Make the bot not crash when a channel mentioned by ID fails to exist

[Throne3d]

Description

If a channel is referenced in Discord, e.g. <#1234>, and the referenced channel does not exist, the bot seems to crash. This commit fixes it to replace this with '#deleted-channel', as Discord does on that side of the bridge.

Present behavior

Writing #blah, <#test> and <#1234> into IRC causes the bot to show (in Discord):

<Throne> #blah
<Throne> <#test>
<Throne> #deleted-channel

and then writing the same into the Discord channel causes (in IRC):

[22:13:39] <test2> <Throne3d> #blah
[22:13:41] <test2> <Throne3d> <#test>
[22:13:44] * test2 has quit (Client exited)

The crash produced:

/home/throne3d/discord-irc/dist/bot.js:159
      return `#${channel.name}`;
                        ^

TypeError: Cannot read property 'name' of undefined
    at text.replace.replace (/home/throne3d/discord-irc/dist/bot.js:159:25)
    at RegExp.[Symbol.replace] (native)
    at String.replace (native)
    at Bot.parseText (/home/throne3d/discord-irc/dist/bot.js:157:45)
    at Bot.sendToIRC (/home/throne3d/discord-irc/dist/bot.js:179:23)
    at Client.discord.on.message (/home/throne3d/discord-irc/dist/bot.js:113:12)
    at emitOne (events.js:96:13)
    at Client.emit (events.js:191:7)
    at MessageCreateHandler.handle (/home/throne3d/discord-irc/node_modules/discord.js/src/client/websocket/packets/handlers/MessageCreate.js:9:34)
    at WebSocketPacketManager.handle (/home/throne3d/discord-irc/node_modules/discord.js/src/client/websocket/packets/WebSocketPacketManager.js:120:65)

The new test (and stubbing behavior) I add with this patch fails on master as follows:

  1) Bot should use #deleted-channel when referenced channel fails to exist:
     TypeError: Cannot read property 'name' of null
      at text.replace.replace (lib/bot.js:7:2326)
      at RegExp.[Symbol.replace] (native)
      at String.replace (native)
      at Bot.parseText (lib/bot.js:7:2147)
      at Bot.sendToIRC (lib/bot.js:8:652)
      at Context.<anonymous> (test/bot.test.js:271:14)

Modified behavior

With the change, it only returns the channel's name where the channel is truthy. (I'm not very acquainted with modern techniques so this might not be the best way to do it? It seems to be undefined as returned by this.discord.channels.get(channelId) but null as returned by the stub, so checking channel === undefined didn't catch that.)

Otherwise, it returns #deleted-channel (and so writes that into the IRC channel), mirroring the behavior seen in Discord for such invalid channel IDs. This doesn't break any other tests (at least not on my system). The && value == undefined condition is to check for when a second parameter isn't given – I wasn't sure whether to use && !value or something else instead.

[coveralls]

Coverage increased (+0.02%) to 97.368% when pulling f882e15 on Throne3d:fix/crash-on-undefined-channel into 26626e5 on reactiflux:master.

[ekmartin]

Great, thank you!

[ekmartin]

Released in 2.3.0!