Source Code + Form by reasonable means in a timely manner, at a charge no more + than the cost of distribution to the recipient; and + +(b) You may distribute such Executable Form under the terms of this + License, or sublicense it under different terms, provided that the + license for the Executable Form does not attempt to limit or alter + the recipients' rights in the Source Code Form under this License. + +3.3. Distribution of a Larger Work + +You may create and distribute a Larger Work under terms of Your choice, +provided that You also comply with the requirements of this License for +the Covered Software. If the Larger Work is a combination of Covered +Software with a work governed by one or more Secondary Licenses, and the +Covered Software is not Incompatible With Secondary Licenses, this +License permits You to additionally distribute such Covered Software +under the terms of such Secondary License(s), so that the recipient of +the Larger Work may, at their option, further distribute the Covered +Software under the terms of either this License or such Secondary +License(s). + +3.4. Notices + +You may not remove or alter the substance of any license notices +(including copyright notices, patent notices, disclaimers of warranty, +or limitations of liability) contained within the Source Code Form of +the Covered Software, except that You may alter any license notices to +the extent required to remedy known factual inaccuracies. + +3.5. Application of Additional Terms + +You may choose to offer, and to charge a fee for, warranty, support, +indemnity or liability obligations to one or more recipients of Covered +Software. However, You may do so only on Your own behalf, and not on +behalf of any Contributor. You must make it absolutely clear that any +such warranty, support, indemnity, or liability obligation is offered by +You alone, and You hereby agree to indemnify every Contributor for any +liability incurred by such Contributor as a result of warranty, support, +indemnity or liability terms You offer. You may include additional +disclaimers of warranty and limitations of liability specific to any +jurisdiction. + +4. Inability to Comply Due to Statute or Regulation +--------------------------------------------------- + +If it is impossible for You to comply with any of the terms of this +License with respect to some or all of the Covered Software due to +statute, judicial order, or regulation then You must: (a) comply with +the terms of this License to the maximum extent possible; and (b) +describe the limitations and the code they affect. Such description must +be placed in a text file included with all distributions of the Covered +Software under this License. Except to the extent prohibited by statute +or regulation, such description must be sufficiently detailed for a +recipient of ordinary skill to be able to understand it. + +5. Termination +-------------- + +5.1. The rights granted under this License will terminate automatically +if You fail to comply with any of its terms. However, if You become +compliant, then the rights granted under this License from a particular +Contributor are reinstated (a) provisionally, unless and until such +Contributor explicitly and finally terminates Your grants, and (b) on an +ongoing basis, if such Contributor fails to notify You of the +non-compliance by some reasonable means prior to 60 days after You have +come back into compliance. Moreover, Your grants from a particular +Contributor are reinstated on an ongoing basis if such Contributor +notifies You of the non-compliance by some reasonable means, this is the +first time You have received notice of non-compliance with this License +from such Contributor, and You become compliant prior to 30 days after +Your receipt of the notice. + +5.2. If You initiate litigation against any entity by asserting a patent +infringement claim (excluding declaratory judgment actions, +counter-claims, and cross-claims) alleging that a Contributor Version +directly or indirectly infringes any patent, then the rights granted to +You by any and all Contributors for the Covered Software under Section +2.1 of this License shall terminate. + +5.3. In the event of termination under Sections 5.1 or 5.2 above, all +end user license agreements (excluding distributors and resellers) which +have been validly granted by You or Your distributors under this License +prior to termination shall survive termination. + +************************************************************************ +* * +* 6. Disclaimer of Warranty * +* ------------------------- * +* * +* Covered Software is provided under this License on an "as is" * +* basis, without warranty of any kind, either expressed, implied, or * +* statutory, including, without