Add a Gargantext.API.Errors module

gargantext.cabal

@@ -51,6 +51,7 @@ library
       Gargantext.API.Admin.Types
       Gargantext.API.Auth.PolicyCheck
       Gargantext.API.Dev
+      Gargantext.API.Errors
       Gargantext.API.HashedResponse
       Gargantext.API.Ngrams
       Gargantext.API.Ngrams.Prelude

src/Gargantext/API/Errors.hs

+
+module Gargantext.API.Errors where
+
+import Prelude
+import GHC.Stack
+import Control.Exception
+import qualified Data.Text as T
+
+-- | A 'WithStacktrace' carries an error alongside its
+-- 'CallStack', to be able to print the correct source location
+-- of where the error originated.
+data WithStacktrace e =
+  WithStacktrace {
+    ct_callStack :: !CallStack
+  , ct_error     :: !e
+  } deriving Show
+
+instance Exception e => Exception (WithStacktrace e) where
+  displayException WithStacktrace{..}
+    = displayException ct_error <> "\n" <> prettyCallStack ct_callStack
+
+-- | An error that can be returned to the frontend. It carries a human-friendly
+-- diagnostic, the 'type' of the error as well as some context-specific data.
+data FrontendError a
+  = FrontendError
+    { fe_diagnostic :: !T.Text
+    , fe_type       :: !BackendErrorType
+    , fe_data       :: Maybe a
+    } deriving (Show, Eq)
+
+-- | A (hopefully and eventually) exhaustive list of backend errors.
+data BackendErrorType
+  = BE_phylo_corpus_not_ready
+  | BE_not_good_enough_ratio
+  | BE_node_not_found
+  deriving (Show, Eq)