Exemplary real world backend API built with Haskell/Scotty https://realworld.io

License: MIT License

Haskell 98.76% Shell 0.30% Standard ML 0.94%

haskell realworld scotty restful-api tutorial

haskell-scotty-realworld-example-app's Introduction

Haskell/Scotty codebase containing real world examples (CRUD, auth, advanced patterns, etc) that adheres to the RealWorld spec and API.

Demo RealWorld

This codebase was created to demonstrate a fully fledged fullstack application built with Haskell/Scotty including CRUD operations, authentication, routing, pagination, and more.

We've gone to great lengths to adhere to the Haskell/Scotty community styleguides & best practices.

For more information on how to this works with other frontends/backends, head over to the RealWorld repo.

How it works

Environment Variables

Name	Desc	Default Value
`DATABASE_URL`	PostgreSQL Database URL	`postgresql://localhost/realworld`
`ENABLE_HTTPS`	Server will run on HTTPS if True	`True`
`PORT`	Port	`3000`
`JWK_PATH`	Path to JWK signature file	`secrets/jwk.sig`
`JWT_EXPIRATION_SECS`	How long until JWT expire (in secs)	`7200`

Notable Dependencies

classy-prelude - Better Prelude for Haskell
scotty - Web ~~framework~~ library
postgresql-simple - PostgreSQL library
aeson - JSON serialization & deserialization
digestive-functors & digestive-functors-aeson - Input parsing & validation
jose-jwt - JWT encode & decode
slug - Slug string builder
hspec - Test framework

Quick Repo Walkthrough

/postgresql - Database migration scripts.
/secrets - Default HTTPS & JWT configuration files for development. Please replace with something else for production.
/scripts - Bash scripts to help development.
/app - Haskell files for application entry point.
/test - Haskell test files.
/src - Main Haskell code.

Getting started

Installation

Install Stack.

Install PostgreSQL.

Clone the repository and cd to repo

git clone https://github.com/eckyputrady/haskell-scotty-realworld-example-app.git

cd haskell-scotty-realworld-example-app

Install GHC

stack setup

Install dependencies and build project

stack build

Run project

stack exec realworld-exe

Alternatively, to watch file changes and start the server automatically

./scripts/dev.sh

Alternatively, to watch file changes and run the tests automatically

stack test --file-watch --coverage

To setup deployment to Heroku, please configure this custom buildpack

heroku buildpacks:set https://github.com/mfine/heroku-buildpack-stack

Misc

Logo image - credits to @EricSimmon

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haskell-scotty-realworld-example-app's Issues

Failed to compile

I've got following compiling error

/Users/hao/Sandbox/form-as-api/src/Feature/Auth/JWT.hs:19:5: error:
    • Could not deduce (Control.Monad.Fail.MonadFail
                          (Either TokenError))
        arising from a do statement
        with the failable pattern ‘Jws (_, claimsRaw)’
      from the context: JWT r m
        bound by the type signature for:
                   resolveToken :: forall r (m :: * -> *).
                                   JWT r m =>
                                   Token -> m (Either TokenError CurrentUser)
        at src/Feature/Auth/JWT.hs:13:1-71
    • In a stmt of a 'do' block:
        Jws (_, claimsRaw) <- first (TokenErrorMalformed . show) eitherJwt
      In the second argument of ‘($)’, namely
        ‘do Jws (_, claimsRaw) <- first
                                    (TokenErrorMalformed . show) eitherJwt
            jwtClaims <- first TokenErrorMalformed
                           $ Aeson.eitherDecode $ fromStrict claimsRaw
            let (IntDate expiredAt)
                  = fromMaybe (IntDate curTime) $ jwtExp jwtClaims
            when (expiredAt < curTime) $ Left TokenErrorExpired
            ....’
      In a stmt of a 'do' block:
        userId <- either throwError return
                    $ do Jws (_, claimsRaw) <- first
                                                 (TokenErrorMalformed . show) eitherJwt
                         jwtClaims <- first TokenErrorMalformed
                                        $ Aeson.eitherDecode $ fromStrict claimsRaw
                         let (IntDate expiredAt)
                               = fromMaybe (IntDate curTime) $ jwtExp jwtClaims
                         when (expiredAt < curTime) $ Left TokenErrorExpired
                         ....
   |
19 |     Jws (_, claimsRaw) <- first (TokenErrorMalformed . show) eitherJwt
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

