app.use should include a 4-arity example

[kevinburkeshyp]

It was unclear on http://expressjs.com/en/4x/api.html#app.use how you can call app.use with a 4-arity middleware, or where you're supposed to integrate a 4-arity middleware; the error handling docs (http://expressjs.com/en/guide/error-handling.html) cover this, but I also expected to see at least a mention of this behavior in the main app.use docs.

I tried:

• scanning the docs, checking the arity of all the examples
• searching using ctrl+f for (err
• clicking through to "Application settings"

The app.use docs link to the middleware page, which discuss this, but it would be nice if there was at least one example in the Application docs that covered the 4-arity argument, app.use(function(err, req, res, next)).

(at least until expressjs/express#2896 gets resolved)

[kevinburkeshyp]

(It might also be worth discussing what happens if the middleware throws an unhandled exception in the current or later ticks - in a brief scan of the app.use docs and the middleware docs, it seems like that is not covered)

[crandmck]

It's a god point and a reasonable suggestion. That section has lots of examples, so it should have at least one of error-handling mw.

I'll add something as soon as I have a chance.
@kevinburkeshyp If you're inspired, feel free to open a PR.

[kevinburkeshyp]

@kevinburkeshyp If you're inspired, feel free to open a PR.

prolly not gonna have time, sorry :(

[hacksparrow]

34cc3f3 fixes this.

[kevinburkeshyp]

Thanks!

Kevin Burke
925.271.7005 | kev.inburke.com

On Mon, Jun 27, 2016 at 1:18 PM, Hage Yaapa [email protected]
wrote:

Closed #635 #635.

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[crandmck]

Thanks @hacksparrow !