feat: add @typescript-eslint/no-unnecessary-condition

BREAKING CHANGE: New rule introduced

.eslintrc.json

@@ -129,7 +129,6 @@
     "no-var": "error",
     "no-void": ["error", { "allowAsStatement": true }],
     "no-with": "error",
-    "no-return-await": "error",
     "object-shorthand": ["error", "properties"],
     "one-var": ["error", { "initialized": "never" }],
     "prefer-const": ["error", { "destructuring": "all" }],
@@ -229,6 +228,12 @@
         "no-useless-constructor": "off",
         "@typescript-eslint/no-useless-constructor": "error",
         "@typescript-eslint/no-unnecessary-template-expression": "error",
+        "@typescript-eslint/no-unnecessary-condition": [
+          "error",
+          {
+            "allowConstantLoopConditions": true
+          }
+        ],
 
         "@typescript-eslint/adjacent-overload-signatures": "error",
         "@typescript-eslint/array-type": [
@@ -253,6 +258,7 @@
           }
         ],
         "@typescript-eslint/method-signature-style": "error",
+        "@typescript-eslint/unbound-method": "error",
         "@typescript-eslint/naming-convention": [
           "error",
           {
@@ -263,8 +269,10 @@
           }
         ],
         "@typescript-eslint/no-base-to-string": "error",
+        "@typescript-eslint/no-deprecated": "error",
         "@typescript-eslint/no-dynamic-delete": "error",
         "@typescript-eslint/no-extra-non-null-assertion": "error",
+        "@typescript-eslint/no-redundant-type-constituents": "error",
         "@typescript-eslint/no-extraneous-class": [
           "error",
           { "allowWithDecorator": true }
@@ -283,6 +291,7 @@
         "@typescript-eslint/no-unnecessary-type-assertion": "error",
         "@typescript-eslint/no-require-imports": "error",
         "@typescript-eslint/no-unsafe-unary-minus": "error",
+        "@typescript-eslint/no-unsafe-declaration-merging": "error",
         "@typescript-eslint/no-array-delete": "error",
         "@typescript-eslint/prefer-as-const": "error",
         "@typescript-eslint/prefer-function-type": "error",
@@ -314,8 +323,6 @@
           "error",
           { "allowNumber": true }
         ],
-        "no-return-await": "off",
-        "@typescript-eslint/return-await": "error",
         "@typescript-eslint/strict-boolean-expressions": [
           "error",
           {

README.md

@@ -56,8 +56,8 @@ If you want to use **TypeScript**, you also need to install:
 ```sh
 npm install --save-dev \
   "typescript@^5.6.2" \
-  "@typescript-eslint/eslint-plugin@^8.0.0" \
-  "@typescript-eslint/parser@^8.0.0"
+  "@typescript-eslint/eslint-plugin@^8.3.0" \
+  "@typescript-eslint/parser@^8.3.0"
 ```
 
 Dependencies are:

eslintrc.json

@@ -1,6 +1,6 @@
 {
   "extends": "./index.js",
   "parserOptions": {
-    "project": "./tsconfig.json"
+    "projectService": true
   }
 }

test/validate-config.js

@@ -16,8 +16,31 @@ test("ensure we validate correctly JavaScript files", async () => {
   const [withErrors] = await eslint.lintFiles(
     "test/fixtures/javascript-with-errors.js",
   )
-  assert.strictEqual(noErrors?.errorCount, 0)
-  assert.strictEqual(withErrors?.errorCount, 3)
+  assert.strictEqual(noErrors?.errorCount, 0, JSON.stringify(noErrors, null, 2))
+  assert.strictEqual(
+    withErrors?.errorCount,
+    3,
+    JSON.stringify(withErrors, null, 2),
+  )
+})
+
+test("ensure we do not use deprecated rules", async () => {
+  const [javascriptLintResult] = await eslint.lintFiles(
+    "test/fixtures/javascript-no-errors.js",
+  )
+  const [typescriptLintResult] = await eslint.lintFiles(
+    "test/fixtures/typescript-no-errors.ts",
+  )
+  assert.strictEqual(
+    javascriptLintResult.usedDeprecatedRules.length,
+    0,
+    JSON.stringify(javascriptLintResult, null, 2),
+  )
+  assert.strictEqual(
+    typescriptLintResult.usedDeprecatedRules.length,
+    0,
+    JSON.stringify(typescriptLintResult, null, 2),
+  )
 })
 
 test("ensure we validate correctly TypeScript files", async () => {
@@ -27,20 +50,32 @@ test("ensure we validate correctly TypeScript files", async () => {
   const [withErrors] = await eslint.lintFiles(
     "test/fixtures/javascript-with-errors.js",
   )
-  assert.strictEqual(noErrors?.errorCount, 0)
-  assert.strictEqual(withErrors?.errorCount, 3)
+  assert.strictEqual(noErrors?.errorCount, 0, JSON.stringify(noErrors, null, 2))
+  assert.strictEqual(
+    withErrors?.errorCount,
+    3,
+    JSON.stringify(withErrors, null, 2),
+  )
 })
 
 test("ensure we allow top-level await", async () => {
   const [lintResult] = await eslint.lintFiles(
     "test/fixtures/top-level-await.mjs",
   )
-  assert.strictEqual(lintResult?.errorCount, 0)
+  assert.strictEqual(
+    lintResult?.errorCount,
+    0,
+    JSON.stringify(lintResult, null, 2),
+  )
 })
 
 test("ensure we allow to ignore floating promise with void operator (@typescript-eslint/no-floating-promises)", async () => {
   const [lintResult] = await eslint.lintFiles(
     "test/fixtures/typescript-no-errors-ignore-promise.ts",
   )
-  assert.strictEqual(lintResult?.errorCount, 0)
+  assert.strictEqual(
+    lintResult?.errorCount,
+    0,
+    JSON.stringify(lintResult, null, 2),
+  )
 })