Nullability

Nullability Work

Binding Files /src/*.cs

When

• ASAP - there’s nothing blocking us

How

• the generator handle them using [NullAllowed] attributes
• xtro report warnings for missing and extra null allowed, based on ObjC headers
  • important: headers are not always 100% accurate so it’s worth checking:
    • git history if we allowed it (and headers disagree) and
    • if we have unit tests for the API (that prove it works)

Manual Bindings /src/**/*.cs

When (pre-condition)

• For each framework then xtro entries must all be fixed before starting on the manual bindings
  • because doing binding files later would introduce issues (and re-work)
  • Quick-check (for ARKit, empty result means it’s complete)

cd tests/xtro-sharpie
git grep null-allowed *.ignore | grep ARKit

How

• For all .cs files
  • should have #nullable enable
    • quick check git grep -L "#nullable enable" . inside framework directory, e.g. src/ARKit. No output means every file has the pragma directive
• build without errors
  • warnaserror is enabled for nullability (so make is all that should be needed)
• Use ObjCRuntime.ThrowHelper.Throw``**ArgumentNullException** instead of directly throwing
  • it’s a size saving optimization - but it also shows we reviewed the code for nullability
  • quick check: git grep " ArgumentNullException" . inside framework directory, e.g. ARKit. No output means nothing throw an ArgumentNullException manually (without the helper)
• Replace == null and != null with the newer is null and is not null to avoid using any == or != overrides.