diff --git a/CHANGELOG.md b/CHANGELOG.md new file mode 100644 --- /dev/null +++ b/CHANGELOG.md @@ -0,0 +1,11 @@ +# Changelog + +`type-errors-pretty` uses [PVP Versioning][1]. +The changelog is available [on GitHub][2]. + +## 0.0.0.0 — Jul 15, 2019 + +* Initially created. + +[1]: https://pvp.haskell.org +[2]: https://github.com/chshersh/type-errors-pretty/releases 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 +1,44 @@ +# type-errors-pretty + +![pretty-bug](https://user-images.githubusercontent.com/4276606/61183911-eda86300-a679-11e9-9b8e-34c129469075.png) +[![Build status](https://img.shields.io/travis/chshersh/type-errors-pretty.svg?logo=travis)](https://travis-ci.org/chshersh/type-errors-pretty) +[![Hackage](https://img.shields.io/hackage/v/type-errors-pretty.svg?logo=haskell)](https://hackage.haskell.org/package/type-errors-pretty) +[![Stackage Lts](http://stackage.org/package/type-errors-pretty/badge/lts)](http://stackage.org/lts/package/type-errors-pretty) +[![Stackage Nightly](http://stackage.org/package/type-errors-pretty/badge/nightly)](http://stackage.org/nightly/package/type-errors-pretty) +[![MPL-2.0 license](https://img.shields.io/badge/license-MPL--2.0-blue.svg)](LICENSE) + +> "It is important that we forgive ourselves for making mistakes. We need to learn +> from our errors and move on." +> +> ― Steve Maraboli, Life, the Truth, and Being Free + +Combinators for writing pretty type errors easily. The word **pretty** here +doesn't mean that the resulting type errors will be pretty (though, I believe +they will be awesome), but the way the type errors are defined in your code is +pretty. + +If you're interested in motivation behind using type errors at first place, you +can read the following blog post: + +* [A story told by Type Errors](https://kodimensional.dev/type-errors) + +The `type-errors-pretty` library allows you to write the text of custom +compile-time error messages with less effort in the following way: + +```haskell +import Type.Errors.Pretty (type (<>), type (%)) + + +type MessageText (e1 :: k) (e2 :: k) (es :: [k]) + = "You require the following two effects from your computation:" + % "" + % " '" <> e1 <> "' and '" <> e2 <> "'" + % "" + % "However, your monad is capable of performing only the following effects:" + % "" + % " " <> es +``` + +## Acknowledgement + +Icons made by [Freepik](http://www.freepik.com) from [www.flaticon.com](https://www.flaticon.com/) is licensed by [CC 3.0 BY](http://creativecommons.org/licenses/by/3.0/). diff --git a/src/Type/Errors/Pretty.hs b/src/Type/Errors/Pretty.hs new file mode 100644 --- /dev/null +++ b/src/Type/Errors/Pretty.hs @@ -0,0 +1,110 @@ +{-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE TypeInType #-} +{-# LANGUAGE TypeOperators #-} +{-# LANGUAGE UnicodeSyntax #-} + +{- | +This module provides type-level functions and operators to make the job of +writing text of custom type errors easier. The motivation behind using custom +type errors is described in detail in the following blog post: + +* [A story told by Type Errors](https://kodimensional.dev/type-errors) + +If you want to write the text of a custom error message, you need to use +constructors of the 'ErrorMessage' data type. But this gets messy and +inconvenient pretty quickly. Consider the following examples: + +@ +__type__ MessageText (e1 :: k) (e2 :: k) (es :: [k]) = + ''Text' "You require the following two effects from your computation:" + '':$$:' ''Text' "" + '':$$:' ''Text' " '" '':<>:' ''ShowType' e1 '':<>:' ''Text' "' and '" '':<>:' ''ShowType' e2 '':<>:' ''Text' "'" + '':$$:' ''Text' "" + '':$$:' ''Text' "However, your monad is capable of performing only the following effects:" + '':$$:' ''Text' "" + '':$$:' ''Text' " " '':<>:' ''ShowType' es +@ + +Using combinators from this library, you can define error messages in a simpler +way: + +@ +__type__ MessageText (e1 :: k) (e2 :: k) (es :: [k]) + = "You require the following two effects from your computation:" + '%' "" + '%' " '" 'Type.Errors.Pretty.<>' e1 'Type.Errors.Pretty.<>' "' and '" 'Type.Errors.Pretty.<>' e2 'Type.Errors.Pretty.