[clang] [clang-format] Disable short blocks if brace is on the new line (PR #196021)

[Gedare Bloom via cfe-commits]

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@@ -895,6 +889,11 @@ class LineJoiner {
         Line.startsWithExportBlock()) {
       if (IsSplitBlock)
         return 0;
+      // The construct-specific options AllowShortIfStatementsOnASingleLine and
+      // AllowShortLoopsOnASingleLine take precedence over
+      // AllowShortBlocksOnASingleLine: a statement whose specific option
+      // disallows merging is not put on a single line even when short blocks
+      // are always allowed.
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gedare wrote:

I see. That appears to be different than the open issues that your PR is solving though. I'm not sure this was an explicitly supported format, but I guess it appears to have been working. Can you point to a format style guide that documents this style to help [justify additional style options](https://clang.llvm.org/docs/ClangFormatStyleOptions.html#adding-additional-style-options)?

This style requires the brace wrapping to be overridden in some cases, but not in others. I could see making an argument that `AllowShortXyzOnASingleLine` could be made to override the BraceWrapping, as suggested also by owenca, but there are also strange interactions such as with `BraceWrapping.SplitEmptyFunction`. You could instead propose a new option to `BraceWrapping` that prevents wrapping the brace if the function is empty. This, along with the `AllowShortBlocksOnASingleLine.Attached` (and `NotAttached`) should be able to satisfy your requirements.

The preference for fixing the open issues as regressions would be to have a minimal change to existing style files. Thus my recommended route of deprecating `Always` in favor of explicit `Attached` and `NotAttached` options, since `Always` did not really mean always.

Another possibility could be to have `AllowShortBlocksonASingleLine` to "inherit" from the `AllowShortXyzOnASingleLine` when the brace is attached.

https://github.com/llvm/llvm-project/pull/196021