FED-1728 Migrate to null safety

[greglittlefield-wf]

Motivation

This package needs to be upgraded to null safety in order for it to be used in other null-safe packages, and is a prerequisite for being consumed in Dart 3.

This PR contains the bulk of the changes that will make up the react-dart 7.0.0 major release.

A separate PR will be made into the v7_wip branch to perform other planned deprecated API removals. We can do a more complete audit of public API changes either at that point, or in the PR to merge the v7_wip branch.

Changes

• Migrate to null safety
• Additional changes that were prerequisites for null safety
  • Fix null key handling in JsBackedMap, required due to null-safe typing of getProperty/setProperty when implicit-casts are disabled, add tests
  • Update mocks to work in null safety by using mockito's builder, update CI and introduce dart_dev for formatting that excludes generated files
• Add new asserts that callback ref args aren’t non-nullable, add tests
• Major API changes
  • Update types to help fix implicit casts, as well as generally improve typing
    • Update ReactComponentFactoryProxy.call return type from dynamic to ReactElement
    • Update typing of top-level DOM factories from dynamic to ReactDomComponentFactoryProxy
  • API removals (more will be coming in a later PR)
    • Deprecated APIs with replacements: forwardRef, memo, main
    • All public ReducerHook and StateHook constructors
    • All public Ref constructors except for .fromJs
• Cleanup
  • Fully disable implicit casts, fix remaining implicit casts not fixed in https://github.com/Workiva/react-dart/pull/366
  • Remove ddc_emulated_function_name_bug - not needed, unnecessary to migrate
  • Tests: sync copy of RefTestCaseCollection w/ copy in over_react null safety branch

Testing

• Smoke test examples
• CI passes
  • Verify newly-added test files are run in CI
• Verify CI passes on over_react test branches
  • 4.x (current release line) - https://github.com/Workiva/over_react/pull/845
  • null safety WIP branch - https://github.com/Workiva/over_react/pull/828
    • Failures for VM tests (over_react builder tests) are expected and can be ignored; so long as dart2js and DDC tests pass, we're good

[aviary3-wk]

Security Insights

No security relevant content was detected by automated scans.

Action Items

• Review PR for security impact; comment "security review required" if needed or unsure

• Verify aviary.yaml coverage of security relevant code

  Questions or Comments? Reach out on Slack: #support-infosec.

[aaronlademann-wf]

+10

[greglittlefield-wf]

@Workiva/release-management-p