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Nesting APIs and ReaderT environments in Haskell's Servant

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Compare using a stack of transformers vs. the ReaderT pattern for a web service.

See files:

• Transformers.hs
• Reader.hs

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App-wide vs. Handler-specific environments in Haskell's Servant

See files:

• Bad.hs
• Good.hs

Client requests:

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module AsyncMonadBaseControlExample where

import Blammo.Logging (LoggingT)
import Control.Concurrent.Async.Lifted.Safe (concurrently)
import Control.Monad.Base (MonadBase)
import Control.Monad.Reader (MonadIO, MonadReader, MonadTrans (lift), ReaderT)
import Control.Monad.Trans.Control (MonadBaseControl (liftBaseWith, restoreM), StM)
import Data.Text.Lazy qualified as TL
import Web.Scotty.Trans (ActionT, text)

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#!/usr/bin/env stack
{- stack
  --resolver lts-13.4
  --install-ghc
  script
  --ghc-options "-Wall"
  --package aeson
  --package aeson-pretty
  --package aeson-typescript
  --package base

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Emulating "enums" in JSDoc version of TypeScript

Problem

TypeScript has support for type-checking plain JavaScript files, which is very useful if you have an existing JS codebase and you want to test the waters and gradually add types.

There are some limitations in what you can do in JSDoc, but a lot of them can be worked-around by using type-definition files .d.ts (for example in a types/ directory). These files don't generate any JavaScript code, they are just there to provide extra type definitions to the compiler.

One thing you can't do in those .d.ts files though, is use enums. You could define them of course, but you won't get the runtime representation since the files don't generate JS code.

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CLOSURE_COMPILER_VERSION := 20180101
CLOSURE_COMPILER_URL := http://dl.google.com/closure-compiler/compiler-$(CLOSURE_COMPILER_VERSION).tar.gz

closure-compiler:
  mkdir -p vendor
	curl -o vendor/closure-compiler.tar.gz $(CLOSURE_COMPILER_URL)
	tar -C vendor/ -zxf vendor/closure-compiler.tar.gz
	mv vendor/closure-compiler-v$(CLOSURE_COMPILER_VERSION).jar vendor/closure-compiler.jar
	rm vendor/COPYING vendor/README.md vendor/closure-compiler.tar.gz
  

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node_modules
dist

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Instructions

Go to http://astexplorer.net/, select babylon6 as the parser, and babelv6 as the transform option.

Paste in the babel-plugin-react-string.js code in the transform area.

Paste the following example source code:

function profile(props) {

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{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE OverloadedStrings     #-}
{-# LANGUAGE TemplateHaskell       #-}
{-# LANGUAGE DeriveGeneric         #-}

module Main where

import Data.Monoid ((<>))
import qualified Data.Text as T
import Text.Shakespeare.I18N (mkMessage, renderMessage, RenderMessage())