[lldb] Support alternatives for scope format entries (#137751)

This PR implements support for specifying multiple alternatives for
scope format entries. Scopes are used to enclose things that should only
be printed when everything in the scope resolves.

For example, the following scope only resolves if both
`${line.file.basename}` and `${line.number}` resolve. `

```
{ at ${line.file.basename}:${line.number}}
```

However, the current implementation doesn't let you specify what to
print when they don't resolve. This PR adds support for specifying
multiple alternative scopes, which are evaluated left-to-right.

For example:

```
{ at ${line.file.basename}:${line.number}| in ${function.name}| <unknown location>}
```

This will resolve to:

- ` at ${line.file.basename}:${line.number}` if the corresponding
variables resolve.
- Otherwise, this resolves to ` in ${function.name}` if
`${function.name}` resolves.
- Otherwise, this resolves to ` <unknown location>` which always
resolves.

This PR makes the `|` character a special character within a scope, but
allows it to be escaped.

I ended up with this approach because it fit quite nicely in the
existing architecture of the format entries and by limiting the
functionality to scopes, it sidesteps some complexity, like dealing with
recursion.
3 files changed
tree: f0ee36a4da78a10f7189a25e50df2b5e7c8dbc2c
  1. .ci/
  2. .github/
  3. bolt/
  4. clang/
  5. clang-tools-extra/
  6. cmake/
  7. compiler-rt/
  8. cross-project-tests/
  9. flang/
  10. flang-rt/
  11. libc/
  12. libclc/
  13. libcxx/
  14. libcxxabi/
  15. libunwind/
  16. lld/
  17. lldb/
  18. llvm/
  19. llvm-libgcc/
  20. mlir/
  21. offload/
  22. openmp/
  23. polly/
  24. pstl/
  25. runtimes/
  26. third-party/
  27. utils/
  28. .clang-format
  29. .clang-format-ignore
  30. .clang-tidy
  31. .git-blame-ignore-revs
  32. .gitattributes
  33. .gitignore
  34. .mailmap
  35. CODE_OF_CONDUCT.md
  36. CONTRIBUTING.md
  37. LICENSE.TXT
  38. pyproject.toml
  39. README.md
  40. SECURITY.md
README.md

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