How can I validate an ejs template of a typescript file with typescript-eslint

Question

I have an ejs template for a typescript file, I need to write a Unit Test with #jest to validate the rendered typescript output of my template using #typescript-eslint (not tslint because it will be deprecated soon: https://medium.com/palantir/tslint-in-2019-1a144c2317a9)

So, I need to require the typescript-eslint module in my spec file and run the validation of my rendered ejs by code like:

it('should be valid typescript file', () => {
        return ejs.renderFile('my-ejs-template.ts.ejs', {}).then(async (view) => {
            const eslint = require('@typescript-eslint/eslint-plugin');
            // what is next ???
        });
    });

Any help will be very appreciated

Answer 1

First install the following modules in devDependencies:

• @typescript-eslint/eslint-plugin
• @typescript-eslint/parser

Second, import the module eslint in your spec file as follows:

const eslint = require('eslint');

Third, create an .eslintrc.js configuration file to parse typescript files, like:

module.exports = {
  env: {
    node: true,
    es6: true,
  },
  extends: ['plugin:@typescript-eslint/recommended'],
  parser: '@typescript-eslint/parser',
  parserOptions: {
    sourceType: 'module',
    typescript: true,
    modules: true,
    ecmaVersion: 6,
    ecmaFeatures: {
      experimentalObjectRestSpread: true,
    },
  },
  plugins: ['@typescript-eslint'],
  rules: {
    indent: ['error', 4],
    'linebreak-style': ['error', 'unix'],
    quotes: ['error', 'single'],
    semi: ['error', 'always'],
  },
};

Then, import the above config file in your spec file and create a function to get the linter:

const configTsEslint = require('.eslintrc-typescript');
const tsLinter = () => {
    const Linter = eslint.Linter;
    return new Linter();
};

Finally, validate your typescript file as follows:

it('should be valid typescript file', () => {
        return ejs.renderFile('my-ejs-template.ts.ejs', {}).then(async (view) => {
            const result = tsLinter().verifyAndFix(view);
            expect(result.messages).toStrictEqual([]);
            expect(result.fixed).toBe(true);
        });
    });

You can add rules that are supported by [typescript-eslint][1]