<>' "'" + '%' "" + '%' "However, your monad is capable of performing only the following effects:" + '%' "" + '%' " " 'Type.Errors.Pretty.<>' es +@ + +If you prefer, you can use unicode operators to contstruct messages: + +@ +__type__ MessageText (e1 :: k) (e2 :: k) (es :: [k]) + = "You require the following two effects from your computation:" + '•' "" + '•' " '" '⊕' e1 '⊕' "' and '" '⊕' e2 '⊕' "'" + '•' "" + '•' "However, your monad is capable of performing only the following effects:" + '•' "" + '•' " " '⊕' es +@ +-} + +module Type.Errors.Pretty + ( -- * Combinators + type (<>) + , type (⊕) + , type (%) + , type (•) + + -- * Reexports from "GHC.TypeLits" + , TypeError + + -- * Helper internal type families + , ToErrorMessage + ) where + +import GHC.TypeLits (ErrorMessage (..), Symbol, TypeError) + + +{- | Append two types automatically converting them to corresponding +'ErrorMessage' constructors. + +>>> :kind! "Integer values have type: " <> Int +"Integer values have type: " <> Int :: ErrorMessage += 'Text "Integer values have type: " ':<>: 'ShowType Int +-} +infixl 5 <> +type family (<>) (l :: k1) (r :: k2) :: ErrorMessage where + l <> r = ToErrorMessage l ':<>: ToErrorMessage r + +{- | Unicode version of the 'Type.Errors.Pretty.<>' type-level operator. +-} +infixl 5 ⊕ +type (⊕) (l :: k1) (r :: k2) = l <> r + +{- | Append two types on top of each other automatically converting them to +corresponding 'ErrorMessage' constructors. + +>>> :kind! "Expecting value of type: " % " " <> Integer +"Expecting value of type: " % " " <> Integer :: ErrorMessage += 'Text "Expecting value of type: " + ':$$: ('Text " " ':<>: 'ShowType Integer) +-} +infixr 4 % +type family (%) (t :: k1) (b :: k2) :: ErrorMessage where + t % b = ToErrorMessage t ':$$: ToErrorMessage b + +{- | Unicode version of the '%' type-level operator. +-} +infixr 4 • +type (•) (t :: k1) (b :: k2) = t % b + +-- | Type family to convert any type to 'ErrorMessage'. +type family ToErrorMessage (t :: k) :: ErrorMessage where + ToErrorMessage (t :: Symbol) = 'Text t + ToErrorMessage (t :: ErrorMessage) = t + ToErrorMessage t = 'ShowType t diff --git a/test/Doctest.hs b/test/Doctest.hs new file mode 100644 --- /dev/null +++ b/test/Doctest.hs @@ -0,0 +1,13 @@ +module Main (main) where + +import System.FilePath.Glob (glob) +import Test.DocTest (doctest) + + +main :: IO () +main = do + sourceFiles <- glob "src/**/*.hs" + doctest + $ "-XDataKinds" + : "-XTypeOperators" + : sourceFiles diff --git a/type-errors-pretty.cabal b/type-errors-pretty.cabal new file mode 100644 --- /dev/null +++ b/type-errors-pretty.cabal @@ -0,0 +1,66 @@ +cabal-version: 2.4 +name: type-errors-pretty +version: 0.0.0.0 +synopsis: Combinators for writing pretty type errors easily +description: + This library provides replacements for the @ErrorMessage@ constructors to + write the text of custom error messages easily. +homepage: https://github.com/chshersh/type-errors-pretty +bug-reports: https://github.com/chshersh/type-errors-pretty/issues +license: MPL-2.0 +license-file: LICENSE +author: Dmitrii Kovanikov +maintainer: Dmitrii Kovanikov +copyright: 2019 Dmitrii Kovanikov +category: Types, Type Errors +build-type: Simple +extra-doc-files: README.md + , CHANGELOG.md +tested-with: GHC == 8.2.2 + , GHC == 8.4.4 + , GHC == 8.6.5 + +source-repository head + type: git + location: https://github.com/chshersh/type-errors-pretty.git + +common common-options + build-depends: base >= 4.10.1.0 && < 4.13 + ghc-options: -Wall + -Wincomplete-uni-patterns + -Wincomplete-record-updates + -Wcompat + -Widentities + -Wredundant-constraints + -fhide-source-paths + + default-language: Haskell2010 + default-extensions: ConstraintKinds + DeriveGeneric + GeneralizedNewtypeDeriving + InstanceSigs + KindSignatures + LambdaCase + OverloadedStrings + RecordWildCards + ScopedTypeVariables + StandaloneDeriving + TupleSections + TypeApplications + ViewPatterns + +library + import: common-options + hs-source-dirs: src + exposed-modules: Type.Errors.Pretty + +test-suite doctest + import: common-options + type: exitcode-stdio-1.0 + hs-source-dirs: test + main-is: Doctest.hs + + build-depends: doctest ^>= 0.16 + , Glob + + ghc-options: -threaded