dillon1000/react

Add Fragment as a named export to React (#10783)

* Add Fragment as a named export to React

* Remove extra tests for Fragment

* Change React.Fragment export to be a string '#fragment'

* Fix fragment special case to work with 1 child

* Add single child test for fragment export

* Move fragment definition to ReactEntry.js and render components for key warning tests

* Inline createFiberFromElementType into createFiberFromElement

* Update reconciliation to special case fragments

* Use same semantics as implicit childsets for ReactFragment

* Add more fragment state preservation tests

* Export symbol instead of string for fragments

* Fix rebase breakages

* Re-apply prettier at 1.2.2

* Merge branches in updateElement

* Remove unnecessary check

* Re-use createFiberFromFragment for fragment case

* Simplyify branches by adding type field to fragment fiber

* Move branching logic for fragments to broader methods when possible.

* Add more tests for fragments

* Address Dan's feedback

* Move REACT_FRAGMENT_TYPE into __DEV__ block for DCE

* Change hex representation of REACT_FRAGMENT_TYPE to follow convention

* Remove unnecessary branching and isArray checks

* Update test for preserving children state when keys are same

* Fix updateSlot bug and add more tests

* Make fragment tests more robust by using ops pattern

* Update jsx element validator to allow numbers and symbols

* Remove type field from fragment fiber

* Fork reconcileChildFibers instead of recursing

* Use ternary if condition

* Revamp fragment test suite:

- Add more coverage to fragment tests
- Use better names
- Remove useless Fragment component inside tests
- Remove useless tests so that tests are more concise

* Check output of renderer in fragment tests to ensure no silly business despite states being preserved

* Finish implementation of fragment reconciliation with desired behavior

* Add reverse render direction for fragment tests

* Remove unneeded fragment branch in updateElement

* Add more test cases for ReactFragment

* Handle childless fragment in reconciler

* Support fragment flattening in SSR

* Clean up ReactPartialRenderer

* Warn when non-key and children props are passed to fragments

* Add non-null key check back to updateSlot's array's case

* Add test for positional reconciliation in fragments

* Add warning for refs in fragments with stack trace