Extend res.links() to allow adding multiple links with the same rel #2729

[andvea]

This pr fixes #2729

I've done the following:

• Added a new test that covers my changes
• Runned linter

[andvea]

Hi @dougwilson,
seems like there is a problem with the Node.js 6.x ci test in the master branch, which runs with supertest@6.1.6. This problem doesn't occur in 4.18 branch, which has the Node.js 6.x ci test with supertest@3.4.2.
Should I do something? Maybe should I close this PR and open the same for the 4.18 branch?
Let me know 😊

[dougwilson]

Hi @andvea no need to do anything. We'll get it fixed up as it get close to landing. Sorry for any confusion there. An issue like that which is not caused by your PR can typically be ignored as it won't be held against your PR or anything :)

[andvea]

Great, wish you good work!

[wesleytodd]

Since we are now targeting v5 we can use nice things like template literals. Just made a few small tweaks but it should be true to the original and if we get a few approvals (I posted in our slack asking for some eyes) then I will land this for the next release.

[wesleytodd]

Ah, I was continuing down the list of PRs and I saw this similar one: https://github.com/expressjs/express/pull/2738/files

While it has no description about this, it supports something which I am realizing now we are missing: multiple params in the link.

https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Link

I am thinking I should rebase that commit on top of this and clean it up to include both.

[ctcpip]

re: combining with the related PR

method overloading via type checking. sure. might want to clean up / optimize how we are building strings here as well

[wesleytodd]

method overloading via type checking. sure. might want to clean up / optimize how we are building strings here as well

There are two parts you could be referring to, so just to clarify, I want the value to be either a string or an object with an href key. I do not want to pull over the top level shape change (Object|Array). The more I think about it the more I am worried any change like this could be breaking though. For example, in the current api if you passed an Object with a toString you would get expected behavior but if we checked typeof links[rel] !== 'string' and used .href we would break folks.

Is this being too paranoid?

[wesleytodd]

After sleeping on it, and also taking a little poll on bluesky, I think it is not too paranoid and should not land with this PR. So I marked that one with the updated labels and will go forward with this as is.