limitation, warranties that the * +* Covered Software is free of defects, merchantable, fit for a * +* particular purpose or non-infringing. The entire risk as to the * +* quality and performance of the Covered Software is with You. * +* Should any Covered Software prove defective in any respect, You * +* (not any Contributor) assume the cost of any necessary servicing, * +* repair, or correction. This disclaimer of warranty constitutes an * +* essential part of this License. No use of any Covered Software is * +* authorized under this License except under this disclaimer. * +* * +************************************************************************ + +************************************************************************ +* * +* 7. Limitation of Liability * +* -------------------------- * +* * +* Under no circumstances and under no legal theory, whether tort * +* (including negligence), contract, or otherwise, shall any * +* Contributor, or anyone who distributes Covered Software as * +* permitted above, be liable to You for any direct, indirect, * +* special, incidental, or consequential damages of any character * +* including, without limitation, damages for lost profits, loss of * +* goodwill, work stoppage, computer failure or malfunction, or any * +* and all other commercial damages or losses, even if such party * +* shall have been informed of the possibility of such damages. This * +* limitation of liability shall not apply to liability for death or * +* personal injury resulting from such party's negligence to the * +* extent applicable law prohibits such limitation. Some * +* jurisdictions do not allow the exclusion or limitation of * +* incidental or consequential damages, so this exclusion and * +* limitation may not apply to You. * +* * +************************************************************************ + +8. Litigation +------------- + +Any litigation relating to this License may be brought only in the +courts of a jurisdiction where the defendant maintains its principal +place of business and such litigation shall be governed by laws of that +jurisdiction, without reference to its conflict-of-law provisions. +Nothing in this Section shall prevent a party's ability to bring +cross-claims or counter-claims. + +9. Miscellaneous +---------------- + +This License represents the complete agreement concerning the subject +matter hereof. If any provision of this License is held to be +unenforceable, such provision shall be reformed only to the extent +necessary to make it enforceable. Any law or regulation which provides +that the language of a contract shall be construed against the drafter +shall not be used to construe this License against a Contributor. + +10. Versions of the License +--------------------------- + +10.1. New Versions + +Mozilla Foundation is the license steward. Except as provided in Section +10.3, no one other than the license steward has the right to modify or +publish new versions of this License. Each version will be given a +distinguishing version number. + +10.2. Effect of New Versions + +You may distribute the Covered Software under the terms of the version +of the License under which You originally received the Covered Software, +or under the terms of any subsequent version published by the license +steward. + +10.3. Modified Versions + +If you create software not governed by this License, and you want to +create a new license for such software, you may create and use a +modified version of this License if you rename the license and remove +any references to the name of the license steward (except to note that +such modified license differs from this License). + +10.4. Distributing Source Code Form that is Incompatible With Secondary +Licenses + +If You choose to distribute Source Code Form that is Incompatible With +Secondary Licenses under the terms of this version of the License, the +notice described in Exhibit B of this License must be attached. + +Exhibit A - Source Code Form License Notice +------------------------------------------- + + This Source Code Form is subject to the terms of the Mozilla Public + License, v. 2.0. If a copy of the MPL was not distributed with this + file, You can obtain one at https://mozilla.org/MPL/2.0/. + +If it is not possible or desirable to put the notice in a particular +file, then You may include the notice in a location (such as a LICENSE +file in a relevant directory) where a recipient would be likely to look +for such a notice. + +You may add additional accurate notices of copyright ownership. + +Exhibit B - "Incompatible With Secondary Licenses" Notice +--------------------------------------------------------- + + This Source Code Form is "Incompatible With Secondary Licenses", as + defined by