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migration_1x_2x.rst

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1.x to 2.x

dejafu-2.0.0.0 is a super-major release which breaks compatibility with dejafu-1.x <dejafu-1.12.0.0>.

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.

Need help?

  • For general help talk to me in IRC (barrucadu in #haskell) or shoot me an email (mike@barrucadu.co.uk)
  • For bugs, issues, or requests, please file an issue <>.