polytropos-reader-soup (empty) → 0.1.0.2

raw patch · 7 files changed

+1238/−0 lines, 7 filesdep +basedep +exceptionsdep +monad-control

Dependencies added: base, exceptions, monad-control, mtl, polytropos-core, polytropos-plugin, polytropos-reader-soup, primitive, resourcet, safe-exceptions, tasty, tasty-hunit, transformers, transformers-base, unliftio, unliftio-core

Files

• CHANGELOG.md +22/−0
• LICENSE +391/−0
• README.md +78/−0
• polytropos-reader-soup.cabal +82/−0
• src/Polytropos/ReaderSoup.hs +446/−0
• src/Polytropos/ReaderSoup/Resource.hs +59/−0
• test/Main.hs +160/−0

@@ -0,0 +1,22 @@+# Revision history for polytropos-reader-soup++## 0.1.0.2 -- 2026-10-21++* Added comprehensive worked examples and when-to-use guidance to front-door Haddock documentation.+* Coordinated version bump across all Polytropos packages.++## 0.1.0.1 -- 2026-10-20++* Coordinated release with `polytropos-core-0.1.0.1`.++## 0.1.0.0 -- 2026-10-19++* First release.+* Re-architected from Yves Parès's `reader-soup` (from the Porcupine pipeline framework) onto Polytropos's native contiguous flat array representation (`Polytropos.Core.Rep`) and compile-time dictionary synthesis (`Polytropos.Plugin`).+* Core `ReaderSoup` type: a flat, single-layer environment for hosting multiple Reader-like contexts without exponential mtl class boilerplate.+* Direct context access: `askSoup` with $O(1)$ indexing.+* Row slicing: `filtering` with $O(K)$ flat array copy via `SubRow` evidence synthesis.+* MonadReader projection: `Spoon` exposing single contexts as standard `MonadReader` instances with local modification support.+* Context bridging: `SoupContext` with `picking`, `scooping`, and `pouring` for seamless integration with ReaderT-like monads.+* Modular runner composition: `ContextRunner`, `pickTopping`, `eatTopping`, `finishBroth`, and `consumeSoup`.+* Resource management: `Polytropos.ReaderSoup.Resource` providing `SoupContext InternalState ResourceT` and `MonadResource (ReaderSoup ctxs)` support.

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@@ -0,0 +1,78 @@+# polytropos-reader-soup++Composable multi-context Reader monad with zero-overhead row polymorphism for [polytropos](https://github.com/NadiaYvette/polytropos).++## Overview++In traditional Haskell application design, managing multiple configuration environments, connection pools, and runtime capabilities typically forces one of two unsatisfactory choices:+1. **MTL Class Proliferation:** Defining distinct `MonadDatabase`, `MonadConfig`, `MonadLogger`, `MonadMetrics` classes with $O(N^2)$ quadratic boilerplate instances across every layer of the transformer stack.+2. **Monolithic AppEnv:** Bundling everything into a single nominal `AppEnv` record, coupling small, self-contained sub-routines to the entire global environment and hindering modularity.++`polytropos-reader-soup` solves this dilemma by re-architecting Yves Parès's `reader-soup` on top of Polytropos's high-performance flat contiguous array representation (`Polytropos.Core.Rep`). A `ReaderSoup` hosts an arbitrary open row of labeled contexts in a single `ReaderT (Record ctxs) IO` layer. Subsystems declare exactly the slice of contexts they require, accessing them in $O(1)$ time via compile-time synthesized dictionary offsets, with structural narrowing via `filtering` taking $O(K)$ flat array copy time.++## Features++- **`ReaderSoup`**: Single-layer multi-context Reader environment (`ReaderT (Record ctxs) IO a`).+- **`askSoup`**: $O(1)$ context retrieval using type-level label symbols or `OverloadedRecordDot`.+- **`filtering`**: Zero-boilerplate structural subtyping via `SubRow`, allowing sub-actions to run seamlessly inside larger environments.+- **`Spoon`**: Isolates a single labeled context from the broth and equips it with a standard `MonadReader` instance supporting `ask` and `local`.+- **`SoupContext`**: Bridges existing third-party ReaderT-like monads (e.g. `ResourceT`, `KatipContextT`) via `picking`, `scooping`, and `pouring`.+- **`consumeSoup`**: Composes modular `ContextRunner` handlers to peel and execute contexts sequentially until the base broth is reached.+- **`Polytropos.ReaderSoup.Resource`**: Turnkey `resourcet` integration with `SoupContext InternalState ResourceT` and `MonadResource` instances.++## Quick Example++```haskell+{-# LANGUAGE DataKinds #-}+{-# LANGUAGE OverloadedRecordDot #-}+{-# LANGUAGE OverloadedStrings #-}+{-# OPTIONS_GHC -fplugin=Polytropos.Plugin #-}++module Main where++import Control.Monad.IO.Class (liftIO)+import Polytropos+import Polytropos.ReaderSoup++data DBConn = DBConn String+data Logger = Logger (String -> IO ())++type AppCtx =+  '[ "db"     := DBConn+   , "logger" := Logger+   , "port"   := Int+   ]++-- | A database worker only requires the DBConn context:+runQuery :: ReaderSoup '[ "db" := DBConn ] String+runQuery = do+  DBConn connStr <- askSoup (Field @"db")+  pure ("Executed on " ++ connStr)++-- | Main application running with the full AppCtx:+app :: ReaderSoup AppCtx ()+app = do+  Logger logFn <- askSoup (Field @"logger")+  liftIO (logFn "Application starting...")++  -- Narrow the environment from AppCtx down to '[ "db" := DBConn ]:+  res <- filtering runQuery+  liftIO (logFn ("Query result: " ++ res))++main :: IO ()+main = do+  let env = insertField (Field @"db") (DBConn "postgres://localhost:5432/prod")+          $ insertField (Field @"logger") (Logger putStrLn)+          $ insertField (Field @"port") (8080 :: Int)+          $ emptyRecord++  runReaderSoup app env+```++## Attribution & Precedents++This package is inspired by and directly acknowledges Yves Parès's work on `reader-soup` within the [Porcupine](https://github.com/funflow/porcupine) pipeline framework. The original package pioneered the concept of representing open collections of Reader-like monads via Vinyl extensible records. `polytropos-reader-soup` preserves those ergonomic and architectural insights while re-grounding them entirely on Polytropos's native flat array physics, compile-time literal index resolution, and structural `SubRow` evidence synthesis.++## License++Dual-licensed under `EUPL-1.2 OR Apache-2.0`.