the Mozilla Public License, v. 2.0. diff --git a/README.md b/README.md new file mode 100644 --- /dev/null +++ b/README.md @@ -0,0 +1,41 @@ +# jsonrpc + +A lightweight Haskell implementation of +[JSON-RPC 2.0](https://www.jsonrpc.org/specification) protocol types with +[Aeson](https://hackage.haskell.org/package/aeson) serialisation. + +## Features + +- Core message types: requests, responses, notifications, and errors +- `IsJSONRPCRequest` / `IsJSONRPCNotification` type classes for automatic + method dispatch via `DerivingVia` +- Standard error codes from the specification +- Spec-compliant JSON encoding (optional `params`, error `data` field, etc.) + +## Quick start + +```haskell +{-# LANGUAGE DeriveGeneric #-} +{-# LANGUAGE DerivingVia #-} +{-# LANGUAGE DuplicateRecordFields #-} +{-# LANGUAGE TypeFamilies #-} + +import JSONRPC +import Data.Aeson (FromJSON, ToJSON) +import GHC.Generics (Generic) + +-- Define your request type +data PingRequest = PingRequest + { id :: RequestId + , params :: Maybe () + } + deriving stock (Show, Eq, Generic) + deriving (ToJSON, FromJSON) via ViaJSONRPCRequest PingRequest + +instance IsJSONRPCRequest PingRequest where + requestMethod _ = "ping" +``` + +## License + +[MPL-2.0](LICENSE) diff --git a/jsonrpc.cabal b/jsonrpc.cabal new file mode 100644 --- /dev/null +++ b/jsonrpc.cabal @@ -0,0 +1,88 @@ +cabal-version: 2.2 +name: jsonrpc +version: 0.2.0.0 +license: MPL-2.0 +license-file: LICENSE +copyright: (c) 2026 DPella AB +author: DPella AB +tested-with: ghc ==9.12.2 +extra-doc-files: + README.md + CHANGELOG.md + +maintainer: + matti@dpella.io, + lobo@dpella.io + +synopsis: JSON-RPC 2.0 types and type classes for Haskell +description: + A lightweight implementation of the JSON-RPC 2.0 protocol types for Haskell + with Aeson serialisation. Provides the core request, response, notification, + and error types along with type classes for deriving JSON-RPC method dispatch + via @DerivingVia@. + . + Implements the specification at . + +homepage: https://github.com/DPella/jsonrpc +bug-reports: https://github.com/DPella/jsonrpc/issues +category: Web, Network + +source-repository head + type: git + location: https://github.com/DPella/jsonrpc.git + +library + default-language: + Haskell2010 + + default-extensions: + DataKinds + FlexibleInstances + GADTs + GeneralizedNewtypeDeriving + ImportQualifiedPost + OverloadedStrings + PolyKinds + RankNTypes + TypeApplications + TypeFamilies + + hs-source-dirs: + src + + exposed-modules: + JSONRPC + + build-depends: + aeson >=2.1 && <2.3, + base >=4.18 && <4.22, + text >=2.0 && <2.2, + +test-suite test-jsonrpc + type: exitcode-stdio-1.0 + default-language: + Haskell2010 + + default-extensions: + DataKinds + FlexibleInstances + GADTs + GeneralizedNewtypeDeriving + ImportQualifiedPost + OverloadedStrings + PolyKinds + RankNTypes + TypeApplications + TypeFamilies + + hs-source-dirs: + test + + main-is: + Main.hs + + build-depends: + aeson >=2.1 && <2.3, + base >=4.18 && <4.22, + hspec >=2.10 && <2.12, + jsonrpc, diff --git a/src/JSONRPC.hs b/src/JSONRPC.hs new file mode 100644 --- /dev/null +++ b/src/JSONRPC.hs @@ -0,0 +1,498 @@ +{-# LANGUAGE DefaultSignatures #-} +{-# LANGUAGE DeriveAnyClass #-} +{-# LANGUAGE DeriveGeneric #-} +{-# LANGUAGE DerivingVia #-} +{-# LANGUAGE DuplicateRecordFields #-} +{-# LANGUAGE FlexibleContexts #-} +{-# LANGUAGE FunctionalDependencies #-} +{-# LANGUAGE InstanceSigs #-} +{-# LANGUAGE LambdaCase #-} +{-# LANGUAGE OverloadedStrings #-} +{-# LANGUAGE RecordWildCards #-} +{-# LANGUAGE ScopedTypeVariables #-} +{-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE TypeOperators #-} +{-# LANGUAGE UndecidableInstances #-} + +{- | +Module : JSONRPC +Description : JSON-RPC 2.0 types and type classes +Copyright : (c) 2026 DPella AB +License : MPL-2.0 +Maintainer : matti@dpella.io, lobo@dpella.io +Stability : experimental +Portability : GHC + +An implementation of the [JSON-RPC 2.0](https://www.jsonrpc.org/specification) +protocol types for Haskell, with Aeson serialisation. + += Core types + +The four message kinds defined by the specification: + +* 'JSONRPCRequest' — a method call expecting a response +* 'JSONRPCResponse' — a successful response +* 'JSONRPCError' — an error response +* 'JSONRPCNotification' — a one-way message (no response) + +'JSONRPCMessage' is a tagged union of all four, useful when reading messages +off the wire without knowing the kind in advance. + += Deriving support + +'IsJSONRPCRequest' and 'IsJSONRPCNotification' let you define strongly-typed +request\/notification types and derive their JSON-RPC encoding via +@DerivingVia@: + +@ +data PingRequest = PingRequest + { id :: RequestId, params :: Maybe () } + deriving (ToJSON, FromJSON) via ViaJSONRPCRequest PingRequest + +instance