diff --git a/ChangeLog.md b/ChangeLog.md new file mode 100644 --- /dev/null +++ b/ChangeLog.md @@ -0,0 +1,3 @@ +# Changelog for haskell-zio + +## Unreleased changes diff --git a/LICENSE b/LICENSE new file mode 100644 --- /dev/null +++ b/LICENSE @@ -0,0 +1,373 @@ +Mozilla Public License Version 2.0 +================================== + +1. Definitions +-------------- + +1.1. "Contributor" + means each individual or legal entity that creates, contributes to + the creation of, or owns Covered Software. + +1.2. "Contributor Version" + means the combination of the Contributions of others (if any) used + by a Contributor and that particular Contributor's Contribution. + +1.3. "Contribution" + means Covered Software of a particular Contributor. + +1.4. "Covered Software" + means Source Code Form to which the initial Contributor has attached + the notice in Exhibit A, the Executable Form of such Source Code + Form, and Modifications of such Source Code Form, in each case + including portions thereof. + +1.5. "Incompatible With Secondary Licenses" + means + + (a) that the initial Contributor has attached the notice described + in Exhibit B to the Covered Software; or + + (b) that the Covered Software was made available under the terms of + version 1.1 or earlier of the License, but not also under the + terms of a Secondary License. + +1.6. "Executable Form" + means any form of the work other than Source Code Form. + +1.7. "Larger Work" + means a work that combines Covered Software with other material, in + a separate file or files, that is not Covered Software. + +1.8. "License" + means this document. + +1.9. "Licensable" + means having the right to grant, to the maximum extent possible, + whether at the time of the initial grant or subsequently, any and + all of the rights conveyed by this License. + +1.10. "Modifications" + means any of the following: + + (a) any file in Source Code Form that results from an addition to, + deletion from, or modification of the contents of Covered + Software; or + + (b) any new file in Source Code Form that contains any Covered + Software. + +1.11. "Patent Claims" of a Contributor + means any patent claim(s), including without limitation, method, + process, and apparatus claims, in any patent Licensable by such + Contributor that would be infringed, but for the grant of the + License, by the making, using, selling, offering for sale, having + made, import, or transfer of either its Contributions or its + Contributor Version. + +1.12. "Secondary License" + means either the GNU General Public License, Version 2.0, the GNU + Lesser General Public License, Version 2.1, the GNU Affero General + Public License, Version 3.0, or any later versions of those + licenses. + +1.13. "Source Code Form" + means the form of the work preferred for making modifications. + +1.14. "You" (or "Your") + means an individual or a legal entity exercising rights under this + License. For legal entities, "You" includes any entity that + controls, is controlled by, or is under common control with You. For + purposes of this definition, "control" means (a) the power, direct + or indirect, to cause the direction or management of such entity, + whether by contract or otherwise, or (b) ownership of more than + fifty percent (50%) of the outstanding shares or beneficial + ownership of such entity. + +2. License Grants and Conditions +-------------------------------- + +2.1. Grants + +Each Contributor hereby grants You a world-wide, royalty-free, +non-exclusive license: + +(a) under intellectual property rights (other than patent or trademark) + Licensable by such Contributor to use, reproduce, make available, + modify, display, perform, distribute, and otherwise exploit its + Contributions, either on an unmodified basis, with Modifications, or + as part of a Larger Work; and + +(b) under Patent Claims of such Contributor to make, use, sell, offer + for sale, have made, import, and otherwise transfer either its + Contributions or its Contributor Version. + +2.2. Effective Date + +The licenses granted in Section 2.1 with respect to any Contribution +become effective for each Contribution on the date the Contributor first +distributes such Contribution. + +2.3. Limitations on Grant Scope + +The licenses