-- This pragma is needed for allowQueryActionExecuter {-# OPTIONS_GHC -fno-warn-redundant-constraints #-} module Hasura.GraphQL.Resolve.Action ( resolveActionMutation , resolveAsyncActionQuery , asyncActionsProcessor , resolveActionQuery , mkJsonAggSelect , QueryActionExecuter , allowQueryActionExecuter , restrictActionExecuter ) where import Hasura.Prelude import Control.Concurrent (threadDelay) import Control.Exception (try) import Control.Lens import Control.Monad.Trans.Control (MonadBaseControl) import Data.Has import Data.IORef import qualified Control.Concurrent.Async.Lifted.Safe as LA import qualified Data.Environment as Env import qualified Data.Aeson as J import qualified Data.Aeson.Casing as J import qualified Data.Aeson.TH as J import qualified Data.ByteString.Lazy as BL import qualified Data.CaseInsensitive as CI import qualified Data.HashMap.Strict as Map import qualified Data.Text as T import qualified Data.UUID as UUID import qualified Database.PG.Query as Q import qualified Language.GraphQL.Draft.Syntax as G import qualified Network.HTTP.Client as HTTP import qualified Network.HTTP.Types as HTTP import qualified Network.Wreq as Wreq import qualified Hasura.GraphQL.Resolve.Select as GRS import qualified Hasura.RQL.DML.RemoteJoin as RJ import qualified Hasura.RQL.DML.Select as RS import qualified Hasura.Tracing as Tracing import Hasura.EncJSON import Hasura.GraphQL.Resolve.Context import Hasura.GraphQL.Resolve.InputValue import Hasura.GraphQL.Resolve.Select (processTableSelectionSet) import Hasura.GraphQL.Validate.SelectionSet import Hasura.HTTP import Hasura.RQL.DDL.Headers (makeHeadersFromConf, toHeadersConf) import Hasura.RQL.DDL.Schema.Cache import Hasura.RQL.DML.Select (asSingleRowJsonResp) import Hasura.RQL.Types import Hasura.RQL.Types.Run import Hasura.Server.Utils (mkClientHeadersForward, mkSetCookieHeaders) import Hasura.Server.Version (HasVersion) import Hasura.Session import Hasura.SQL.Types import Hasura.SQL.Value (PGScalarValue (..), toTxtValue) newtype ActionContext = ActionContext {_acName :: ActionName} deriving (Show, Eq) $(J.deriveJSON (J.aesonDrop 3 J.snakeCase) ''ActionContext) data ActionWebhookPayload = ActionWebhookPayload { _awpAction :: !ActionContext , _awpSessionVariables :: !SessionVariables , _awpInput :: !J.Value } deriving (Show, Eq) $(J.deriveJSON (J.aesonDrop 4 J.snakeCase) ''ActionWebhookPayload) data ActionWebhookErrorResponse = ActionWebhookErrorResponse { _awerMessage :: !Text , _awerCode :: !(Maybe Text) } deriving (Show, Eq) $(J.deriveJSON (J.aesonDrop 5 J.snakeCase) ''ActionWebhookErrorResponse) data ActionWebhookResponse = AWRArray ![J.Object] | AWRObject !J.Object deriving (Show, Eq) instance J.FromJSON ActionWebhookResponse where parseJSON v = case v of J.Array{} -> AWRArray <$> J.parseJSON v J.Object o -> pure $ AWRObject o _ -> fail $ "expecting object or array of objects for action webhook response" instance J.ToJSON ActionWebhookResponse where toJSON (AWRArray objects) = J.toJSON objects toJSON (AWRObject object) = J.toJSON object data ActionRequestInfo = ActionRequestInfo { _areqiUrl :: !Text , _areqiBody :: !J.Value , _areqiHeaders :: ![HeaderConf] } deriving (Show, Eq) $(J.deriveToJSON (J.aesonDrop 6 J.snakeCase) ''ActionRequestInfo) data ActionResponseInfo = ActionResponseInfo { _aresiStatus :: !Int , _aresiBody :: !J.Value , _aresiHeaders :: ![HeaderConf] } deriving (Show, Eq) $(J.deriveToJSON (J.aesonDrop 6 J.snakeCase) ''ActionResponseInfo) data ActionInternalError = ActionInternalError { _aieError :: !J.Value , _aieRequest :: !ActionRequestInfo , _aieResponse :: !