feat(http): Add --header option to file_server

[lino-levan]

A big thanks to @plohm12 for the initial work in #2589.

This PR adds --cache (or -C) as an option for file_server. It follows a similar spec to http_server over on the node side where --cache=-1 means no-store.

[timreichen]

Is there a use case of maxAge=0? Or why is it -1 for no-store?

[lino-levan]

@timreichen good question. maxAge=0 essentially behaves something like must-revalidate. no-store is subtly different than this:

• must-revalidate caches the response on the client, but always checks with the server to get the latest information
• no-store NEVER caches the response on the client. This is usually for security reasons.

There may be a point to be made that there is no value in having both supported in file_server, but given that it costs essentially nothing to support both (and c=-1 is already standard in http_server) I thought that there wasn't much of a downside.

[kt3k]

Adding specific option for each header feels problematic to me as there are many HTTP headers. How about adding option for appending any kind of headers by the pairs of keys and values.

[lino-levan]

@kt3k 100% agree in theory, but I think this should be an addition feature. I think that caching is a very basic header that should really have been an option.

What are you thinking for cli inputs for adding arbitrary http headers?

I would imagine something like: --headers="Set-Cookie: example=hi" but I have no idea how we would parse multiple headers. Is there a standard separator that we could use (I'm pretty sure's it is newlines but we can't exactly use newlines in this situation)?

[kt3k]

I would imagine something like: --headers="Set-Cookie: example=hi" but I have no idea how we would parse multiple headers. Is there a standard separator that we could use (I'm pretty sure's it is newlines but we can't exactly use newlines in this situation)?

How about following curl's -H, --header option?

--header "set-cookie: example=hi" --header "cache-control: no-cache" -H "x-custom-header: xyz"

parse of flags module has collect option, which enables the usage of the same cli arg multiple times

parse(Deno.args, { collect: ["header"] });

[lino-levan]

@kt3k that makes a lot of sense. So now to move forward, should we :

• Change this PR to add --header and remove --cache
• Merge this PR, and then open a separate PR for --header

I'm game for either, though I personally do see value in --cache so I would lean towards option 2.

[kt3k]

I prefer the first option. --cache option seems needing further design work about what ranges of values to support with it, but that kind of stuff is out of scope of file_server in my view. (One of the purposes of http/file_server is to show the example of implementing simple static file server in Deno, rather than providing a complete static file server with large number of useful options.

[lino-levan]

Sounds good to me, I will rework this PR when I get the chance (probably this weekend).

[lino-levan]

@kt3k PTAL

Thanks!

[kt3k]

LGTM. Nice work!