contra-tracers (empty) → 1.0.0
raw patch · 6 files changed
+765/−0 lines, 6 filesdep +aesondep +basedep +contra-tracer
Dependencies added: aeson, base, contra-tracer
Files
- CHANGELOG.md +18/−0
- LICENSE +373/−0
- README.md +61/−0
- contra-tracers.cabal +79/−0
- src/Data/Generics/Tracers.hs +185/−0
- src/Data/Severity.hs +49/−0
+ CHANGELOG.md view
@@ -0,0 +1,18 @@+# Changelog++## [1.0.0] -- 2021-19-12++### Added++- Initial release. Key features:+ - Contravariant tracers, easily composable with parent context+ - Concurrent-safe, simple, structured (JSON), stdout writer+ - Generic definition of record of tracers for multi-component logging++### Changed ++N/A++### Removed++N/A
+ LICENSE view
@@ -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.
+ README.md view
@@ -0,0 +1,61 @@+# contra-tracers++## Overview ++An opinionated, simple and easy-to-use logging library leveraging contravariant functors to provide structured multi-component logger capability to real application. ++## Usage++```hs+-- Some HTTP log message represented as Haskell values.++data HttpLog+ = SomeHttpLog+ | SomeHttpWarning+ deriving stock (Generic)+ deriving anyclass (ToJSON)++nstance HasSeverityAnnotation HttpLog+ getSeverityAnnotation = \case+ SomeHttpLog -> Info+ SomeHttpWarning -> Warning++-- Some DB log message represented as Haskell values.++data DbLog = SomeDbLog+ deriving stock (Generic)+ deriving anyclass (ToJSON)++nstance HasSeverityAnnotation HttpLog+ getSeverityAnnotation = \case+ SomeHttpLog -> Info+ SomeHttpWarning -> Warning++-- Applications tracers, defined as a record of higher-kinded types. We+-- have in particular 'TracerHKD Concrete a ~ a', which effectively makes+-- the 'Tracers' record a plain record of tracers once instantiated.++data Tracers m (kind :: TracerDefinition) = Tracers+ { tracerHttp :: TracerHKD kind (Tracer m HttpLog)+ , tracerDb :: TracerHKD kind (Tracer m DbLog)+ } deriving stock (Generic)++-- The default configuration, setting all tracers to 'Info' min severity.+-- In practice, you may want to obtain the configuration from a config+-- file or from command-line options.+emptyConfiguration :: Tracers m MinSeverities+emptyConfiguration = defaultTracers Info++main :: IO ()+main = do+ withStdoutTracer mempty emptyConfiguration $ \tracers -> do+ concurrently_+ (myHttpApplication (tracerHttp tracers))+ (myDbApplication (tracerDb tracers))+```++<p align="center">+ <a href="../../../CONTRIBUTING.md">:gift: Contributing</a>+ |+ <a href="CHANGELOG.md">:floppy_disk: Changelog</a>+</p>
+ contra-tracers.cabal view
@@ -0,0 +1,79 @@+cabal-version: 1.12++-- This file has been generated from package.yaml by hpack version 0.34.4.+--+-- see: https://github.com/sol/hpack++name: contra-tracers+version: 1.0.0+synopsis: A logging library built on top of contra-tracer to make configuring and declaring multiple tracers easy (via generics).+description: Please see the README on GitHub at <https://github.com/cardanosolutions/ogmios/tree/master/server/modules/contra-tracers>+category: Logging, Contravariant, Generics+homepage: https://github.com/cardanosolutions/ogmios#readme+bug-reports: https://github.com/cardanosolutions/ogmios/issues+author: KtorZ <matthias.benkort@gmail.com>+maintainer: matthias.benkort@gmail.com+copyright: 2021 KtorZ+license: MPL-2.0+license-file: LICENSE+build-type: Simple+extra-source-files:+ LICENSE+ README.md+ CHANGELOG.md++source-repository head+ type: git+ location: https://github.com/cardanosolutions/ogmios++library+ exposed-modules:+ Data.Generics.Tracers+ Data.Severity+ other-modules:+ Paths_contra_tracers+ hs-source-dirs:+ src+ default-extensions:+ BangPatterns+ BinaryLiterals+ ConstraintKinds+ DataKinds+ DefaultSignatures+ DeriveDataTypeable+ DeriveFoldable+ DeriveFunctor+ DeriveGeneric+ DeriveTraversable+ EmptyDataDecls+ ExistentialQuantification+ FlexibleContexts+ FlexibleInstances+ FunctionalDependencies+ GADTs+ InstanceSigs+ KindSignatures+ LambdaCase+ MultiParamTypeClasses+ MultiWayIf+ NamedFieldPuns+ NoImplicitPrelude+ NumericUnderscores+ OverloadedStrings+ PartialTypeSignatures+ PatternGuards+ RankNTypes+ ScopedTypeVariables+ StandaloneDeriving+ TupleSections+ TypeFamilies+ TypeSynonymInstances+ ViewPatterns+ ghc-options: -Wall -Wcompat -Widentities -Wincomplete-record-updates -Wincomplete-uni-patterns -Wpartial-fields -Wredundant-constraints -Wunused-packages+ build-depends:+ aeson+ , base >=4.7 && <5+ , contra-tracer+ if true+ ghc-options: -O2+ default-language: Haskell2010
