1.x to 2.x

dejafu-2.0.0.0 is a super-major release which breaks compatibility with dejafu-1.x.

Highlights reel:

  • Test cases are written in terms of a new Program type.
  • The Failure type has been replaced with a Condition type (actually in 1.12).
  • Random testing takes an optional length bound.
  • Atomically-checked invariants over shared mutable state.

See the changelogs for the full details.

The Program type

The ConcT type is now an alias for Program Basic.

A Program Basic has all the instances ConcT did, defined using the ~ instance trick, so this shouldn’t be a breaking change:

instance (pty ~ Basic)            => MonadTrans (Program pty)
instance (pty ~ Basic)            => MonadCatch (Program pty n)
instance (pty ~ Basic)            => MonadThrow (Program pty n)
instance (pty ~ Basic)            => MonadMask  (Program pty n)
instance (pty ~ Basic, Monad   n) => MonadConc  (Program pty n)
instance (pty ~ Basic, MonadIO n) => MonadIO    (Program pty n)

The dontCheck function has been removed in favour of withSetup:

do x <- dontCheck setup
   action x

-- becomes

withSetup setup action

The subconcurrency function has been removed in favour of withSetupAndTeardown:

do x <- setup
   y <- subconcurrency (action x)
   teardown x y

-- becomes

withSetupAndTeardown setup teardown action

The dontCheck and subconcurrency functions used to throw runtime errors if nested. This is not possible with withSetup and withSetupAndTeardown due to their types:

withSetup
  :: Program Basic n x
  -- ^ Setup action
  -> (x -> Program Basic n a)
  -- ^ Main program
  -> Program (WithSetup x) n a

withSetupAndTeardown
  :: Program Basic n x
  -- ^ Setup action
  -> (x -> Either Condition y -> Program Basic n a)
  -- ^ Teardown action
  -> (x -> Program Basic n y)
  -- ^ Main program
  -> Program (WithSetupAndTeardown x y) n a

Previously, multiple calls to subconcurrency could be sequenced in the same test case. This is not possible using withSetupAndTeardown. If you rely on this behaviour, please file an issue.

The Condition type

This is a change in dejafu-1.12.0.0, but the alias Failure = Condition is removed in dejafu-2.0.0.0.

  • The STMDeadlock and Deadlock constructors have been merged.
  • Internal errors have been split into the Error type and are raised as exceptions, instead of being returned as conditions.

The name “failure” has been a recurring source of confusion, because an individual execution can “fail” without the predicate as a whole failing. My hope is that the more neutral “condition” will prevent this confusion.

Deprecated functions

All the deprecated special-purpose functions have been removed. Use more general *WithSettings functions instead.

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