1 files changed, 210 insertions, 0 deletions
diff --git a/tools/node_modules/eslint/lib/rules/no-constant-condition.js b/tools/node_modules/eslint/lib/rules/no-constant-condition.js
new file mode 100644
index 0000000000..0cd445dfdb
--- /dev/null
+++ b/tools/node_modules/eslint/lib/rules/no-constant-condition.js
@@ -0,0 +1,210 @@
+/**
+ * @fileoverview Rule to flag use constant conditions
+ * @author Christian Schulz <http://rndm.de>
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+    meta: {
+        docs: {
+            description: "disallow constant expressions in conditions",
+            category: "Possible Errors",
+            recommended: true
+        },
+
+        schema: [
+            {
+                type: "object",
+                properties: {
+                    checkLoops: {
+                        type: "boolean"
+                    }
+                },
+                additionalProperties: false
+            }
+
+        ]
+    },
+
+    create(context) {
+        const options = context.options[0] || {},
+            checkLoops = options.checkLoops !== false,
+            loopSetStack = [];
+
+        let loopsInCurrentScope = new Set();
+
+        //--------------------------------------------------------------------------
+        // Helpers
+        //--------------------------------------------------------------------------
+
+
+        /**
+         * Checks if a branch node of LogicalExpression short circuits the whole condition
+         * @param {ASTNode} node The branch of main condition which needs to be checked
+         * @param {string} operator The operator of the main LogicalExpression.
+         * @returns {boolean} true when condition short circuits whole condition
+         */
+        function isLogicalIdentity(node, operator) {
+            switch (node.type) {
+                case "Literal":
+                    return (operator === "||" && node.value === true) ||
+                           (operator === "&&" && node.value === false);
+
+                case "UnaryExpression":
+                    return (operator === "&&" && node.operator === "void");
+
+                case "LogicalExpression":
+                    return isLogicalIdentity(node.left, node.operator) ||
+                             isLogicalIdentity(node.right, node.operator);
+
+                // no default
+            }
+            return false;
+        }
+
+        /**
+         * Checks if a node has a constant truthiness value.
+         * @param {ASTNode} node The AST node to check.
+         * @param {boolean} inBooleanPosition `false` if checking branch of a condition.
+         *  `true` in all other cases
+         * @returns {Bool} true when node's truthiness is constant
+         * @private
+         */
+        function isConstant(node, inBooleanPosition) {
+            switch (node.type) {
+                case "Literal":
+                case "ArrowFunctionExpression":
+                case "FunctionExpression":
+                case "ObjectExpression":
+                case "ArrayExpression":
+                    return true;
+
+                case "UnaryExpression":
+                    if (node.operator === "void") {
+                        return true;
+                    }
+
+                    return (node.operator === "typeof" && inBooleanPosition) ||
+                        isConstant(node.argument, true);
+
+                case "BinaryExpression":
+                    return isConstant(node.left, false) &&
+                            isConstant(node.right, false) &&
+                            node.operator !== "in";
+
+                case "LogicalExpression": {
+                    const isLeftConstant = isConstant(node.left, inBooleanPosition);
+                    const isRightConstant = isConstant(node.right, inBooleanPosition);
+                    const isLeftShortCircuit = (isLeftConstant && isLogicalIdentity(node.left, node.operator));
+                    const isRightShortCircuit = (isRightConstant && isLogicalIdentity(node.right, node.operator));
+
+                    return (isLeftConstant && isRightConstant) || isLeftShortCircuit || isRightShortCircuit;
+                }
+
+                case "AssignmentExpression":
+                    return (node.operator === "=") && isConstant(node.right, inBooleanPosition);
+
+                case "SequenceExpression":
+                    return isConstant(node.expressions[node.expressions.length - 1], inBooleanPosition);
+
+                // no default
+            }
+            return false;
+        }
+
+        /**
+         * Tracks when the given node contains a constant condition.
+         * @param {ASTNode} node The AST node to check.
+         * @returns {void}
+         * @private
+         */
+        function trackConstantConditionLoop(node) {
+            if (node.test && isConstant(node.test, true)) {
+                loopsInCurrentScope.add(node);
+            }
+        }
+
+        /**
+         * Reports when the set contains the given constant condition node
+         * @param {ASTNode} node The AST node to check.
+         * @returns {void}
+         * @private
+         */
+        function checkConstantConditionLoopInSet(node) {
+            if (loopsInCurrentScope.has(node)) {
+                loopsInCurrentScope.delete(node);
+                context.report({ node: node.test, message: "Unexpected constant condition." });
+            }
+        }
+
+        /**
+         * Reports when the given node contains a constant condition.
+         * @param {ASTNode} node The AST node to check.
+         * @returns {void}
+         * @private
+         */
+        function reportIfConstant(node) {
+            if (node.test && isConstant(node.test, true)) {
+                context.report({ node: node.test, message: "Unexpected constant condition." });
+            }
+        }
+
+        /**
+         * Stores current set of constant loops in loopSetStack temporarily
+         * and uses a new set to track constant loops
+         * @returns {void}
+         * @private
+         */
+        function enterFunction() {
+            loopSetStack.push(loopsInCurrentScope);
+            loopsInCurrentScope = new Set();
+        }
+
+        /**
+         * Reports when the set still contains stored constant conditions
+         * @param {ASTNode} node The AST node to check.
+         * @returns {void}
+         * @private
+         */
+        function exitFunction() {
+            loopsInCurrentScope = loopSetStack.pop();
+        }
+
+        /**
+         * Checks node when checkLoops option is enabled
+         * @param {ASTNode} node The AST node to check.
+         * @returns {void}
+         * @private
+         */
+        function checkLoop(node) {
+            if (checkLoops) {
+                trackConstantConditionLoop(node);
+            }
+        }
+
+        //--------------------------------------------------------------------------
+        // Public
+        //--------------------------------------------------------------------------
+
+        return {
+            ConditionalExpression: reportIfConstant,
+            IfStatement: reportIfConstant,
+            WhileStatement: checkLoop,
+            "WhileStatement:exit": checkConstantConditionLoopInSet,
+            DoWhileStatement: checkLoop,
+            "DoWhileStatement:exit": checkConstantConditionLoopInSet,
+            ForStatement: checkLoop,
+            "ForStatement > .test": node => checkLoop(node.parent),
+            "ForStatement:exit": checkConstantConditionLoopInSet,
+            FunctionDeclaration: enterFunction,
+            "FunctionDeclaration:exit": exitFunction,
+            YieldExpression: () => loopsInCurrentScope.clear()
+        };
+
+    }
+};