+ src/Data/Generics/Tracers.hs view
@@ -0,0 +1,185 @@+-- 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/.++{-# LANGUAGE TypeOperators #-}++{-# OPTIONS_GHC -fno-warn-unticked-promoted-constructors #-}+{-# OPTIONS_HADDOCK prune #-}++-- | This module provides a way to generically define and configure multiple+-- tracers for multiple logging components.+--+-- This is useful in order to associate separate configuration (e.g. minimum+-- severity) to tracers corresponding to different parts of an application. For+-- example, in a webserver, one may imagine wanting to lower the verbosity of a+-- tracer used for all HTTP requests, but keep the database tracer at a debug+-- level.+--+-- While this is possible to do without generics, it usually requires a bit of+-- boilerplate and repetitions. This module makes it easy to define one-single+-- data object as a record, for representing both severities configurations and+-- concrete instantiated tracers. Type signatures are a bit frightening, but the+-- usage is pretty simple (see 'Control.Tracer' for examples)+--+module Data.Generics.Tracers+ ( -- * Definition+ IsRecordOfTracers+ , TracerDefinition (..)+ , type TracerHKD++ -- * Construction+ , configureTracers+ , defaultTracers++ -- Internal+ , SomeMsg (..)+ ) where++import Prelude++import GHC.Generics++import Control.Tracer+ ( Tracer (..), nullTracer )+import Data.Aeson+ ( ToJSON (..) )+import Data.Functor.Const+ ( Const (..) )+import Data.Functor.Contravariant+ ( contramap )+import Data.Kind+ ( Type )+import Data.Severity+ ( HasSeverityAnnotation (..), Severity )++-- * Definition++-- | A constraint-alias defining generic record of tracers.+type IsRecordOfTracers tracers m =+ ( GConfigureTracers m (Rep (tracers m MinSeverities)) (Rep (tracers m Concrete))+ , Generic (tracers m MinSeverities)+ , Generic (tracers m Concrete)+ )++-- | A data kind to control what's defined in a generic record of tracer.+--+-- Use 'configureTracers' to turn a record of configuration into a record of+-- concrete tracers.+data TracerDefinition = Concrete | MinSeverities++-- | A high-kinded type family to make definitions of tracers more readable. For+-- example, one can define a multi-component set of tracers as such:+--+-- data Tracers m (kind :: TracerDefinition) = Tracers+-- { tracerHttp :: TracerHKD kind (Tracer m HttpLog)+-- , tracerStart :: TracerHKD kind (Tracer m StartLog)+-- }+type family TracerHKD (definition :: TracerDefinition) (tracer :: Type) :: Type where+ TracerHKD MinSeverities tracer = Const (Maybe Severity) tracer+ TracerHKD Concrete tracer = tracer++-- * Construction++-- | Convert a 'MinSeverities' of tracers into a 'Concrete' record of tracers,+-- using a base opaque 'Tracer'.+configureTracers+ :: ( IsRecordOfTracers tracers m )+ => tracers m MinSeverities+ -> Tracer m SomeMsg+ -> tracers m Concrete+configureTracers f tr =+ to . gConfigureTracers mempty tr . from $ f++class GConfigureTracers m (f :: Type -> Type) (g :: Type -> Type) where+ gConfigureTracers+ :: String+ -> Tracer m SomeMsg+ -> f (Const (Maybe Severity) tr)+ -> g tr++instance GConfigureTracers m f g => GConfigureTracers m (D1 c f) (D1 c g) where+ gConfigureTracers field tr = M1 . gConfigureTracers field tr . unM1++instance GConfigureTracers m f g => GConfigureTracers m (C1 c f) (C1 c g) where+ gConfigureTracers field tr = M1 . gConfigureTracers field tr . unM1++instance (Selector s, GConfigureTracers m f g) => GConfigureTracers