Add typescript linting.

.node-version

@@ -0,0 +1 @@
+11.9.0

package.json

@@ -15,6 +15,7 @@
     "test": "npm run lint && npm run smoke"
   },
   "dependencies": {
+    "@typescript-eslint/eslint-plugin": "^1.4.2",
     "babel-eslint": "^10.0.0",
     "chalk": "^2.4.1",
     "eslint-import-resolver-babel-module": "^5.0.0-beta.0",

rules/errors.js

@@ -1,3 +1,5 @@
+var hasTypescript = require('../util/babel').hasTypescript();
+
 module.exports = {
   // For complete listing of rules and what they do, check out the docs.
   // See: https://github.com/eslint/eslint/tree/master/docs/rules
@@ -190,3 +192,7 @@ module.exports = {
     'block-scoped-var': 2,
   },
 };
+
+if (hasTypescript) {
+  module.exports.rules['no-unused-vars'] = 0;
+}

rules/typescript.js

@@ -0,0 +1,41 @@
+var hasPrettier = require('../util/babel').hasPrettier();
+
+module.exports = {
+  rules: {
+    'metalab/typescript/adjacent-overload-signatures': 'error',
+    'metalab/typescript/array-type': 'error',
+    'metalab/typescript/ban-types': 'error',
+    'metalab/typescript/camelcase': 'error',
+    'metalab/typescript/class-name-casing': 'error',
+    'metalab/typescript/explicit-function-return-type': 'warn',
+    'metalab/typescript/explicit-member-accessibility': 'error',
+    'metalab/typescript/indent': hasPrettier ? 'off' : 'error',
+    'metalab/typescript/interface-name-prefix': 'error',
+    'metalab/typescript/member-delimiter-style': 'error',
+    'metalab/typescript/no-angle-bracket-type-assertion': 'error',
+    'metalab/typescript/no-array-constructor': 'error',
+    'metalab/typescript/no-empty-interface': 'error',
+    'metalab/typescript/no-explicit-any': 'warn',
+    'metalab/typescript/no-inferrable-types': 'error',
+    'metalab/typescript/no-misused-new': 'error',
+    'metalab/typescript/no-namespace': 'error',
+    'metalab/typescript/no-non-null-assertion': 'error',
+    'metalab/typescript/no-object-literal-type-assertion': 'error',
+    'metalab/typescript/no-parameter-properties': 'error',
+    'metalab/typescript/no-triple-slash-reference': 'error',
+    'metalab/typescript/no-unused-vars': [
+      2,
+      {
+        // TODO: Maybe add `caughtErrors: "all"`
+        varsIgnorePattern: '^_',
+        argsIgnorePattern: '^_',
+        caughtErrorsIgnorePattern: '^_',
+      },
+    ],
+    'metalab/typescript/no-use-before-define': 'error',
+    'metalab/typescript/no-var-requires': 'error',
+    'metalab/typescript/prefer-interface': 'error',
+    'metalab/typescript/prefer-namespace-keyword': 'error',
+    'metalab/typescript/type-annotation-spacing': 'error',
+  },
+};

test/smoke/typescript/a.tsx

@@ -0,0 +1,3 @@
+export const Test = (a: number): string => {
+  return (a + 5).toString();
+};

test/smoke/typescript/index.ts

@@ -0,0 +1 @@
+import {Test} from './a';

util/babel.js

@@ -17,6 +17,19 @@ exports.hasPrettier = function() {
   return false;
 };
 
+exports.hasTypescript = function() {
+  // Determine if we are using typescript or not.
+  try {
+    resolve.sync('typescript', {
+      basedir: basedir,
+    });
+    return true;
+  } catch (err) {
+    // If we can't load prettier then stop caring.
+  }
+  return false;
+};
+
 exports.hasBabel = function() {
   // Determine if we are using babel 7+ or not.
   try {
@@ -40,6 +53,7 @@ exports.hasBabel = function() {
 };
 
 exports.hasBabelResolver = function() {
+  var message;
   // Determine if we are using babel resolver or not.
   try {
     resolve.sync('babel-plugin-module-resolver', {
@@ -50,12 +64,13 @@ exports.hasBabelResolver = function() {
   } catch (err) {
     if (/SyntaxError/.test(err.toString())) {
       if (/v4/.test(process.version)) {
-        console.log( // eslint-disable-line no-console
-          chalk.red('error'),
+        message = [
           'babel-plugin-module-resolver does not work with node@4\n',
-          'See: ' +
-          'https://github.com/tleunen/babel-plugin-module-resolver/pull/222'
-        );
+          'See:',
+          'https://github.com/tleunen/babel-plugin-module-resolver/pull/222',
+        ].join(' ');
+        // eslint-disable-next-line no-console
+        console.log(chalk.red('error'), message);
         process.exit(1);
       }
     }