Export mimetypes

[HerrNaN]

As a developer using this library I would like to use these already defined mimetypes instead of matching on string literals so that if something changes I don't have to worry and I don't have to double check that I've written the right mimetype correctly.

Eg.

mime, _ := mimetype.DetectFile(file)
if mime.Is(mimetype.SVG) ...

instead of

mime, _ := mimetype.DetectFile(file)
if mime.Is("image/svg+xml") ...

However this seems like something pretty obvious so if there is any reason this isn't already implemented please explain?

[tomcruise81]

Agreed. Happy to create a PR to that extent!

[gabriel-vasile]

I'm open for discussion on this.
The reason why I'm not convinced this is a good change is I don't think the benefits out-weight the pollution from 150+ constants added in library scope.

arg 1.

use these already defined mimetypes instead of matching on string literals so that if something changes I don't have to worry

If I have to rename a mimetype, then I will use the old mimetype as an alias.
Code like:

if mime.Is("image/svg+xml") ...

will continue to work the same.

arg 2.

I don't have to double check that I've written the right mimetype correctly

Ok, this would help with compile time errors, but I'd argue in general, one needs to pay attention to what he writes when coding.

[tomcruise81]

The challenge with the current approach is that from a developer perspective, I need to explicitly know the full type/subtype of the mimetype I want to reference, rather than just it's generalized name. With the exporting of these, it will muddy the namespace scope a bit, but will make finding the given mimetypes substantially faster.

Additionally, instead of:

mime, _ := mimetype.DetectFile(file)
if mime.Is("image/svg+xml") ...

the code becomes:

mime, _ := mimetype.DetectFile(file)
if mime == mimetype.SVG ...

[tomcruise81]

The alternative use-case that interests me more is something like:

contentTypeHeader := resp.Header.Get("Content-Type")
mime := mimetype.Lookup(contentTypeHeader)
if mime == mimetype.SVG ...

It's desirable to have in a library like this, since it is not going to be added to net/http - golang/go#31572

[tomcruise81]

@gabriel-vasile - Is this something you're considering? If so, do you want anything else done on the PR?

Thanks!