https://github.com/ktonon/elm-serverless-cors

CORS middleware for elm-serverless
https://github.com/ktonon/elm-serverless-cors

cors elm elm-serverless middleware serverless

Last synced: about 1 month ago
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CORS middleware for elm-serverless

• Host: GitHub
• URL: https://github.com/ktonon/elm-serverless-cors
• Owner: ktonon
• License: mit
• Created: 2017-02-01T03:03:13.000Z (almost 8 years ago)
• Default Branch: master
• Last Pushed: 2017-08-15T10:56:05.000Z (over 7 years ago)
• Last Synced: 2023-08-08T20:39:30.760Z (over 1 year ago)
• Topics: cors, elm, elm-serverless, middleware, serverless
• Language: Elm
• Size: 15.6 KB
• Stars: 5
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE.txt

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README

        
# elm-serverless-cors

[![serverless](http://public.serverless.com/badges/v3.svg)](http://www.serverless.com)

[![Elm Package](https://img.shields.io/badge/elm-1.0.1-blue.svg)](http://package.elm-lang.org/packages/ktonon/elm-serverless-cors/latest)

[![CircleCI](https://img.shields.io/circleci/project/github/ktonon/elm-serverless-cors.svg)](https://circleci.com/gh/ktonon/elm-serverless-cors)

This is [CORS][] middleware for [elm-serverless][].

There are two ways to use it.

1. Set the headers that you need, individually.

2. Set the headers using externally provided configuration.

## Method 1

Set the headers that you need, individually.

```elm

import Serverless.Conn.Request exposing (Method(..))

import Serverless.Cors exposing (..)

import Serverless.Plug exposing (pipeline, plug)

myPipeline =

    pipeline

        -- Sets access-control-allow-origin

        -- the same as the origin request header

        -- or if that is not found then "*"

        |>

            plug (allowOrigin ReflectRequest)

        -- Sets access-control-allow-methods

        |>

            plug (allowMethods [ GET, OPTIONS ])

```

## Method 2

Set the headers using externally provided configuration (i.e. AWS Environment variables), and decode them into your app's config record. This method is demonstrated in [elm-serverless-demo][]. In summary, you need to do the following.

First add CORS configuration to your Serverless app's `Config` type. And decode it with the provided `Cors.configDecoder`.

```elm

import Json.Decode exposing (Decoder, list, string)

import Json.Decode.Pipeline exposing (required, decode, hardcoded)

import Serverless.Cors as Cors

type alias Config =

    { cors : Cors.Config

    -- ...

    }

configDecoder : Json.Decode.Decoder Config

configDecoder =

    decode Config

        |> required "cors" Cors.configDecoder

        -- ...

```

Then you can access the config from your `Conn` and use it to configure CORS.

```elm

import Serverless.Conn exposing (config)

import Serverless.Plug exposing (pipeline, plug)

import Serverless.Cors exposing (cors)

myPipeline =

    pipeline

        |> plug (Cors.fromConfig .cors)

```

On the JavaScript side, you can do something like this to map AWS Lambda environment variables to a JavaScript object.

```javascript

const elmServerless = require('elm-serverless');

const rc = require('strip-debug!shebang!rc');

const elm = require('./API.elm');

// Use AWS Lambda environment variables to override these values

// See the npm rc package README for more details

const config = rc('myApi', {

  cors: {

    origin: '*',

    methods: 'get,post,options',

  },

});

module.exports.handler = elmServerless.httpApi({

  handler: elm.API,

  config,

});

```

So in the [AWS Lambda console][], you can set environment variables, which will get loaded by [rc][] into a JavaScript configuration object, and passed into elm for decoding. In this example, you could set

* `myApi_cors__origin=foo.com,bar.com`: decodes to `Exactly ["foo.com", "bar.com"]` for `origin`

* `myApi_cors__credentials=true`: decodes to `True` for `credentials`

[AWS Lambda console]:https://console.aws.amazon.com/lambda/home

[CORS]:https://en.wikipedia.org/wiki/Cross-origin_resource_sharing

[elm-serverless]:http://package.elm-lang.org/packages/ktonon/elm-serverless/latest

[elm-serverless-demo]:https://github.com/ktonon/elm-serverless-demo

[rc]:https://www.npmjs.com/package/rc#standards