node/tools/eslint/lib/rules/constructor-super.js

/**
 * @fileoverview A rule to verify `super()` callings in constructor.
 * @author Toru Nagashima
 * @copyright 2015 Toru Nagashima. All rights reserved.
 */

"use strict";

//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------

var astUtils = require("../ast-utils");

//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------

/**
 * Checks whether or not a given node is a constructor.
 * @param {ASTNode} node - A node to check. This node type is one of
 *   `Program`, `FunctionDeclaration`, `FunctionExpression`, and
 *   `ArrowFunctionExpression`.
 * @returns {boolean} `true` if the node is a constructor.
 */
function isConstructorFunction(node) {
    return (
        node.type === "FunctionExpression" &&
        node.parent.type === "MethodDefinition" &&
        node.parent.kind === "constructor"
    );
}

//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------

module.exports = function(context) {

    /*
     * {{hasExtends: boolean, scope: Scope, codePath: CodePath}[]}
     * Information for each constructor.
     * - upper:      Information of the upper constructor.
     * - hasExtends: A flag which shows whether own class has a valid `extends`
     *               part.
     * - scope:      The scope of own class.
     * - codePath:   The code path object of the constructor.
     */
    var funcInfo = null;

    /*
     * {Map<string, {calledInSomePaths: boolean, calledInEveryPaths: boolean}>}
     * Information for each code path segment.
     * - calledInSomePaths:  A flag of be called `super()` in some code paths.
     * - calledInEveryPaths: A flag of be called `super()` in all code paths.
     * - validNodes:
     */
    var segInfoMap = Object.create(null);

    /**
     * Gets the flag which shows `super()` is called in some paths.
     * @param {CodePathSegment} segment - A code path segment to get.
     * @returns {boolean} The flag which shows `super()` is called in some paths
     */
    function isCalledInSomePath(segment) {
        return segInfoMap[segment.id].calledInSomePaths;
    }

    /**
     * Gets the flag which shows `super()` is called in all paths.
     * @param {CodePathSegment} segment - A code path segment to get.
     * @returns {boolean} The flag which shows `super()` is called in all paths.
     */
    function isCalledInEveryPath(segment) {

        /*
         * If specific segment is the looped segment of the current segment,
         * skip the segment.
         * If not skipped, this never becomes true after a loop.
         */
        if (segment.nextSegments.length === 1 &&
            segment.nextSegments[0].isLoopedPrevSegment(segment)
        ) {
            return true;
        }
        return segInfoMap[segment.id].calledInEveryPaths;
    }

    return {

        /**
         * Stacks a constructor information.
         * @param {CodePath} codePath - A code path which was started.
         * @param {ASTNode} node - The current node.
         * @returns {void}
         */
        "onCodePathStart": function(codePath, node) {
            if (isConstructorFunction(node)) {

                // Class > ClassBody > MethodDefinition > FunctionExpression
                var classNode = node.parent.parent.parent;

                funcInfo = {
                    upper: funcInfo,
                    isConstructor: true,
                    hasExtends: Boolean(
                        classNode.superClass &&
                        !astUtils.isNullOrUndefined(classNode.superClass)
                    ),
                    codePath: codePath
                };
            } else {
                funcInfo = {
                    upper: funcInfo,
                    isConstructor: false,
                    hasExtends: false,
                    codePath: codePath
                };
            }
        },

        /**
         * Pops a constructor information.
         * And reports if `super()` lacked.
         * @param {CodePath} codePath - A code path which was ended.
         * @param {ASTNode} node - The current node.
         * @returns {void}
         */
        "onCodePathEnd": function(codePath, node) {

            // Skip if own class which has a valid `extends` part.
            var hasExtends = funcInfo.hasExtends;

            funcInfo = funcInfo.upper;

            if (!hasExtends) {
                return;
            }

            // Reports if `super()` lacked.
            var segments = codePath.returnedSegments;
            var calledInEveryPaths = segments.every(isCalledInEveryPath);
            var calledInSomePaths = segments.some(isCalledInSomePath);

            if (!calledInEveryPaths) {
                context.report({
                    message: calledInSomePaths ?
                        "Lacked a call of 'super()' in some code paths." :
                        "Expected to call 'super()'.",
                    node: node.parent
                });
            }
        },

