uncaught-exception (empty) → 0.1.0
raw patch · 6 files changed
+573/−0 lines, 6 filesdep +basedep +uncaught-exception
Dependencies added: base, uncaught-exception
Files
- CHANGELOG.md +3/−0
- LICENSE +312/−0
- README.md +23/−0
- demo/Main.hs +35/−0
- src/Control/Exception/Uncaught.hs +140/−0
- uncaught-exception.cabal +60/−0
+ CHANGELOG.md view
@@ -0,0 +1,3 @@+0.1.0+=====+* Initial version.
+ LICENSE view
@@ -0,0 +1,312 @@+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.
+ README.md view
@@ -0,0 +1,23 @@+# uncaught-exception++[](https://github.com/serokell/uncaught-exception/actions)+[](https://hackage.haskell.org/package/uncaught-exception)+[](http://stackage.org/lts/package/uncaught-exception)+[](http://stackage.org/nightly/package/uncaught-exception)+[](https://github.com/serokell/o-clock/blob/master/LICENSE)++The goal of this small library is to make it easy to customize handling of uncaught exceptions in Haskell applications.+The default handler of uncaught exceptions uses the `Show` type class to print the exception.+However, in some cases you may want to use `displayException` which renders the exception value in a human-friendly manner.+You can find more details about motivation and implementation of this library in its Haddock documentation and [this blog post](https://serokell.io/blog/uncaught-exception-handling).++## For Contributors++Please see [CONTRIBUTING.md](.github/CONTRIBUTING.md) for more information.++## About Serokell++`uncaught-exception` is maintained and funded with ❤️ by [Serokell](https://serokell.io/).+The names and logo for Serokell are trademark of Serokell OÜ.++We love open source software! See [our other projects](https://serokell.io/community?utm_source=github) or [hire us](https://serokell.io/hire-us?utm_source=github) to design, develop and grow your idea!
+ demo/Main.hs view
@@ -0,0 +1,35 @@+-- SPDX-FileCopyrightText: 2020 Serokell <https://serokell.io>+--+-- SPDX-License-Identifier: MPL-2.0++{-# LANGUAGE DerivingStrategies #-}+{-# LANGUAGE LambdaCase #-}++module Main+ ( main+ ) where++import Control.Exception (Exception(..), throwIO)+import System.Environment (getArgs)++import Control.Exception.Uncaught++data MyException = MyException+ deriving stock Show++instance Exception MyException where+ displayException MyException = "displayException"++main :: IO ()+main = do+ method <- getArgs >>= \case+ [m] -> pure m+ _ -> fail "Pass only one argument"+ f method $ throwIO MyException+ where+ f :: String -> IO a -> IO a+ f "id" = id+ f "displayUncaughtException" = displayUncaughtException+ f "withDisplayExceptionHandler" = withDisplayExceptionHandler+ f "setDisplayExceptionHandler" = (setDisplayExceptionHandler >>)+ f method = const $ fail $ "Unknown method: " <> method
+ src/Control/Exception/Uncaught.hs view
@@ -0,0 +1,140 @@+-- SPDX-FileCopyrightText: 2020 Serokell <https://serokell.io>+--+-- SPDX-License-Identifier: MPL-2.0++-- | Customize uncaught exception handler.+--+-- When any thread of your Haskell application throws an exception+-- that does not get caught explicitly, the Haskell runtime system will+-- handle it and print based on the 'Show' instance (by default). This+-- behavior can be customized using the 'setUncaughtExceptionHandler'+-- function. However, implementing your own uncaught exception handler+-- sounds like a tricky task because you should keep a bunch of things+-- in mind:+--+-- 1. You should flush stdout.+-- 2. You should print output to stderr rather than stdout.+-- 3. You should take care of the exit code of your application and the+-- 'ExitCode' data type.+--+-- The aim of this module is to handle all these concerns and provide+-- easy-to-use functions that capture common cases when you want to+-- modify behavior of the default uncaught exception handler.+-- Currently we consider only one case: using 'displayException' instead+-- of the 'Show' methods. It's debatable whether 'displayException' is+-- more appropriate to print uncaught exceptions. Even though+-- 'displayException' is not used by default, we believe there are cases+-- when it makes sense to use it for printing.+--+-- We intentionally provide more than one implementation with similar types+-- and semantics. We expect that over time these functions+-- will be better tested and some feedback will be gathered that+-- will let us figure out which approach is better.++module Control.Exception.Uncaught+ ( displayUncaughtException+ , withDisplayExceptionHandler+ , setDisplayExceptionHandler++ -- * Exported just in case you want to do something special+ , DisplayExceptionInShow (..)+ , wrapException+ ) where++import Control.Exception+ (Deadlock, Exception(..), SomeAsyncException, SomeException, handle, throwIO)+import Data.Maybe (isNothing)+import GHC.Conc.Sync (getUncaughtExceptionHandler, setUncaughtExceptionHandler)+import System.Exit (ExitCode)++-- | Customise default uncaught exception handling to use+-- 'displayException' instead of 'show'. This function is supposed to+-- be applied to the body of @main@. Note that it only affects exceptions+-- in the current thread, other threads are not affected.+-- It is adviced to use the @async@ package that propagates exceptions+-- from the child thread to the parent thread.+--+-- It works by catching all exceptions and wrapping them into+-- a wrapper data type whose 'show' method uses 'displayException'.+-- The wrapped exception is re-thrown and the default exception+-- handler will handle it. 