@@ -0,0 +1,82 @@+cabal-version: 3.0+name: polytropos-reader-soup+version: 0.1.0.2+synopsis: Composable multi-context Reader monad with zero-overhead row polymorphism+description:+  A composable, extensible multi-context Reader environment for <https://hackage.haskell.org/package/polytropos polytropos>.+  Instead of defining exponentially growing @MonadFoo@ / @MonadBar@ type class stacks or deeply nested+  @ReaderT@ hierarchies, 'Polytropos.ReaderSoup.ReaderSoup' collects all application contexts in a single+  flat contiguous row ('Polytropos.Record').+  .+  Inspired by and acknowledging Yves Parès's pioneering @reader-soup@ package from the+  <https://github.com/funflow/porcupine porcupine> ecosystem, re-architected from scratch+  on top of Polytropos's high-performance flat array representation ('Polytropos.Core.Rep')+  and compile-time dictionary synthesis ('Polytropos.Plugin').+  .+  Key Features:+  .+  * Flat multi-context environment ('Polytropos.ReaderSoup.ReaderSoup') backed by Polytropos's $O(1)$ flat array representation.+  * Direct context access ('Polytropos.ReaderSoup.askSoup') via type-level labels or @OverloadedRecordDot@.+  * Structural sub-soup slicing ('Polytropos.ReaderSoup.filtering') via compile-time 'Polytropos.SubRow' projection.+  * Single-context projection ('Polytropos.ReaderSoup.Spoon') giving standard @MonadReader@ instances for isolated subsystems.+  * Context bridging ('Polytropos.ReaderSoup.SoupContext') with 'Polytropos.ReaderSoup.picking', 'Polytropos.ReaderSoup.scooping', and 'Polytropos.ReaderSoup.pouring'.+  * Modular runner composition ('Polytropos.ReaderSoup.ContextRunner', 'Polytropos.ReaderSoup.consumeSoup').+  * Resource management integration ('Polytropos.ReaderSoup.Resource') supporting @resourcet@'s 'Control.Monad.Trans.Resource.ResourceT'.+  .+  Start at the front door module "Polytropos.ReaderSoup" for comprehensive documentation and worked examples.+license: EUPL-1.2 OR Apache-2.0+license-file: LICENSE+author: Nadia Yvette Chambers+maintainer: nadia.yvette.chambers@ik.me+category: Control, Monads, Records+homepage: https://github.com/NadiaYvette/polytropos+bug-reports: https://github.com/NadiaYvette/polytropos/issues+extra-doc-files:+    README.md+  , CHANGELOG.md+build-type: Simple++source-repository head+  type:     git+  location: https://github.com/NadiaYvette/polytropos+  subdir:   packages/polytropos-reader-soup++library+  default-language: GHC2021+  hs-source-dirs: src+  exposed-modules:+    Polytropos.ReaderSoup+    Polytropos.ReaderSoup.Resource+  ghc-options: -Wall+  build-depends:+    base >= 4.14 && < 5,+    exceptions >= 0.10 && < 0.11,+    monad-control >= 1.0 && < 1.1,+    mtl >= 2.2 && < 2.4,+    polytropos-core >= 0.1 && < 0.2,+    polytropos-plugin >= 0.1 && < 0.2,+    primitive >= 0.8 && < 1.0,+    resourcet >= 1.2 && < 1.4,+    safe-exceptions >= 0.1 && < 0.2,+    transformers >= 0.5 && < 0.7,+    transformers-base >= 0.4 && < 0.5,+    unliftio >= 0.2 && < 0.3,+    unliftio-core >= 0.2 && < 0.3++test-suite polytropos-reader-soup-test+  type: exitcode-stdio-1.0+  default-language: GHC2021+  hs-source-dirs: test+  main-is: Main.hs+  ghc-options: -Wall -fplugin=Polytropos.Plugin+  build-depends:+    base,+    mtl,+    polytropos-core,+    polytropos-plugin,+    polytropos-reader-soup,+    resourcet,+    tasty,+    tasty-hunit,+    transformers,+    unliftio-core

@@ -0,0 +1,446 @@+{-# LANGUAGE AllowAmbiguousTypes #-}+{-# LANGUAGE BangPatterns #-}+{-# LANGUAGE ConstraintKinds #-}+{-# LANGUAGE DataKinds #-}+{-# LANGUAGE DeriveFunctor #-}+{-# LANGUAGE FlexibleContexts #-}+{-# LANGUAGE FlexibleInstances #-}+{-# LANGUAGE FunctionalDependencies #-}+{-# LANGUAGE GeneralizedNewtypeDeriving #-}+{-# LANGUAGE KindSignatures #-}+{-# LANGUAGE MultiParamTypeClasses #-}+{-# LANGUAGE OverloadedLabels #-}+{-# LANGUAGE RankNTypes #-}+{-# LANGUAGE ScopedTypeVariables #-}+{-# LANGUAGE TypeApplications #-}+{-# LANGUAGE TypeFamilies #-}+{-# LANGUAGE TypeOperators #-}+{-# LANGUAGE UndecidableInstances #-}++-- |+-- Module      : Polytropos.ReaderSoup+-- Description : Composable multi-context Reader monad with zero-overhead row polymorphism+-- Copyright   : (c) 2026, Nadia Yvette Chambers+-- License     : EUPL-1.2 OR Apache-2.0+-- Maintainer  : nadia.yvette.chambers@ik.me+-- Stability   : experimental+--+-- A composable, extensible multi-context Reader environment for+-- <https://hackage.haskell.org/package/polytropos polytropos>.