haskell/zap/lib/Zap/Errors.hs

{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE UndecidableInstances #-}

-- |
-- Module: Zap.Errors
-- Description: Error handling utilities
module Zap.Errors
  ( Error (..),
  )
where

import Control.Monad.Catch (Exception)
import Data.Text.Encoding.Error (UnicodeException)

-- | An error that may occur when processing a zap message.
data Error
  = -- | A 'BoundsError' indicates an attempt to access an illegal
    -- index 'index' within a sequence of length 'maxIndex'.
    BoundsError
      { index :: !Int,
        maxIndex :: !Int
        -- TODO: choose a better name than maxIndex; this is confusing
        -- since it's supposed to be the length, rather than the maximum
        -- legal index. The latter would make it impossible to represent
        -- an error for an empty sequence. I(zenhack) also think there may
        -- be places in the library where we are misusing this field.
      }
  | -- | A 'RecursionLimitError' indicates that the recursion depth limit
    -- was exceeded.
    RecursionLimitError
  | -- | A 'TraversalLimitError' indicates that the traversal limit was
    -- exceeded.
    TraversalLimitError
  | -- | An 'InvalidDataError' indicates that a part of a message being
    -- parsed was malformed. The argument to the data constructor is a
    -- human-readable error message.
    InvalidDataError String
  | -- | A 'SizeError' indicates that an operation would have resulted in
    -- a message that violated the library's limit on either segment size
    -- or number of segments.
    SizeError
  | -- | A 'SchemaViolationError' indicates that part of the message does
    -- not match the schema. The argument to the data construtor is a
    -- human-readable error message.
    SchemaViolationError String
  | -- | An 'InvalidUtf8Error' indicates that a text value in the message
    -- was invalid utf8.
    --
    -- Note well: Most parts of the library don't actually check for valid
    -- utf8 -- don't assume the check is made unless an interface says it is.
    InvalidUtf8Error UnicodeException
  deriving (Show, Eq)

instance Exception Error