Add @typescript-eslint recommended rules that require type checking (#8)

.eslintrc.js

@@ -8,6 +8,7 @@ module.exports = {
   extends: [
     'eslint:recommended',
     'plugin:@typescript-eslint/recommended',
+    'plugin:@typescript-eslint/recommended-requiring-type-checking',
     'plugin:react/recommended',
     'prettier',
     'prettier/react',
@@ -22,7 +23,21 @@ module.exports = {
       jsx: true,
     },
     ecmaVersion: 2020,
+    // See: https://github.com/typescript-eslint/typescript-eslint/issues/1928#issuecomment-617969784
+    project: ['./tsconfig.eslint.json'],
     sourceType: 'module',
+    // `.eslintrc.js` needs to be a JavaScript file to access `__dirname` since we want linting to
+    // work if we run it from a different current working directory.
+    // See: https://github.com/typescript-eslint/typescript-eslint/issues/101#issuecomment-499303058
+    //
+    // However, that gives an error message because `__dirname` is defined within `@types/node` which
+    // we do not currently load. Therefore, we disable the following rule because the project is a
+    // mixture of browser-based and Node-based code, and the solutions to this are either overkill
+    // or unelegant (e.g. solution-style `tsconfig.json`s, or for linting only using overrides to enable
+    // TypeScript eslint rules only on TypeScript files).
+    // TODO: https://github.com/jpmorganchase/modular/issues/9
+    // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
+    tsconfigRootDir: __dirname,
   },
   plugins: ['@typescript-eslint', 'react'],
   rules: {},

tsconfig.eslint.json

@@ -0,0 +1,4 @@
+{
+  "extends": "./tsconfig.json",
+  "include": [".eslintrc.js", "**/*.ts", "**/*.tsx"]
+}