+--+-- In traditional application architectures, applications requiring multiple capabilities+-- (e.g. database connections, metrics collectors, logging handles, configuration schemas)+-- are often forced to choose between two unappealing designs:+--+-- 1. __The MTL class explosion__: Defining a dedicated type class (@MonadDB@, @MonadLogger@,+--    @MonadMetrics@) for every capability and writing $O(N^2)$ quadratic passthrough instances+--    for every layer of the transformer stack.+-- 2. __The monolithic AppEnv__: Defining a single massive record containing all subsystem+--    handles, tightly coupling isolated subroutines to the entire application's footprint.+--+-- 'ReaderSoup' solves this dilemma by adapting Yves Parès's pioneering @reader-soup@+-- package from the <https://github.com/funflow/porcupine porcupine> pipeline ecosystem+-- to Polytropos's high-performance contiguous flat array representation ('Polytropos.Core.Rep')+-- and compile-time dictionary synthesis ('Polytropos.Plugin').+--+-- Key Properties:+--+-- * __Flat Storage__: All contexts live in a single contiguous @SmallArray@ inside 'Record'.+--   Field retrieval via 'askSoup' resolves at compile time to a direct slot offset ($O(1)$).+-- * __Sub-soup Projection__: Sub-actions declare only the contexts they need. Structural+--   narrowing via 'filtering' copies the required slice in $O(K)$ time via 'SubRow' evidence.+-- * __Context Isolation__: 'Spoon' extracts any labeled context into a standard 'MonadReader'+--   instance supporting 'ask' and 'local'.+-- * __Third-Party Monad Bridging__: 'SoupContext' connects external monads (such as+--   'Control.Monad.Trans.Resource.ResourceT') using 'picking', 'scooping', and 'pouring'.+-- * __Modular Consumption__: 'ContextRunner' and 'consumeSoup' allow contexts to be peeled+--   and evaluated in dependency order until the base broth is reached.+--+-- = When to Use This Module+--+-- * When developing modular services requiring access to multiple independent+--   subsystems (databases, loggers, metrics, config handles) without monolithic+--   environment records.+-- * When avoiding quadratic $O(N^2)$ instance boilerplate of classic MTL typeclass+--   hierarchies across multiple transformer layers.+-- * When composing sub-routines that require only a localized subset of capabilities,+--   narrowing environments via zero-cost structural sub-row projections ('filtering').+--+-- = Worked Example+--+-- Managing multi-capability application environments and narrowing to sub-actions:+--+-- > {-# LANGUAGE DataKinds #-}+-- > {-# LANGUAGE OverloadedStrings #-}+-- > {-# OPTIONS_GHC -fplugin=Polytropos.Plugin #-}+-- >+-- > import Control.Monad.Reader.Class (ask, local)+-- > import Polytropos+-- > import Polytropos.ReaderSoup+-- >+-- > data DBConn = DBConn String deriving (Eq, Show)+-- >+-- > type AppCtx =+-- >   '[ "db"       ':= DBConn+-- >    , "port"     ':= Int+-- >    , "greeting" ':= String+-- >    ]+-- >+-- > mkAppEnv :: DBConn -> Int -> String -> Record AppCtx+-- > mkAppEnv db p g =+-- >   insertField (Field @"db") db+-- >     $ insertField (Field @"port") p+-- >     $ insertField (Field @"greeting") g+-- >     $ emptyRecord+-- >+-- > -- A sub-worker declaring only the capabilities it actually needs:+-- > subWorker :: ReaderSoup '[ "db" ':= DBConn, "greeting" ':= String ] String+-- > subWorker = do+-- >   db <- askSoup (Field @"db")+-- >   g  <- askSoup (Field @"greeting")+-- >   pure (g ++ " connected to " ++ show db)+-- >+-- > main :: IO ()+-- > main = do+-- >   let env = mkAppEnv (DBConn "pg://cluster") 8080 "Welcome"+-- >   -- Run localized subWorker against full AppCtx via structural sub-row filtering:+-- >   msg <- runReaderSoup (filtering subWorker) env+-- >   putStrLn msg+-- >+-- >   -- Project a single context into standard MonadReader with ask and local:+-- >   port <- runReaderSoup (dipping (Field @"port") (local (+ 100) ask)) env+-- >   print port  -- 8180+module Polytropos.ReaderSoup+  ( -- * Core ReaderSoup Monad+    ReaderSoupT(..)