IsJSONRPCRequest PingRequest where + requestMethod _ = \"ping\" +@ +-} +module JSONRPC ( + -- * Request identifiers + RequestId (..), + + -- * Type classes + IsJSONRPCRequest (..), + IsJSONRPCNotification (..), + + -- * Deriving-via wrappers + ViaJSONRPCRequest (..), + ViaJSONRPCNotification (..), + + -- * JSON-RPC message types + JSONRPCRequest (..), + JSONRPCResponse (..), + JSONRPCError (..), + JSONRPCNotification (..), + JSONRPCMessage (..), + JSONRPCErrorInfo (..), + + -- * Helpers + EmptyParams, + + -- * Standard JSON-RPC 2.0 error codes + pARSE_ERROR, + iNVALID_REQUEST, + mETHOD_NOT_FOUND, + iNVALID_PARAMS, + iNTERNAL_ERROR, + + -- * Constants + rPC_VERSION, +) where + +import Control.Applicative ((<|>)) +import Data.Aeson +import Data.Aeson qualified as Aeson +import Data.Data (Proxy (..), Typeable, typeRep) +import Data.Kind (Type) +import Data.Text (Text) +import GHC.Generics +import GHC.Records (HasField (getField)) +import GHC.TypeError (ErrorMessage (..), TypeError) + +-- --------------------------------------------------------------------------- +-- RequestId +-- --------------------------------------------------------------------------- + +{- | A uniquely identifying ID for a request in JSON-RPC. + +The JSON-RPC 2.0 specification requires that each request has a unique +identifier. The ID can be a string, number, or null value. Numbers +SHOULD NOT contain fractional parts. +-} +newtype RequestId = RequestId Value + deriving stock (Show, Eq) + deriving newtype (ToJSON, FromJSON) + +-- --------------------------------------------------------------------------- +-- Constants +-- --------------------------------------------------------------------------- + +{- | JSON-RPC protocol version string (@\"2.0\"@). + +Every request, response, and notification includes a @jsonrpc@ field +that MUST be exactly this value. +-} +rPC_VERSION :: Text +rPC_VERSION = "2.0" + +-- --------------------------------------------------------------------------- +-- EmptyParams +-- --------------------------------------------------------------------------- + +{- | Placeholder type for methods that take no parameters. + +'EmptyParams' serialises to JSON @null@ and always fails to parse +(it is only used as a type-level marker; the 'FromJSON' instance for +'JSONRPCRequest' defaults missing params to 'Null'). +-} +data EmptyParams + deriving stock (Generic) + +instance Show EmptyParams where + show :: EmptyParams -> String + show _ = show Aeson.Null + +instance Eq EmptyParams where + (==) :: EmptyParams -> EmptyParams -> Bool + _ == _ = True + +instance ToJSON EmptyParams where + toJSON :: EmptyParams -> Value + toJSON _ = Aeson.Null + +instance FromJSON EmptyParams where + parseJSON _ = fail "EmptyParams can only be used as a placeholder for empty params" + +-- --------------------------------------------------------------------------- +-- JSON-RPC error information +-- --------------------------------------------------------------------------- + +{- | Structured error information inside a JSON-RPC error response. + +@ +{ "code": -32601, "message": "Method not found", "data": ... } +@ + +The @code@ and @message@ fields are mandatory; @data@ is optional and may +contain any additional information about the error. +-} +data JSONRPCErrorInfo = JSONRPCErrorInfo + { code :: Int + -- ^ A number indicating the error type that occurred. + , message :: Text + -- ^ A short description of the error. + , errorData :: Maybe Value + -- ^ Additional information about the error (serialised as @\"data\"@ in JSON). + } + deriving stock (Show, Eq, Generic) + +-- | Custom 'ToJSON' that maps the Haskell field @errorData@ to the JSON key @\"data\"@ +-- as required by the JSON-RPC 2.0 specification. +instance ToJSON JSONRPCErrorInfo where + toJSON (JSONRPCErrorInfo c m d) = + object $ + [ "code" .= c + , "message" .= m + ] + <> maybe [] (\v -> ["data" .= v]) d + +-- | Custom 'FromJSON' that reads the JSON key @\"data\"@ into the Haskell field @errorData@. +instance FromJSON JSONRPCErrorInfo where + parseJSON = withObject "JSONRPCErrorInfo" $ \o -> + JSONRPCErrorInfo + <$> o .: "code" + <*> o .: "message" + <*> o .:? "data" + +-- --------------------------------------------------------------------------- +-- Core message types +-- --------------------------------------------------------------------------- + +{- | A JSON-RPC request that expects a response. + +@ +{ "jsonrpc": "2.0", "id": 1, "method": "foo", "params": { ... } } +@ +-} +data JSONRPCRequest = JSONRPCRequest + { jsonrpc :: Text + -- ^ Always @\"2.0\"@. + , id :: RequestId + -- ^ A unique identifier for the request. + , method :: Text + -- ^ The method to invoke. + , params :: Value + -- ^ The method parameters (defaults to 'Null' if omitted). + } + deriving stock (Show, Eq, Generic) + deriving anyclass (ToJSON) + +-- | Custom 'FromJSON' instance that treats a missing @params@ key as 'Null'. +-- JSON-RPC 2.0 allows the @params@ field to be omitted. +instance FromJSON JSONRPCRequest where + parseJSON = withObject "JSONRPCRequest" $ \o -> + JSONRPCRequest + <$> o .: "jsonrpc" + <*> o .: "id" + <*> o .: "method" + <*> o .:? "params" .!