m (S1 s f) (S1 s g) where+ gConfigureTracers _ tr = M1 . gConfigureTracers field tr . unM1+ where+ field = selName (undefined :: S1 s f a)++instance (GConfigureTracers m f0 g0, GConfigureTracers m f1 g1)+ => GConfigureTracers m (f0 :*: f1) (g0 :*: g1)+ where+ gConfigureTracers field tr (f0 :*: f1) =+ gConfigureTracers field tr f0+ :*:+ gConfigureTracers field tr f1++instance (ToJSON msg, HasSeverityAnnotation msg, Applicative m)+ => GConfigureTracers m (K1 i (Const (Maybe Severity) (Tracer m msg))) (K1 i (Tracer m msg))+ where+ gConfigureTracers field tr = \case+ K1 (Const (Just minSeverity)) ->+ K1 (contramap (SomeMsg minSeverity field) tr)+ K1 (Const Nothing) ->+ K1 nullTracer++-- | Assign a default value to a record of tracers.+--+-- This is useful when used in conjunction with 'Const' and a record of tracer+-- severities:+--+-- defaultTracers Info == Tracers+-- { tracerHttp = Const (Just Info)+-- , tracerDb = Const (Just Info)+-- }+--+defaultTracers+ :: forall tracers (m :: Type -> Type).+ ( Generic (tracers m MinSeverities)+ , GDefaultRecord (Rep (tracers m MinSeverities))+ , GDefaultRecordType (Rep (tracers m MinSeverities)) ~ Maybe Severity+ )+ => Maybe Severity+ -> tracers m MinSeverities+defaultTracers =+ to . gDefaultRecord++-- | This generic class allows for defining a default value to a record of+-- functors wrapping some type 'a'.+class GDefaultRecord (f :: Type -> Type) where+ type GDefaultRecordType f :: Type+ gDefaultRecord :: GDefaultRecordType f -> f (Const (GDefaultRecordType f) b)++instance GDefaultRecord f => GDefaultRecord (D1 c f) where+ type GDefaultRecordType (D1 c f) = GDefaultRecordType f+ gDefaultRecord a = M1 (gDefaultRecord a)++instance GDefaultRecord f => GDefaultRecord (C1 c f) where+ type GDefaultRecordType (C1 c f) = GDefaultRecordType f+ gDefaultRecord a = M1 (gDefaultRecord a)++instance GDefaultRecord f => GDefaultRecord (S1 c f) where+ type GDefaultRecordType (S1 c f) = GDefaultRecordType f+ gDefaultRecord a = M1 (gDefaultRecord a)++instance (GDefaultRecord f, GDefaultRecord g, GDefaultRecordType f ~ GDefaultRecordType g) => GDefaultRecord (f :*: g) where+ type GDefaultRecordType (f :*: g) = GDefaultRecordType f+ gDefaultRecord a = gDefaultRecord a :*: gDefaultRecord a++instance GDefaultRecord (K1 i (Const a b)) where+ type GDefaultRecordType (K1 i (Const a b)) = a+ gDefaultRecord a = K1 (Const a)++-- Internal++-- A GADT capturing constraints as existential.+data SomeMsg where+ SomeMsg+ :: forall msg. (ToJSON msg, HasSeverityAnnotation msg)+ => Severity+ -> String+ -> msg+ -> SomeMsg
+ src/Data/Severity.hs view
@@ -0,0 +1,49 @@+-- 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/.++{-# LANGUAGE DeriveAnyClass #-}+{-# LANGUAGE DerivingStrategies #-}++module Data.Severity+ ( Severity (..)+ , HasSeverityAnnotation (..)+ ) where++import Prelude++import Data.Aeson+ ( FromJSON, ToJSON )+import GHC.Generics+ ( Generic )++-- | Define a log-level severity.+--+-- +----------+----------------------------------------------------------------------------------++-- | Severity | Semantic |+-- +==========+==================================================================================++-- | Debug | Messages that contain information normally of use only when debugging a program. |+-- | Info | Informational messages. |+-- | Notice | Normal but significant conditions. |+-- | Warning | A situation that may become an error. |+-- | Error | Unexpected problem. |+-- +----------+----------------------------------------------------------------------------------++--+data Severity+ = Debug+ | Info+ | Notice+ | Warning+ | Error+ deriving stock (Generic, Eq, Ord, Enum, Bounded, Show, Read)+ deriving anyclass (ToJSON, FromJSON)++-- | Associate a 'Severity' to a typed log message.+--+-- data MyLog = MyLog+-- instance HasSeverityAnnotation MyLog where+-- getSeverityAnnotation = \case+-- MyLog -> Info+--+class HasSeverityAnnotation a where+ getSeverityAnnotation :: a -> Severity