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87 lines
3.0 KiB
87 lines
3.0 KiB
/**
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* @fileoverview Rule to flag fall-through cases in switch statements.
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* @author Matt DuVall <http://mattduvall.com/>
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*/
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"use strict";
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//------------------------------------------------------------------------------
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// Requirements
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//------------------------------------------------------------------------------
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var getLast = require("../util").getLast;
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//------------------------------------------------------------------------------
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// Helpers
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//------------------------------------------------------------------------------
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var FALLTHROUGH_COMMENT = /falls?\s?through/i;
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/**
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* Checks whether or not a given node has a fallthrough comment.
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* @param {ASTNode} node - A SwitchCase node to get comments.
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* @param {RuleContext} context - A rule context which stores comments.
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* @returns {boolean} `true` if the node has a fallthrough comment.
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*/
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function hasFallthroughComment(node, context) {
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var sourceCode = context.getSourceCode();
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var comment = getLast(sourceCode.getComments(node).leading);
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return Boolean(comment && FALLTHROUGH_COMMENT.test(comment.value));
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}
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/**
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* Checks whether or not a given code path segment is reachable.
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* @param {CodePathSegment} segment - A CodePathSegment to check.
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* @returns {boolean} `true` if the segment is reachable.
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*/
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function isReachable(segment) {
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return segment.reachable;
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}
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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module.exports = function(context) {
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var currentCodePath = null;
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// We need to use leading comments of the next SwitchCase node because
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// trailing comments is wrong if semicolons are omitted.
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var fallthroughCase = null;
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return {
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"onCodePathStart": function(codePath) {
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currentCodePath = codePath;
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},
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"onCodePathEnd": function() {
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currentCodePath = currentCodePath.upper;
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},
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"SwitchCase": function(node) {
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// Checks whether or not there is a fallthrough comment.
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// And reports the previous fallthrough node if that does not exist.
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if (fallthroughCase && !hasFallthroughComment(node, context)) {
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context.report({
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message: "Expected a 'break' statement before '{{type}}'.",
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data: {type: node.test ? "case" : "default"},
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node: node
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});
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}
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fallthroughCase = null;
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},
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"SwitchCase:exit": function(node) {
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// `reachable` meant fall through because statements preceded by
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// `break`, `return`, or `throw` are unreachable.
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// And allows empty cases and the last case.
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if (currentCodePath.currentSegments.some(isReachable) &&
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node.consequent.length > 0 &&
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getLast(node.parent.cases) !== node
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) {
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fallthroughCase = node;
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}
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}
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};
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};
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module.exports.schema = [];
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