From 301d0c05229dbd6cfb1045d716524e8ec46fa2c1 Mon Sep 17 00:00:00 2001
From: Milos Djermanovic <milos.djermanovic@gmail.com>
Date: Fri, 18 Dec 2020 19:07:34 +0100
Subject: [PATCH] Fix: no-constant-condition false positives with unary
 expressions (#13927)

---
 lib/rules/no-constant-condition.js       | 12 +++++++++---
 tests/lib/rules/no-constant-condition.js | 13 +++++++++++++
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/lib/rules/no-constant-condition.js b/lib/rules/no-constant-condition.js
index 790d5ea8811..7d324634244 100644
--- a/lib/rules/no-constant-condition.js
+++ b/lib/rules/no-constant-condition.js
@@ -147,12 +147,18 @@ module.exports = {
                 }
 
                 case "UnaryExpression":
-                    if (node.operator === "void") {
+                    if (
+                        node.operator === "void" ||
+                        node.operator === "typeof" && inBooleanPosition
+                    ) {
                         return true;
                     }
 
-                    return (node.operator === "typeof" && inBooleanPosition) ||
-                        isConstant(node.argument, true);
+                    if (node.operator === "!") {
+                        return isConstant(node.argument, true);
+                    }
+
+                    return isConstant(node.argument, false);
 
                 case "BinaryExpression":
                     return isConstant(node.left, false) &&
diff --git a/tests/lib/rules/no-constant-condition.js b/tests/lib/rules/no-constant-condition.js
index b83b337a65f..565a8a53dd6 100644
--- a/tests/lib/rules/no-constant-condition.js
+++ b/tests/lib/rules/no-constant-condition.js
@@ -32,6 +32,10 @@ ruleTester.run("no-constant-condition", rule, {
         "if (`foo${a}` === 'fooa');",
         "if (tag`a`);",
         "if (tag`${a}`);",
+        "if (+(a || true));",
+        "if (-(a || true));",
+        "if (~(a || 1));",
+        "if (+(a && 0) === +(b && 0));",
         "while(~!a);",
         "while(a = b);",
         "while(`${a}`);",
@@ -162,6 +166,15 @@ ruleTester.run("no-constant-condition", rule, {
         { code: "if(`foo${0 || 1}`);", errors: [{ messageId: "unexpected", type: "TemplateLiteral" }] },
         { code: "if(`foo${bar}`);", errors: [{ messageId: "unexpected", type: "TemplateLiteral" }] },
         { code: "if(`${bar}foo`);", errors: [{ messageId: "unexpected", type: "TemplateLiteral" }] },
+        { code: "if(!(true || a));", errors: [{ messageId: "unexpected", type: "UnaryExpression" }] },
+        { code: "if(!(a && void b && c));", errors: [{ messageId: "unexpected", type: "UnaryExpression" }] },
+        { code: "if(0 || !(a && null));", errors: [{ messageId: "unexpected", type: "LogicalExpression" }] },
+        { code: "if(1 + !(a || true));", errors: [{ messageId: "unexpected", type: "BinaryExpression" }] },
+        { code: "if(!(null && a) > 1);", errors: [{ messageId: "unexpected", type: "BinaryExpression" }] },
+        { code: "if(+(!(a && 0)));", errors: [{ messageId: "unexpected", type: "UnaryExpression" }] },
+        { code: "if(!typeof a === 'string');", errors: [{ messageId: "unexpected", type: "BinaryExpression" }] },
+        { code: "if(-('foo' || a));", errors: [{ messageId: "unexpected", type: "UnaryExpression" }] },
+        { code: "if(+(void a && b) === ~(1 || c));", errors: [{ messageId: "unexpected", type: "BinaryExpression" }] },
 
 
         { code: "while([]);", errors: [{ messageId: "unexpected", type: "ArrayExpression" }] },