granted in this Section 2 are the only rights granted under +this License. No additional rights or licenses will be implied from the +distribution or licensing of Covered Software under this License. +Notwithstanding Section 2.1(b) above, no patent license is granted by a +Contributor: + +(a) for any code that a Contributor has removed from Covered Software; + or + +(b) for infringements caused by: (i) Your and any other third party's + modifications of Covered Software, or (ii) the combination of its + Contributions with other software (except as part of its Contributor + Version); or + +(c) under Patent Claims infringed by Covered Software in the absence of + its Contributions. + +This License does not grant any rights in the trademarks, service marks, +or logos of any Contributor (except as may be necessary to comply with +the notice requirements in Section 3.4). + +2.4. Subsequent Licenses + +No Contributor makes additional grants as a result of Your choice to +distribute the Covered Software under a subsequent version of this +License (see Section 10.2) or under the terms of a Secondary License (if +permitted under the terms of Section 3.3). + +2.5. Representation + +Each Contributor represents that the Contributor believes its +Contributions are its original creation(s) or it has sufficient rights +to grant the rights to its Contributions conveyed by this License. + +2.6. Fair Use + +This License is not intended to limit any rights You have under +applicable copyright doctrines of fair use, fair dealing, or other +equivalents. + +2.7. Conditions + +Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted +in Section 2.1. + +3. Responsibilities +------------------- + +3.1. Distribution of Source Form + +All distribution of Covered Software in Source Code Form, including any +Modifications that You create or to which You contribute, must be under +the terms of this License. You must inform recipients that the Source +Code Form of the Covered Software is governed by the terms of this +License, and how they can obtain a copy of this License. You may not +attempt to alter or restrict the recipients' rights in the Source Code +Form. + +3.2. Distribution of Executable Form + +If You distribute Covered Software in Executable Form then: + +(a) such Covered Software must also be made available in Source Code + Form, as described in Section 3.1, and You must inform recipients of + the Executable Form how they can obtain a copy of such Source Code + Form by reasonable means in a timely manner, at a charge no more + than the cost of distribution to the recipient; and + +(b) You may distribute such Executable Form under the terms of this + License, or sublicense it under different terms, provided that the + license for the Executable Form does not attempt to limit or alter + the recipients' rights in the Source Code Form under this License. + +3.3. Distribution of a Larger Work + +You may create and distribute a Larger Work under terms of Your choice, +provided that You also comply with the requirements of this License for +the Covered Software. If the Larger Work is a combination of Covered +Software with a work governed by one or more Secondary Licenses, and the +Covered Software is not Incompatible With Secondary Licenses, this +License permits You to additionally distribute such Covered Software +under the terms of such Secondary License(s), so that the recipient of +the Larger Work may, at their option, further distribute the Covered +Software under the terms of either this License or such Secondary +License(s). + +3.4. Notices + +You may not remove or alter the substance of any license notices +(including copyright notices, patent notices, disclaimers of warranty, +or limitations of liability) contained within the Source Code Form of +the Covered Software, except that You may alter any license notices to +the extent required to remedy known factual inaccuracies. + +3.5. Application of Additional Terms + +You may choose to offer, and to charge a fee for, warranty, support, +indemnity or liability obligations to one or more recipients of Covered +Software. However, You may do so only on Your own behalf, and not on +behalf of any Contributor. You must make it absolutely clear that any +such