✨ add typescript rules

Author: dudeofawesome

eslint-config-typescript/base.yaml

@@ -1,14 +1,55 @@
 extends:
-  - 'plugin:@typescript-eslint/strict'
-  # - 'plugin:@shopify/typescript'
+  - 'plugin:@typescript-eslint/strict-type-checked'
+  - 'plugin:@typescript-eslint/stylistic-type-checked'
   - 'plugin:import/typescript'
 
 parserOptions:
   project: true
-
 rules:
+  # allow specifying a type that could be inferred
   '@typescript-eslint/no-inferrable-types': 'off'
+
+  # prevent unused vars
   '@typescript-eslint/no-unused-vars':
     ['warn', { args: 'none', destructuredArrayIgnorePattern: '^_' }]
-  '@typescript-eslint/naming-convention': 'off'
-  '@shopify/binary-assignment-parens': 'off'
+
+  # ensure only boolean types are used for conditions
+  '@typescript-eslint/strict-boolean-expressions':
+    - 'error'
+    - allowString: false
+      allowNumber: false
+      allowNullableObject: false
+
+  # ensure switches on union types handle all cases
+  '@typescript-eslint/switch-exhaustiveness-check': 'error'
+
+  # ensure any constant numbers are properly named to increase readability
+  '@typescript-eslint/no-magic-numbers':
+    - 'error'
+    - enforceConst: true
+      ignoreArrayIndexes: true
+      ignoreDefaultValues: true
+      ignoreClassFieldInitialValues: true
+
+      ignoreEnums: true
+      ignoreNumericLiteralTypes: true
+      ignoreReadonlyClassProperties: true
+      ignoreTypeIndexes: true
+  no-magic-numbers: 'off'
+
+  # TODO: do we want this?
+  # require enum values to be initialized in order to prevent value shifting
+  '@typescript-eslint/prefer-enum-initializers': 'error'
+
+  # allow use of both `type` and `interface`
+  '@typescript-eslint/consistent-type-definitions': 'off'
+
+  # ensure private members are marked readonly when possible
+  '@typescript-eslint/prefer-readonly': 'error'
+
+  # allow `indexOf()`
+  '@typescript-eslint/prefer-includes': 'off'
+
+  # typescript handles these rules for us
+  consistent-return: 'off'
+  no-invalid-this: 'off'

eslint-config-typescript/package.json

@@ -20,8 +20,9 @@
     "test": "node --require ts-node/register --test test/index.ts"
   },
   "dependencies": {
-    "@typescript-eslint/eslint-plugin": "^5.30.7",
-    "@typescript-eslint/parser": "^5.30.7"
+    "@typescript-eslint/eslint-plugin": "^6.7.3",
+    "@typescript-eslint/parser": "^6.7.3",
+    "eslint-plugin-import": "^2.28.1"
   },
   "peerDependencies": {
     "@dudeofawesome/eslint-config": "^1.3.0",

eslint-config-typescript/test/index.ts

@@ -23,8 +23,12 @@ describe('eslint-config-typescript', () => {
     it(`should fail radix`, async () =>
       testRuleFail(linter, `parseInt('10');\n`, 'radix', true));
 
-    // TODO: test for shopify rule
-
-    // TODO: test for prettier rule
+    it(`should fail @typescript-eslint/strict-boolean-expressions`, async () =>
+      testRuleFail(
+        linter,
+        `let foo: unknown = 'foo';\nfoo = 'bar';\nif (foo) Number();\n`,
+        '@typescript-eslint/strict-boolean-expressions',
+        true,
+      ));
   });
 });

eslint-config/rules/readability.yaml

@@ -3,7 +3,12 @@ rules:
   no-lonely-if: 'error'
 
   # ensure any constant numbers are properly named to increase readability
-  no-magic-numbers: 'error'
+  no-magic-numbers:
+    - 'error'
+    - enforceConst: true
+      ignoreArrayIndexes: true
+      ignoreDefaultValues: true
+      ignoreClassFieldInitialValues: true
 
   # don't allow multiple variable creation with single keyword
   one-var: ['error', 'never']

utils/testing/eslint.ts

@@ -9,7 +9,15 @@ export function filePath(typescript: boolean = false): string {
 export function defaultTestSet(linter: ESLint) {
   describe('[standard tests] passes', () => {
     it(`should parse javascript`, () =>
-      testNoFail(linter, `((a) => a.split(''))()\n`));
+      testNoFail(
+        linter,
+        `
+(
+  /** @param {string} a */
+  (a) => a.split('')
+)('test');
+`,
+      ));
 
     it(`should allow nested ternaries`, () =>
       testNoFail(