+  , ReaderSoup+  , CookedReaderSoup+  , runReaderSoup+  , runReaderSoupT++    -- * Context Access & Narrowing+  , Label+  , askSoup+  , filtering++    -- * Single Context Projection (Spoon)+  , Spoon(..)+  , LookupContext+  , dipping+  , rioToSpoon+  , spoonToReaderT++    -- * Third-Party Monad Bridging (SoupContext)+  , ContextFromName+  , SoupContext(..)+  , CanBeScoopedIn+  , withSpoon+  , picking+  , scooping+  , pouring++    -- * Modular Context Peeling & Runner Composition+  , ContextRunner(..)+  , splitRecordHead+  , consRecord+  , pickTopping+  , eatTopping+  , finishBroth+  , ArgsForSoupConsumption(..)+  ) where++import Control.Applicative (Alternative(..))+import Control.Monad (MonadPlus(..))+import Control.Monad.Base (MonadBase(..))+import Control.Monad.Catch (MonadCatch, MonadMask, MonadThrow)+import Control.Monad.IO.Class (MonadIO(..))+import Control.Monad.IO.Unlift (MonadUnliftIO(..))+import Control.Monad.Reader.Class (MonadReader(..))+import Control.Monad.Trans.Class (MonadTrans(..))+import Control.Monad.Trans.Control (MonadBaseControl(..))+import Control.Monad.Trans.Reader (ReaderT(..), asks)+import Data.Functor.Identity (Identity(..))+import Data.Kind (Type)+import Data.Primitive.SmallArray (indexSmallArray)+import GHC.Exts (toList)+import GHC.TypeLits (KnownSymbol, Symbol)+import Polytropos.Core+  ( Pair(..), RowRep(..), Rep(..), productRep+  , FieldIndex(..), SubRow, Field(..)+  )+import Polytropos (Record, emptyRecord, setField, projectRecord)+import Unsafe.Coerce (unsafeCoerce)++-- | Fetch a field value from a 'Record' using its compile-time synthesized index.+getField :: forall n a r. FieldIndex n r a => Field n -> Record r -> a+getField _ (RowRep (Rep _ v)) =+  case indexSmallArray v (fieldIndex @_ @n @r @a) of+    Identity val -> unsafeCoerce val++--------------------------------------------------------------------------------+-- 1. Core ReaderSoup Monad+--------------------------------------------------------------------------------++-- | 'ReaderSoupT' holds a row-polymorphic collection of Reader contexts within+-- a single 'ReaderT' layer over a base monad @m@.+--+-- Unlike deeply nested transformer stacks, all contexts reside in a single flat+-- contiguous 'Record', eliminating pointer chasing and wrapper allocations.+newtype ReaderSoupT (ctxs :: [Pair Symbol Type]) m a = ReaderSoupT+  { unReaderSoupT :: ReaderT (Record ctxs) m a }+  deriving+    ( Functor+    , Applicative+    , Alternative+    , Monad+    , MonadFail+    , MonadPlus+    , MonadIO+    , MonadUnliftIO+    , MonadThrow+    , MonadCatch+    , MonadMask+    )++-- | The canonical 'ReaderSoup' type operating over 'IO'.+type ReaderSoup ctxs = ReaderSoupT ctxs IO++-- | In Porcupine, 'CookedReaderSoup' denoted a soup ready to have its toppings peeled.+-- In Polytropos, both cooked and raw representations share the same flat 'Record'.+type CookedReaderSoup ctxs = ReaderSoup ctxs++-- | Convenient alias for field labels.+type Label = Field++instance MonadTrans (ReaderSoupT ctxs) where+  lift = ReaderSoupT . lift++instance (MonadBase b m) => MonadBase b (ReaderSoupT ctxs m) where+  liftBase = ReaderSoupT . liftBase++instance (MonadBaseControl b m) => MonadBaseControl b (ReaderSoupT ctxs m) where+  type StM (ReaderSoupT ctxs m) a = StM (ReaderT (Record ctxs) m) a+  liftBaseWith f = ReaderSoupT $ liftBaseWith $ \runInBase ->+    f (runInBase . unReaderSoupT)+  restoreM = ReaderSoupT . restoreM++-- | Access the full underlying 'Record' environment.+instance (Monad m) => MonadReader (Record ctxs) (ReaderSoupT ctxs m) where+  ask = ReaderSoupT ask+  local f (ReaderSoupT act) = ReaderSoupT (local f act)++-- | Run a 'ReaderSoup' action by supplying the full contiguous context 'Record'.+runReaderSoup :: ReaderSoup ctxs a -> Record ctxs -> IO a+runReaderSoup (ReaderSoupT (ReaderT act)) = act++-- | Run a transformer 'ReaderSoupT' action over any base monad @m@.