= Null + +{- | A successful (non-error) response to a request. + +@ +{ "jsonrpc": "2.0", "id": 1, "result": { ... } } +@ +-} +data JSONRPCResponse = JSONRPCResponse + { jsonrpc :: Text + -- ^ Always @\"2.0\"@. + , id :: RequestId + -- ^ Must match the @id@ of the corresponding request. + , result :: Value + -- ^ The result of the method invocation. + } + deriving stock (Show, Eq, Generic) + deriving anyclass (FromJSON, ToJSON) + +{- | A response to a request that indicates an error occurred. + +@ +{ "jsonrpc": "2.0", "id": 1, "error": { "code": -32601, "message": "..." } } +@ +-} +data JSONRPCError = JSONRPCError + { jsonrpc :: Text + -- ^ Always @\"2.0\"@. + , id :: RequestId + -- ^ Must match the @id@ of the corresponding request (or 'Null' for parse errors). + , error :: JSONRPCErrorInfo + -- ^ Structured error information. + } + deriving stock (Show, Eq, Generic) + deriving anyclass (FromJSON, ToJSON) + +{- | A notification which does not expect a response. + +@ +{ "jsonrpc": "2.0", "method": "update", "params": { ... } } +@ + +Notifications have no @id@ field. The server MUST NOT reply to a notification. +-} +data JSONRPCNotification = JSONRPCNotification + { jsonrpc :: Text + -- ^ Always @\"2.0\"@. + , method :: Text + -- ^ The method name. + , params :: Value + -- ^ The method parameters (omitted from JSON when 'Null'). + } + deriving stock (Show, Eq, Generic) + +-- | Custom 'ToJSON' instance that omits @params@ when it is 'Null'. +instance ToJSON JSONRPCNotification where + toJSON (JSONRPCNotification j m Null) = + object ["jsonrpc" .= j, "method" .= m] + toJSON (JSONRPCNotification j m p) = + object ["jsonrpc" .= j, "method" .= m, "params" .= p] + +-- | Custom 'FromJSON' instance that treats a missing @params@ key as 'Null'. +-- JSON-RPC 2.0 allows notifications to omit the @params@ field entirely. +instance FromJSON JSONRPCNotification where + parseJSON = withObject "JSONRPCNotification" $ \o -> + JSONRPCNotification + <$> o .: "jsonrpc" + <*> o .: "method" + <*> o .:? "params" .!= Null + +{- | Any valid JSON-RPC message that can be decoded off the wire. + +Useful when reading from a transport where the message kind is unknown. +-} +data JSONRPCMessage + = RequestMessage JSONRPCRequest + | ResponseMessage JSONRPCResponse + | ErrorMessage JSONRPCError + | NotificationMessage JSONRPCNotification + deriving stock (Show, Eq, Generic) + +instance ToJSON JSONRPCMessage where + toJSON (RequestMessage r) = toJSON r + toJSON (ResponseMessage r) = toJSON r + toJSON (ErrorMessage e) = toJSON e + toJSON (NotificationMessage n) = toJSON n + +instance FromJSON JSONRPCMessage where + parseJSON v = + (RequestMessage <$> parseJSON v) + <|> (ResponseMessage <$> parseJSON v) + <|> (ErrorMessage <$> parseJSON v) + <|> (NotificationMessage <$> parseJSON v) + +-- --------------------------------------------------------------------------- +-- IsJSONRPCRequest +-- --------------------------------------------------------------------------- + +-- | Type family to extract the type of the @params@ field from a generic representation. +type family RequestParamType (rep :: Type -> Type) :: Type where + RequestParamType (D1 _ (C1 _ (S1 _ (K1 _ RequestId) :*: S1 _ (K1 _ p)))) = p + RequestParamType (D1 ('MetaData nm _ _ _) _) = + TypeError + ( ('Text "Error when defining IsJSONRPCRequest for " :<>: 'Text nm :<>: 'Text ":") + :$$: 'Text "The request datatype must be a record with fields 'id' and 'params'" + ) + +{- | Type class for Haskell types that represent a specific JSON-RPC request method. + +Instances define the method name via 'requestMethod'. Serialisation and +deserialisation are provided by default using GHC Generics: the type must +be a two-field record with @id :: RequestId@ and @params :: SomeParamsType@. + +Use 'ViaJSONRPCRequest' for @DerivingVia@-based 'ToJSON'\/'FromJSON' instances. +-} +class + ( HasField "id" a RequestId + , HasField "params" a (RequestParams a) + , Typeable a + , ToJSON (RequestParams a) + , FromJSON (RequestParams a) + ) => + IsJSONRPCRequest a + where + -- | The type of the @params@ field. + type RequestParams a + type RequestParams a = RequestParamType (Rep a) + + -- | The JSON-RPC method name (e.g. @\"initialize\"@, @\"tools\/list\"@). + requestMethod :: Proxy a -> Text + + -- | Convert a typed request to a raw 'JSONRPCRequest'. + toJSONRPCRequest :: a -> JSONRPCRequest + toJSONRPCRequest (req :: a) = + JSONRPCRequest