Implement eslint-plugin-import (#1)

This is the first draft of @xpring-eng/eslint-config-base.

I'm tired of porting over the same ESLint configuration every time we spin up a new repo, and it's hard to keep the configuration in sync across so many different repos. A good lint configuration can help us write better TypeScript by avoiding code smells.

Airbnb has the eslint-config-airbnb, and this repo implements the start of a @xpring-eng/eslint-config-base that can be used by all our TS projects. Then we can publish our ESLint configuration and import it across our repos.

This will give us a single source of truth for lint configuration, and will ensure consistency across all our repos.

I'm demoing this locally with the payid repo, and once I put all our shared ESLint config in here, I'll publish this to npm and we can start actually using it.

.eslintrc.js

@@ -0,0 +1,11 @@
+// This is the ESLint file for _this_ package
+// We don't need all the rules that
+
+module.exports = {
+  extends: './index.js',
+  rules: {
+    'import/unambiguous': 'off',
+    'import/no-commonjs': 'off',
+    'import/no-unused-modules': 'off',
+  },
+}

index.js

@@ -1,9 +1,17 @@
 module.exports = {
-  globals: {
-    MyGlobal: true,
+  parserOptions: {
+    sourceType: 'module', // Allow the use of imports / ES modules
+    ecmaFeatures: {
+      impliedStrict: true, // Enable global strict mode
+    },
   },
 
-  rules: {
-    semi: [2, 'always'],
+  // Specify global variables that are predefined
+  env: {
+    node: true, // Enable node global variables & Node.js scoping
+    es2020: true, // Add all ECMAScript 2020 globals and automatically set the ecmaVersion parser option to ES2020
   },
+
+  extends: ['./rules/imports'].map(require.resolve),
+  rules: {},
 }