+runReaderSoupT :: ReaderSoupT ctxs m a -> Record ctxs -> m a+runReaderSoupT (ReaderSoupT (ReaderT act)) = act++--------------------------------------------------------------------------------+-- 2. Context Access & Narrowing+--------------------------------------------------------------------------------++-- | Type-level lookup of the context type associated with label @l@ in row @ctxs@.+type family LookupContext (l :: Symbol) (ctxs :: [Pair Symbol Type]) :: Type where+  LookupContext l ((l ':= c) ': _) = c+  LookupContext l (_ ': rest)      = LookupContext l rest++-- | Retrieve a specific context @c@ labeled @l@ from the soup in $O(1)$ time.+--+-- The compiler plugin synthesizes the literal slot index for @l@ at compile time,+-- ensuring zero dictionary traversal overhead at runtime.+--+-- Example:+--+-- >>> askSoup (Field @"db")+-- >>> askSoup #db+askSoup :: forall l c ctxs. (c ~ LookupContext l ctxs, FieldIndex l ctxs c)+        => Field l -> ReaderSoup ctxs c+askSoup fld = ReaderSoupT (asks (getField fld))++-- | Locally restrict a 'ReaderSoup' computation to a smaller sub-soup @sub@.+--+-- 'filtering' enables clean modularity: a self-contained helper function can specify+-- only the subset of contexts it actually touches. When invoked within an application+-- carrying a larger @super@ row, 'filtering' projects the flat array in $O(K)$ time+-- (where $K = |sub|$) via compile-time synthesized 'SubRow' evidence.+filtering :: forall sub super a. SubRow sub super+          => ReaderSoup sub a -> ReaderSoup super a+filtering (ReaderSoupT (ReaderT act)) =+  ReaderSoupT (ReaderT (act . projectRecord))++--------------------------------------------------------------------------------+-- 3. Single Context Projection (Spoon)+--------------------------------------------------------------------------------++-- | 'Spoon' isolates a single labeled context @l@ from the soup, equipping it with+-- a standard 'MonadReader' instance.+--+-- This bridges the multi-context soup with standard MTL code expecting @MonadReader c@,+-- while retaining the full global environment for downstream calls.+newtype Spoon (ctxs :: [Pair Symbol Type]) (l :: Symbol) a = Spoon+  { unSpoon :: ReaderSoup ctxs a }+  deriving+    ( Functor+    , Applicative+    , Alternative+    , Monad+    , MonadFail+    , MonadPlus+    , MonadIO+    , MonadUnliftIO+    , MonadThrow+    , MonadCatch+    , MonadMask+    )++instance (MonadBase IO (ReaderSoup ctxs)) => MonadBase IO (Spoon ctxs l) where+  liftBase = Spoon . liftBase++instance (MonadBaseControl IO (ReaderSoup ctxs)) => MonadBaseControl IO (Spoon ctxs l) where+  type StM (Spoon ctxs l) a = StM (ReaderSoup ctxs) a+  liftBaseWith f = Spoon $ liftBaseWith $ \runInBase ->+    f (runInBase . unSpoon)+  restoreM = Spoon . restoreM++-- | Expose a standard 'MonadReader' instance for the selected context @l@.+--+-- 'local' modifies only field @l@ in the flat array while leaving all other+-- contexts intact.+instance (c ~ LookupContext l ctxs, FieldIndex l ctxs c) => MonadReader c (Spoon ctxs l) where+  ask = Spoon (askSoup (Field @l))+  local f (Spoon (ReaderSoupT (ReaderT act))) =+    Spoon $ ReaderSoupT $ ReaderT $ \rec ->+      let !old = getField (Field @l) rec+          !new = f old+          !rec' = setField (Field @l) new rec+      in act rec'++-- | Bring forth a single context from the soup to run a 'Spoon' computation.+dipping :: Field l -> Spoon ctxs l a -> ReaderSoup ctxs a+dipping _ = unSpoon++-- | Convert a legacy @ReaderT c IO@ action directly into a 'Spoon'.+rioToSpoon :: forall l c ctxs a. (c ~ ContextFromName l, FieldIndex l ctxs c)+           => ReaderT c IO a -> Spoon ctxs l a+rioToSpoon (ReaderT act) = Spoon $ ReaderSoupT $ ReaderT $ \rec ->+  act (getField (Field @l) rec)++-- | Convert a 'Spoon' action into a 'ReaderT' running inside the outer 'ReaderSoup'.