Prevent committing tests with .only. (#1883)

Adds an eslint rule for mocha tests and suites marked with .only,
including a version for our tests/suites wrapped with tag functionality.

Adds eslint in to the precommit hook in addition to running the
formatter.

Author: plemarquand

.eslintrc.json

@@ -6,14 +6,22 @@
     "sourceType": "module",
     "project": true
   },
-  "plugins": ["@typescript-eslint"],
+  "plugins": ["@typescript-eslint", "mocha"],
   "rules": {
     "curly": "error",
     "eqeqeq": "warn",
     "no-throw-literal": "warn",
     // TODO "@typescript-eslint/semi" rule moved to https://eslint.style
     "semi": "error",
     "no-console": "warn",
+    "mocha/no-exclusive-tests": "error",
+    "no-restricted-syntax": [
+      "error",
+      {
+        "selector": "CallExpression[callee.object.object.callee.name='tag'][callee.property.name='only']",
+        "message": "Unexpected exclusive mocha test with tag().suite.only() or tag().test.only()"
+      }
+    ],
     "@typescript-eslint/no-floating-promises": ["warn", { "checkThenables": true }],
     "@typescript-eslint/await-thenable": "warn",
     // Mostly fails tests, ex. expect(...).to.be.true returns a Chai.Assertion

package-lock.json

@@ -2009,6 +2009,10 @@
     "prepare": "husky"
   },
   "lint-staged": {
+    "**/*.ts": [
+      "eslint --max-warnings=0",
+      "prettier --write"
+    ],
     "**/*": "prettier --write --ignore-unknown"
   },
   "devDependencies": {
@@ -2051,6 +2055,7 @@
     "esbuild": "^0.25.10",
     "eslint": "^8.57.0",
     "eslint-config-prettier": "^10.1.8",
+    "eslint-plugin-mocha": "^10.5.0",
     "fantasticon": "^1.2.3",
     "husky": "^9.1.7",
     "lint-staged": "^16.2.3",

package.json

@@ -144,11 +144,13 @@ export function tag(size: TestSize): MochaFunctions {
     };
     wrappedSuite.only = (title: string, fn?: (this: Suite) => void): Suite => {
         if (fn) {
+            // eslint-disable-next-line mocha/no-exclusive-tests
             return suite.only(title, function () {
                 applyTags(this);
                 fn.call(this);
             });
         }
+        // eslint-disable-next-line mocha/no-exclusive-tests
         return suite.only(title);
     };
     wrappedSuite.skip = (title: string, fn: (this: Suite) => void): Suite | void => {
@@ -164,6 +166,7 @@ export function tag(size: TestSize): MochaFunctions {
     };
     wrappedTest.only = (titleOrFn: string | AsyncFunc | Func, fn?: AsyncFunc | Func): Test => {
         return applyTags(
+            // eslint-disable-next-line mocha/no-exclusive-tests
             typeof titleOrFn === "string" ? test.only(titleOrFn, fn) : test.only(titleOrFn)
         );
     };