| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Servant.Exception
- data Throws (e :: *)
- class (Typeable e, Show e) => ToServantErr e where
- data ServantException
- toServantException :: (Exception e, ToJSON e, ToServantErr e) => e -> SomeException
- fromServantException :: Exception e => SomeException -> Maybe e
- class (Typeable * e, Show e) => Exception e where
- mapException :: (Exception e1, Exception e2, MonadCatch m) => (e1 -> e2) -> m a -> m a
Documentation
Instances
| HasServer * ((:<|>) ((:>) * * (Throws e) api1) ((:>) * * (Throws e) api2)) context => HasServer * ((:>) * * (Throws e) ((:<|>) api1 api2)) context Source # | Transitive application of |
| HasServer * ((:>) k * api ((:>) * k1 (Throws e) upstream)) context => HasServer * ((:>) * * (Throws e) ((:>) k k1 api upstream)) context Source # | Push |
| (Exception e, ToServantErr e, AllMimeRender ct e, HasServer * (Verb k * mt st ct a) context) => HasServer * ((:>) * * (Throws e) (Verb k * mt st ct a)) context Source # | Main |
| type ServerT * ((:>) * * (Throws e) ((:<|>) api1 api2)) m Source # | |
| type ServerT * ((:>) * * (Throws e) ((:>) k k1 api upstream)) m Source # | |
| type ServerT * ((:>) * * (Throws e) (Verb k * mt st ct a)) m Source # | |
data ServantException Source #
A root exception type (see Control.Exception) to provide a common
rendering format via MimeRender for builtin content types JSON and
PlainText.
toServantException :: (Exception e, ToJSON e, ToServantErr e) => e -> SomeException Source #
fromServantException :: Exception e => SomeException -> Maybe e Source #
class (Typeable * e, Show e) => Exception e where #
Any type that you wish to throw or catch as an exception must be an
instance of the Exception class. The simplest case is a new exception
type directly below the root:
data MyException = ThisException | ThatException
deriving Show
instance Exception MyExceptionThe default method definitions in the Exception class do what we need
in this case. You can now throw and catch ThisException and
ThatException as exceptions:
*Main> throw ThisException `catch` \e -> putStrLn ("Caught " ++ show (e :: MyException))
Caught ThisException
In more complicated examples, you may wish to define a whole hierarchy of exceptions:
---------------------------------------------------------------------
-- Make the root exception type for all the exceptions in a compiler
data SomeCompilerException = forall e . Exception e => SomeCompilerException e
instance Show SomeCompilerException where
show (SomeCompilerException e) = show e
instance Exception SomeCompilerException
compilerExceptionToException :: Exception e => e -> SomeException
compilerExceptionToException = toException . SomeCompilerException
compilerExceptionFromException :: Exception e => SomeException -> Maybe e
compilerExceptionFromException x = do
SomeCompilerException a <- fromException x
cast a
---------------------------------------------------------------------
-- Make a subhierarchy for exceptions in the frontend of the compiler
data SomeFrontendException = forall e . Exception e => SomeFrontendException e
instance Show SomeFrontendException where
show (SomeFrontendException e) = show e
instance Exception SomeFrontendException where
toException = compilerExceptionToException
fromException = compilerExceptionFromException
frontendExceptionToException :: Exception e => e -> SomeException
frontendExceptionToException = toException . SomeFrontendException
frontendExceptionFromException :: Exception e => SomeException -> Maybe e
frontendExceptionFromException x = do
SomeFrontendException a <- fromException x
cast a
---------------------------------------------------------------------
-- Make an exception type for a particular frontend compiler exception
data MismatchedParentheses = MismatchedParentheses
deriving Show
instance Exception MismatchedParentheses where
toException = frontendExceptionToException
fromException = frontendExceptionFromExceptionWe can now catch a MismatchedParentheses exception as
MismatchedParentheses, SomeFrontendException or
SomeCompilerException, but not other types, e.g. IOException:
*Main> throw MismatchedParenthesescatche -> putStrLn ("Caught " ++ show (e :: MismatchedParentheses)) Caught MismatchedParentheses *Main> throw MismatchedParenthesescatche -> putStrLn ("Caught " ++ show (e :: SomeFrontendException)) Caught MismatchedParentheses *Main> throw MismatchedParenthesescatche -> putStrLn ("Caught " ++ show (e :: SomeCompilerException)) Caught MismatchedParentheses *Main> throw MismatchedParenthesescatche -> putStrLn ("Caught " ++ show (e :: IOException)) *** Exception: MismatchedParentheses
Methods
toException :: e -> SomeException #
fromException :: SomeException -> Maybe e #
displayException :: e -> String #
Instances
| Exception Void | Since: 4.8.0.0 |
| Exception BlockedIndefinitelyOnMVar | Since: 4.1.0.0 |
| Exception BlockedIndefinitelyOnSTM | Since: 4.1.0.0 |
| Exception Deadlock | Since: 4.1.0.0 |
| Exception AllocationLimitExceeded | Since: 4.8.0.0 |
| Exception CompactionFailed | Since: 4.10.0.0 |
| Exception AssertionFailed | Since: 4.1.0.0 |
| Exception SomeAsyncException | Since: 4.7.0.0 |
| Exception AsyncException | Since: 4.7.0.0 |
| Exception ArrayException | Since: 4.1.0.0 |
| Exception ExitCode | Since: 4.1.0.0 |
| Exception IOException | Since: 4.1.0.0 |
| Exception ErrorCall | Since: 4.0.0.0 |
| Exception ArithException | Since: 4.0.0.0 |
| Exception SomeException | Since: 3.0 |
| Exception ASCII7_Invalid | |
| Exception ISO_8859_1_Invalid | |
| Exception UTF16_Invalid | |
| Exception UTF32_Invalid | |
| Exception InvalidAccess | |
| Exception ResourceCleanupException | |
| Exception ServantErr | |
| Exception ServantException # | |
mapException :: (Exception e1, Exception e2, MonadCatch m) => (e1 -> e2) -> m a -> m a Source #
Catch and rethrow using mapping function f.