rules/imports.js

@@ -0,0 +1,219 @@
+module.exports = {
+  env: {
+    node: true, // Enable node global variables & Node.js scoping
+    es2020: true, // Add all ECMAScript 2020 globals and automatically set the ecmaVersion parser option to ES2020
+  },
+  parserOptions: {
+    sourceType: 'module',
+  },
+
+  plugins: ['import'],
+  extends: [
+    'plugin:import/warnings',
+    'plugin:import/errors',
+    'plugin:import/typescript',
+  ],
+
+  // These rules are not captured in the standard warnings/errors/typescript configurations we extend above.
+  rules: {
+    /* STATIC ANALYSIS */
+    // Forbid import of modules using absolute paths
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-absolute-path.md
+    'import/no-absolute-path': 'error',
+
+    // Forbid require() calls with expressions
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-dynamic-require.md
+    'import/no-dynamic-require': 'error',
+
+    // Forbid Webpack loader syntax in imports
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-webpack-loader-syntax.md
+    'import/no-webpack-loader-syntax': 'error',
+
+    // Forbid a module from importing itself
+    // https://github.com/benmosher/eslint-plugin-import/blob/44a038c06487964394b1e15b64f3bd34e5d40cde/docs/rules/no-self-import.md
+    'import/no-self-import': 'error',
+
+    // Forbid cyclical dependencies between modules
+    // https://github.com/benmosher/eslint-plugin-import/blob/d81f48a2506182738409805f5272eff4d77c9348/docs/rules/no-cycle.md
+    'import/no-cycle': 'error',
+
+    // Ensures that there are no useless path segments
+    // https://github.com/benmosher/eslint-plugin-import/blob/ebafcbf59ec9f653b2ac2a0156ca3bcba0a7cf57/docs/rules/no-useless-path-segments.md
+    'import/no-useless-path-segments': 'error',
+
+    // Reports modules without any exports, or with unused exports
+    // https://github.com/benmosher/eslint-plugin-import/blob/f63dd261809de6883b13b6b5b960e6d7f42a7813/docs/rules/no-unused-modules.md
+    'import/no-unused-modules': [
+      'error',
+      {
+        // TODO: I would like to enable missingExports, but it doesn't work for files that only export types:
+        // https://github.com/benmosher/eslint-plugin-import/issues/1680
+        missingExports: false,
+        unusedExports: true,
+      },
+    ],
+
+
+
+    /* HELPFUL WARNINGS */
+    // disallow use of jsdoc-marked-deprecated imports
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-deprecated.md
+    'import/no-deprecated': 'warn',
+
+    // Forbid the use of extraneous packages
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-extraneous-dependencies.md
+    'import/no-extraneous-dependencies': 'error',
+
+    // Forbid mutable exports
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-mutable-exports.md
+    'import/no-mutable-exports': 'error',
+
+    /* MODULE SYSTEMS */
+    // Warn if a module could be mistakenly parsed as a script by a consumer leveraging Unambiguous JavaScript Grammar
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/unambiguous.md
+    'import/unambiguous': 'error',
+
+    // disallow require()
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-commonjs.md
+    'import/no-commonjs': 'error',
+
+    // disallow AMD require/define
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-amd.md
+    'import/no-amd': 'error',
+
+
+
+    /* STYLE GUIDE */
+    // disallow non-import statements appearing before import statements
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/first.md
+    'import/first': 'error',
+
+    // Ensure consistent use of file extension within the import path
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/extensions.md
+    'import/extensions': [
+      'error',
+      'ignorePackages',
+      {
+        js: 'never',
+        mjs: 'never',
+        jsx: 'never',
+        ts: 'never',
+        tsx: 'never',
+      },
+    ],
+
+    // ensure absolute imports are above relative imports and that unassigned imports are ignored
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/order.md
+    'import/order': [
+      'error',
+      {
+        groups: [
+          'builtin',
+          'external',
+          'internal',
+          'parent',
+          'sibling',
+          'index',
+        ],
+        'newlines-between': 'always',
+        alphabetize: { order: 'asc', caseInsensitive: true },
+      },
+    ],
+
+    // Require newlines after the last import/require in a group
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/newline-after-import.md
+    'import/newline-after-import': ['error', { count: 1 }],
+
+    // Require modules with a single export to use a default export
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/prefer-default-export.md
+    'import/prefer-default-export': 'error',
+
+    // Warn when modules have too many dependencies (code smell)
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/max-dependencies.md
+    'import/max-dependencies': ['warn', { max: 5 }],
+
+    // Prevent unassigned imports
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-unassigned-import.md
+    // importing for side effects is perfectly acceptable, if you need side effects.
+    'import/no-unassigned-import': 'warn',
+
+    // Prevent importing the default as if it were named
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-named-default.md
+    'import/no-named-default': 'error',
+
+    // Reports if a module's default export is unnamed
+    // https://github.com/benmosher/eslint-plugin-import/blob/d9b712ac7fd1fddc391f7b234827925c160d956f/docs/rules/no-anonymous-default-export.md
+    'import/no-anonymous-default-export': 'error',
+
+    // Reports when named exports are not grouped together in a single export declaration
+    // or when multiple assignments to CommonJS module.exports or exports object are present
+    // in a single file.
+    // https://github.com/benmosher/eslint-plugin-import/blob/44a038c06487964394b1e15b64f3bd34e5d40cde/docs/rules/group-exports.md
+    // TODO: Make this an error once we migrate our code
+    'import/group-exports': 'warn',
+
+    // dynamic imports require a leading comment with a webpackChunkName
+    // https://github.com/benmosher/eslint-plugin-import/blob/ebafcbf59ec9f653b2ac2a0156ca3bcba0a7cf57/docs/rules/dynamic-import-chunkname.md
+    'import/dynamic-import-chunkname': 'warn',
+
+
+
+    /* DISABLED RULES */
+    // Enforces that all exports are declared at the bottom of the file
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/exports-last.md
+    'import/exports-last': 'off',
+
+    // Prohibit default exports. Mostly an inverse of prefer-default-export.
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-default-export.md
+    'import/no-default-export': 'off',
+
+    // Note: This is a TERRIBLE rule.
+    // Prohibit named exports. Mostly an inverse of no-default-export.
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-named-export.md
+    'import/no-named-export': 'off',
+
+    // Note: This is a TERRIBLE rule.
+    // Use this rule to prevent importing the submodules of other modules.
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-internal-modules.md
+    'import/no-internal-modules': 'off',
+
+    // Note: Decent rule, but some JS libraries require using a wildcard import.
+    // Enforce a convention of not using namespace (a.k.a. "wildcard" *) imports.
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-namespace.md
+    'import/no-namespace': 'off',
+
+    // Forbid the use of Node.js builtin modules. Can be useful for client-side web projects that do not have access to those modules.
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-nodejs-modules.md
+    'import/no-nodejs-modules': 'off',
+
+    // Use this rule to prevent imports to folders in relative parent paths.
+    // This rule is useful for enforcing tree-like folder structures instead of complex graph-like folder structures.
+    // While this restriction might be a departure from Node's default resolution style, it can lead large, complex codebases to be easier to maintain.
+    // If you've ever had debates over "where to put files" this rule is for you.
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-relative-parent-imports.md
+    // TODO: Enable this rule later to `warn`?
+    'import/no-relative-parent-imports': 'off',
+
+    // Some projects contain files which are not always meant to be executed in the same environment.
+    // For example consider a web application that contains specific code for the server and some specific code for the browser/client.
+    // In this case you don’t want to import server-only files in your client code.
+    // In order to prevent such scenarios this rule allows you to define restricted zones where you can forbid files from imported if they match a specific path.
+    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/no-restricted-paths.md
+    'import/no-restricted-paths': 'off',
+  },
+
+  overrides: [
+    {
+      files: ['test/**/*.test.ts'],
+      rules: {
+        // Our Mocha test files never export anything.
+        'import/no-unused-modules': 'off',
+        // Importing mocha is a side-effecting import
+        'import/no-unassigned-import': ['error', { allow: ['mocha'] }],
+        // Warn when modules have too many dependencies (code smell)
+        // Increased the max for test files, since tests usually need to import more things
+        'import/max-dependencies': ['warn', { max: 8 }],
+      },
+    },
+  ],
+}