feat: Treat Class/New Expressions as truthy in no-constant-condition (#…

…15326)
eslint · Dec 2, 2021 · d041f34 · d041f34
1 parent aeac3b3
commit d041f34
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Showing 3 changed files with 24 additions and 3 deletions.
diff --git a/docs/rules/no-constant-condition.md b/docs/rules/no-constant-condition.md
@@ -32,6 +32,14 @@ if (x &&= false) {
     doSomethingNever();
 }
 
+if (class {}) {
+    doSomethingAlways();
+}
+
+if (new Boolean(x)) {
+    doSomethingAlways();
+}
+
 if (x ||= true) {
     doSomethingAlways();
 }

diff --git a/lib/rules/no-constant-condition.js b/lib/rules/no-constant-condition.js
@@ -139,6 +139,7 @@ module.exports = {
                 case "ArrowFunctionExpression":
                 case "FunctionExpression":
                 case "ObjectExpression":
+                case "ClassExpression":
                     return true;
                 case "TemplateLiteral":
                     return (inBooleanPosition && node.quasis.some(quasi => quasi.value.cooked.length)) ||
@@ -180,7 +181,8 @@ module.exports = {
                         isLeftShortCircuit ||
                         isRightShortCircuit;
                 }
-
+                case "NewExpression":
+                    return inBooleanPosition;
                 case "AssignmentExpression":
                     if (node.operator === "=") {
                         return isConstant(node.right, inBooleanPosition);

diff --git a/tests/lib/rules/no-constant-condition.js b/tests/lib/rules/no-constant-condition.js
@@ -174,7 +174,8 @@ ruleTester.run("no-constant-condition", rule, {
         "function* foo() {for (; ; yield) {}}",
         "function* foo() {while (true) {function* foo() {yield;}yield;}}",
         "function* foo() { for (let x = yield; x < 10; x++) {yield;}yield;}",
-        "function* foo() { for (let x = yield; ; x++) { yield; }}"
+        "function* foo() { for (let x = yield; ; x++) { yield; }}",
+        "if (new Number(x) + 1 === 2) {}"
     ],
     invalid: [
         { code: "for(;true;);", errors: [{ messageId: "unexpected", type: "Literal" }] },
@@ -387,6 +388,16 @@ ruleTester.run("no-constant-condition", rule, {
         { code: "if(0b1n);", parserOptions: { ecmaVersion: 11 }, errors: [{ messageId: "unexpected", type: "Literal" }] },
         { code: "if(0o1n);", parserOptions: { ecmaVersion: 11 }, errors: [{ messageId: "unexpected", type: "Literal" }] },
         { code: "if(0x1n);", parserOptions: { ecmaVersion: 11 }, errors: [{ messageId: "unexpected", type: "Literal" }] },
-        { code: "if(0x1n || foo);", parserOptions: { ecmaVersion: 11 }, errors: [{ messageId: "unexpected", type: "LogicalExpression" }] }
+        { code: "if(0x1n || foo);", parserOptions: { ecmaVersion: 11 }, errors: [{ messageId: "unexpected", type: "LogicalExpression" }] },
+
+        // Classes and instances are always truthy
+        { code: "if(class {}) {}", errors: [{ messageId: "unexpected" }] },
+        { code: "if(new Foo()) {}", errors: [{ messageId: "unexpected" }] },
+
+        // Boxed primitives are always truthy
+        { code: "if(new Boolean(foo)) {}", errors: [{ messageId: "unexpected" }] },
+        { code: "if(new String(foo)) {}", errors: [{ messageId: "unexpected" }] },
+        { code: "if(new Number(foo)) {}", errors: [{ messageId: "unexpected" }] }
+
     ]
 });