warranty, support, indemnity, or liability obligation is offered by +You alone, and You hereby agree to indemnify every Contributor for any +liability incurred by such Contributor as a result of warranty, support, +indemnity or liability terms You offer. You may include additional +disclaimers of warranty and limitations of liability specific to any +jurisdiction. + +4. Inability to Comply Due to Statute or Regulation +--------------------------------------------------- + +If it is impossible for You to comply with any of the terms of this +License with respect to some or all of the Covered Software due to +statute, judicial order, or regulation then You must: (a) comply with +the terms of this License to the maximum extent possible; and (b) +describe the limitations and the code they affect. Such description must +be placed in a text file included with all distributions of the Covered +Software under this License. Except to the extent prohibited by statute +or regulation, such description must be sufficiently detailed for a +recipient of ordinary skill to be able to understand it. + +5. Termination +-------------- + +5.1. The rights granted under this License will terminate automatically +if You fail to comply with any of its terms. However, if You become +compliant, then the rights granted under this License from a particular +Contributor are reinstated (a) provisionally, unless and until such +Contributor explicitly and finally terminates Your grants, and (b) on an +ongoing basis, if such Contributor fails to notify You of the +non-compliance by some reasonable means prior to 60 days after You have +come back into compliance. Moreover, Your grants from a particular +Contributor are reinstated on an ongoing basis if such Contributor +notifies You of the non-compliance by some reasonable means, this is the +first time You have received notice of non-compliance with this License +from such Contributor, and You become compliant prior to 30 days after +Your receipt of the notice. + +5.2. If You initiate litigation against any entity by asserting a patent +infringement claim (excluding declaratory judgment actions, +counter-claims, and cross-claims) alleging that a Contributor Version +directly or indirectly infringes any patent, then the rights granted to +You by any and all Contributors for the Covered Software under Section +2.1 of this License shall terminate. + +5.3. In the event of termination under Sections 5.1 or 5.2 above, all +end user license agreements (excluding distributors and resellers) which +have been validly granted by You or Your distributors under this License +prior to termination shall survive termination. + +************************************************************************ +* * +* 6. Disclaimer of Warranty * +* ------------------------- * +* * +* Covered Software is provided under this License on an "as is" * +* basis, without warranty of any kind, either expressed, implied, or * +* statutory, including, without limitation, warranties that the * +* Covered Software is free of defects, merchantable, fit for a * +* particular purpose or non-infringing. The entire risk as to the * +* quality and performance of the Covered Software is with You. * +* Should any Covered Software prove defective in any respect, You * +* (not any Contributor) assume the cost of any necessary servicing, * +* repair, or correction. This disclaimer of warranty constitutes an * +* essential part of this License. No use of any Covered Software is * +* authorized under this License except under this disclaimer. * +* * +************************************************************************ + +************************************************************************ +* * +* 7. Limitation of Liability * +* -------------------------- * +* * +* Under no circumstances and under no legal theory, whether tort * +* (including negligence), contract, or otherwise, shall any * +* Contributor, or anyone who distributes Covered Software as * +* permitted above, be liable to You for any direct, indirect, * +* special, incidental, or consequential damages of any character * +* including, without limitation, damages for lost profits, loss of * +* goodwill, work stoppage, computer failure or malfunction, or