+spoonToReaderT :: forall l c ctxs a. (c ~ ContextFromName l, KnownSymbol l, FieldIndex l ctxs c)+               => Spoon ctxs l a -> ReaderT c (ReaderSoup ctxs) a+spoonToReaderT (Spoon (ReaderSoupT (ReaderT act))) =+  ReaderT $ \v -> ReaderSoupT $ ReaderT $ \rec ->+    act (setField (Field @l) v rec)++--------------------------------------------------------------------------------+-- 4. Third-Party Monad Bridging (SoupContext)+--------------------------------------------------------------------------------++-- | Type family mapping a label symbol to its canonical context type.+--+-- Applications can instantiate this family to establish global naming conventions:+--+-- > type instance ContextFromName "resource" = InternalState+-- > type instance ContextFromName "db"       = ConnectionPool+type family ContextFromName (l :: Symbol) :: Type++-- | Type class identifying monad transformers that can be converted to and from+-- a 'ReaderT' of their context.+class SoupContext c t | c -> t where+  -- | Convert transformer to 'ReaderT'.+  toReaderT   :: Monad m => t m a -> ReaderT c m a+  -- | Reconstruct transformer from 'ReaderT'.+  fromReaderT :: Monad m => ReaderT c m a -> t m a+++-- | Constraint required to scoop a Reader-like monad @t@ from context @l@.+type CanBeScoopedIn t ctxs l =+  ( KnownSymbol l+  , FieldIndex l ctxs (ContextFromName l)+  , SoupContext (ContextFromName l) t+  )++-- | Convert an action in a Reader-like monad @t@ into a 'Spoon'.+withSpoon :: forall l ctxs t a. (CanBeScoopedIn t ctxs l)+          => t (ReaderSoup ctxs) a -> Spoon ctxs l a+withSpoon act = Spoon $ ReaderSoupT $ ReaderT $ \rec ->+  let val = getField (Field @l) rec :: ContextFromName l+  in runReaderSoup (runReaderT (toReaderT @(ContextFromName l) act) val) rec++-- | Run a single-context Reader-like monad (such as @ResourceT IO@) inside 'ReaderSoup'.+picking :: forall l ctxs t a. (CanBeScoopedIn t ctxs l)+        => Field l -> t IO a -> ReaderSoup ctxs a+picking lbl = dipping lbl . rioToSpoon @l . toReaderT @(ContextFromName l)++-- | Run a Reader-like monad over the whole 'ReaderSoup' (preserving access to all contexts).+scooping :: (CanBeScoopedIn t ctxs l)+         => Field l -> t (ReaderSoup ctxs) a -> ReaderSoup ctxs a+scooping lbl act = dipping lbl (withSpoon act)++-- | The dual of 'scooping': lift a 'ReaderSoup' action into the target monad @t@.+pouring :: forall l ctxs t a. (CanBeScoopedIn t ctxs l)+        => Field l -> ReaderSoup ctxs a -> t (ReaderSoup ctxs) a+pouring _ act = fromReaderT $ spoonToReaderT (Spoon act :: Spoon ctxs l a)++--------------------------------------------------------------------------------+-- 5. Modular Context Peeling & Runner Composition+--------------------------------------------------------------------------------++-- | Splits the first field off a contiguous 'Record'.+splitRecordHead :: Record ((n ':= a) ': rest) -> (a, Record rest)+splitRecordHead (RowRep (Rep _ v)) =+  let !h = unsafeCoerce (indexSmallArray v 0)+      !tl = drop 1 (toList v)+  in (h, RowRep (productRep tl))++-- | Conses a field onto the front of a 'Record'.+consRecord :: forall n a rest. Field n -> a -> Record rest -> Record ((n ':= a) ': rest)+consRecord _ val (RowRep (Rep _ v)) =+  RowRep (productRep (unsafeCoerce val : toList v))++-- | Extract a 'ReaderT' of the first context from the soup, leaving the remaining toppings.+pickTopping :: forall l c rest a.+               ReaderSoup ((l ':= c) ': rest) a+            -> ReaderT c (ReaderSoup rest) a+pickTopping (ReaderSoupT (ReaderT actInSoup)) =+  ReaderT $ \ctx1 -> ReaderSoupT $ ReaderT $ \restCtxs ->+    actInSoup (consRecord (Field @l) ctx1 restCtxs)++-- | Consume the head context @c@ from the soup, leaving a smaller soup of remaining contexts.+eatTopping :: forall l c rest a.+              ReaderSoup ((l ':= c) ': rest) a+           -> c+           -> ReaderSoup rest a+eatTopping soup c = runReaderT (pickTopping soup) c++-- | When all contexts have been consumed, finish the broth by executing the empty record in 'IO'.+finishBroth :: ReaderSoup '[] a -> IO a+finishBroth (ReaderSoupT (ReaderT act)) = act emptyRecord++-- | Encapsulates a runner function capable of executing a monad transformer @t@.+newtype ContextRunner t m = ContextRunner+  { runContext :: forall r. t m r -> m r }++-- | Class for peeling contexts iteratively using an extensible record of 'ContextRunner's.