support loading of plugins in a smart order based on dependency

[salmanm]

Fixes #29

• Auto loads plugins in the order they are needed (checks for the dependencies array).
• Checks for cyclic dependencies and returns error, if found.

[Eomm]

Hi,
thanks for the PR!

Could you fix the error for Node.js 6?
It should be necessary replace the Object.value with a Object.keys() and then grab the value.

Meanwhile, I'll check deeper the code, for now, I'm thinking that a hidden limit is that it will be not possible load twice a plugin with the same name but I need to think if it is a real use case

[mcollina]

Good work! Instead of extending the “basic” app, can you create a new one?

[mcollina]

I think we should throw if two plugins have the same name.z

[salmanm]

Thanks @mcollina, done those changes.

[salmanm]

@Eomm I tried to think about the hidden limit you mentioned. Loading a plugin twice in the same load chain is a result of cyclic dependency. I couldn't think of a case where one would load a plugin twice in the same load chain and still not cause cyclic dependency.

It's however fine to load a plugin from two separate load sequence. i.e. plugin-a & plugin-b both needs plugin-c.

[mcollina]

Can you add some decorators/checks in the dependency test plugins so that it won't load unless we the order is correct?

[mcollina]

Also, CI is failing.

[salmanm]

Yep, good idea.
I didn't do it earlier as I thought fastify already blocks when dependencies aren't loaded already.
But no harm checking.

All done now.

[mcollina]

LGTM

[Eomm]

Add 2 hints

[salmanm]

@Eomm Done

[Eomm]

I will release it by the week end as semver-minor 👍