flow all the things

.eslintrc

@@ -1,4 +1,5 @@
 {
+  "parser": "babel-eslint",
   "parserOptions": {
     "ecmaVersion": "2018"
   },

.flowconfig

@@ -0,0 +1,11 @@
+[ignore]
+
+[include]
+
+[libs]
+
+[lints]
+
+[options]
+
+[strict]

package-lock.json

@@ -13,6 +13,48 @@
         "@babel/highlight": "^7.0.0"
       }
     },
+    "@babel/generator": {
+      "version": "7.0.0",
+      "resolved": "https://registry.npmjs.org/@babel/generator/-/generator-7.0.0.tgz",
+      "integrity": "sha512-/BM2vupkpbZXq22l1ALO7MqXJZH2k8bKVv8Y+pABFnzWdztDB/ZLveP5At21vLz5c2YtSE6p7j2FZEsqafMz5Q==",
+      "dev": true,
+      "requires": {
+        "@babel/types": "^7.0.0",
+        "jsesc": "^2.5.1",
+        "lodash": "^4.17.10",
+        "source-map": "^0.5.0",
+        "trim-right": "^1.0.1"
+      }
+    },
+    "@babel/helper-function-name": {
+      "version": "7.0.0",
+      "resolved": "https://registry.npmjs.org/@babel/helper-function-name/-/helper-function-name-7.0.0.tgz",
+      "integrity": "sha512-Zo+LGvfYp4rMtz84BLF3bavFTdf8y4rJtMPTe2J+rxYmnDOIeH8le++VFI/pRJU+rQhjqiXxE4LMaIau28Tv1Q==",
+      "dev": true,
+      "requires": {
+        "@babel/helper-get-function-arity": "^7.0.0",
+        "@babel/template": "^7.0.0",
+        "@babel/types": "^7.0.0"
+      }
+    },
+    "@babel/helper-get-function-arity": {
+      "version": "7.0.0",
+      "resolved": "https://registry.npmjs.org/@babel/helper-get-function-arity/-/helper-get-function-arity-7.0.0.tgz",
+      "integrity": "sha512-r2DbJeg4svYvt3HOS74U4eWKsUAMRH01Z1ds1zx8KNTPtpTL5JAsdFv8BNyOpVqdFhHkkRDIg5B4AsxmkjAlmQ==",
+      "dev": true,
+      "requires": {
+        "@babel/types": "^7.0.0"
+      }
+    },
+    "@babel/helper-split-export-declaration": {
+      "version": "7.0.0",
+      "resolved": "https://registry.npmjs.org/@babel/helper-split-export-declaration/-/helper-split-export-declaration-7.0.0.tgz",
+      "integrity": "sha512-MXkOJqva62dfC0w85mEf/LucPPS/1+04nmmRMPEBUB++hiiThQ2zPtX/mEWQ3mtzCEjIJvPY8nuwxXtQeQwUag==",
+      "dev": true,
+      "requires": {
+        "@babel/types": "^7.0.0"
+      }
+    },
     "@babel/highlight": {
       "version": "7.0.0",
       "resolved": "https://registry.npmjs.org/@babel/highlight/-/highlight-7.0.0.tgz",
@@ -24,6 +66,51 @@
         "js-tokens": "^4.0.0"
       }
     },
+    "@babel/parser": {
+      "version": "7.0.0",
+      "resolved": "https://registry.npmjs.org/@babel/parser/-/parser-7.0.0.tgz",
+      "integrity": "sha512-RgJhNdRinpO8zibnoHbzTTexNs4c8ROkXFBanNDZTLHjwbdLk8J5cJSKulx/bycWTLYmKVNCkxRtVCoJnqPk+g==",
+      "dev": true
+    },
+    "@babel/template": {
+      "version": "7.0.0",
+      "resolved": "https://registry.npmjs.org/@babel/template/-/template-7.0.0.tgz",
+      "integrity": "sha512-VLQZik/G5mjYJ6u19U3W2u7eM+rA/NGzH+GtHDFFkLTKLW66OasFrxZ/yK7hkyQcswrmvugFyZpDFRW0DjcjCw==",
+      "dev": true,
+      "requires": {
+        "@babel/code-frame": "^7.0.0",
+        "@babel/parser": "^7.0.0",
+        "@babel/types": "^7.0.0"
+      }
+    },
+    "@babel/traverse": {
+      "version": "7.0.0",
+      "resolved": "https://registry.npmjs.org/@babel/traverse/-/traverse-7.0.0.tgz",
+      "integrity": "sha512-ka/lwaonJZTlJyn97C4g5FYjPOx+Oxd3ab05hbDr1Mx9aP1FclJ+SUHyLx3Tx40sGmOVJApDxE6puJhd3ld2kw==",
+      "dev": true,
+      "requires": {
+        "@babel/code-frame": "^7.0.0",
+        "@babel/generator": "^7.0.0",
+        "@babel/helper-function-name": "^7.0.0",
+        "@babel/helper-split-export-declaration": "^7.0.0",
+        "@babel/parser": "^7.0.0",
+        "@babel/types": "^7.0.0",
+        "debug": "^3.1.0",
+        "globals": "^11.1.0",