+class ArgsForSoupConsumption args where+  -- | Maps runner arguments to the corresponding context row.+  type ContextsFromArgs args :: [Pair Symbol Type]+  -- | Iteratively consume and execute contexts until 'finishBroth' is reached.+  consumeSoup :: Record args -> ReaderSoup (ContextsFromArgs args) a -> IO a++instance ArgsForSoupConsumption '[] where+  type ContextsFromArgs '[] = '[]+  consumeSoup _ = finishBroth++instance ( KnownSymbol l+         , SoupContext (ContextFromName l) t+         , ArgsForSoupConsumption rest+         , m ~ ReaderSoup (ContextsFromArgs rest)+         ) => ArgsForSoupConsumption ((l ':= ContextRunner t m) ': rest) where+  type ContextsFromArgs ((l ':= ContextRunner t m) ': rest) =+    (l ':= ContextFromName l) ': ContextsFromArgs rest+  consumeSoup runnerRec soup =+    let (!runner, !restRunners) = splitRecordHead runnerRec+    in consumeSoup restRunners (runContext runner (fromReaderT (pickTopping soup)))

@@ -0,0 +1,59 @@+{-# LANGUAGE DataKinds #-}+{-# LANGUAGE FlexibleContexts #-}+{-# LANGUAGE FlexibleInstances #-}+{-# LANGUAGE MultiParamTypeClasses #-}+{-# LANGUAGE ScopedTypeVariables #-}+{-# LANGUAGE TypeApplications #-}+{-# LANGUAGE TypeFamilies #-}+{-# LANGUAGE UndecidableInstances #-}+{-# OPTIONS_GHC -fno-warn-orphans #-}++-- |+-- Module      : Polytropos.ReaderSoup.Resource+-- Description : ResourceT integration for Polytropos ReaderSoup+-- Copyright   : (c) 2026, Nadia Yvette Chambers+-- License     : EUPL-1.2 OR Apache-2.0+-- Maintainer  : nadia.yvette.chambers@ik.me+-- Stability   : experimental+--+-- Provides turnkey 'ResourceT' integration for 'Polytropos.ReaderSoup.ReaderSoup',+-- connecting @resourcet@'s 'InternalState' to the @"resource"@ labeled context in the+-- soup.+--+-- Applications can simply add @("resource" ':= InternalState)@ to their soup context row+-- to automatically gain 'MonadResource' instances, enabling safe deterministic acquisition+-- and release of sockets, database handles, and file descriptors.+module Polytropos.ReaderSoup.Resource+  ( ContextFromName+  , useResource+  ) where++import Control.Monad.IO.Unlift (MonadUnliftIO)+import Control.Monad.Trans.Reader (ReaderT(..))+import Control.Monad.Trans.Resource+  ( InternalState+  , MonadResource(..)+  , ResourceT+  , runInternalState+  , runResourceT+  , withInternalState+  )+import Polytropos.Core (Field(..), FieldIndex)+import Polytropos.ReaderSoup++-- | Associates the @"resource"@ label with @resourcet@'s 'InternalState'.+type instance ContextFromName "resource" = InternalState++-- | Bridges 'ResourceT' with 'ReaderSoup' via 'InternalState'.+instance SoupContext InternalState ResourceT where+  toReaderT act = ReaderT $ runInternalState act+  fromReaderT (ReaderT act) = withInternalState act++-- | Canonical 'ContextRunner' for 'ResourceT', executing acquired resources safely.+useResource :: MonadUnliftIO m => ContextRunner ResourceT m+useResource = ContextRunner runResourceT++-- | Equips any 'ReaderSoup' carrying @"resource"@ with 'MonadResource'.+instance (FieldIndex "resource" ctxs InternalState)+      => MonadResource (ReaderSoup ctxs) where+  liftResourceT act = picking (Field @"resource") act

@@ -0,0 +1,160 @@+{-# LANGUAGE DataKinds #-}+{-# LANGUAGE OverloadedLabels #-}+{-# LANGUAGE OverloadedRecordDot #-}+{-# LANGUAGE OverloadedStrings #-}+{-# LANGUAGE TypeFamilies #-}+{-# OPTIONS_GHC -fplugin=Polytropos.Plugin -Wno-orphans #-}++module Main (main) where++import Control.Monad.Reader.Class (ask, local)+import Control.Monad.Trans.Reader (ReaderT(..))+import Control.Monad.Trans.Resource+  ( InternalState+  , MonadResource(..)