Safe Haskell | None |
---|---|
Language | Haskell2010 |
- 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
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 # | |
class (Typeable e, Show e) => ToServantErr e where 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 MyException
The 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 = frontendExceptionFromException
We can now catch a MismatchedParentheses
exception as
MismatchedParentheses
, SomeFrontendException
or
SomeCompilerException
, but not other types, e.g. IOException
:
*Main> throw MismatchedParenthesescatch
e -> putStrLn ("Caught " ++ show (e :: MismatchedParentheses)) Caught MismatchedParentheses *Main> throw MismatchedParenthesescatch
e -> putStrLn ("Caught " ++ show (e :: SomeFrontendException)) Caught MismatchedParentheses *Main> throw MismatchedParenthesescatch
e -> putStrLn ("Caught " ++ show (e :: SomeCompilerException)) Caught MismatchedParentheses *Main> throw MismatchedParenthesescatch
e -> putStrLn ("Caught " ++ show (e :: IOException)) *** Exception: MismatchedParentheses
toException :: e -> SomeException #
fromException :: SomeException -> Maybe e #
displayException :: e -> String #
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
.