        /**
         * Initialize information of a given code path segment.
         * @param {CodePathSegment} segment - A code path segment to initialize.
         * @returns {void}
         */
        "onCodePathSegmentStart": function(segment) {

            /*
             * Skip if this is not in a constructor of a class which has a
             * valid `extends` part.
             */
            if (!(funcInfo && funcInfo.isConstructor && funcInfo.hasExtends)) {
                return;
            }

            // Initialize info.
            var info = segInfoMap[segment.id] = {
                calledInSomePaths: false,
                calledInEveryPaths: false,
                validNodes: []
            };

            // When there are previous segments, aggregates these.
            var prevSegments = segment.prevSegments;

            if (prevSegments.length > 0) {
                info.calledInSomePaths = prevSegments.some(isCalledInSomePath);
                info.calledInEveryPaths = prevSegments.every(isCalledInEveryPath);
            }
        },

        /**
         * Update information of the code path segment when a code path was
         * looped.
         * @param {CodePathSegment} fromSegment - The code path segment of the
         *      end of a loop.
         * @param {CodePathSegment} toSegment - A code path segment of the head
         *      of a loop.
         * @returns {void}
         */
        "onCodePathSegmentLoop": function(fromSegment, toSegment) {

            /*
             * Skip if this is not in a constructor of a class which has a
             * valid `extends` part.
             */
            if (!(funcInfo && funcInfo.isConstructor && funcInfo.hasExtends)) {
                return;
            }

            // Update information inside of the loop.
            var isRealLoop = toSegment.prevSegments.length >= 2;

            funcInfo.codePath.traverseSegments(
                {first: toSegment, last: fromSegment},
                function(segment) {
                    var info = segInfoMap[segment.id];

                    // Updates flags.
                    var prevSegments = segment.prevSegments;

                    info.calledInSomePaths = prevSegments.some(isCalledInSomePath);
                    info.calledInEveryPaths = prevSegments.every(isCalledInEveryPath);

                    // If flags become true anew, reports the valid nodes.
                    if (info.calledInSomePaths || isRealLoop) {
                        var nodes = info.validNodes;

                        info.validNodes = [];

                        for (var i = 0; i < nodes.length; ++i) {
                            var node = nodes[i];

                            context.report({
                                message: "Unexpected duplicate 'super()'.",
                                node: node
                            });
                        }
                    }
                }
            );
        },

        /**
         * Checks for a call of `super()`.
         * @param {ASTNode} node - A CallExpression node to check.
         * @returns {void}
         */
        "CallExpression:exit": function(node) {

            // Skip if the node is not `super()`.
            if (node.callee.type !== "Super") {
                return;
            }

            // Skip if this is not in a constructor.
            if (!(funcInfo && funcInfo.isConstructor)) {
                return;
            }

            // Reports if needed.
            if (funcInfo.hasExtends) {

                /*
                 * This class has a valid `extends` part.
                 * Checks duplicate `super()`;
                 */
                var segments = funcInfo.codePath.currentSegments;
                var duplicate = false;

                for (var i = 0; i < segments.length; ++i) {
                    var info = segInfoMap[segments[i].id];

                    duplicate = duplicate || info.calledInSomePaths;
                    info.calledInSomePaths = info.calledInEveryPaths = true;
                }

                if (duplicate) {
                    context.report({
                        message: "Unexpected duplicate 'super()'.",
                        node: node
                    });
                } else {
                    info.validNodes.push(node);
                }
            } else {

                /*
                 * This class does not have a valid `extends` part.
                 * Disallow `super()`.
                 */
                context.report({
                    message: "Unexpected 'super()'.",
                    node: node
                });
            }
        },

        /**
         * Resets state.
         * @returns {void}
         */
        "Program:exit": function() {
            segInfoMap = Object.create(null);
        }
    };
};

module.exports.schema = [];