rPC_VERSION (getField @"id" req) (requestMethod (Proxy @a)) (toJSON (getField @"params" req)) + + -- | Parse a raw 'JSONRPCRequest' into a typed request. + fromJSONRPCRequest :: JSONRPCRequest -> Either String a + default fromJSONRPCRequest :: + ( Generic a + , Rep a ~ D1 c0 (C1 i0 (S1 s0 (K1 i1 RequestId) :*: S1 s1 (K1 i30 (RequestParams a)))) + ) => + JSONRPCRequest -> + Either String a + fromJSONRPCRequest JSONRPCRequest{id = req_id, params = req_params} = + case fromJSON @(RequestParams a) req_params of + Success p -> Right $ to $ M1 (M1 (M1 (K1 req_id) :*: M1 (K1 p))) + Aeson.Error err -> Left err + +-- | Newtype wrapper for deriving 'ToJSON' and 'FromJSON' via 'IsJSONRPCRequest'. +newtype ViaJSONRPCRequest a = ViaJSONRPCRequest {unViaJSONRPCRequest :: a} + +instance (IsJSONRPCRequest a) => ToJSON (ViaJSONRPCRequest a) where + toJSON = toJSON . toJSONRPCRequest . unViaJSONRPCRequest + +instance (IsJSONRPCRequest a) => FromJSON (ViaJSONRPCRequest a) where + parseJSON = withObject (show $ typeRep (Proxy @a)) $ \o -> do + m <- o .: "method" + req_id <- o .: "id" + if m == requestMethod (Proxy @a) + then do + p <- o .:? "params" .!= Null + case fromJSONRPCRequest (JSONRPCRequest rPC_VERSION req_id m p) of + Right r -> return (ViaJSONRPCRequest r) + Left err -> fail $ "Failed to parse params for " <> show (typeRep (Proxy @a)) <> ": " <> err + else fail $ "Expected method '" <> show (requestMethod (Proxy @a)) <> "'" + +-- --------------------------------------------------------------------------- +-- IsJSONRPCNotification +-- --------------------------------------------------------------------------- + +-- | Type family to extract the type of the @params@ field from a notification's generic representation. +type family NotificationParamType (rep :: Type -> Type) :: Type where + NotificationParamType (D1 _ (C1 _ (S1 _ (K1 _ p)))) = p + NotificationParamType (D1 ('MetaData nm _ _ _) _) = + TypeError + ( ('Text "Error when defining IsJSONRPCNotification for " :<>: 'Text nm :<>: 'Text ":") + :$$: 'Text "The notification datatype must be a record with a single field 'params'" + ) + +{- | Type class for Haskell types that represent a specific JSON-RPC notification method. + +Similar to 'IsJSONRPCRequest' but for notifications (no @id@ field). +Use 'ViaJSONRPCNotification' for @DerivingVia@-based instances. +-} +class + ( HasField "params" a (NotificationParams a) + , Typeable a + , ToJSON (NotificationParams a) + , FromJSON (NotificationParams a) + ) => + IsJSONRPCNotification a + where + -- | The type of the @params@ field. + type NotificationParams a + type NotificationParams a = NotificationParamType (Rep a) + + -- | The JSON-RPC method name. + notificationsMethod :: Proxy a -> Text + + -- | Convert a typed notification to a raw 'JSONRPCNotification'. + toJSONRPCNotification :: a -> JSONRPCNotification + toJSONRPCNotification (req :: a) = + JSONRPCNotification rPC_VERSION (notificationsMethod (Proxy @a)) (toJSON (getField @"params" req)) + + -- | Parse a raw 'JSONRPCNotification' into a typed notification. + fromJSONRPCNotification :: JSONRPCNotification -> Either String a + default fromJSONRPCNotification :: + ( Generic a + , Rep a ~ D1 c0 (C1 i0 (S1 s1 (K1 i30 (NotificationParams a)))) + ) => + JSONRPCNotification -> + Either String a + fromJSONRPCNotification JSONRPCNotification{params = notification_params} = + case fromJSON @(NotificationParams a) notification_params of + Success p -> Right $ to $ M1 (M1 (M1 (K1 p))) + Aeson.Error err -> Left err + +-- | Newtype wrapper for deriving 'ToJSON' and 'FromJSON' via 'IsJSONRPCNotification'. +newtype ViaJSONRPCNotification a = ViaJSONRPCNotification {unViaJSONRPCNotification :: a} + +instance (IsJSONRPCNotification a) => ToJSON (ViaJSONRPCNotification a) where + toJSON = toJSON . toJSONRPCNotification . unViaJSONRPCNotification + +instance (IsJSONRPCNotification a) => FromJSON (ViaJSONRPCNotification a) where + parseJSON = withObject (show $ typeRep (Proxy @a)) $ \o -> do + m <- o .: "method" + if m == notificationsMethod (Proxy @a) + then do + p <- o .:? "params" .!