[all-commits] [llvm/llvm-project] 4bf10f: [YAMLTraits] Fix std::optional input on empty docu...

[akirchhoff-modular via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 4bf10f3da7ab32d70d5c7c43b7705c06c108d326
      https://github.com/llvm/llvm-project/commit/4bf10f3da7ab32d70d5c7c43b7705c06c108d326
  Author: akirchhoff-modular <github-work at kirchhoff.digital>
  Date:   2023-10-16 (Mon, 16 Oct 2023)

  Changed paths:
    M llvm/lib/Support/YAMLTraits.cpp
    M llvm/unittests/Support/YAMLIOTest.cpp

  Log Message:
  -----------
  [YAMLTraits] Fix std::optional input on empty documents (#68947)

When the input document is non-empty, `mapOptional` works as expected,
setting `std::optional` to `std::nullopt` when the field is not present.
When the input document is empty, we hit a special case inside of
`Input::preflightKey` that results in `UseDefault = false`, which
results in the `std::optional` erroneously being set to a non-nullopt
value. `preflightKey` is changed to set `UseDefault = true` in this case
to make the behavior consistent between empty and non-empty documents.