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app_vue/node_modules/eslint/lib/rules/no-unmodified-loop-condition.js

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+/**
+ * @fileoverview Rule to disallow use of unmodified expressions in loop conditions
+ * @author Toru Nagashima
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const Traverser = require("../shared/traverser"),
+    astUtils = require("./utils/ast-utils");
+
+//------------------------------------------------------------------------------
+// Helpers
+//------------------------------------------------------------------------------
+
+const SENTINEL_PATTERN = /(?:(?:Call|Class|Function|Member|New|Yield)Expression|Statement|Declaration)$/u;
+const LOOP_PATTERN = /^(?:DoWhile|For|While)Statement$/u; // for-in/of statements don't have `test` property.
+const GROUP_PATTERN = /^(?:BinaryExpression|ConditionalExpression)$/u;
+const SKIP_PATTERN = /^(?:ArrowFunction|Class|Function)Expression$/u;
+const DYNAMIC_PATTERN = /^(?:Call|Member|New|TaggedTemplate|Yield)Expression$/u;
+
+/**
+ * @typedef {Object} LoopConditionInfo
+ * @property {eslint-scope.Reference} reference - The reference.
+ * @property {ASTNode} group - BinaryExpression or ConditionalExpression nodes
+ *      that the reference is belonging to.
+ * @property {Function} isInLoop - The predicate which checks a given reference
+ *      is in this loop.
+ * @property {boolean} modified - The flag that the reference is modified in
+ *      this loop.
+ */
+
+/**
+ * Checks whether or not a given reference is a write reference.
+ * @param {eslint-scope.Reference} reference A reference to check.
+ * @returns {boolean} `true` if the reference is a write reference.
+ */
+function isWriteReference(reference) {
+    if (reference.init) {
+        const def = reference.resolved && reference.resolved.defs[0];
+
+        if (!def || def.type !== "Variable" || def.parent.kind !== "var") {
+            return false;
+        }
+    }
+    return reference.isWrite();
+}
+
+/**
+ * Checks whether or not a given loop condition info does not have the modified
+ * flag.
+ * @param {LoopConditionInfo} condition A loop condition info to check.
+ * @returns {boolean} `true` if the loop condition info is "unmodified".
+ */
+function isUnmodified(condition) {
+    return !condition.modified;
+}
+
+/**
+ * Checks whether or not a given loop condition info does not have the modified
+ * flag and does not have the group this condition belongs to.
+ * @param {LoopConditionInfo} condition A loop condition info to check.
+ * @returns {boolean} `true` if the loop condition info is "unmodified".
+ */
+function isUnmodifiedAndNotBelongToGroup(condition) {
+    return !(condition.modified || condition.group);
+}
+
+/**
+ * Checks whether or not a given reference is inside of a given node.
+ * @param {ASTNode} node A node to check.
+ * @param {eslint-scope.Reference} reference A reference to check.
+ * @returns {boolean} `true` if the reference is inside of the node.
+ */
+function isInRange(node, reference) {
+    const or = node.range;
+    const ir = reference.identifier.range;
+
+    return or[0] <= ir[0] && ir[1] <= or[1];
+}
+
+/**
+ * Checks whether or not a given reference is inside of a loop node's condition.
+ * @param {ASTNode} node A node to check.
+ * @param {eslint-scope.Reference} reference A reference to check.
+ * @returns {boolean} `true` if the reference is inside of the loop node's
+ *      condition.
+ */
+const isInLoop = {
+    WhileStatement: isInRange,
+    DoWhileStatement: isInRange,
+    ForStatement(node, reference) {
+        return (
+            isInRange(node, reference) &&
+            !(node.init && isInRange(node.init, reference))
+        );
+    }
+};
+
+/**
+ * Gets the function which encloses a given reference.
+ * This supports only FunctionDeclaration.
+ * @param {eslint-scope.Reference} reference A reference to get.
+ * @returns {ASTNode|null} The function node or null.
+ */
+function getEncloseFunctionDeclaration(reference) {
+    let node = reference.identifier;
+
+    while (node) {
+        if (node.type === "FunctionDeclaration") {
+            return node.id ? node : null;
+        }
+
+        node = node.parent;
+    }
+
+    return null;
+}
+
+/**
+ * Updates the "modified" flags of given loop conditions with given modifiers.
+ * @param {LoopConditionInfo[]} conditions The loop conditions to be updated.
+ * @param {eslint-scope.Reference[]} modifiers The references to update.
+ * @returns {void}
+ */
+function updateModifiedFlag(conditions, modifiers) {
+
+    for (let i = 0; i < conditions.length; ++i) {
+        const condition = conditions[i];
+
+        for (let j = 0; !condition.modified && j < modifiers.length; ++j) {
+            const modifier = modifiers[j];
+            let funcNode, funcVar;
+
+            /*
+             * Besides checking for the condition being in the loop, we want to
+             * check the function that this modifier is belonging to is called
+             * in the loop.
+             * FIXME: This should probably be extracted to a function.
