Feat/bootstrapping

[benjamin-es-hall]

About the changes

This PR adds bootstrapping of toggles and has taken inspiration from both the js and Android client SDKs.

I also took the opportunity to tidy up the folder structure so the files are more focused are structured more where expected.

For the bootstrapping I added it to both initialisation of UnleashClient & Poller, and also when calling start on the client.

Bootstrapping is passed into each of above via an enum specifying whether it is from a list of Toggle's, or from a json file hosted with the host application. The .jsonFile(path) is meant to be explicit enough so that it is up to the host application to correctly specify file location. Further, if file cannot be found I settled on a fatalError since if the file doesn't exist in the project it should inform the developer.

For passing in toggles at client initialisation, due to existing way client is initialised (e.g. passing in all parameters for the Poller, and also the poller), if bootstrap and a poller is injected, the bootstrap injected into the client will be ignored and must be directly included into Poller instead. I considered updating this initialiser so that there aren't redundant injected properties in case of Poller added, but that felt like a breaking change better suited for a major release.

Closes #92

Important files

Unfortunately due to way files are tracked when moving, the PR gives impression more files changed than actually are since I moved into more logically arrangements that makes it significantly easier to read.

Discussion points

If this approach is suitable, I will add a commit to update the readme on usage as well, just wanted to confirm approach first.

[kwasniew]

with bootstrap going as a first parameter isn't it gonna be a breaking API change?

[benjamin-es-hall]

I don't think it should since it has a default argument. However, if printToConsole is used, it now needs to be explicit since without, at the call-site it would be like this:

// Without explicit printToConsole argument, confusing what the "true" applies to at a glance
await start(bootstrap: .toggles([...]), true)`

// With explicit printToConsole argument, clearer what the bool input applies to
await start(bootstrap: .toggles([...]), printToConsole: true)

// Default arguments so following should work
await start() // default: no bootstrap toggles, and printToConsole false

await start(bootstrap: .toggles([...])) // boostrapped, default: printToConsole false

await start(printToConsole: true) // default: no bootstrap toggles, override: printToConsole

[kwasniew]

fair point

[kwasniew]

I'm wondering if we could make it more similar to the android SDK where we pass a pre-existing file instead of a path to a file. Would it eliminate the fata error where file cannot be found and move it to the user space? From a quick check android SDK checks if the provided file exists and uses default when it doesn't.

[benjamin-es-hall]

Ah I did want to do this but Swift doesn't really have a concept of a File object. However for the fatal error we could instead default to an empty list of toggles (a default). I wasn't sure whether to do that or not as since it may be misleading to a user that they input a file path and seemingly no issues reading from it even if invalid. Hence alerting the user earlier seemed more appropriate telling them the file they expected to exist is not actually on their filesystem. What do you think?

[kwasniew]

maybe printing warning to the console that the file was not found and using a default empty list?

[benjamin-es-hall]

Sure! I'll change that over and put some doc comment on it which should hopefully surface it :)

[kwasniew]

Awesome work. The change looks really solid. I add some minor comments inline. I'm curious what you think about them.
Also one question comment about the docs? Would you prefer to handle a docs change in this PR or a separate one?

[benjamin-es-hall]

Awesome work. The change looks really solid. I add some minor comments inline. I'm curious what you think about them. Also one question comment about the docs? Would you prefer to handle a docs change in this PR or a separate one?

Thank you for the review :) I responded to the comments and would like to know what you think. Also I'm happy to update README here, just wanted to confirm approach was appropriate first :)

[kwasniew]

Your design decisions seem to be spot on :) I'm willing to approve it and merge asap so that others can benefit from your work.

[benjamin-es-hall]

Your design decisions seem to be spot on :) I'm willing to approve it and merge asap so that others can benefit from your work.

Awesome! I just pushed up change to use default empty list of toggles if json file cannot be found, and also updated the readme :)

I re-requested review just for a double check

[kwasniew]

We're good to go live with it