[clang] [clang-format] Add DiagHandler for getStyle function (PR #91317)

[Owen Pan via cfe-commits]

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@@ -4026,12 +4030,13 @@ Expected<FormatStyle> getStyle(StringRef StyleName, StringRef FileName,
   // Reset possible inheritance
   Style.InheritsParentConfig = false;
 
-  auto dropDiagnosticHandler = [](const llvm::SMDiagnostic &, void *) {};
+  auto diagHandlerOrDropHandling =
+      DiagHandler ? DiagHandler : [](llvm::SMDiagnostic const &, void *) {};
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owenca wrote:

Do you need to move the `const`?

https://github.com/llvm/llvm-project/pull/91317