= Null + case fromJSONRPCNotification (JSONRPCNotification rPC_VERSION m p) of + Right r -> return (ViaJSONRPCNotification r) + Left err -> fail $ "Failed to parse params for " <> show (typeRep (Proxy @a)) <> ": " <> err + else fail $ "Expected method '" <> show (notificationsMethod (Proxy @a)) <> "'" + +-- --------------------------------------------------------------------------- +-- Standard JSON-RPC 2.0 error codes +-- --------------------------------------------------------------------------- + +{- | Parse error (@-32700@). + +Invalid JSON was received by the server. +-} +pARSE_ERROR :: Int +pARSE_ERROR = -32700 + +{- | Invalid request (@-32600@). + +The JSON sent is not a valid Request object. +-} +iNVALID_REQUEST :: Int +iNVALID_REQUEST = -32600 + +{- | Method not found (@-32601@). + +The method does not exist or is not available. +-} +mETHOD_NOT_FOUND :: Int +mETHOD_NOT_FOUND = -32601 + +{- | Invalid params (@-32602@). + +Invalid method parameter(s). +-} +iNVALID_PARAMS :: Int +iNVALID_PARAMS = -32602 + +{- | Internal error (@-32603@). + +Internal JSON-RPC error. +-} +iNTERNAL_ERROR :: Int +iNTERNAL_ERROR = -32603 diff --git a/test/Main.hs b/test/Main.hs new file mode 100644 --- /dev/null +++ b/test/Main.hs @@ -0,0 +1,224 @@ +{-# LANGUAGE DataKinds #-} +{-# LANGUAGE DeriveGeneric #-} +{-# LANGUAGE DerivingVia #-} +{-# LANGUAGE DuplicateRecordFields #-} +{-# LANGUAGE OverloadedStrings #-} +{-# LANGUAGE TypeFamilies #-} + +module Main (main) where + +import Data.Aeson +import Data.Aeson.KeyMap qualified as KM +import Data.Maybe (isNothing) +import GHC.Generics (Generic) +import JSONRPC +import Test.Hspec +import Prelude hiding (error, id) +import Prelude qualified + +-- --------------------------------------------------------------------------- +-- Example types for DerivingVia tests +-- --------------------------------------------------------------------------- + +data PingRequest = PingRequest + { id :: RequestId + , params :: Maybe Value + } + deriving stock (Show, Eq, Generic) + deriving (ToJSON, FromJSON) via ViaJSONRPCRequest PingRequest + +instance IsJSONRPCRequest PingRequest where + requestMethod _ = "ping" + +data InitNotification = InitNotification + { params :: Maybe Value + } + deriving stock (Show, Eq, Generic) + deriving (ToJSON, FromJSON) via ViaJSONRPCNotification InitNotification + +instance IsJSONRPCNotification InitNotification where + notificationsMethod _ = "notifications/initialized" + +-- | Helper to extract an Object from a Value, failing on non-objects. +asObject :: Value -> KM.KeyMap Value +asObject (Object o) = o +asObject _ = Prelude.error "expected object" + +-- --------------------------------------------------------------------------- +-- Tests +-- --------------------------------------------------------------------------- + +main :: IO () +main = hspec $ do + describe "JSONRPC" $ do + describe "Constants" $ do + it "rPC_VERSION is \"2.0\"" $ + rPC_VERSION `shouldBe` "2.0" + + describe "Error codes" $ do + it "pARSE_ERROR is -32700" $ + pARSE_ERROR `shouldBe` (-32700) + it "iNVALID_REQUEST is -32600" $ + iNVALID_REQUEST `shouldBe` (-32600) + it "mETHOD_NOT_FOUND is -32601" $ + mETHOD_NOT_FOUND `shouldBe` (-32601) + it "iNVALID_PARAMS is -32602" $ + iNVALID_PARAMS `shouldBe` (-32602) + it "iNTERNAL_ERROR is -32603" $ + iNTERNAL_ERROR `shouldBe` (-32603) + + describe "RequestId" $ do + it "round-trips a numeric id" $ do + let rid = RequestId (Number 42) + decode (encode rid) `shouldBe` Just rid + + it "round-trips a string id" $ do + let rid = RequestId (String "abc-123") + decode (encode rid) `shouldBe` Just rid + + it "round-trips a null id" $ do + let rid = RequestId Null + decode (encode rid) `shouldBe` Just rid + + describe "JSONRPCErrorInfo" $ do + it "serialises errorData as \"data\" (spec compliance)" $ do + let info = JSONRPCErrorInfo (-32601) "Method not found" (Just (String "details")) + obj = asObject (toJSON info) + KM.member "data" obj `shouldBe` True + KM.member "errorData" obj `shouldBe` False + + it "omits \"data\" when errorData is Nothing" $ do + let info = JSONRPCErrorInfo (-32601) "Method not found" Nothing + obj = asObject (toJSON info) + KM.member "data" obj `shouldBe` False + + it "round-trips with data" $ do + let info = JSONRPCErrorInfo (-32700) "Parse error" (Just (String "unexpected")) + decode (encode info) `shouldBe` Just info + + it "round-trips without data" $ do + let info = JSONRPCErrorInfo (-32600) "Invalid Request" Nothing + decode (encode info) `shouldBe` Just info + + it "parses JSON with \"data\" key into errorData field" $ do + let json = "{\"code\":-32601,\"message\":\"Method not found\",\"data\":\"extra\"}" + case decode json :: Maybe JSONRPCErrorInfo of + Just info -> errorData info `shouldBe` Just (String "extra") + Nothing -> expectationFailure "Failed to parse JSONRPCErrorInfo" + + it "parses JSON without \"data\" key as Nothing" $ do + let json = "{\"code\":-32601,\"message\":\"Method not found\"}" + case decode json :: Maybe JSONRPCErrorInfo of + Just info -> isNothing (errorData info) `shouldBe` True + Nothing -> expectationFailure "Failed to parse JSONRPCErrorInfo" + + describe "JSONRPCRequest" $ do + it "round-trips a request with params" $ do + let req = JSONRPCRequest "2.0" (RequestId (Number 1)) "test" (object ["x" .