(Maybe ActionResponseInfo) } deriving (Show, Eq) $(J.deriveToJSON (J.aesonDrop 4 J.snakeCase) ''ActionInternalError) resolveActionMutation :: ( HasVersion , MonadReusability m , MonadError QErr m , MonadReader r m , MonadIO m , Has FieldMap r , Has OrdByCtx r , Has SQLGenCtx r , Has HTTP.Manager r , Has [HTTP.Header] r , Tracing.MonadTrace m , MonadIO tx , MonadTx tx , Tracing.MonadTrace tx ) => Env.Environment -> Field -> ActionMutationExecutionContext -> UserInfo -> m (tx EncJSON, HTTP.ResponseHeaders) resolveActionMutation env field executionContext userInfo = case executionContext of ActionMutationSyncWebhook executionContextSync -> resolveActionMutationSync env field executionContextSync userInfo ActionMutationAsync -> (,[]) <$> resolveActionMutationAsync field userInfo -- | Synchronously execute webhook handler and resolve response to action "output" resolveActionMutationSync :: ( HasVersion , MonadReusability m , MonadError QErr m , MonadReader r m , MonadIO m , Has FieldMap r , Has OrdByCtx r , Has SQLGenCtx r , Has HTTP.Manager r , Has [HTTP.Header] r , Tracing.MonadTrace m , MonadIO tx , MonadTx tx , Tracing.MonadTrace tx ) => Env.Environment -> Field -> ActionExecutionContext -> UserInfo -> m (tx EncJSON, HTTP.ResponseHeaders) resolveActionMutationSync env field executionContext userInfo = do let inputArgs = J.toJSON $ fmap annInpValueToJson $ _fArguments field actionContext = ActionContext actionName sessionVariables = _uiSession userInfo handlerPayload = ActionWebhookPayload actionContext sessionVariables inputArgs manager <- asks getter reqHeaders <- asks getter (webhookRes, respHeaders) <- callWebhook env manager outputType outputFields reqHeaders confHeaders forwardClientHeaders resolvedWebhook handlerPayload let webhookResponseExpression = RS.AEInput $ UVSQL $ toTxtValue $ WithScalarType PGJSONB $ PGValJSONB $ Q.JSONB $ J.toJSON webhookRes selSet <- asObjectSelectionSet $ _fSelSet field selectAstUnresolved <- processOutputSelectionSet webhookResponseExpression outputType definitionList (_fType field) selSet astResolved <- RS.traverseAnnSimpleSelect resolveValTxt selectAstUnresolved let (astResolvedWithoutRemoteJoins,maybeRemoteJoins) = RJ.getRemoteJoins astResolved jsonAggType = mkJsonAggSelect outputType return $ (,respHeaders) $ case maybeRemoteJoins of Just remoteJoins -> let query = Q.fromBuilder $ toSQL $ RS.mkSQLSelect jsonAggType astResolvedWithoutRemoteJoins in RJ.executeQueryWithRemoteJoins env manager reqHeaders userInfo query [] remoteJoins Nothing -> liftTx $ asSingleRowJsonResp (Q.fromBuilder $ toSQL $ RS.mkSQLSelect jsonAggType astResolved) [] where ActionExecutionContext actionName outputType outputFields definitionList resolvedWebhook confHeaders forwardClientHeaders = executionContext -- QueryActionExecuter is a type for a higher function, this is being used -- to allow or disallow where a query action can be executed. We would like -- to explicitly control where a query action can be run. -- Example: We do not explain a query action, so we use the `restrictActionExecuter` -- to prevent resolving the action query. type QueryActionExecuter = forall m a. (MonadError QErr m) => (HTTP.Manager -> [HTTP.Header] -> m a) -> m a allowQueryActionExecuter :: HTTP.Manager -> [HTTP.Header] -> QueryActionExecuter allowQueryActionExecuter manager reqHeaders actionResolver = actionResolver manager reqHeaders restrictActionExecuter :: Text -> QueryActionExecuter restrictActionExecuter errMsg _ = throw400 NotSupported errMsg resolveActionQuery :: ( HasVersion , MonadReusability m , MonadError QErr m , MonadReader r m , MonadIO m , Has FieldMap r , Has OrdByCtx r , Has SQLGenCtx r , Tracing.MonadTrace m ) => Env.Environment -> Field -> ActionExecutionContext -> SessionVariables -> HTTP.Manager -> [HTTP.Header] -> m (RS.AnnSimpleSelG UnresolvedVal) resolveActionQuery env field executionContext sessionVariables httpManager reqHeaders = do let inputArgs = J.toJSON $ fmap annInpValueToJson $ _fArguments field actionContext = ActionContext actionName handlerPayload = ActionWebhookPayload actionContext sessionVariables inputArgs (webhookRes, _) <- callWebhook env httpManager outputType outputFields reqHeaders confHeaders forwardClientHeaders resolvedWebhook handlerPayload let webhookResponseExpression = RS.AEInput $ UVSQL $ toTxtValue $ WithScalarType PGJSONB $ PGValJSONB $ Q.JSONB $ J.toJSON webhookRes selSet <- asObjectSelectionSet $ _fSelSet field selectAstUnresolved <- processOutputSelectionSet webhookResponseExpression outputType definitionList (_fType field) selSet return selectAstUnresolved where ActionExecutionContext actionName outputType outputFields definitionList resolvedWebhook confHeaders forwardClientHeaders = executionContext {- Note: [Async action architecture] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In async actions, acquiring the action result is deferred. The async action mutation is made to initiate the action which returns an UUID. The UUID is used to query/subsribe for actions response. On mutation, the server makes an action log record in hdb_catalog.hdb_action_log table with request headers and input arguments. The `asyncActionsProcessor` background thread processes the async actions by executing the webhook handler and writing back the response payload or errors if any in the database. When an async action query/subscription is made, the server fetches the relavent data from the hdb_action_log table provides the action response. See Note [Resolving async action query/subscription] below. -} -- | Resolve asynchronous action mutation which returns only the action uuid resolveActionMutationAsync :: ( MonadError QErr m , MonadReader r m , Has [HTTP.Header] r , MonadTx tx ) => Field -> UserInfo -> m (tx EncJSON) resolveActionMutationAsync field userInfo = do let sessionVariables = _uiSession userInfo reqHeaders <- asks getter let inputArgs = J.toJSON $ fmap annInpValueToJson $ _fArguments field pure $ liftTx do actionId <- runIdentity . Q.getRow <$> Q.withQE defaultTxErrorHandler [Q.sql| INSERT INTO "hdb_catalog"."hdb_action_log" ("action_name", "session_variables", "request_headers", "input_payload", "status") VALUES ($1, $2, $3, $4, $5) RETURNING "id" |] (actionName, Q.AltJ sessionVariables, Q.AltJ $ toHeadersMap reqHeaders, Q.AltJ inputArgs, "created"::Text) False pure $ encJFromJValue $ UUID.toText actionId where actionName = G.unName $ _fName field toHeadersMap = Map.fromList . map ((bsToTxt . CI.original) *** bsToTxt) {- Note: [Resolving async action query/subscription] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Resolving async action query involves in selecting fields from hdb_catalog.hdb_action_log table. See Note [Async action architecture] above. See the table's Postgres schema in src-rsr/initialise.sql. The webhook's response JSON stored in "response_payload" column has to be fetched as "output" along with relationships (if any) to other tables. The in-built pg_catalog function `jsonb_to_record` helps in converting any JSON object to Postgres record type. Thus generated record is used to resolve action's type. Here, we treat the "output" field as a computed field to hdb_action_log table with `jsonb_to_record` as custom SQL function. -} resolveAsyncActionQuery :: ( MonadReusability m , MonadError QErr m , MonadReader r m , Has FieldMap r , Has OrdByCtx r , Has SQLGenCtx r ) => UserInfo -> ActionSelectOpContext -> Field -> m GRS.AnnSimpleSelect resolveAsyncActionQuery userInfo selectOpCtx field = do actionId <- withArg (_fArguments field) "id" parseActionId stringifyNumerics <- stringifyNum <$> asks getter selSet <- asObjectSelectionSet $ _fSelSet field annotatedFields <- fmap (map (first FieldName)) $ traverseObjectSelectionSet selSet $ \fld -> case _fName fld of "__typename" -> return $ RS.AFExpression $ G.unName $ G.unNamedType $ _fType field "output" -> do -- See Note [Resolving async action query/subscription] let inputTableArgument = RS.AETableRow $ Just $ Iden "response_payload" ActionSelectOpContext outputType definitionList = selectOpCtx jsonAggSelect = mkJsonAggSelect outputType fldSelSet <- asObjectSelectionSet $ _fSelSet fld (RS.AFComputedField . RS.CFSTable jsonAggSelect) <$> processOutputSelectionSet inputTableArgument outputType definitionList (_fType fld) fldSelSet -- The metadata columns "id" -> return $ mkAnnFieldFromPGCol "id" PGUUID "created_at" -> return $ mkAnnFieldFromPGCol "created_at" PGTimeStampTZ "errors" -> return $ mkAnnFieldFromPGCol "errors" PGJSONB G.Name t -> throw500 $ "unexpected field in actions' httpResponse : " <> t let tableFromExp = RS.FromTable actionLogTable tableArguments = RS.noSelectArgs { RS._saWhere = Just $ mkTableBoolExpression actionId} tablePermissions = RS.TablePerm annBoolExpTrue Nothing selectAstUnresolved = RS.AnnSelectG annotatedFields tableFromExp tablePermissions tableArguments stringifyNumerics return selectAstUnresolved where actionLogTable = QualifiedObject (SchemaName "hdb_catalog") (TableName "hdb_action_log") -- TODO:- Avoid using PGColumnInfo mkAnnFieldFromPGCol column columnType = flip RS.mkAnnColumnField Nothing $ PGColumnInfo (unsafePGCol column) (G.Name column) 0 (PGColumnScalar columnType) True Nothing parseActionId annInpValue = mkParameterizablePGValue <$> asPGColumnValue annInpValue mkTableBoolExpression actionId = let actionIdColumnInfo = PGColumnInfo (unsafePGCol "id") "id" 0 (PGColumnScalar PGUUID) False Nothing actionIdColumnEq = BoolFld $ AVCol actionIdColumnInfo [AEQ True actionId] sessionVarsColumnInfo = PGColumnInfo (unsafePGCol "session_variables") "session_variables" 0 (PGColumnScalar PGJSONB) False Nothing sessionVarValue = UVPG $ AnnPGVal Nothing False $ WithScalarType PGJSONB $ PGValJSONB $ Q.JSONB $ J.toJSON $ _uiSession userInfo sessionVarsColumnEq = BoolFld $ AVCol sessionVarsColumnInfo [AEQ True sessionVarValue] -- For non-admin roles, accessing an async action's response should be allowed only for the user -- who initiated the action through mutation. The action's response is accessible for a query/subscription -- only when it's session variables are equal to that of action's. in if isAdmin (_uiRole userInfo) then actionIdColumnEq else BoolAnd [actionIdColumnEq, sessionVarsColumnEq] data ActionLogItem = ActionLogItem { _aliId :: !UUID.UUID , _aliActionName :: !ActionName , _aliRequestHeaders :: ![HTTP.Header] , _aliSessionVariables :: !SessionVariables , _aliInputPayload :: !J.Value } deriving (Show, Eq) -- | Process async actions from hdb_catalog.hdb_action_log table. This functions is executed in a background thread. -- See Note [Async action architecture] above asyncActionsProcessor :: forall m void . ( HasVersion , MonadIO m , MonadBaseControl IO m , LA.Forall (LA.Pure m) , Tracing.HasReporter m ) => Env.Environment -> IORef (RebuildableSchemaCache Run, SchemaCacheVer) -> Q.PGPool -> HTTP.Manager -> m void asyncActionsProcessor env cacheRef pgPool httpManager = forever $ do asyncInvocations <- liftIO getUndeliveredEvents actionCache <- scActions . lastBuiltSchemaCache . fst <$> liftIO (readIORef cacheRef) LA.mapConcurrently_ (callHandler actionCache) asyncInvocations liftIO $ threadDelay (1 * 1000 * 1000) where runTx :: (Monoid a) => Q.TxE QErr a -> IO a runTx q = do res <- runExceptT $ Q.runTx' pgPool q either mempty return res callHandler :: ActionCache -> ActionLogItem -> m () callHandler actionCache actionLogItem = Tracing.runTraceT "async actions processor" do let ActionLogItem actionId actionName reqHeaders sessionVariables inputPayload = actionLogItem