'displayException' will be used for printing+-- because that's how 'show' of the wrapper data type is implemented.+-- Some exceptions are not wrapped:+--+-- 1. 'ExitCode' exception because it's treated specially and affects+-- exit code of the application. If we catch 'ExitSuccess', wrap it into+-- another data type and re-throw, the program will end with non-zero code+-- which is not desirable.+-- 2. Asynchronous exceptions. There are not many of them and applying+-- 'displayException' to them usually does not give big benefit.+-- However, some of them may be handled somewhat specially by the runtime+-- system and we don't want to mess up with that.+-- We recognize asynchronous exceptions by casting to 'SomeAsyncException'+-- the same way as the @safe-exceptions@ library.+displayUncaughtException :: IO a -> IO a+displayUncaughtException = handle (throwIO . wrapException)++-- | Customise default uncaught exception handling to use+-- 'displayException' instead of 'show'. This function is supposed to+-- be applied to the body of @main@.+--+-- It works similarly to 'displayUncaughtException', but instead of+-- catching and throwing exceptions it modifies the uncaught exception+-- handler to wrap the exception before processing it.+-- As a consequence, it affects __all__ threads.+-- When the action finishes, the uncaught exception handler+-- is restored (normally it should not matter because the function is+-- supposed to be applied to the whole @main@).+--+-- Note that it may cause race condition if the passed action spawns another+-- thread that throws an uncaught exception when the passed action stops.+-- There is a global variable that stores the uncaught exception handler.+-- Hence it's recommended to use functions from the @async@ package to spawn+-- threads, so that they are stopped before their parent.+--+-- The handler won't be restored in case of exception thrown by the passed action+-- because otherwise it wouldn't work.+-- Specifically, if we restored the handler in case of+-- exception (e. g. using @bracket@), it would be restored before the+-- uncaught exception handler would be called (because the uncaught+-- exception handler is called after everything).+withDisplayExceptionHandler :: IO a -> IO a+withDisplayExceptionHandler action = do+ handler <- getUncaughtExceptionHandler+ setUncaughtExceptionHandler (handler . wrapException)+ action <* setUncaughtExceptionHandler handler++-- | A version of 'withDisplayExceptionHandler' that updates the handler forever.+-- The only difference is that it doesn't restore the default handler.+-- This function should give more predictable behavior in case there are+-- multiple threads.+setDisplayExceptionHandler :: IO ()+setDisplayExceptionHandler = do+ handler <- getUncaughtExceptionHandler+ setUncaughtExceptionHandler (handler . wrapException)++----------------------------------------------------------------------------+-- Helpers+----------------------------------------------------------------------------++-- | Helper data type used by 'displayUncaughtException'.+-- It causes @show@ to call @displayException@.+-- When an exception of this type is caught, it will be @show@n and+-- that will call @displayException@ of the wrapped exception.+newtype DisplayExceptionInShow = DisplayExceptionInShow SomeException++instance Show DisplayExceptionInShow where+ show (DisplayExceptionInShow se) = displayException se++instance Exception DisplayExceptionInShow++wrapException :: SomeException -> SomeException+wrapException e+ | isSyncException e+ , Nothing <- fromException @Deadlock e+ , Nothing <- fromException @ExitCode e =+ toException $ DisplayExceptionInShow e+ | otherwise = e+ where+ isSyncException :: SomeException -> Bool+ isSyncException = isNothing . fromException @SomeAsyncException
+ uncaught-exception.cabal view
@@ -0,0 +1,60 @@+cabal-version: 2.2++-- SPDX-FileCopyrightText: 2020 Serokell <https://serokell.io>+--+-- SPDX-License-Identifier: MPL-2.0++name: uncaught-exception+version: 0.1.0+synopsis: Customize uncaught exception handling.+description: See README.md for details.+homepage: https://github.com/serokell/uncaught-exception+bug-reports: https://github.com/serokell/uncaught-exception/issues+license: MPL-2.0+license-file: LICENSE+author: Serokell+maintainer: Serokell <hi@serokell.io>+copyright: 2020 Serokell <https://serokell.io>+build-type: Simple+extra-doc-files: CHANGELOG.md+ , README.md+tested-with: GHC == 8.6.5+ , GHC == 8.8.3+ , GHC == 8.10.1++source-repository head+ type: git+ location: git@github.com:serokell/uncaught-exception.git++common common-options+ build-depends: base >= 4.9 && < 5+ ghc-options:+ -- Source: https://medium.com/mercury-bank/enable-all-the-warnings-a0517bc081c3+ -Weverything+ -Wno-missing-exported-signatures+ -Wno-missing-import-lists+ -Wno-missed-specialisations+ -Wno-all-missed-specialisations+ -Wno-unsafe+ -Wno-safe+ -Wno-missing-local-signatures+ -Wno-monomorphism-restriction+ -Wno-implicit-prelude+ if impl(ghc >= 8.10.1)+ ghc-options: -Wno-prepositive-qualified-module+ -Wno-missing-safe-haskell-mode++ default-language: Haskell2010+++library+ import: common-options+ hs-source-dirs: src+ exposed-modules: Control.Exception.Uncaught+ default-extensions: TypeApplications++executable uncaught-exception-demo+ import: common-options+ main-is: Main.hs+ hs-source-dirs: demo+ build-depends: uncaught-exception