What's new in 4.2

What 4.2 adds to a 4.1 bot, area by area, the options that bring 5.0's defaults early, and what a working bot may notice.

4.2 adds to 4.1 without breaking it: a 4.1 bot and its tests build and run without edits. By default, startup errors arrive together, a few warnings are new or say more, and customId patterns rank segment by segment, which changes the handler only for pairs 4.1 warned about. Upgrading from 4.1 to 4.2 lists each, with what to check. Every release's notes are in the changelog.

Starting the bot

• Every startup error at once. MeoCordFactory.create() and a testing module's compile() report every error their checks find, each with the file it comes from, then throw the first as before: the same error, with the same message. A decorator's error names the handler or class it was applied to, as error.declaration, and its file, as error.file. See Every startup error at once.
• startupErrors: 'all' in meocord.config.ts has decorators keep their errors too, so a bot with three mistakes shows all three in one run. In a test, reportAllStartupErrors() does the same. See Configuration.

Routing

• @Controller({ inheritedRoutes: 'replace' }) makes a handler the class re-decorates answer only the routes the class declares for it, dropping the ones a base class declares for that method. See A subclass's routes.
• customId patterns rank segment by segment, the way most routers rank paths: at the first segment where one pattern is literal and the other a param, the literal one runs, whatever the listing. Only pairs 4.1's startup warning named can change handler. findRouteConflicts lists only the pairs still tied, and resolveRoute's alsoMatches the patterns that lost. See Overlapping patterns.
• {id:snowflake} and {id:uuid} are customId param types for a Discord ID and a UUID, which the handler gets as text and route().build() checks. Use snowflake for a Discord ID: {id:number} rounds one. See Typed params.

Message commands

• messages: { handlers: 'concurrent' } runs a message's command and its listeners side by side, so a slow command no longer holds back logging and moderation. See Running them side by side.
• A slow handler that holds listeners back for 5 seconds or more is named in a warning, once, with the option that frees them. slowHandlerWarning: false turns it off.

Testing

• useMockFn(vi.fn) has every mock from meocord/testing made with your test runner's own mock function, so clearMocks, mockReset and vi.mocked reach them. A new project's setup file calls it. See Your test runner's mocks.
• useStrictMocks() has mocks compute what discord.js computes, such as whether a message is editable or a member kickable, where they read a placeholder otherwise. A new project's setup file calls it. See Strict mocks.
• createMockRawMember() builds the member Discord sends from a server the bot isn't in, to test a user-installed command there. See A server the bot isn't in.

Getting ready for 5.0

Three options bring a 5.0 default into 4.2, so a bot can move to it one change at a time: inheritedRoutes: 'replace', startupErrors: 'all' and useStrictMocks(). Where the default would change what a bot does, a warning says so and names the option, and 4.2 behaves as 4.1 until you set it.