any * +* and all other commercial damages or losses, even if such party * +* shall have been informed of the possibility of such damages. This * +* limitation of liability shall not apply to liability for death or * +* personal injury resulting from such party's negligence to the * +* extent applicable law prohibits such limitation. Some * +* jurisdictions do not allow the exclusion or limitation of * +* incidental or consequential damages, so this exclusion and * +* limitation may not apply to You. * +* * +************************************************************************ + +8. Litigation +------------- + +Any litigation relating to this License may be brought only in the +courts of a jurisdiction where the defendant maintains its principal +place of business and such litigation shall be governed by laws of that +jurisdiction, without reference to its conflict-of-law provisions. +Nothing in this Section shall prevent a party's ability to bring +cross-claims or counter-claims. + +9. Miscellaneous +---------------- + +This License represents the complete agreement concerning the subject +matter hereof. If any provision of this License is held to be +unenforceable, such provision shall be reformed only to the extent +necessary to make it enforceable. Any law or regulation which provides +that the language of a contract shall be construed against the drafter +shall not be used to construe this License against a Contributor. + +10. Versions of the License +--------------------------- + +10.1. New Versions + +Mozilla Foundation is the license steward. Except as provided in Section +10.3, no one other than the license steward has the right to modify or +publish new versions of this License. Each version will be given a +distinguishing version number. + +10.2. Effect of New Versions + +You may distribute the Covered Software under the terms of the version +of the License under which You originally received the Covered Software, +or under the terms of any subsequent version published by the license +steward. + +10.3. Modified Versions + +If you create software not governed by this License, and you want to +create a new license for such software, you may create and use a +modified version of this License if you rename the license and remove +any references to the name of the license steward (except to note that +such modified license differs from this License). + +10.4. Distributing Source Code Form that is Incompatible With Secondary +Licenses + +If You choose to distribute Source Code Form that is Incompatible With +Secondary Licenses under the terms of this version of the License, the +notice described in Exhibit B of this License must be attached. + +Exhibit A - Source Code Form License Notice +------------------------------------------- + + This Source Code Form is subject to the terms of the Mozilla Public + License, v. 2.0. If a copy of the MPL was not distributed with this + file, You can obtain one at http://mozilla.org/MPL/2.0/. + +If it is not possible or desirable to put the notice in a particular +file, then You may include the notice in a location (such as a LICENSE +file in a relevant directory) where a recipient would be likely to look +for such a notice. + +You may add additional accurate notices of copyright ownership. + +Exhibit B - "Incompatible With Secondary Licenses" Notice +--------------------------------------------------------- + + This Source Code Form is "Incompatible With Secondary Licenses", as + defined by the Mozilla Public License, v. 2.0. diff --git a/README.md b/README.md new file mode 100644 --- /dev/null +++ b/README.md @@ -0,0 +1,75 @@ +# haskell-zio + +A [small](src/ZIO/Trans.hs) monad-transformer analogue to the +Scala [ZIO](https://github.com/zio/zio) +library (basically, [UIO](http://hackage.haskell.org/package/unexceptionalio) + +[Reader](hackage.haskell.org/package/transformers/docs/Control-Monad-Trans-Reader.html) + +[Either/ExceptT](hackage.haskell.org/package/mtl/docs/Control-Monad-Except.html)). + +I like to call `ZIO` a *best-practices monad for applications*. It +wraps in a `Reader` monad for carrying around configuration and +environment data, and slightly more controversially, makes +error-handling more explicit by making all recoverable\ +[exceptions and errors](https://wiki.haskell.org/Error_vs._Exception) +part of the return-type of functions. + +Note that this is meant to provide the same basic functionality of the `ZIO` monad. +While I'm not immediately looking into other features of ZIO-the-library, such as +concurrency, I welcome suggestions via issues or pull requests. + +## Comparison to other Haskell libraries + +- [UIO](http://hackage.haskell.org/package/unexceptionalio) This ZIO library +builds upon UIO (Unexceptional-IO) as a dependency, and it is the +inner-most monad in the transformer stack. We use UIO, in conjunction +with `ExceptT`, to model possible error states (or the lack thereof) +more explicitly. In other words, we are trying to make all errors or +exceptions. +[checked exceptions](https://en.wikibooks.org/wiki/Java_Programming/Checked_Exceptions), where possible. See the [blog post](https://singpolyma.net/2018/05/error-handling-in-haskell/) (or [backup](docs/UIO.md)) for more details. +- [RIO](https://hackage.haskell.org/package/rio) +[integrates](hackage.haskell.org/package/rio/docs/src/RIO.Prelude.RIO.html#RIO) `ReaderT` with `IO`, but somewhat like Scala ZIO, provides +much additional functionality, and providing much of that functionality\ +will be a goal of haskell-zio as well. +- [Trio](https://github.com/snoyberg/trio) has essentially the same goals +as ZIO (and I believe it is isomorphic to ZIO), but is a self-described +experiment at the moment. The major experimental aspect I'm aware of is +that it is avoiding usage of `ExceptT` to improve performance, which +I have not investigated. We are currently aiming for stability here, +but ideally any code written for haskell-ZIO could easily be transferred +to using `Trio`, or vice versa. If you see a difference, **please raise an +issue** so we can document it or fix it. + +## The Scala-Haskell ZIO dictionary + +### Type Aliases +The Scala ZIO type parameters and +[aliases](https://zio.dev/docs/overview/overview_index#type-aliases) are +largely reproduced in Haskell, though in some cases we can't exactly +reproduce them. For instance, `IO` is already taken in Haskell at +a very fundamental level. As well, `UIO` has the same meaning as in +the Scala implementation, but it isn't an alias, since it is an inner +monad of the `ZIO` type. + +An apparent downsize of having `UIO`, `EIO`, and `ZIO` as distinct +(non-aliased) types is that one might feel inclined to provide APIs +for one or more of these when warranted. For this reason `UEIO e`, +`UZIO a`, and other aliases along with associated lift and unlift +functions are provided. These aliases have `Void` in the expanded type, +and in some cases, it is more appropriate to use a universal quantifier, +e.g., when lifting into a type, we usually have some Error type in mind +other than `Void` (that's one big reason why we're using this library!), +so we'd prefer to have e.g. `uelift :: ∀ e a. UIO a -> EIO e a`, +not `uelift :: UIO a -> UEIO a`. + +[//]: # (Table generated from docs/type_aliases.csv using https://www.tablesgenerator.com/markdown_tables) + +| Haskell Type | Alias for | Scala Type | Notes | +|-------------- |------------------------------------- |-------------- |------------------------------------------------------------------------------------------------------- | +| `ZIO r e a` | | `ZIO[R,E,A]` | | +| `UIO a` | | `UIO[A]` | This is a type alias in Scala but a concrete type in Haskell due to UIO being an inner monadic type. | +| `EIO e a` | | `IO[E, A]` | This is a type alias in Scala but a concrete type in Haskell due to EIO being an inner monadic type. | +| `RIO r a` | `ZIO r SomeNonPseudoException a` | `RIO[R, A]` | Same idea as in Scala. Not to be confused with the RIO library's `RIO` monad, but they are isomorphic. | +| `Task a` | `ZIO Void SomeNonPseudoException a` | `Task[A]` | | +| `UEIO a` | `EIO Void a` | `UIO[A]` | | +| `URIO r a` | `ZIO r Void a` | `URIO[R, A]` | Same idea as in Scala; a ZIO value isomorphic to a RIO value (can be projected to the RIO value). | +| `UZIO a` | `ZIO Void Void a` | `UIO[A]` | | diff --git a/Setup.hs b/Setup.hs new file mode 100644 --- /dev/null +++ b/Setup.hs @@ -0,0 +1,2 @@ +import Distribution.Simple +main = defaultMain diff --git