Optional completion handler

[robertmryan]

Goals ⚽

The goals are:

• More concise API:

  When downloading images (e.g. as part of a prefetch process), you don’t need a completion handler closure, but right now we have to supply one although the parameter is optional. For example, if you don’t have a completion handler, you have to do:

  imageDownloader.download(request, completion: nil)
  

  With this change, we can omit that completion parameter entirely:

  imageDownloader.download(request)
  

• More consistent API:

  Everywhere else in the API, the optional completion handlers have a default value of nil. But the download method of ImageDownloader does not.

Implementation Details 🚧

Just supplied a default parameter of nil for the completion handler for this one method.

Testing Details 🔍

[robertmryan]

FWIW, I don’t know why that iOS test target is failing as part of the CI, as it’s not failing when I run tests locally. Perhaps because the two requests are downloading the exact same image?

[jshier]

Those tests are racy in a way that only shows up in CI. We’re still trying to figure it out. In the meantime, it’s fine for PRs.

[jshier]

👍 The documentation for the method already says it defaults to nil, so this just seems like a bug.