Only enable typescript when detected

lib/base-config.js

@@ -1,11 +1,8 @@
 'use strict';
 
-const path = require('path');
-
 const baseConfig = {
     extends: [
         'airbnb-base',
-        path.resolve(__dirname, 'typescript.js'),
         'plugin:node/recommended',
         'plugin:promise/recommended',
         'plugin:jest/recommended',

lib/eslint-config.js

@@ -2,17 +2,21 @@
 
 const path = require('path');
 const featuresEnabled = require('./utils/features-enabled');
+const eslintConfig = require('./base-config');
 
-let eslintConfig = null;
+function addPresetToExtends(pathname) {
+    const currentExtends = eslintConfig.extends;
+    const prettierLocation = currentExtends.indexOf('prettier');
 
-if (eslintConfig === null) {
-    eslintConfig = {
-        extends: [path.resolve(__dirname, 'base-config.js')],
-    };
+    currentExtends.splice(prettierLocation, 0, pathname);
+}
+
+if (featuresEnabled.typescript === true) {
+    addPresetToExtends(path.resolve(__dirname, 'typescript.js'));
+}
 
-    if (featuresEnabled.flow === true) {
-        eslintConfig.extends.push(path.resolve(__dirname, 'flow.js'));
-    }
+if (featuresEnabled.flow === true) {
+    addPresetToExtends(path.resolve(__dirname, 'flow.js'));
 }
 
 module.exports = eslintConfig;

lib/utils/features-enabled.js

@@ -1,9 +1,11 @@
 'use strict';
 
 const flowEnabled = require('./flow-enabled');
+const typescriptEnabled = require('./typescript-enabled');
 
 const featuresEnabled = {
     flow: flowEnabled,
+    typescript: typescriptEnabled,
 };
 
 module.exports = featuresEnabled;

lib/utils/typescript-enabled.js

@@ -0,0 +1,13 @@
+'use strict';
+
+const fs = require('fs');
+const path = require('path');
+
+const typescriptEnabled = (function checkForTypescript() {
+    const typescriptConfigFile = path.resolve(process.cwd(), 'tsconfig.json');
+    const typescriptExists = fs.existsSync(typescriptConfigFile);
+
+    return typescriptExists;
+})();
+
+module.exports = typescriptEnabled;

lib/utils/typescript-enabled.test.js

@@ -0,0 +1,34 @@
+'use strict';
+
+const { TempSandbox } = require('temp-sandbox');
+
+const sandbox = new TempSandbox();
+const cwd = process.cwd();
+
+beforeEach(() => {
+    process.chdir(sandbox.dir);
+    // Remove all files/directories inside sandbox
+    sandbox.cleanSync();
+});
+
+afterAll(() => {
+    // delete sandbox and sandbox instance
+    sandbox.destroySandboxSync();
+    process.chdir(cwd);
+});
+
+describe('detectTypescript', () => {
+    test('detects typescript with tsconfig.json', () => {
+        sandbox.createFileSync('tsconfig.json');
+
+        const typescriptEnabled = require('./typescript-enabled');
+
+        expect(typescriptEnabled).toEqual(true);
+    });
+
+    test('no tsconfig.json found', () => {
+        const typescriptEnabled = require('./typescript-enabled');
+
+        expect(typescriptEnabled).toEqual(false);
+    });
+});