+  , allocate+  , createInternalState+  , closeInternalState+  )+import Data.IORef+import Polytropos+import Polytropos.ReaderSoup+import Polytropos.ReaderSoup.Resource ()+import Test.Tasty+import Test.Tasty.HUnit++data DBConn = DBConn String deriving (Eq, Show)++type AppCtx =+  '[ "db"       := DBConn+   , "port"     := Int+   , "greeting" := String+   ]++type instance ContextFromName "x" = Int+type instance ContextFromName "y" = String++newtype IntEnv m a = IntEnv { unIntEnv :: ReaderT Int m a }+  deriving (Functor, Applicative, Monad)++instance SoupContext Int IntEnv where+  toReaderT = unIntEnv+  fromReaderT = IntEnv++newtype StrEnv m a = StrEnv { unStrEnv :: ReaderT String m a }+  deriving (Functor, Applicative, Monad)++instance SoupContext String StrEnv where+  toReaderT = unStrEnv+  fromReaderT = StrEnv++mkAppEnv :: DBConn -> Int -> String -> Record AppCtx+mkAppEnv db p g =+  insertField (Field @"db") db+    $ insertField (Field @"port") p+    $ insertField (Field @"greeting") g+    $ emptyRecord++-- Sub-soup requiring only DBConn and greeting:+subWorker :: ReaderSoup '[ "db" := DBConn, "greeting" := String ] String+subWorker = do+  db <- askSoup (Field @"db")+  g <- askSoup (Field @"greeting")+  pure (g ++ " from " ++ show db)++type RunnerRow =+  '[ "x" := ContextRunner IntEnv (ReaderSoup '[ "y" := String ])+   , "y" := ContextRunner StrEnv (ReaderSoup '[])+   ]++type ResCtx = '[ "resource" := InternalState, "tag" := String ]++main :: IO ()+main = defaultMain tests++tests :: TestTree+tests = testGroup "Polytropos.ReaderSoup"+  [ testCase "askSoup retrieves individual contexts in O(1)" $ do+      let env = mkAppEnv (DBConn "pg://prod") 5432 "Hello"+      res <- runReaderSoup (do+        db <- askSoup (Field @"db")+        p  <- askSoup (Field @"port")+        g  <- askSoup (Field @"greeting")+        pure (db, p, g)+        ) env+      res @?= (DBConn "pg://prod", 5432, "Hello")++  , testCase "filtering narrows full AppCtx down to sub-soup" $ do+      let env = mkAppEnv (DBConn "pg://cluster") 9000 "Welcome"+      msg <- runReaderSoup (filtering subWorker) env+      msg @?= "Welcome from DBConn \"pg://cluster\""++  , testCase "Spoon provides MonadReader with ask and local" $ do+      let env = mkAppEnv (DBConn "pg://local") 8080 "Hi"+      res <- runReaderSoup (dipping (Field @"port") $ do+        p1 <- ask+        p2 <- local (+ 100) ask+        p3 <- ask+        pure (p1, p2, p3)+        ) env+      res @?= (8080 :: Int, 8180 :: Int, 8080 :: Int)++  , testCase "pickTopping and eatTopping peel contexts iteratively" $ do+      let soup :: ReaderSoup '[ "a" := Int, "b" := String ] String+          soup = do+            a <- askSoup (Field @"a")+            b <- askSoup (Field @"b")+            pure (b ++ show a)++      -- Peel first topping ("a" := Int):+      let toppingA = pickTopping soup+          soupB = runReaderT toppingA (42 :: Int)++      -- Peel second topping ("b" := String):+      let toppingB = pickTopping soupB+          baseSoup = runReaderT toppingB "Answer: "++      result <- finishBroth baseSoup+      result @?= "Answer: 42"++  , testCase "consumeSoup executes runners iteratively" $ do+      let soup :: ReaderSoup '[ "x" := Int, "y" := String ] (Int, String)+          soup = do+            x <- askSoup (Field @"x")+            y <- askSoup (Field @"y")+            pure (x, y)++      let runners :: Record RunnerRow+          runners =+            insertField (Field @"x") (ContextRunner (\(IntEnv act) -> runReaderT act (123 :: Int)))+              $ insertField (Field @"y") (ContextRunner (\(StrEnv act) -> runReaderT act "dynamic"))+              $ emptyRecord++      res <- consumeSoup runners soup+      res @?= (123, "dynamic")++  , testCase "ResourceT integration via Polytropos.ReaderSoup.Resource" $ do+      cleanedUpRef <- newIORef False+      istate <- createInternalState++      let env :: Record ResCtx+          env = insertField (Field @"resource") istate+              $ insertField (Field @"tag") "res-test"+              $ emptyRecord++      res <- runReaderSoup (do+        t <- askSoup (Field @"tag")+        -- Allocate resource with cleanup hook:+        (_key, val) <- liftResourceT (allocate (pure ("resource-" ++ t)) (\_ -> writeIORef cleanedUpRef True))+        pure val+        ) env++      res @?= "resource-res-test"+      wasCleanedBefore <- readIORef cleanedUpRef+      wasCleanedBefore @?= False++      -- Close internal state and verify cleanup hook ran:+      closeInternalState istate+      wasCleanedAfter <- readIORef cleanedUpRef+      wasCleanedAfter @?= True+  ]