Avoid repeated calculations of default SwiftUI view name

[square-tomb]

Goal

Prior to this change, BugsnagTracedView reevaluates getViewName(content:) each time it is initialized without the viewName parameter.

After this change, the default view name is calculated only once for each specialization of the BugsnagTracedView generic type (and is still calculated lazily due to the lazy behavior of static let).

Testing

CI only.

[clr182]

Hi @square-tomb

Thank you for opening this PR with us. The change you have suggested seems reasonable and as I have added it to our backlog to review when priorities allow. We'll be sure to let you know of any updates.

[kstenerud]

Hi @square-tomb

Unfortunately, this won't work because static stored properties are not supported in generic types. This was a language policy decision by the Swift team in order to avoid requiring separate property storage per parametric type. There's a good explanation of the issue here: https://stackoverflow.com/questions/45467329/extension-may-not-contain-stored-property-but-why-is-static-allowed

If you try to run the unit tests, you should see the Xcode error pop up.

[square-tomb]

Ah, thank you for pointing that out! I should have attempted to compile the entire type before opening this PR 🙈