Add a definition of multimap

[BurtHarris]

The INFRA spec currently has a good definition of ordered map, but its definition requires key uniqueness. Sometimes the uniqueness constraint isn't desirable. For example whatwg/fetch describes header-list as multimap, saying:

A header list is essentially a specialized multimap. An ordered list of key-value pairs with potentially duplicate keys.

I would suggest it is useful to define multimap in the general whatwg/infra spec. The language above, making multimap an ordered list of key-value pairs, seems perfectly acceptable to me.

[annevk]

It would be interesting to see if a specialized data structure would simplify defining Headers/URLSearchParams/FormData a lot. Currently they use a list underneath, which is somewhat reasonable too.

[domenic]

Headers went back to single-map, right?

[annevk]

Ah, right, Headers did, but header list cannot (due to Set-Cookie which isn't exposed through Headers).

[BurtHarris]

I drafted a pull request for this, but for some reason can't get bikeshed to process it (even the online version at https://api.csswg.org/bikeshed/). The output page appears to contain the single character "#".

I"m running Windows 10, so it might be a line ending problem, anyone familiar with this?

[domenic]

I haven't had this problem myself; I also use Windows 10. But yes, please make sure you are using LF line endings; our gitattributes and editorconfig should be enforcing that.

Maybe first try compiling the spec as-is, to make sure that works?

[BurtHarris]

@domenic, same result when I paste the original into https://api.csswg.org/bikeshed/ (as text.)

If I use the upload file option, I get this message:

FATAL ERROR: Found unmatched text macro [SNAPSHOT-LINK]. Correct the macro, or escape it with a leading backslash.
✘ Did not generate, due to fatal errors

[domenic]

Right, you need to set the SNAPSHOT-LINK macro, per the makefile.

[BurtHarris]

Can you recommend what Make tool I should be using on Windows?

[domenic]

You'll need https://curl.haxx.se/download.html. You can either copy and paste the commands from the Makefile, or use http://gnuwin32.sourceforge.net/packages/make.htm.

(We should probably have this stuff documented in the contributing.md...)

[BurtHarris]

Got it. Thanks.

[BurtHarris]

Hmm, now I'm wondering if pairs is/should be a synonym for multimap.

[annevk]

For clarity, if we adopt multimap it has to simplify these standards:

• https://url.spec.whatwg.org/#interface-urlsearchparams
• https://xhr.spec.whatwg.org/#interface-formdata
• https://fetch.spec.whatwg.org/#terminology-headers

I think that's all the multimaps we have in the platform.