= (1 :: Int)]) + decode (encode req) `shouldBe` Just req + + it "defaults missing params to Null" $ do + let json = "{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"ping\"}" + case decode json :: Maybe JSONRPCRequest of + Just (JSONRPCRequest _ _ _ p) -> p `shouldBe` Null + Nothing -> expectationFailure "Failed to parse JSONRPCRequest" + + it "accepts explicit null params" $ do + let json = "{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"ping\",\"params\":null}" + case decode json :: Maybe JSONRPCRequest of + Just (JSONRPCRequest _ _ _ p) -> p `shouldBe` Null + Nothing -> expectationFailure "Failed to parse JSONRPCRequest" + + describe "JSONRPCResponse" $ do + it "round-trips a response" $ do + let resp = JSONRPCResponse "2.0" (RequestId (Number 1)) (String "ok") + decode (encode resp) `shouldBe` Just resp + + describe "JSONRPCError" $ do + it "round-trips an error" $ do + let err = JSONRPCError "2.0" (RequestId (Number 1)) (JSONRPCErrorInfo (-32601) "Not found" Nothing) + decode (encode err) `shouldBe` Just err + + it "round-trips an error with data" $ do + let err = JSONRPCError "2.0" (RequestId Null) (JSONRPCErrorInfo pARSE_ERROR "Parse error" (Just (String "detail"))) + decode (encode err) `shouldBe` Just err + + describe "JSONRPCNotification" $ do + it "round-trips a notification with params" $ do + let notif = JSONRPCNotification "2.0" "update" (object ["key" .= ("val" :: String)]) + decode (encode notif) `shouldBe` Just notif + + it "omits params when Null in serialised JSON" $ do + let notif = JSONRPCNotification "2.0" "update" Null + obj = asObject (toJSON notif) + KM.member "params" obj `shouldBe` False + + it "defaults missing params to Null on parse" $ do + let json = "{\"jsonrpc\":\"2.0\",\"method\":\"update\"}" + case decode json :: Maybe JSONRPCNotification of + Just (JSONRPCNotification _ _ p) -> p `shouldBe` Null + Nothing -> expectationFailure "Failed to parse JSONRPCNotification" + + describe "JSONRPCMessage" $ do + it "parses a request as RequestMessage" $ do + let json = "{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"foo\",\"params\":{}}" + case decode json :: Maybe JSONRPCMessage of + Just (RequestMessage _) -> pure () + other -> expectationFailure $ "Expected RequestMessage, got: " <> show other + + it "parses a response as ResponseMessage" $ do + let json = "{\"jsonrpc\":\"2.0\",\"id\":1,\"result\":42}" + case decode json :: Maybe JSONRPCMessage of + Just (ResponseMessage _) -> pure () + other -> expectationFailure $ "Expected ResponseMessage, got: " <> show other + + it "parses an error as ErrorMessage" $ do + let json = "{\"jsonrpc\":\"2.0\",\"id\":1,\"error\":{\"code\":-32601,\"message\":\"not found\"}}" + case decode json :: Maybe JSONRPCMessage of + Just (ErrorMessage _) -> pure () + other -> expectationFailure $ "Expected ErrorMessage, got: " <> show other + + it "parses a notification as NotificationMessage" $ do + let json = "{\"jsonrpc\":\"2.0\",\"method\":\"update\"}" + case decode json :: Maybe JSONRPCMessage of + Just (NotificationMessage _) -> pure () + other -> expectationFailure $ "Expected NotificationMessage, got: " <> show other + + it "round-trips all message types" $ do + let msgs = + [ RequestMessage $ JSONRPCRequest "2.0" (RequestId (Number 1)) "test" Null + , ResponseMessage $ JSONRPCResponse "2.0" (RequestId (Number 2)) (String "ok") + , ErrorMessage $ JSONRPCError "2.0" (RequestId (Number 3)) (JSONRPCErrorInfo (-32600) "Bad" Nothing) + , NotificationMessage $ JSONRPCNotification "2.0" "ping" Null + ] + mapM_ (\m -> decode (encode m) `shouldBe` Just m) msgs + + describe "ViaJSONRPCRequest (DerivingVia)" $ do + it "serialises a typed request with correct method" $ do + let req = PingRequest (RequestId (Number 1)) Nothing + obj = asObject (toJSON req) + KM.lookup "method" obj `shouldBe` Just (String "ping") + KM.lookup "jsonrpc" obj `shouldBe` Just (String "2.0") + + it "round-trips a typed request" $ do + let req = PingRequest (RequestId (Number 7)) (Just (object ["foo" .= True])) + decode (encode req) `shouldBe` Just req + + it "rejects a request with wrong method" $ do + let json = "{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"wrong\",\"params\":null}" + (decode json :: Maybe PingRequest) `shouldBe` Nothing + + describe "ViaJSONRPCNotification (DerivingVia)" $ do + it "serialises a typed notification with correct method" $ do + let notif = InitNotification Nothing + obj = asObject (toJSON notif) + KM.lookup "method" obj `shouldBe` Just (String "notifications/initialized") + KM.lookup "jsonrpc" obj `shouldBe` Just (String "2.0") + + it "round-trips a typed notification" $ do + let notif = InitNotification (Just (object ["meta" .= (1 :: Int)])) + decode (encode notif) `shouldBe` Just notif + + it "rejects a notification with wrong method" $ do + let json = "{\"jsonrpc\":\"2.0\",\"method\":\"wrong\",\"params\":null}" + (decode json :: Maybe InitNotification) `shouldBe` Nothing