a/src/ZIO/Trans.hs b/src/ZIO/Trans.hs new file mode 100644 --- /dev/null +++ b/src/ZIO/Trans.hs @@ -0,0 +1,97 @@ +{-# LANGUAGE GeneralizedNewtypeDeriving #-} +{-# LANGUAGE RankNTypes #-} +{-# LANGUAGE ScopedTypeVariables #-} +{-# LANGUAGE UnicodeSyntax #-} + + +module ZIO.Trans ( + EIO(..), ZIO(..) + , UEIO, URIO, UZIO, Task, RIO + , elift, ezlift, zlift + , uelift, uzlift + , euUnlift, zuUnlift + , mapEError, mapZError + , runEIO, runZIO + , withEIO, withZIO + , module Control.Monad.Except + , module Control.Monad.Reader + , module UnexceptionalIO + , module UnexceptionalIO.Trans + +) where + +import Control.Monad.Except +import Control.Monad.Reader hiding (lift) +import Data.Void (Void, absurd) +import UnexceptionalIO hiding (fromIO, lift, run) +import UnexceptionalIO.Trans (UIO, fromIO, run) + +-- | Corresponds to IO[E, A] in Scala +newtype EIO e a = EIO { _unEIO :: ExceptT e UIO a } + deriving ( Functor, Applicative, Monad, MonadError e, MonadFix, Unexceptional ) + +newtype ZIO r e a = ZIO { _unZIO :: ReaderT r (EIO e) a } + deriving ( Functor, Applicative, Monad, MonadError e, MonadFix, MonadReader r, Unexceptional ) + +type UEIO a = EIO Void a + +type URIO r a = ZIO r Void a + +type UZIO a = ZIO Void Void a + +type Task a = ZIO Void SomeNonPseudoException a + +type RIO r a = ZIO r SomeNonPseudoException a + +elift :: IO a -> EIO SomeNonPseudoException a +elift = EIO . fromIO + +zlift :: IO a -> ZIO r SomeNonPseudoException a +zlift = ZIO . lift . elift + +ezlift :: forall r e a. EIO e a -> ZIO r e a +ezlift = ZIO . lift + +uelift :: ∀ e a. UIO a -> EIO e a +uelift = EIO . lift + +uzlift :: ∀ r e a. UIO a -> ZIO r e a +uzlift = ezlift . uelift + +euUnlift :: UEIO a -> UIO a +euUnlift ueio = (either absurd id) <$> ((runExceptT . _unEIO) ueio) + +zuUnlift :: UZIO a -> UIO a +zuUnlift = euUnlift . flip runReaderT undefined . _unZIO + +runEIO :: MonadIO m => EIO e a -> (e -> m a) -> m a +runEIO eio handler = do + resEi :: Either e a <- (run . runExceptT . _unEIO) eio + either handler pure resEi + +withEIO :: (e -> e') -> EIO e a -> EIO e' a +withEIO h = EIO + . withExceptT h + . _unEIO + +mapEError :: (e -> e') -> EIO e a -> EIO e' a +mapEError = withEIO + +runZIO :: MonadIO m => ZIO r e a -> r -> (e -> m a) -> m a +runZIO app env handler = do + let eio = runReaderT (_unZIO app) env + runEIO eio handler + +withZIO :: r -> (e -> e') -> ZIO r e a -> ZIO r e' a +withZIO r h = ezlift + . EIO + . withExceptT h + . _unEIO + . flip runReaderT r + . _unZIO + +mapZError :: (e -> e') -> ZIO r e a -> ZIO r e' a +mapZError h m = do + r <- ask + withZIO r h m + diff --git a/test/Spec.hs b/test/Spec.hs new file mode 100644 --- /dev/null +++ b/test/Spec.hs @@ -0,0 +1,2 @@ +main :: IO () +main = putStrLn "Test suite not yet implemented" diff --git a/zio.cabal b/zio.cabal new file mode 100644 --- /dev/null +++ b/zio.cabal @@ -0,0 +1,59 @@ +cabal-version: 1.12 + +-- This file has been generated from package.yaml by hpack version 0.33.0. +-- +-- see: https://github.com/sol/hpack +-- +-- hash: 6be80043f3a5bef1bd4f8f34b4c51639fdb74962f2377876443eab74c7fd669e + +name: zio +version: 0.1.0.0 +description: Please see the README on GitHub at +homepage: https://github.com/githubuser/haskell-zio#readme +bug-reports: https://github.com/githubuser/haskell-zio/issues +author: Brandon Elam Barker +maintainer: brandon.barker@cornell.edu +copyright: 2020 Brandon Elam Barker +license: MPL-2.0 +license-file: LICENSE +build-type: Simple +extra-source-files: + README.md + ChangeLog.md + +source-repository head + type: git + location: https://github.com/githubuser/haskell-zio + +library + exposed-modules: + ZIO.Trans + other-modules: + Paths_zio + hs-source-dirs: + src + ghc-options: -Wall -Wtabs -Wincomplete-record-updates + build-depends: + base >=4.7 && < 5 + , mtl >= 2.2 && < 2.3 + , transformers >= 0.5.6 && < 0.6 + , unexceptionalio >= 0.5.1 && < 0.6 + , unexceptionalio-trans >= 0.5.1 && < 0.6 + default-language: Haskell2010 + +test-suite zio-test + type: exitcode-stdio-1.0 + main-is: Spec.hs + other-modules: + Paths_zio + hs-source-dirs: + test + ghc-options: -threaded -rtsopts -with-rtsopts=-N + build-depends: + base + , mtl + , transformers + , unexceptionalio + , unexceptionalio-trans + , zio + default-language: Haskell2010