zimcheck: check known/expected metadata mimetype

[benoit74]

As mentioned by @rgaudin in openzim/mwoffliner#2470, it seems that all known/expected metadata (but illustrations) should have text/plain or text/plain;charset=UTF-8 mimetype.

It looks like zimcheck is not checking this at all.

Probably worth to add. Not sure if it should be an error or a warning.

[aaryansinhaa]

I'd like to work on this issue; I feel that it should be a warning, and we should default all the undefined to text/plain or text/plain;charset=UTF-8 mimetype. will have to check if that breaks anything

[kelson42]

@aaryansinhaa Thank you for proposing yourself, I just have assigned it to you.

Here a few remarks:

• Should be an error IMHO, considering the specification is clear about it, see https://wiki.openzim.org/wiki/ZIM_file_format#Encodings
• This issue is for zimcheck, therefore impossible to change them.
• Maybe zimwriterfs should be fixed to do that properly, but then do that in an other PR

[aaryansinhaa]

@kelson42 @benoit74 can you provide me with a zim file with correct metadata, and one with incorrect. I have implemented the code, wanted to check before I make a PR

[kelson42]

@aaryansinhaa You should fix zimwriterfs first and then you will easily be able to build one.

[benoit74]

You can find one good and one bad ZIM here:

Archive.zip

The bad one contains 14 metadata with bad mimetype (most are empty, but I've added one bad encoding) ; I failed to set the Counter metadata on my own, looks like creator refuses to let us customize it, so I cannot test that.