here's my stack.yml

# This file was automatically generated by 'stack init'
#
# Some commonly used options have been documented as comments in this file.
# For advanced use and comprehensive documentation of the format, please see:
# https://docs.haskellstack.org/en/stable/yaml_configuration/

# Resolver to choose a 'specific' stackage snapshot or a compiler version.
# A snapshot resolver dictates the compiler version and the set of packages
# to be used for project dependencies. For example:
#
# resolver: lts-3.5
# resolver: nightly-2015-09-21
# resolver: ghc-7.10.2
#
# The location of a snapshot can be provided as a file or url. Stack assumes
# a snapshot provided as a file might change, whereas a url resource does not.
#
# resolver: ./custom-snapshot.yaml
# resolver: https://example.com/snapshots/2018-01-01.yaml
resolver: lts-14.7

# User packages to be built.
# Various formats can be used as shown in the example below.
#
# packages:
# - some-directory
# - https://example.com/foo/bar/baz-0.0.2.tar.gz
# - location:
#    git: https://github.com/commercialhaskell/stack.git
#    commit: e7b331f14bcffb8367cd58fbfc8b40ec7642100a
# - location: https://github.com/commercialhaskell/stack/commit/e7b331f14bcffb8367cd58fbfc8b40ec7642100a
#  subdirs:
#  - auto-update
#  - wai
packages:
- .
# Dependency packages to be pulled from upstream that are not in the resolver
# using the same syntax as the packages field.
# (e.g., acme-missiles-0.3)
extra-deps:
  - digestive-functors-0.8.4.0
  - digestive-functors-aeson-1.1.27
  - string-random-0.1.0.0

# Override default flag values for local packages and extra-deps
flags: {}

# Extra package databases containing global packages
extra-package-dbs: []

# Control whether we use the GHC we find on the path
# system-ghc: true
#
# Require a specific version of stack, using version ranges
# require-stack-version: -any # Default
# require-stack-version: ">=1.9"
#
# Override the architecture used by stack, especially useful on Windows
# arch: i386
# arch: x86_64
#
# Extra directories used by stack for building
# extra-include-dirs: [/path/to/dir]
# extra-lib-dirs: [/path/to/dir]
#
# Allow a newer minor version of GHC than the snapshot specifies
# compiler-check: newer-minor

List all imported functions clear

This real world example app is awesome! I learned a lot from it. Thanks for sharing it.

Just a feedback:

When I was reading the code, it's difficult for me to know which module a specific function is imported from.

For example, the createPool here
https://github.com/eckyputrady/haskell-scotty-realworld-example-app/blob/master/src/Platform/PG.hs#L24

Is it better if the imported functions are all explicitly listed in the import statement?

PostgreSQL > users table should use pgcrypto solution instead of chkpass

Because chkpass is unsecure.

pgcrypto solution reference: https://til.hashrocket.com/posts/a2170ba6b0-salt-and-hash-a-password-with-postgres-pgcrypto

Test failure

I tried to run the test suite with stack test, and I've got an error saying

✔ ~/Sandbox/haskell-scotty-realworld-example-app [master|✔]
22:54 $ stack test
realworld-1.0.0.0: test (suite: realworld-test)

realworld-test: libpq: failed (FATAL:  database "hao" does not exist
)

realworld-1.0.0.0: Test suite realworld-test failed
Test suite failure for package realworld-1.0.0.0
    realworld-test:  exited with: ExitFailure 1
Logs printed to console

would you please what else I have to do to have the test up & running? cheers

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