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/**
* @fileoverview Rule to flag fall-through cases in switch statements.
* @author Matt DuVall <http://mattduvall.com/>
*/
"use strict";
var FALLTHROUGH_COMMENT = /falls\sthrough/;
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = function(context) {
var switches = [];
return {
"SwitchCase": function(node) {
var consequent = node.consequent,
switchData = switches[switches.length - 1],
i,
comments,
comment;
/*
* Some developers wrap case bodies in blocks, so if there is just one
* node and it's a block statement, check inside.
*/
if (consequent.length === 1 && consequent[0].type === "BlockStatement") {
consequent = consequent[0];
}
// checking on previous case
if (!switchData.lastCaseClosed) {
// a fall through comment will be the last trailing comment of the last case
comments = context.getComments(switchData.lastCase).trailing;
comment = comments[comments.length - 1];
// unless the user doesn't like semicolons, in which case it's first leading comment of this case
if (!comment) {
comments = context.getComments(node).leading;
comment = comments[comments.length - 1];
}
// check for comment
if (!comment || !FALLTHROUGH_COMMENT.test(comment.value)) {
context.report(switchData.lastCase,
"Expected a \"break\" statement before \"{{code}}\".",
{ code: node.test ? "case" : "default" });
}
}
// now dealing with the current case
switchData.lastCaseClosed = false;
switchData.lastCase = node;
// try to verify using statements - go backwards as a fast path for the search
if (consequent.length) {
for (i = consequent.length - 1; i >= 0; i--) {
if (/(?:Break|Continue|Return|Throw)Statement/.test(consequent[i].type)) {
switchData.lastCaseClosed = true;
break;
}
}
} else {
// the case statement has no statements, so it must logically fall through
switchData.lastCaseClosed = true;
}
/*
* Any warnings are triggered when the next SwitchCase occurs.
* There is no need to warn on the last SwitchCase, since it can't
* fall through to anything.
*/
},
"SwitchStatement": function(node) {
switches.push({
node: node,
lastCaseClosed: true,
lastCase: null
});
},
"SwitchStatement:exit": function() {
switches.pop();
}
};
};
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