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/**
* @fileoverview Check that there's a Services.(prefs|obs).removeObserver for
* each addObserver.
*
* 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/rules/balanced-observers.html",
},
messages: {
noCorresponding:
"No corresponding 'removeObserver(\"{{observable}}\")' was found.",
},
schema: [],
type: "problem",
},
create(context) {
var addedObservers = [];
var removedObservers = [];
function getObserverAPI(node) {
const object = node.callee.object;
if (
object.type == "MemberExpression" &&
object.property.type == "Identifier"
) {
return object.property.name;
}
return null;
}
function isServicesObserver(api) {
return api == "obs" || api == "prefs";
}
function getObservableName(node, api) {
if (api === "obs") {
return node.arguments[1].value;
}
return node.arguments[0].value;
}
function addAddedObserver(node) {
const api = getObserverAPI(node);
if (!isServicesObserver(api)) {
return;
}
addedObservers.push({
functionName: node.callee.property.name,
observable: getObservableName(node, api),
node: node.callee.property,
});
}
function addRemovedObserver(node) {
const api = getObserverAPI(node);
if (!isServicesObserver(api)) {
return;
}
removedObservers.push({
functionName: node.callee.property.name,
observable: getObservableName(node, api),
});
}
function getUnbalancedObservers() {
const unbalanced = addedObservers.filter(
observer => !hasRemovedObserver(observer)
);
addedObservers = removedObservers = [];
return unbalanced;
}
function hasRemovedObserver(addedObserver) {
return removedObservers.some(
observer => addedObserver.observable === observer.observable
);
}
return {
CallExpression(node) {
if (node.arguments.length === 0) {
return;
}
if (node.callee.type === "MemberExpression") {
var methodName = node.callee.property.name;
if (methodName === "addObserver") {
addAddedObserver(node);
} else if (methodName === "removeObserver") {
addRemovedObserver(node);
}
}
},
"Program:exit": function () {
getUnbalancedObservers().forEach(function (observer) {
context.report({
node: observer.node,
messageId: "noCorresponding",
data: {
observable: observer.observable,
},
});
});
},
};
},
};
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