From c40344566eff2e77a6ae2b2d2dbdbd4ad3e76b67 Mon Sep 17 00:00:00 2001
From: Merlin Mason <merlin@thanksbox.co>
Date: Wed, 16 Jan 2019 17:53:57 +0000
Subject: [PATCH] Fix: warn constant on RHS of || in no-constant-condition
 (fixes #11181) (#11253)

* Fix: handling of string literals on the right side of logical OR (fixes #11181)

* Fix: handling of string literals on the right side of logical OR (fixes #11181)
---
 lib/rules/no-constant-condition.js       |  5 ++++-
 tests/lib/rules/no-constant-condition.js | 12 ++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/lib/rules/no-constant-condition.js b/lib/rules/no-constant-condition.js
index 8d7934d8a59..39c2928eed3 100644
--- a/lib/rules/no-constant-condition.js
+++ b/lib/rules/no-constant-condition.js
@@ -109,7 +109,10 @@ module.exports = {
                     const isLeftShortCircuit = (isLeftConstant && isLogicalIdentity(node.left, node.operator));
                     const isRightShortCircuit = (isRightConstant && isLogicalIdentity(node.right, node.operator));
 
-                    return (isLeftConstant && isRightConstant) || isLeftShortCircuit || isRightShortCircuit;
+                    return (isLeftConstant && isRightConstant) ||
+                        (node.operator === "||" && isRightConstant && node.right.value) || // in the case of an "OR", we need to know if the right constant value is truthy
+                        isLeftShortCircuit ||
+                        isRightShortCircuit;
                 }
 
                 case "AssignmentExpression":
diff --git a/tests/lib/rules/no-constant-condition.js b/tests/lib/rules/no-constant-condition.js
index 69a90dd381a..c89f9080d6e 100644
--- a/tests/lib/rules/no-constant-condition.js
+++ b/tests/lib/rules/no-constant-condition.js
@@ -55,6 +55,12 @@ ruleTester.run("no-constant-condition", rule, {
         "if(true && abc==='str' || def ==='str'){}",
         "if(true && typeof abc==='string'){}",
 
+        // #11181, string literals
+        "if('str' || a){}",
+        "if('str1' && a){}",
+        "if(a && 'str'){}",
+        "if('str' || abc==='str'){}",
+
         // { checkLoops: false }
         { code: "while(true);", options: [{ checkLoops: false }] },
         { code: "for(;true;);", options: [{ checkLoops: false }] },
@@ -116,6 +122,12 @@ ruleTester.run("no-constant-condition", rule, {
         { code: "if(false || true){}", errors: [{ messageId: "unexpected", type: "LogicalExpression" }] },
         { code: "if(typeof abc==='str' || true){}", errors: [{ messageId: "unexpected", type: "LogicalExpression" }] },
 
+        // #11181, string literals
+        { code: "if('str1' || 'str2'){}", errors: [{ messageId: "unexpected", type: "LogicalExpression" }] },
+        { code: "if('str1' && 'str2'){}", errors: [{ messageId: "unexpected", type: "LogicalExpression" }] },
+        { code: "if(abc==='str' || 'str'){}", errors: [{ messageId: "unexpected", type: "LogicalExpression" }] },
+        { code: "if(a || 'str'){}", errors: [{ messageId: "unexpected", type: "LogicalExpression" }] },
+
         {
             code: "function* foo(){while(true){} yield 'foo';}",
             errors: [{ messageId: "unexpected", type: "Literal" }]