Integrate Flow type checker

Closes #1

.flowconfig

@@ -0,0 +1,4 @@
+[ignore]
+.*/build/.*
+.*/coverage/.*
+.*/scripts/.*

.travis.yml

@@ -8,5 +8,6 @@ cache:
     - node_modules
 script:
   - npm run lint
+  - npm run check
   - npm run build
   - npm run test

README.md

@@ -22,7 +22,8 @@ You can use it either just as a playground or a base for your next API project.
 │   ├── /schema.js              # GraphQL schema
 │   └── /server.js              # Node.js server (entry point)
 ├── /test/                      # Unit, integration and load tests
-└── package.json                # The list of project dependencies
+├── package.json                # The list of project dependencies
+└── yarn.lock                   # Fixed versions of all the dependencies
 ```
 
 
@@ -53,6 +54,7 @@ npm run build:watch             # Compiles the app and starts watching for chang
 
 ```bash
 npm run lint                    # Find problematic patterns in code
+npm run check                   # Check source code for type errors
 npm run test                    # Run unit tests once
 npm run test:watch              # Run unit tests in watch mode
 ```

package.json

@@ -22,6 +22,7 @@
     "babel-plugin-syntax-trailing-function-commas": "^6.13.0",
     "babel-plugin-transform-class-properties": "^6.19.0",
     "babel-plugin-transform-es2015-modules-commonjs": "^6.18.0",
+    "babel-plugin-transform-flow-strip-types": "^6.18.0",
     "babel-plugin-transform-object-rest-spread": "^6.19.0",
     "babel-plugin-transform-runtime": "^6.15.0",
     "babel-register": "^6.18.0",
@@ -31,16 +32,18 @@
     "eslint": "^3.11.0",
     "eslint-config-airbnb-base": "^10.0.1",
     "eslint-plugin-import": "^2.2.0",
+    "flow-bin": "^0.36.0",
     "mocha": "^3.2.0",
     "nodemon": "^1.11.0",
     "rimraf": "^2.5.4"
   },
   "babel": {
     "plugins": [
-      "syntax-trailing-function-commas",
-      "transform-es2015-modules-commonjs",
       "syntax-async-functions",
+      "syntax-trailing-function-commas",
       "transform-class-properties",
+      "transform-es2015-modules-commonjs",
+      "transform-flow-strip-types",
       "transform-object-rest-spread"
     ]
   },
@@ -49,6 +52,7 @@
   },
   "scripts": {
     "lint": "eslint src test scripts --ignore-pattern scripts/start.js",
+    "check": "flow check",
     "test": "mocha test/unit --compilers js:babel-core/register",
     "test:watch": "mocha test/unit --compilers js:babel-core/register --reporter min --watch",
     "build": "node scripts/build",

src/app.js

@@ -7,6 +7,8 @@
  * LICENSE.txt file in the root directory of this source tree.
  */
 
+/* @flow */
+
 import express from 'express';
 import cors from 'cors';
 import cookieParser from 'cookie-parser';

src/config.js

@@ -7,6 +7,8 @@
  * LICENSE.txt file in the root directory of this source tree.
  */
 
+/* @flow */
+
 //
 // Node.js server settings
 // -----------------------------------------------------------------------------

src/schema.js

@@ -7,6 +7,8 @@
  * LICENSE.txt file in the root directory of this source tree.
  */
 
+/* @flow */
+
 import { GraphQLSchema, GraphQLObjectType } from 'graphql';
 import Viewer from './types/Viewer';
 

src/server.js

@@ -7,6 +7,8 @@
  * LICENSE.txt file in the root directory of this source tree.
  */
 
+/* @flow */
+
 import app from './app';
 import config from './config';
 

src/types/User.js

@@ -7,6 +7,8 @@
  * LICENSE.txt file in the root directory of this source tree.
  */
 
+/* @flow */
+
 import { GraphQLObjectType, GraphQLNonNull, GraphQLID, GraphQLString } from 'graphql';
 
 export default new GraphQLObjectType({

src/types/Viewer.js

@@ -7,6 +7,8 @@
  * LICENSE.txt file in the root directory of this source tree.
  */
 
+/* @flow */
+
 import { GraphQLObjectType } from 'graphql';
 import User from './User';
 

yarn.lock

@@ -245,6 +245,10 @@ babel-plugin-syntax-class-properties@^6.8.0:
   version "6.13.0"
   resolved "https://registry.yarnpkg.com/babel-plugin-syntax-class-properties/-/babel-plugin-syntax-class-properties-6.13.0.tgz#d7eb23b79a317f8543962c505b827c7d6cac27de"
 
+babel-plugin-syntax-flow@^6.18.0:
+  version "6.18.0"
+  resolved "https://registry.yarnpkg.com/babel-plugin-syntax-flow/-/babel-plugin-syntax-flow-6.18.0.tgz#4c3ab20a2af26aa20cd25995c398c4eb70310c8d"
+
 babel-plugin-syntax-object-rest-spread@^6.8.0:
   version "6.13.0"
   resolved "https://registry.yarnpkg.com/babel-plugin-syntax-object-rest-spread/-/babel-plugin-syntax-object-rest-spread-6.13.0.tgz#fd6536f2bce13836ffa3a5458c4903a597bb3bf5"
@@ -271,6 +275,13 @@ babel-plugin-transform-es2015-modules-commonjs@^6.18.0:
     babel-template "^6.16.0"
     babel-types "^6.18.0"
 
+babel-plugin-transform-flow-strip-types@^6.18.0:
+  version "6.18.0"
+  resolved "https://registry.yarnpkg.com/babel-plugin-transform-flow-strip-types/-/babel-plugin-transform-flow-strip-types-6.18.0.tgz#4d3e642158661e9b40db457c004a30817fa32592"
+  dependencies:
+    babel-plugin-syntax-flow "^6.18.0"
+    babel-runtime "^6.0.0"
+
 babel-plugin-transform-object-rest-spread@^6.19.0:
   version "6.19.0"
   resolved "https://registry.yarnpkg.com/babel-plugin-transform-object-rest-spread/-/babel-plugin-transform-object-rest-spread-6.19.0.tgz#f6ac428ee3cb4c6aa00943ed1422ce813603b34c"
@@ -1144,6 +1155,10 @@ flat-cache@^1.2.1:
     graceful-fs "^4.1.2"
     write "^0.2.1"
 
+flow-bin@^0.36.0:
+  version "0.36.0"
+  resolved "https://registry.yarnpkg.com/flow-bin/-/flow-bin-0.36.0.tgz#557907bd9c2ab0670cfad9e7e906a74b0631e39a"
+
 for-in@^0.1.5:
   version "0.1.6"
   resolved "https://registry.yarnpkg.com/for-in/-/for-in-0.1.6.tgz#c9f96e89bfad18a545af5ec3ed352a1d9e5b4dc8"