+             */
+            const inLoop = condition.isInLoop(modifier) || Boolean(
+                (funcNode = getEncloseFunctionDeclaration(modifier)) &&
+                (funcVar = astUtils.getVariableByName(modifier.from.upper, funcNode.id.name)) &&
+                funcVar.references.some(condition.isInLoop)
+            );
+
+            condition.modified = inLoop;
+        }
+    }
+}
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+    meta: {
+        type: "problem",
+
+        docs: {
+            description: "disallow unmodified loop conditions",
+            category: "Best Practices",
+            recommended: false,
+            url: "https://eslint.org/docs/rules/no-unmodified-loop-condition"
+        },
+
+        schema: [],
+
+        messages: {
+            loopConditionNotModified: "'{{name}}' is not modified in this loop."
+        }
+    },
+
+    create(context) {
+        const sourceCode = context.getSourceCode();
+        let groupMap = null;
+
+        /**
+         * Reports a given condition info.
+         * @param {LoopConditionInfo} condition A loop condition info to report.
+         * @returns {void}
+         */
+        function report(condition) {
+            const node = condition.reference.identifier;
+
+            context.report({
+                node,
+                messageId: "loopConditionNotModified",
+                data: node
+            });
+        }
+
+        /**
+         * Registers given conditions to the group the condition belongs to.
+         * @param {LoopConditionInfo[]} conditions A loop condition info to
+         *      register.
+         * @returns {void}
+         */
+        function registerConditionsToGroup(conditions) {
+            for (let i = 0; i < conditions.length; ++i) {
+                const condition = conditions[i];
+
+                if (condition.group) {
+                    let group = groupMap.get(condition.group);
+
+                    if (!group) {
+                        group = [];
+                        groupMap.set(condition.group, group);
+                    }
+                    group.push(condition);
+                }
+            }
+        }
+
+        /**
+         * Reports references which are inside of unmodified groups.
+         * @param {LoopConditionInfo[]} conditions A loop condition info to report.
+         * @returns {void}
+         */
+        function checkConditionsInGroup(conditions) {
+            if (conditions.every(isUnmodified)) {
+                conditions.forEach(report);
+            }
+        }
+
+        /**
+         * Checks whether or not a given group node has any dynamic elements.
+         * @param {ASTNode} root A node to check.
+         *      This node is one of BinaryExpression or ConditionalExpression.
+         * @returns {boolean} `true` if the node is dynamic.
+         */
+        function hasDynamicExpressions(root) {
+            let retv = false;
+
+            Traverser.traverse(root, {
+                visitorKeys: sourceCode.visitorKeys,
+                enter(node) {
+                    if (DYNAMIC_PATTERN.test(node.type)) {
+                        retv = true;
+                        this.break();
+                    } else if (SKIP_PATTERN.test(node.type)) {
+                        this.skip();
+                    }
+                }
+            });
+
+            return retv;
+        }
+
+        /**
+         * Creates the loop condition information from a given reference.
+         * @param {eslint-scope.Reference} reference A reference to create.
+         * @returns {LoopConditionInfo|null} Created loop condition info, or null.
+         */
+        function toLoopCondition(reference) {
+            if (reference.init) {
+                return null;
+            }
+
+            let group = null;
+            let child = reference.identifier;
+            let node = child.parent;
+
+            while (node) {
+                if (SENTINEL_PATTERN.test(node.type)) {
+                    if (LOOP_PATTERN.test(node.type) && node.test === child) {
+
+                        // This reference is inside of a loop condition.
+                        return {
+                            reference,
+                            group,
+                            isInLoop: isInLoop[node.type].bind(null, node),
+                            modified: false
+                        };
+                    }
+
+                    // This reference is outside of a loop condition.
+                    break;
+                }
+
+                /*
+                 * If it's inside of a group, OK if either operand is modified.
+                 * So stores the group this reference belongs to.
+                 */
+                if (GROUP_PATTERN.test(node.type)) {
+
+                    // If this expression is dynamic, no need to check.
+                    if (hasDynamicExpressions(node)) {
+                        break;
+                    } else {
+                        group = node;
+                    }
+                }
+
+                child = node;
+                node = node.parent;
+            }
+
+            return null;
+        }
+
+        /**
+         * Finds unmodified references which are inside of a loop condition.
+         * Then reports the references which are outside of groups.
+         * @param {eslint-scope.Variable} variable A variable to report.
+         * @returns {void}
+         */
+        function checkReferences(variable) {
+
+            // Gets references that exist in loop conditions.
+            const conditions = variable
+                .references
+                .map(toLoopCondition)
+                .filter(Boolean);
+
+            if (conditions.length === 0) {
+                return;
+            }
+
+            // Registers the conditions to belonging groups.
+            registerConditionsToGroup(conditions);
+
+            // Check the conditions are modified.
+            const modifiers = variable.references.filter(isWriteReference);
+
+            if (modifiers.length > 0) {
+                updateModifiedFlag(conditions, modifiers);
+            }
+
+            /*
+             * Reports the conditions which are not belonging to groups.
+             * Others will be reported after all variables are done.
+             */
+            conditions
+                .filter(isUnmodifiedAndNotBelongToGroup)
+                .forEach(report);
+        }
+
+        return {
+            "Program:exit"() {
+                const queue = [context.getScope()];
+
+                groupMap = new Map();
+
+                let scope;
+
+                while ((scope = queue.pop())) {
+                    queue.push(...scope.childScopes);
+                    scope.variables.forEach(checkReferences);
+                }
+
+                groupMap.forEach(checkConditionsInGroup);
+                groupMap = null;
+            }
+        };
+    }
+};