bug(#209): better defect message in mandatory-home

[h1alexbel]

In this pull I've updated defect message reported by mandatory-home lint, now it says about the need of home URL.

see: #209

[h1alexbel]

waiting for #213

[h1alexbel]

@volodya-lombrozo could you please check this one?

[volodya-lombrozo]

@h1alexbel Thank you for the contribution! It's a bit more clear now, but for me it's not sufficient because I don't know what to do with the url and home meta.

Should it be <home url="x"/> or <meta><home><url>x</url></home></meta> or <meta home="x"/>? It's impossible to say from this message.

@yegor256 Can you help us with this, please? Can we add a link to the description or at least something.

[yegor256]

@volodya-lombrozo we can't explain in one error message how XMIR format is designed. It's expected that the user has certain background knowledge about XMIR and knows what is "meta". We can add information about XMIR into the Javadoc of the Defect class, it may help (but it's a separate problem/ticket).

[volodya-lombrozo]

@volodya-lombrozo we can't explain in one error message how XMIR format is designed. It's expected that the user has certain background knowledge about XMIR and knows what is "meta". We can add information about XMIR into the Javadoc of the Defect class, it may help (but it's a separate problem/ticket).

@yegor256 Maybe we can add a single link to the documentation of XMIR where I will be able to find information about meta objects? Right now I have no idea where to find it. I see only cryptic messages that tell almost nothing.

It will look like:

1. Cryptic error [name-outside-of-abstract-object]
2. Cryptic error [mandatory-home]

XMIR docs is here: URL 

Otherwise, this PR doesn't solve the original issue.

[h1alexbel]

@volodya-lombrozo @yegor256 I think publishing (but not linking actually) our lint motives will help with the understanding what needs to be fixed:

1. Cryptic error [name-outside-of-abstract-object]
2. Cryptic error [mandatory-home]

Lints list is here: URL
XMIR docs is here: URL

So the user will find the rule id, let's say: mandatory-home, go to the lints website, find it and read about it.

Currently we have them here: https://github.com/objectionary/lints/tree/gh-pages/_site/0.0.31, but their are not accessible through website. WDYT?

[yegor256]

@volodya-lombrozo I believe, the links are added in this PR: #229

[yegor256]

@h1alexbel this contribution is good, thanks!

[yegor256]

@volodya-lombrozo as a general rule, a merge PR doesn't mean a closed issue. When PR is good enough to be merged, we should accept it and merge ASAP. Then, we get back to the ticket and discuss whether it may be closed. If not, we make another PR, and so on. "This PR doesn't solve the problem" is not a valid reason for its rejection.