case Map.lookup actionName actionCache of Nothing -> return () Just actionInfo -> do let definition = _aiDefinition actionInfo outputFields = getActionOutputFields $ _aiOutputObject actionInfo webhookUrl = _adHandler definition forwardClientHeaders = _adForwardClientHeaders definition confHeaders = _adHeaders definition outputType = _adOutputType definition actionContext = ActionContext actionName eitherRes <- runExceptT $ callWebhook env httpManager outputType outputFields reqHeaders confHeaders forwardClientHeaders webhookUrl $ ActionWebhookPayload actionContext sessionVariables inputPayload liftIO $ case eitherRes of Left e -> setError actionId e Right (responsePayload, _) -> setCompleted actionId $ J.toJSON responsePayload setError :: UUID.UUID -> QErr -> IO () setError actionId e = runTx $ setErrorQuery actionId e setErrorQuery :: UUID.UUID -> QErr -> Q.TxE QErr () setErrorQuery actionId e = Q.unitQE defaultTxErrorHandler [Q.sql| update hdb_catalog.hdb_action_log set errors = $1, status = 'error' where id = $2 |] (Q.AltJ e, actionId) False setCompleted :: UUID.UUID -> J.Value -> IO () setCompleted actionId responsePayload = runTx $ setCompletedQuery actionId responsePayload setCompletedQuery :: UUID.UUID -> J.Value -> Q.TxE QErr () setCompletedQuery actionId responsePayload = Q.unitQE defaultTxErrorHandler [Q.sql| update hdb_catalog.hdb_action_log set response_payload = $1, status = 'completed' where id = $2 |] (Q.AltJ responsePayload, actionId) False undeliveredEventsQuery :: Q.TxE QErr [ActionLogItem] undeliveredEventsQuery = map mapEvent <$> Q.listQE defaultTxErrorHandler [Q.sql| update hdb_catalog.hdb_action_log set status = 'processing' where id in ( select id from hdb_catalog.hdb_action_log where status = 'created' for update skip locked limit 10 ) returning id, action_name, request_headers::json, session_variables::json, input_payload::json |] () False where mapEvent (actionId, actionName, Q.AltJ headersMap, Q.AltJ sessionVariables, Q.AltJ inputPayload) = ActionLogItem actionId actionName (fromHeadersMap headersMap) sessionVariables inputPayload fromHeadersMap = map ((CI.mk . txtToBs) *** txtToBs) . Map.toList getUndeliveredEvents = runTx undeliveredEventsQuery callWebhook :: forall m. (HasVersion, MonadIO m, MonadError QErr m, Tracing.MonadTrace m) => Env.Environment -> HTTP.Manager -> GraphQLType -> ActionOutputFields -> [HTTP.Header] -> [HeaderConf] -> Bool -> ResolvedWebhook -> ActionWebhookPayload -> m (ActionWebhookResponse, HTTP.ResponseHeaders) callWebhook env manager outputType outputFields reqHeaders confHeaders forwardClientHeaders resolvedWebhook actionWebhookPayload = do resolvedConfHeaders <- makeHeadersFromConf env confHeaders let clientHeaders = if forwardClientHeaders then mkClientHeadersForward reqHeaders else [] contentType = ("Content-Type", "application/json") -- Using HashMap to avoid duplicate headers between configuration headers -- and client headers where configuration headers are preferred hdrs = contentType : (Map.toList . Map.fromList) (resolvedConfHeaders <> clientHeaders) postPayload = J.toJSON actionWebhookPayload url = unResolvedWebhook resolvedWebhook httpResponse <- do initReq <- liftIO $ HTTP.parseRequest (T.unpack url) let req = initReq { HTTP.method = "POST" , HTTP.requestHeaders = addDefaultHeaders hdrs , HTTP.requestBody = HTTP.RequestBodyLBS (J.encode postPayload) } Tracing.tracedHttpRequest req \req' -> liftIO . try $ HTTP.httpLbs req' manager let requestInfo = ActionRequestInfo url postPayload $ confHeaders <> toHeadersConf clientHeaders case httpResponse of Left e -> throw500WithDetail "http exception when calling webhook" $ J.toJSON $ ActionInternalError (J.toJSON $ HttpException e) requestInfo Nothing Right responseWreq -> do let responseBody = responseWreq ^. Wreq.responseBody responseStatus = responseWreq ^. Wreq.responseStatus mkResponseInfo respBody = ActionResponseInfo (HTTP.statusCode responseStatus) respBody $ toHeadersConf $ responseWreq ^. Wreq.responseHeaders case J.eitherDecode responseBody of Left e -> do let responseInfo = mkResponseInfo $ J.String $ bsToTxt $ BL.toStrict responseBody throw500WithDetail "not a valid json response from webhook" $ J.toJSON $ ActionInternalError (J.toJSON $ "invalid json: " <> e) requestInfo $ Just responseInfo Right responseValue -> do let responseInfo = mkResponseInfo responseValue addInternalToErr e = let actionInternalError = J.toJSON $ ActionInternalError (J.String "unexpected response") requestInfo $ Just responseInfo in e{qeInternal = Just actionInternalError} if | HTTP.statusIsSuccessful responseStatus -> do let expectingArray = isListType outputType modifyQErr addInternalToErr $ do webhookResponse <- decodeValue responseValue case webhookResponse of AWRArray objs -> do when (not expectingArray) $ throwUnexpected "expecting object for action webhook response but got array" mapM_ validateResponseObject objs AWRObject obj -> do when expectingArray $ throwUnexpected "expecting array for action webhook response but got object" validateResponseObject obj pure (webhookResponse, mkSetCookieHeaders responseWreq) | HTTP.statusIsClientError responseStatus -> do ActionWebhookErrorResponse message maybeCode <- modifyQErr addInternalToErr $ decodeValue responseValue let code = maybe Unexpected ActionWebhookCode maybeCode qErr = QErr [] responseStatus message code Nothing throwError qErr | otherwise -> do let err = J.toJSON $ "expecting 2xx or 4xx status code, but found " ++ show (HTTP.statusCode responseStatus) throw500WithDetail "internal error" $ J.toJSON $ ActionInternalError err requestInfo $ Just responseInfo where throwUnexpected = throw400 Unexpected -- Webhook response object should conform to action output fields validateResponseObject obj = do -- Fields not specified in the output type shouldn't be present in the response let extraFields = filter (not . flip Map.member outputFields) $ map G.Name $ Map.keys obj when (not $ null extraFields) $ throwUnexpected $ "unexpected fields in webhook response: " <> showNames extraFields void $ flip Map.traverseWithKey outputFields $ \fieldName fieldTy -> -- When field is non-nullable, it has to present in the response with no null value when (not $ G.isNullable fieldTy) $ case Map.lookup (G.unName fieldName) obj of Nothing -> throwUnexpected $ "field " <> fieldName <<> " expected in webhook response, but not found" Just v -> when (v == J.Null) $ throwUnexpected $ "expecting not null value for field " <>> fieldName mkJsonAggSelect :: GraphQLType -> RS.JsonAggSelect mkJsonAggSelect = bool RS.JASSingleObject RS.JASMultipleRows . isListType processOutputSelectionSet :: ( MonadReusability m , MonadError QErr m , MonadReader r m , Has FieldMap r , Has OrdByCtx r , Has SQLGenCtx r ) => RS.ArgumentExp UnresolvedVal -> GraphQLType -> [(PGCol, PGScalarType)] -> G.NamedType -> ObjectSelectionSet -> m GRS.AnnSimpleSelect processOutputSelectionSet tableRowInput actionOutputType definitionList fldTy flds = do stringifyNumerics <- stringifyNum <$> asks getter annotatedFields <- processTableSelectionSet fldTy flds let annSel = RS.AnnSelectG annotatedFields selectFrom RS.noTablePermissions RS.noSelectArgs stringifyNumerics pure annSel where jsonbToPostgresRecordFunction = QualifiedObject "pg_catalog" $ FunctionName $ if isListType actionOutputType then "jsonb_to_recordset" -- Multirow array response else "jsonb_to_record" -- Single object response functionArgs = RS.FunctionArgsExp [tableRowInput] mempty selectFrom = RS.FromFunction jsonbToPostgresRecordFunction functionArgs $ Just definitionList