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diff --git a/tools/node_modules/eslint/lib/rules/no-cond-assign.js b/tools/node_modules/eslint/lib/rules/no-cond-assign.js
new file mode 100644
index 0000000000..7c031c13f0
--- /dev/null
+++ b/tools/node_modules/eslint/lib/rules/no-cond-assign.js
@@ -0,0 +1,139 @@
+/**
+ * @fileoverview Rule to flag assignment in a conditional statement's test expression
+ * @author Stephen Murray <spmurrayzzz>
+ */
+"use strict";
+
+const astUtils = require("../ast-utils");
+
+const NODE_DESCRIPTIONS = {
+    DoWhileStatement: "a 'do...while' statement",
+    ForStatement: "a 'for' statement",
+    IfStatement: "an 'if' statement",
+    WhileStatement: "a 'while' statement"
+};
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+    meta: {
+        docs: {
+            description: "disallow assignment operators in conditional expressions",
+            category: "Possible Errors",
+            recommended: true
+        },
+
+        schema: [
+            {
+                enum: ["except-parens", "always"]
+            }
+        ]
+    },
+
+    create(context) {
+
+        const prohibitAssign = (context.options[0] || "except-parens");
+
+        const sourceCode = context.getSourceCode();
+
+        /**
+         * Check whether an AST node is the test expression for a conditional statement.
+         * @param {!Object} node The node to test.
+         * @returns {boolean} `true` if the node is the text expression for a conditional statement; otherwise, `false`.
+         */
+        function isConditionalTestExpression(node) {
+            return node.parent &&
+                node.parent.test &&
+                node === node.parent.test;
+        }
+
+        /**
+         * Given an AST node, perform a bottom-up search for the first ancestor that represents a conditional statement.
+         * @param {!Object} node The node to use at the start of the search.
+         * @returns {?Object} The closest ancestor node that represents a conditional statement.
+         */
+        function findConditionalAncestor(node) {
+            let currentAncestor = node;
+
+            do {
+                if (isConditionalTestExpression(currentAncestor)) {
+                    return currentAncestor.parent;
+                }
+            } while ((currentAncestor = currentAncestor.parent) && !astUtils.isFunction(currentAncestor));
+
+            return null;
+        }
+
+        /**
+         * Check whether the code represented by an AST node is enclosed in two sets of parentheses.
+         * @param {!Object} node The node to test.
+         * @returns {boolean} `true` if the code is enclosed in two sets of parentheses; otherwise, `false`.
+         */
+        function isParenthesisedTwice(node) {
+            const previousToken = sourceCode.getTokenBefore(node, 1),
+                nextToken = sourceCode.getTokenAfter(node, 1);
+
+            return astUtils.isParenthesised(sourceCode, node) &&
+                astUtils.isOpeningParenToken(previousToken) && previousToken.range[1] <= node.range[0] &&
+                astUtils.isClosingParenToken(nextToken) && nextToken.range[0] >= node.range[1];
+        }
+
+        /**
+         * Check a conditional statement's test expression for top-level assignments that are not enclosed in parentheses.
+         * @param {!Object} node The node for the conditional statement.
+         * @returns {void}
+         */
+        function testForAssign(node) {
+            if (node.test &&
+                (node.test.type === "AssignmentExpression") &&
+                (node.type === "ForStatement"
+                    ? !astUtils.isParenthesised(sourceCode, node.test)
+                    : !isParenthesisedTwice(node.test)
+                )
+            ) {
+
+                // must match JSHint's error message
+                context.report({
+                    node,
+                    loc: node.test.loc.start,
+                    message: "Expected a conditional expression and instead saw an assignment."
+                });
+            }
+        }
+
+        /**
+         * Check whether an assignment expression is descended from a conditional statement's test expression.
+         * @param {!Object} node The node for the assignment expression.
+         * @returns {void}
+         */
+        function testForConditionalAncestor(node) {
+            const ancestor = findConditionalAncestor(node);
+
+            if (ancestor) {
+                context.report({
+                    node: ancestor,
+                    message: "Unexpected assignment within {{type}}.",
+                    data: {
+                        type: NODE_DESCRIPTIONS[ancestor.type] || ancestor.type
+                    }
+                });
+            }
+        }
+
+        if (prohibitAssign === "always") {
+            return {
+                AssignmentExpression: testForConditionalAncestor
+            };
+        }
+
+        return {
+            DoWhileStatement: testForAssign,
+            ForStatement: testForAssign,
+            IfStatement: testForAssign,
+            WhileStatement: testForAssign
+        };
+
+    }
+};