yoga-om-core

Core Om types and operations for writing applications with dependency injection and checked exceptions.

This is the base package that provides the Om type and all core operations. It works in both browser and Node.js environments.

Installation

spago install yoga-om-core

What's Included

• Om type: The core monad transformer stack combining ReaderT, ExceptV, and Aff
• Error handling: throw, handleErrors, expand for mix-and-match error types
• Dependency injection: ask, asks for accessing context
• Parallel computations: race, inParallel for concurrent operations
• Helpers: note, delay, unliftAff and more

Basic Usage

import Yoga.Om (Om)
import Yoga.Om as Om

myApp :: Om { dbUrl :: String } (dbError :: String) Unit
myApp = do
  { dbUrl } <- Om.ask
  -- Your application logic here
  pure unit

main = myApp 
  # Om.launchOm_ 
      { dbUrl: "postgresql://localhost" }
      { exception: \e -> Console.error (show e)
      , dbError: \err -> Console.error err
      }

Features

Context (Dependency Injection)

getUser :: Om { db :: Database } _ User
getUser = do
  { db } <- Om.ask
  -- Use db to fetch user

Error Handling

saveUser :: Om _ (dbError :: String, validationError :: String) Unit
saveUser = do
  -- Can throw either dbError or validationError
  Om.throw { validationError: "Invalid email" }

Parallel Operations

fetchMultiple :: Om _ _ (Array User)
fetchMultiple = Om.inParallel
  [ fetchUser 1
  , fetchUser 2
  , fetchUser 3
  ]

Testing

Tests are colocated with the implementation in the test/ directory:

# Run tests
cd packages/yoga-om-core && spago test

# Or from workspace root
bun test:core

See test/Test/Om/Core.purs for comprehensive test examples.

Package Structure

yoga-om-core/
├── src/
│   └── Yoga/
│       ├── Om.purs          # Main Om implementation
│       └── Om/
│           ├── Error.purs   # Error types and helpers
│           └── Error.js     # FFI for error handling
└── test/                     # Tests colocated here!
    └── Test/
        ├── Main.purs        # Test runner
        └── Om/
            └── Core.purs    # Core Om tests (20 tests)

See Also

• yoga-om-node - Node.js-specific extensions
• yoga-om-rom - Reactive Om: Bolson FRP integration (push-based)
• yoga-om-strom - Stream Om: Pull-based streaming library

For more examples, see the main README and tests.