+        "lodash": "^4.17.10"
+      }
+    },
+    "@babel/types": {
+      "version": "7.0.0",
+      "resolved": "https://registry.npmjs.org/@babel/types/-/types-7.0.0.tgz",
+      "integrity": "sha512-5tPDap4bGKTLPtci2SUl/B7Gv8RnuJFuQoWx26RJobS0fFrz4reUA3JnwIM+HVHEmWE0C1mzKhDtTp8NsWY02Q==",
+      "dev": true,
+      "requires": {
+        "esutils": "^2.0.2",
+        "lodash": "^4.17.10",
+        "to-fast-properties": "^2.0.0"
+      }
+    },
     "acorn": {
       "version": "5.7.3",
       "resolved": "https://registry.npmjs.org/acorn/-/acorn-5.7.3.tgz",
@@ -108,6 +195,32 @@
       "integrity": "sha1-iYUI2iIm84DfkEcoRWhJwVAaSw0=",
       "dev": true
     },
+    "babel-eslint": {
+      "version": "9.0.0",
+      "resolved": "https://registry.npmjs.org/babel-eslint/-/babel-eslint-9.0.0.tgz",
+      "integrity": "sha512-itv1MwE3TMbY0QtNfeL7wzak1mV47Uy+n6HtSOO4Xd7rvmO+tsGQSgyOEEgo6Y2vHZKZphaoelNeSVj4vkLA1g==",
+      "dev": true,
+      "requires": {
+        "@babel/code-frame": "^7.0.0",
+        "@babel/parser": "^7.0.0",
+        "@babel/traverse": "^7.0.0",
+        "@babel/types": "^7.0.0",
+        "eslint-scope": "3.7.1",
+        "eslint-visitor-keys": "^1.0.0"
+      },
+      "dependencies": {
+        "eslint-scope": {
+          "version": "3.7.1",
+          "resolved": "https://registry.npmjs.org/eslint-scope/-/eslint-scope-3.7.1.tgz",
+          "integrity": "sha1-PWPD7f2gLgbgGkUq2IyqzHzctug=",
+          "dev": true,
+          "requires": {
+            "esrecurse": "^4.1.0",
+            "estraverse": "^4.1.1"
+          }
+        }
+      }
+    },
     "balanced-match": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/balanced-match/-/balanced-match-1.0.0.tgz",
@@ -439,6 +552,12 @@
         "write": "^0.2.1"
       }
     },
+    "flow-bin": {
+      "version": "0.81.0",
+      "resolved": "https://registry.npmjs.org/flow-bin/-/flow-bin-0.81.0.tgz",
+      "integrity": "sha512-5e8oL3/5rm3G0Eet3yDCne2R/TLo5Fkn+Z5MtHd4wtz+1miLC35Sgo8XvnbTmiZ9epdTZ1q6GLmJWYh7tUlfGg==",
+      "dev": true
+    },
     "fs.realpath": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/fs.realpath/-/fs.realpath-1.0.0.tgz",
@@ -625,6 +744,12 @@
         "esprima": "^4.0.0"
       }
     },
+    "jsesc": {
+      "version": "2.5.1",
+      "resolved": "https://registry.npmjs.org/jsesc/-/jsesc-2.5.1.tgz",
+      "integrity": "sha1-5CGiqOINawgZ3yiQj3glJrlt0f4=",
+      "dev": true
+    },
     "json-schema-traverse": {
       "version": "0.4.1",
       "resolved": "https://registry.npmjs.org/json-schema-traverse/-/json-schema-traverse-0.4.1.tgz",
@@ -921,6 +1046,12 @@
         "is-fullwidth-code-point": "^2.0.0"
       }
     },
+    "source-map": {
+      "version": "0.5.7",
+      "resolved": "https://registry.npmjs.org/source-map/-/source-map-0.5.7.tgz",
+      "integrity": "sha1-igOdLRAh0i0eoUyA2OpGi6LvP8w=",
+      "dev": true
+    },
     "sprintf-js": {
       "version": "1.0.3",
       "resolved": "https://registry.npmjs.org/sprintf-js/-/sprintf-js-1.0.3.tgz",
@@ -996,6 +1127,18 @@
         "os-tmpdir": "~1.0.2"
       }
     },
+    "to-fast-properties": {
+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/to-fast-properties/-/to-fast-properties-2.0.0.tgz",
+      "integrity": "sha1-3F5pjL0HkmW8c+A3doGk5Og/YW4=",
+      "dev": true
+    },
+    "trim-right": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/trim-right/-/trim-right-1.0.1.tgz",
+      "integrity": "sha1-yy4SAwZ+DI3h9hQJS5/kVwTqYAM=",
+      "dev": true
+    },
     "tslib": {
       "version": "1.9.3",
       "resolved": "https://registry.npmjs.org/tslib/-/tslib-1.9.3.tgz",

