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/**
* @fileoverview Check that there's a removeEventListener for each
* addEventListener and an off for each on.
* Note that for now, this rule is rather simple in that it only checks that
* for each event name there is both an add and remove listener. It doesn't
* check that these are called on the right objects or with the same callback.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
"use strict";
module.exports = {
meta: {
docs: {
url: "https://firefox-source-docs.mozilla.org/code-quality/lint/linters/eslint-plugin-mozilla/balanced-listeners.html",
},
messages: {
noCorresponding:
"No corresponding '{{functionName}}({{type}})' was found.",
},
schema: [],
type: "problem",
},
create(context) {
var DICTIONARY = {
addEventListener: "removeEventListener",
on: "off",
};
// Invert this dictionary to make it easy later.
var INVERTED_DICTIONARY = {};
for (var i in DICTIONARY) {
INVERTED_DICTIONARY[DICTIONARY[i]] = i;
}
// Collect the add/remove listeners in these 2 arrays.
var addedListeners = [];
var removedListeners = [];
function addAddedListener(node) {
var capture = false;
let options = node.arguments[2];
if (options) {
if (options.type == "ObjectExpression") {
if (
options.properties.some(
p => p.key.name == "once" && p.value.value === true
)
) {
// No point in adding listeners using the 'once' option.
return;
}
capture = options.properties.some(
p => p.key.name == "capture" && p.value.value === true
);
} else {
capture = options.value;
}
}
addedListeners.push({
functionName: node.callee.property.name,
type: node.arguments[0].value,
node: node.callee.property,
useCapture: capture,
});
}
function addRemovedListener(node) {
var capture = false;
let options = node.arguments[2];
if (options) {
if (options.type == "ObjectExpression") {
capture = options.properties.some(
p => p.key.name == "capture" && p.value.value === true
);
} else {
capture = options.value;
}
}
removedListeners.push({
functionName: node.callee.property.name,
type: node.arguments[0].value,
useCapture: capture,
});
}
function getUnbalancedListeners() {
var unbalanced = [];
for (var j = 0; j < addedListeners.length; j++) {
if (!hasRemovedListener(addedListeners[j])) {
unbalanced.push(addedListeners[j]);
}
}
addedListeners = removedListeners = [];
return unbalanced;
}
function hasRemovedListener(addedListener) {
for (var k = 0; k < removedListeners.length; k++) {
var listener = removedListeners[k];
if (
DICTIONARY[addedListener.functionName] === listener.functionName &&
addedListener.type === listener.type &&
addedListener.useCapture === listener.useCapture
) {
return true;
}
}
return false;
}
return {
CallExpression(node) {
if (node.arguments.length === 0) {
return;
}
if (node.callee.type === "MemberExpression") {
var listenerMethodName = node.callee.property.name;
if (DICTIONARY.hasOwnProperty(listenerMethodName)) {
addAddedListener(node);
} else if (INVERTED_DICTIONARY.hasOwnProperty(listenerMethodName)) {
addRemovedListener(node);
}
}
},
"Program:exit": function () {
getUnbalancedListeners().forEach(function (listener) {
context.report({
node: listener.node,
messageId: "noCorresponding",
data: {
functionName: DICTIONARY[listener.functionName],
type: listener.type,
},
});
});
},
};
},
};
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