147 lines
5.1 KiB
JavaScript
147 lines
5.1 KiB
JavaScript
/**
|
|
* @fileoverview Rule to flag fall-through cases in switch statements.
|
|
* @author Matt DuVall <http://mattduvall.com/>
|
|
*/
|
|
"use strict";
|
|
|
|
//------------------------------------------------------------------------------
|
|
// Helpers
|
|
//------------------------------------------------------------------------------
|
|
|
|
const DEFAULT_FALLTHROUGH_COMMENT = /falls?\s?through/iu;
|
|
|
|
/**
|
|
* Checks whether or not a given case has a fallthrough comment.
|
|
* @param {ASTNode} caseWhichFallsThrough SwitchCase node which falls through.
|
|
* @param {ASTNode} subsequentCase The case after caseWhichFallsThrough.
|
|
* @param {RuleContext} context A rule context which stores comments.
|
|
* @param {RegExp} fallthroughCommentPattern A pattern to match comment to.
|
|
* @returns {boolean} `true` if the case has a valid fallthrough comment.
|
|
*/
|
|
function hasFallthroughComment(caseWhichFallsThrough, subsequentCase, context, fallthroughCommentPattern) {
|
|
const sourceCode = context.getSourceCode();
|
|
|
|
if (caseWhichFallsThrough.consequent.length === 1 && caseWhichFallsThrough.consequent[0].type === "BlockStatement") {
|
|
const trailingCloseBrace = sourceCode.getLastToken(caseWhichFallsThrough.consequent[0]);
|
|
const commentInBlock = sourceCode.getCommentsBefore(trailingCloseBrace).pop();
|
|
|
|
if (commentInBlock && fallthroughCommentPattern.test(commentInBlock.value)) {
|
|
return true;
|
|
}
|
|
}
|
|
|
|
const comment = sourceCode.getCommentsBefore(subsequentCase).pop();
|
|
|
|
return Boolean(comment && fallthroughCommentPattern.test(comment.value));
|
|
}
|
|
|
|
/**
|
|
* Checks whether or not a given code path segment is reachable.
|
|
* @param {CodePathSegment} segment A CodePathSegment to check.
|
|
* @returns {boolean} `true` if the segment is reachable.
|
|
*/
|
|
function isReachable(segment) {
|
|
return segment.reachable;
|
|
}
|
|
|
|
/**
|
|
* Checks whether a node and a token are separated by blank lines
|
|
* @param {ASTNode} node The node to check
|
|
* @param {Token} token The token to compare against
|
|
* @returns {boolean} `true` if there are blank lines between node and token
|
|
*/
|
|
function hasBlankLinesBetween(node, token) {
|
|
return token.loc.start.line > node.loc.end.line + 1;
|
|
}
|
|
|
|
//------------------------------------------------------------------------------
|
|
// Rule Definition
|
|
//------------------------------------------------------------------------------
|
|
|
|
/** @type {import('../shared/types').Rule} */
|
|
module.exports = {
|
|
meta: {
|
|
type: "problem",
|
|
|
|
docs: {
|
|
description: "disallow fallthrough of `case` statements",
|
|
recommended: true,
|
|
url: "https://eslint.org/docs/rules/no-fallthrough"
|
|
},
|
|
|
|
schema: [
|
|
{
|
|
type: "object",
|
|
properties: {
|
|
commentPattern: {
|
|
type: "string",
|
|
default: ""
|
|
}
|
|
},
|
|
additionalProperties: false
|
|
}
|
|
],
|
|
messages: {
|
|
case: "Expected a 'break' statement before 'case'.",
|
|
default: "Expected a 'break' statement before 'default'."
|
|
}
|
|
},
|
|
|
|
create(context) {
|
|
const options = context.options[0] || {};
|
|
let currentCodePath = null;
|
|
const sourceCode = context.getSourceCode();
|
|
|
|
/*
|
|
* We need to use leading comments of the next SwitchCase node because
|
|
* trailing comments is wrong if semicolons are omitted.
|
|
*/
|
|
let fallthroughCase = null;
|
|
let fallthroughCommentPattern = null;
|
|
|
|
if (options.commentPattern) {
|
|
fallthroughCommentPattern = new RegExp(options.commentPattern, "u");
|
|
} else {
|
|
fallthroughCommentPattern = DEFAULT_FALLTHROUGH_COMMENT;
|
|
}
|
|
|
|
return {
|
|
onCodePathStart(codePath) {
|
|
currentCodePath = codePath;
|
|
},
|
|
onCodePathEnd() {
|
|
currentCodePath = currentCodePath.upper;
|
|
},
|
|
|
|
SwitchCase(node) {
|
|
|
|
/*
|
|
* Checks whether or not there is a fallthrough comment.
|
|
* And reports the previous fallthrough node if that does not exist.
|
|
*/
|
|
if (fallthroughCase && !hasFallthroughComment(fallthroughCase, node, context, fallthroughCommentPattern)) {
|
|
context.report({
|
|
messageId: node.test ? "case" : "default",
|
|
node
|
|
});
|
|
}
|
|
fallthroughCase = null;
|
|
},
|
|
|
|
"SwitchCase:exit"(node) {
|
|
const nextToken = sourceCode.getTokenAfter(node);
|
|
|
|
/*
|
|
* `reachable` meant fall through because statements preceded by
|
|
* `break`, `return`, or `throw` are unreachable.
|
|
* And allows empty cases and the last case.
|
|
*/
|
|
if (currentCodePath.currentSegments.some(isReachable) &&
|
|
(node.consequent.length > 0 || hasBlankLinesBetween(node, nextToken)) &&
|
|
node.parent.cases[node.parent.cases.length - 1] !== node) {
|
|
fallthroughCase = node;
|
|
}
|
|
}
|
|
};
|
|
}
|
|
};
|