package.json

@@ -5,14 +5,19 @@
   "main": "index.js",
   "scripts": {
     "lint": "eslint src",
-    "format": "prettier --write \"**/*.+(js|jsx|json|yml|yaml|css|less|scss|ts|tsx|md|graphql|mdx)\""
+    "flow": "flow",
+    "format": "npm run prettier -- --write",
+    "prettier": "prettier \"**/*.+(js|jsx|json|yml|yaml|css|less|scss|ts|tsx|md|graphql|mdx)\"",
+    "validate": "npm run lint && npm run prettier -- --list-different && npm run flow"
   },
   "keywords": [],
   "author": "Kent C. Dodds <kent@doddsfamily.us> (http://kentcdodds.com/)",
   "license": "MIT",
   "devDependencies": {
+    "babel-eslint": "^9.0.0",
     "eslint": "^5.5.0",
     "eslint-config-prettier": "^3.0.1",
+    "flow-bin": "^0.81.0",
     "prettier": "^1.14.2"
   }
 }

src/example.js

@@ -7,5 +7,4 @@ if (!('serviceWorker' in navigator)) {
 
 const greeting = 'hello'
 console.log(`${greeting} world!`)
-
 ;[(1, 2, 3)].forEach(x => console.log(x))

src/flow-example.js

@@ -0,0 +1,22 @@
+// @flow
+function add(a: number, b: number): number {
+  return a + b
+}
+
+type User = {
+  name: {
+    first: string,
+    middle: string,
+    last: string,
+  },
+}
+function getFullName(user: User): string {
+  const {
+    name: {first, middle, last},
+  } = user
+  return [first, middle, last].filter(Boolean).join('')
+}
+
+add(1, 2)
+
+getFullName({name: {first: 'Joe', middle: 'Bud', last: 'Matthews'}})