David Baker
975518bd88
As hopefully explained by lengthy comment Fixes https://github.com/matrix-org/matrix-js-sdk/issues/1569
51 lines
2.3 KiB
TypeScript
51 lines
2.3 KiB
TypeScript
/*
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Copyright 2015, 2016 OpenMarket Ltd
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Copyright 2017 Vector Creations Ltd
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Copyright 2017 New Vector Ltd
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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import { EventEmitter } from "events";
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export class ReEmitter {
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private target: EventEmitter;
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constructor(target: EventEmitter) {
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this.target = target;
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}
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reEmit(source: EventEmitter, eventNames: string[]) {
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for (const eventName of eventNames) {
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// We include the source as the last argument for event handlers which may need it,
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// such as read receipt listeners on the client class which won't have the context
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// of the room.
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const forSource = (...args) => {
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// EventEmitter special cases 'error' to make the emit function throw if no
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// handler is attached, which sort of makes sense for making sure that something
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// handles an error, but for re-emitting, there could be a listener on the original
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// source object so the test doesn't really work. We *could* try to replicate the
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// same logic and throw if there is no listener on either the source or the target,
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// but this behaviour is fairly undesireable for us anyway: the main place we throw
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// 'error' events is for calls, where error events are usually emitted some time
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// later by a different part of the code where 'emit' throwing because the app hasn't
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// added an error handler isn't terribly helpful. (A better fix in retrospect may
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// have been to just avoid using the event name 'error', but backwards compat...)
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if (eventName === 'error' && this.target.listenerCount('error') === 0) return;
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this.target.emit(eventName, ...args, source);
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};
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source.on(eventName, forSource);
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}
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}
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}
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